Next Article in Journal
Natural Pyrolusite-Catalyzed Ozonation for Nanoplastics Degradation
Previous Article in Journal
Support Effects on Fe- or Cu-Promoted Ni Catalysts Used in the Catalytic Deoxygenation of Tristearin to Fuel-like Hydrocarbons
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 15
Issue 5
10.3390/catal15050503
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting

by
Zichen Cheng
1,
Zekun Li
1,
Shou Huang
1,
Junfan Pan
1,
Jiaxian Mei
1,
Siqi Zhang
1,
Xingyu Peng
1,
Wen Lu
2,* and
Lei Yan
1,*
1
Institute of Nanocatalysis and Energy Conversion, College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou 311300, China
2
Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China
*
Authors to whom correspondence should be addressed.
Catalysts 2025, 15(5), 503; https://doi.org/10.3390/catal15050503
Submission received: 17 April 2025 / Revised: 8 May 2025 / Accepted: 19 May 2025 / Published: 21 May 2025
(This article belongs to the Special Issue Recent Progress on Electrocatalytic Hydrogen Evolution Reaction)
Browse Figures
Versions Notes

Abstract

:
The efficient mass transport and enhanced accessibility of active sites are crucial for high-performance electrocatalysts in water splitting. Inspired by the hierarchical structure of natural wood, we engineered a monolithic electrocatalyst, cobalt nanoparticles encapsulated in nitrogen-doped carbon layers on carbonized wood (Co@NC/CW), by carbonizing wood to create a three-dimensional framework with vertically aligned macropores. The unique architecture encapsulates cobalt nanoparticles within in situ-grown nitrogen-doped graphene layers on wood-derived microchannels, facilitating ultrafast electrolyte infusion and anisotropic electron transport. As a result, the optimized freestanding Co@NC/CW electrode exhibits remarkable bifunctional activity, achieving overpotentials of 403 mV and 227 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, at a current density of 50 mA cm−2. Furthermore, the integrated hybrid electrolyzer combining the HER and the OER delivers an impressive 50 A cm−2 at a cell voltage of 1.72 V while maintaining a Faradaic efficiency near 99.5% and sustaining long-term stability over 120 h of continuous operation. Co@NC/CW also demonstrates performance in the complete decomposition of alkaline seawater, underscoring its potential for scalable applications. This wood-derived catalyst design not only leverages the natural hierarchical porosity of wood but also offers a sustainable platform for advanced electrochemical systems.

Graphical Abstract

1. Introduction

The accelerating pace of industrialization, coupled with growing concerns over energy security and worsening environmental degradation, has created an urgent need for clean and sustainable energy technologies [1,2,3]. Among the various strategies under development, electrocatalytic water splitting stands out as a promising and scalable solution for converting renewable electricity into energy-dense hydrogen fuel [4,5,6]. However, the practical implementation of water electrolysis is significantly hampered by the sluggish kinetics of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which are plagued by high overpotentials and inefficient charge transfer [7]. To overcome these challenges, noble metal-based electrocatalysts, such as Pt-based materials for the HER and RuO2/IrO2 for the OER, have set the performance benchmark due to their high activity and selectivity, but the high cost and scarcity of these materials severely restrict large-scale deployment [8,9]. As a result, researchers have sought alternatives based on earth-abundant transition metals, including phosphides [10], nitrides [11], and sulfides [12], yet these alternatives often suffer from poor long-term stability under harsh electrochemical conditions, with active species undergoing corrosion, oxidation, and dissolution at high overpotentials.
Electrolysis in seawater introduces additional challenges, as the presence of chloride ions can cause catalyst corrosion, promote undesirable side reactions, and compromise overall efficiency [13,14,15]. To mitigate these issues, hybridizing catalysts with carbon matrices has emerged as an effective strategy [16]. Robust π–d orbital interactions between graphitic carbon and metal species facilitate charge redistribution, improve electrical conductivity, and suppress metal leaching, while three-dimensional conductive carbon frameworks provide spatial confinement that prevents nanoparticle agglomeration and forms corrosion-resistant metal–carbon bonds to stabilize the catalytic interface [17,18]. However, most powder-form catalysts require slurry-coating techniques that involve polymeric binders and conductive additives, which increase interfacial resistance and induce mechanical stress during electrode fabrication [19]. This complicates catalyst accessibility and limits performance for the OER and HER [20,21]. Consequently, there is growing interest in the development of binder-free, self-supporting electrode architectures that enable direct integration into electrochemical cells. These freestanding systems minimize interfacial resistance, and offer improved mechanical and chemical stability. Recent studies highlight that hierarchical porosity in such electrodes plays a pivotal role in mass transfer kinetics: vertically aligned microchannels enable rapid electrolyte penetration and directional ion transport, while interconnected mesopores maximize active site exposure. Simultaneously, macroporous networks facilitate instantaneous gas bubble detachment, minimizing concentration polarization and ensuring sustained reaction rates [22].
While traditional freestanding substrates such as carbon cloth and carbon paper have been extensively explored, their limited pore architectures and high manufacturing costs pose significant scalability challenges [23]. In contrast, biomass-derived carbon materials, particularly carbonized wood, offer a compelling alternative owing to their inherent structural advantages. Natural wood features a highly ordered, anisotropic microstructure composed of vertically aligned microchannels and interconnected mesoporous walls [24,25]. Upon pyrolysis, this unique architecture is preserved, yielding a lightweight yet mechanically robust framework with hierarchical porosity, high electrical conductivity, and corrosion resistance [26]. The anisotropic 3D microchannels not only act as “ion highways” for ultrafast mass transport but also provide a scaffold for uniform catalyst loading, while the carbonized cell walls serve as conductive pathways for accelerated electron transfer [27]. Such carbonized wood-based electrodes allow rapid and uniform electrolyte diffusion, efficient gas evolution due to low bubble adhesion energy, and structural integrity, making them highly attractive for high-performance electrocatalysis [28,29]. Moreover, the scalable synthesis of carbonized wood—achieved through direct pyrolysis of abundant natural wood without complex processing—offers a cost-effective and sustainable route for industrial-scale electrode production [30,31].
Herein, we report a wood-derived, hierarchically porous electrocatalyst in which cobalt nanoparticles are encapsulated within in situ-grown, nitrogen-doped carbon layers on carbonized wood (Co@NC/CW). Leveraging the innate anisotropic three-dimensional (3D) microchannels of natural wood, this catalyst enables ultrafast mass transport and accelerated electron transfer. Consequently, the Co@NC/CW electrode demonstrates outstanding bifunctional performance, delivering overpotentials of 403 mV for the OER and 227 mV for the HER at 50 mA cm−2. When assembled in a two-electrode electrolyzer, seawater splitting is achieved at a cell voltage of 1.72 V at 50 mA cm−2 with a faradaic efficiency near 100% and stability over 120 h of continuous operation. In overall alkaline seawater splitting tests, the Co@NC/CW electrode requires only 1.86 V to attain a current density of 50 mA cm−2. This work combines biomass-derived structural catalyst design to address critical challenges in energy conversion systems.

2. Results and Discussion

The fabrication process of the freestanding Co@NC/CW electrode is schematically illustrated in Figure 1. Initially, natural fir wood slices underwent alkaline hydrolysis to partially remove lignin and hemicellulose, exposing the three-dimensional (3D) porous skeleton of cellulose [32,33]. The hydrolyzed wood was then immersed in an aqueous solution of CoCl2·6H2O, allowing Co2+ ions to deeply infiltrate the matrix and coordinate with hydroxyl-rich cellulose fibrils via chelation interactions. Pyrolysis was then conducted in the presence of melamine, which simultaneously served as a nitrogen source and a chemical reducing agent [34]. Melamine, due to its high nitrogen content, thermally decomposes in a stepwise manner under an inert atmosphere to release NH3 and volatile CN radicals [35]. These nitrogen-rich species chemically interact with the carbonized wood matrix, achieving uniform in situ nitrogen doping. Concurrently, the reactive decomposition products of melamine also facilitate the reduction of Co2+ to metallic Co nanoparticles within the carbon framework [36,37]. This dual function of melamine—nitrogen doping and metal ion reduction—leads to the formation of a robust Co@NC/CW composite. The final architecture retains the native wood-derived macroporous structure, with Co nanoparticles uniformly distributed and firmly anchored within the nitrogen-doped carbon matrix. The conductive nitrogen-doped carbon (NC) network enhances electron transport while simultaneously improving the structural stability and catalytic accessibility of the embedded cobalt nanoparticles.
The scanning electron microscope (SEM) images (Figure 2a) reveal that Co@NC/CW retains the hierarchical porosity of the natural wood, exhibiting highly aligned open channels which facilitate rapid vertical gas bubble release and radial electrolyte transport [38]. Top-view SEM images of Co@NC/CW (Figure 2b) show that the average channel diameter is around 20 μm. Higher magnification images (Figure 2c) indicate that numerous Co nanoparticles are uniformly deposited along the inner channel walls. These in situ-formed Co nanoparticles are tightly integrated into the carbon framework, ensuring efficient electron conduction during electrocatalysis. Transmission electron microscopy (TEM) (Figure 2d) further confirms that the hierarchical structure consists of a carbon matrix interspersed with Co nanoparticles, with an interplanar spacing of 0.21 nm corresponding to the (111) crystal plane of metallic Co. Additionally, graphitic carbon layers with an interlayer spacing of 0.35 nm, corresponding to the (002) plane, are observed on the surfaces of the Co nanoparticles, which may enhance the electrocatalytic activity by facilitating electronic interactions between the metal cores and the surrounding carbon shells [39]. Elemental mapping (Figure 2e–g) shows the uniform distribution of Co, N, and C across the carbon matrix, verifying the successful incorporation of all elements. For comparison, the control sample Co/CW was prepared without melamine (Figure S1), and CW calcined from pure wood was prepared (Figure S2).
X-ray diffraction (XRD) patterns (Figure 2h) display distinct peaks at 44.2°, 51.5°, and 75.9°, corresponding to the (111), (200), and (220) planes of metallic Co, respectively. Additionally, characteristic peaks at 24.8° and 43.6° are attributed to the (002) and (101) planes of graphite carbon, respectively, consistent with the TEM results. Raman spectroscopy further exhibits two prominent bands at 1345 cm−1 (D band) and 1590 cm−1 (G band), assigned to the disordered and graphitized carbon, respectively (Figure S3). The intensity ratio (ID/IG) values of Co@NC/CW, Co/CW, and WC are 1.04, 1.02, and 0.99, respectively, implying an increased level of structural disorder upon the introduction of Co species and nitrogen-doped carbon frameworks [40]. The N2 adsorption/desorption isotherms of Co@NC/CW (Figure S4) exhibit a type IV profile with a hysteresis loop at relative pressures above 0.3, indicating the presence of mesopores. The Brunauer–Emmett–Teller (BET) surface area is measured to be 21.6 m2 g−1, and the pore size is mainly distributed in the range of 3–4 nm and 5–20 nm. This high porosity and surface area are advantageous for exposing more electroactive sites and promoting efficient ion transport through shortened diffusion pathways [41].
X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface chemical composition and electronic structure of material. The survey XPS spectra confirmed the presence of C, N, and Co elements (Table S1), in good agreement with the elemental mapping data (Figure S5). The high-resolution C 1s spectrum of Co@NC/CW (Figure S6) reveals deconvoluted peaks at 284.5, 285.2, and 287.2 eV, assigned to C=C/C–C, C–N, and C=O species, respectively [42]. In the Co 2p region (Figure 2i), peaks at 778.7 and 793.7 eV are assigned to metallic Co, while additional features at 780.1 and 795.1 eV correspond to Co3+. Additionally, the signals at 781.9 and 796.9 eV are attributed to Co2+, indicating the coexistence of multiple Co oxidation states, with metallic Co being predominant [36]. This suggests partial surface oxidation of cobalt during exposure to air. The high-resolution N 1s spectrum (Figure 2j) displays five nitrogen configurations: pyridinic N (398.2 eV), Co-N (399.3 eV), pyrrolic N (400.7 eV), and graphitic N (401.7 eV), confirming successful nitrogen doping of the carbon matrix and participates in coordination with cobalt atoms [43]. Such coordination environments are beneficial for tuning the electronic structure and catalytic activity of the composite material. The surface wetting behavior of the carbon-based materials was evaluated via static water contact angle measurements. As shown in Figure 2k, the Co@NC/CW sample exhibits a moderate water contact angle of 72°, indicative of hydrophilic character, which stands in stark contrast to the highly hydrophobic nature of CW (water contact angle: 104°). Such hydrophilicity is favorable for rapid gas bubble detachment during electrocatalytic reactions, while maintaining sufficient electrolyte accessibility to the active surface [44]. Interfacial bubble dynamics were further investigated through gas adhesion experiments. As shown in Figure 2l, the Co@NC/CW electrode enables near-instantaneous bubble diffusion within 60 ms, validating its hydrophilic and gas-transport surface configuration.
Benefiting from the unique wood-derived architecture and the uniform dispersion of Co nanoparticles, the electrocatalytic performance of the freestanding Co@NC/CW electrode was systematically evaluated for both the OER and HER in 1.0 M KOH, using a standard three-electrode configuration. For comparison, Co/CW and CW electrodes were also tested under identical conditions. Linear sweep voltammetry (LSV) was conducted at a scan rate of 5 mV s−1. As shown in Figure 3a, the Co@NC/CW electrode achieves superior OER activity compared to the benchmark RuO2 catalyst. Specifically, it achieves low overpotentials of 361 mV and 403 mV at 50 and 100 mA cm−2 (Figure 3b), respectively, which are significantly lower than those required for Co/CW (385 and 438 mV) and CW (567 and 725 mV). Tafel slope analysis further reveals that Co@NC/CW has a slope of 138 mV dec−1, which is smaller than those of Co/CW (188 mV dec−1) and CW (356 mV dec−1) (Figure 3c), confirming an enhancement in OER kinetics. Compared with other reported wood-based OER catalysts (Figure 3d and Table S2), Co@NC/CW demonstrates excellent electrocatalytic performance [24,41,45,46,47,48,49].
To gain further insight into the catalytic activity, the electrochemically active surface area (ECSA) was estimated by measuring the double-layer capacitance (Cdl) via cyclic voltammetry test (Figure S7). The Co@NC/CW electrode shows a higher Cdl of 36.8 mF cm−2 compared to Co/CW (26.9 mF cm−2) and CW (24.7 mF cm−2) (Figure 3e), suggesting a larger accessible surface area and a greater number of active sites. When the LSV curves are normalized by the ECSA (Figure S8), Co@NC/CW still delivers superior intrinsic OER activity compared to Co/CW and CW, indicating that the formation of Co@NC sites effectively enhances the catalytic efficiency. Electrochemical impedance spectroscopy (EIS) was conducted to probe the interfacial charge transfer resistance (Rct) (Figure 3f). Among all samples, the Co@NC/CW electrode exhibited the lowest Rct value of 0.73 Ω, suggesting more efficient electron transfer and improved electrocatalytic kinetics. To further evaluate the ion diffusion behavior, the Warburg coefficient (σ) was extracted by fitting the EIS data with the equation Z = R + σω−1/2, where ω is the angular frequency (ω = 2πf), Z’ is the real part of the impedance, and σ quantifies the ion diffusion resistance [50]. A lower σ value corresponds to faster ion diffusion [51]. Notably, the Co@NC/CW electrode exhibits an σ value of 0.002 (Figure 3g), which is considerably lower than those of Co/CW (0.42) and CW (1.77), indicating reduced ion diffusion resistance, attributable to the Co@NC heterostructure and its hydrophilic interface. Additionally, long-term durability tests demonstrate that Co@NC/CW exhibits excellent operational stability (Figure 3h), with negligible potential increase over 180 h of continuous testing, confirming its robustness under harsh alkaline conditions.
To elucidate the influence of the hydrophilic structure on electron transfer and surface material behavior, EIS measurements at different potentials were conducted (Figure 4a–c). These measurements provide insights into the electrochemical kinetics and mass transport characteristics of the catalysts under working conditions. The Nyquist plots obtained were fitted using a well-established equivalent circuit model (Figure 4d), which includes components such as solution resistance (Rs), Cdl, Rct, mass transport resistance (Rmt), and the capacitance associated with the electrochemical reaction process (Crxn) [52]. As illustrated in Figure 4e, the Co@NC/CW electrode exhibits a notably lower Rct compared to individual Co/CW and CW counterparts. This reduction in charge transfer resistance indicates significantly improved charge transfer kinetics, likely due to the synergistic electronic interactions between Co and graphite carbon. Furthermore, the Rmt component reflects the resistance to mass transport of reactants (e.g., O2, OH−) and products during the catalytic process. It is closely related to factors such as the electrode’s pore architecture, surface wettability, and the viscosity of the electrolyte. The Co@NC/CW electrode displays a substantially reduced Rmt value (Figure 4f), implying enhanced mass diffusion efficiency. This can be attributed to the presence of vertically aligned open channels and the intimate coupling of metal–carbon bond domains, which collectively facilitate efficient reactant access and rapid product release. The hydrophilic surface of the catalyst further promotes electrolyte infiltration and minimizes bubble accumulation, thereby lowering local diffusion barriers. Together, these characteristics contribute to the superior catalytic performance of Co@NC/CW in alkaline media.
The HER performance of the prepared catalysts was systematically evaluated via comparative electrochemical measurements. As illustrated in Figure 5a, the Co@NC/CW demonstrates better catalytic activity among all the samples, but is inferior to Pt/C. Specifically, Co@NC/CW achieves current densities of −50 and −100 mA cm−2 at relatively low overpotentials of 227 and 292 mV, respectively (Figure 5b). In contrast, Co/CW and pristine CW require much higher overpotentials of 294 and 582 mV to reach the current densities of −50 mA cm−2. The Tafel slope for Co@NC/CW is determined to be 180 mV dec−1 (Figure S9), indicating that the HER proceeds via a Volmer-limited mechanism in alkaline media, where the initial adsorption of hydrogen species (H*) is the rate-determining step. In addition, Co@NC/CW demonstrates acceptable long-term durability. During chronoamperometric testing at −50 mA cm−2, the catalyst exhibits less than 8% potential decay over 180 h of continuous operation (Figure 5c), underscoring its electrochemical stability for HERs under alkaline conditions.
Inspired by its outstanding bifunctional electrocatalytic performance, the Co@NC/CW electrode was further applied in an overall water splitting system configured with a two-electrode setup, where two identical catalyst monoliths served as both the anode and cathode (Figure 5d). The assembled device requires a low cell voltage of only 1.72 V to deliver a current density of 50 mA cm−2 (Figure 5e). Moreover, this performance is on par with or even surpasses that of many recently reported transition-metal-based bifunctional electrocatalysts (Figure 5f and Table S3), underscoring the high intrinsic activity and efficiency of the Co@NC/CW system. The long-term operational durability of the overall water splitting device was also evaluated under continuous alkaline electrolysis conditions. Impressively, the system maintains stable output with negligible voltage fluctuation over a 120 h period at a constant current density of 50 mA cm−2 (Figure 5g), highlighting the stability of the catalyst. To validate gas production efficiency, two pieces of Co@NC/CW electrodes were employed as both the hydrogen-evolving cathode and the oxygen-evolving anode. Gas quantification confirms the simultaneous generation of H2 and O2 at a near-ideal volume ratio of approximately 2:1 (Figure 5h), which is consistent with the theoretical stoichiometry of water electrolysis. The calculated Faradaic efficiency reaches ~99.5%, indicating highly efficient charge-to-gas conversion with minimal side reactions. During electrolysis, inverted centrifuge tubes were employed to collect the evolved hydrogen and oxygen gases simultaneously (Figure 5i), further corroborating the system’s practical applicability and gas evolution symmetry.
In addition, the applicability of the Co@NC/CW catalyst for seawater electrolysis—a critical step toward industrial-scale hydrogen production—was systematically investigated. In a simulated seawater electrolyte (1.0 M KOH + 0.5 M NaCl), the catalyst exhibited bifunctional electrocatalytic performance. For the OER, Co@NC/CW delivered a low potential of 1.61 V at a current density of 50 mA cm−2 (Figure 6a), indicating efficient oxygen generation even in chloride-rich environments. Simultaneously, the catalyst achieved an HER potential of 0.32 V at −50 mA cm−2 (Figure 6b), demonstrating hydrogen production capability. The polarization curves exhibit deviations at low overpotentials, likely due to capacitive effects and initial surface interactions in complex chloride-containing electrolytes [53]. The catalyst also showed long-term stability under alkaline saline conditions. In constant-current stability tests, Co@NC/CW maintained consistent performance for over 200 h for the OER and 100 h for the HER (Figure 6c) without significant decay in catalytic activity, underscoring its durability under realistic electrolysis conditions.
Furthermore, full-cell water-splitting experiments conducted directly in natural seawater reinforced the catalyst’s practical potential [42]. The Co@NC/CW-based two-electrode system required a cell voltage of 1.86 V to achieve a current density of 50 mA cm−2 (Figure 6d). Remarkably, the device exhibited excellent voltage retention, with only 5.2% decay after 120 h of continuous electrolysis (Figure 6e), confirming its resistance to corrosion, surface passivation, and chloride-induced side reactions. Collectively, these findings demonstrate that Co@NC/CW not only delivers high catalytic activity for both OERs and HERs in saline environments but also ensures long-term operational stability and structural integrity. This positions it as a highly promising and scalable candidate for practical hydrogen production via direct seawater electrolysis.

3. Materials and Methods

3.1. Materials

All reagents used in this work are of analytical grade, purchased from Shanghai Chemical Reagent Factory (Shanghai, China) and used as received without further purification.

3.2. Synthesis of Co@NC/CW

Fir wood slices (40 × 20 × 5 mm) were first immersed in a 5 wt% aqueous KOH solution at room temperature for 14 h to induce partial alkaline hydrolysis and pore activation. The treated wood samples were then thoroughly rinsed with deionized water to remove residual KOH and dried in an oven at 80 °C overnight. Subsequently, the pretreated wood slices were immersed in 100 mL of an aqueous solution containing 0.546 g of cobalt chloride hexahydrate (CoCl2·6H2O). Each impregnation cycle consisted of soaking for 30 min, followed by drying at 80 °C for another 30 min. This cycle was repeated three times to achieve homogeneous cobalt loading throughout the wood matrix. After the final cycle, the samples were further dried at 80 °C for 6 h without washing. For pyrolysis, the cobalt-loaded wood samples were placed in a ceramic crucible with 1 g of melamine positioned underneath the wood slice. The entire setup was then carbonized at 900 °C for 2 h under an N2 atmosphere with a heating rate of 5 °C min−1 to obtain the final product Co@NC/CW.

3.3. Synthesis of Co/CW and CW

The Co/CW control sample was synthesized following the same procedure as Co@NC/CW, except that no melamine was added during the pyrolysis step. The pure CW control sample was prepared using the same carbonization process as Co@NC/CW, but without cobalt precursor impregnation and without melamine.
Other experimental details, including material characterizations and electrochemical ORR and OER measurements, can be found in the Supplementary Materials.

4. Conclusions

In summary, we have developed a hierarchically porous, monolithic electrocatalyst (Co@NC/CW) by directly carbonizing natural wood and embedding cobalt nanoparticles within in situ-grown nitrogen-doped graphene layers. This unique structure integrates vertically aligned microchannels and conductive carbon frameworks, enabling rapid electrolyte diffusion, efficient gas evolution, and electron transport. Benefiting from its binder-free, self-supporting architecture, Co@NC/CW delivers remarkable bifunctional catalytic activity for both HERs and OERs, achieving low overpotentials (227 mV for HERs and 403 mV for OERs at 50 mA cm−2) and excellent long-term operational stability. The assembled electrolyzer exhibits efficient overall water and seawater splitting with a low cell voltage and near-99.5% Faradaic efficiency over 120 h of continuous operation. This work demonstrates a sustainable and scalable strategy for designing high-performance electrocatalysts using biomass-derived materials, offering a promising avenue for future energy conversion and storage technologies.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal15050503/s1. Refs. [54,55,56,57,58,59,60] are cited in the Supplementary Materials.

Author Contributions

Conceptualization, Z.C. and L.Y.; methodology, Z.C. and J.P.; validation, Z.L., S.H. and S.Z.; formal analysis, J.M.; data curation, Z.C. and X.P.; writing—original draft preparation, L.Y.; writing—review and editing, Z.C., W.L. and L.Y.; visualization, Z.L.; supervision, W.L. and L.Y.; funding acquisition, L.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Natural Science Foundation of China, grant number 52403392; Zhejiang Provincial Natural Science Foundation of China, grant number LQ24B030013, LQN25B030008; Talent Start–up Project of Zhejiang A&F University Scientific Research Development Foundation, grant number 2023LFR051, 2024LFR003.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author(s).

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
OEROxygen evolution reaction
HERHydrogen evolution reaction
SEMScanning electron microscope
TEMTransmission electron microscopy
XRDX-ray diffraction
BETBrunauer–Emmett–Teller
XPSX-ray photoelectron spectroscopy
LSVLinear sweep voltammetry
CdlDouble-layer capacitance
ECSAElectrochemically active surface area
EISElectrochemical impedance spectroscopy
RsSolution resistance
RmtMass transport resistance

References

  1. Chu, S.; Majumdar, A. Opportunities and challenges for a sustainable energy future. Nature 2012, 488, 294–303. [Google Scholar] [CrossRef] [PubMed]
  2. Stamenkovic, V.R.; Strmcnik, D.; Lopes, P.P.; Markovic, N.M. Energy and fuels from electrochemical interfaces. Nat. Mater. 2016, 16, 57–69. [Google Scholar] [CrossRef] [PubMed]
  3. Rao, P.; Yu, Y.; Wang, S.; Zhou, Y.; Wu, X.; Li, K.; Qi, A.; Deng, P.; Cheng, Y.; Li, J.; et al. Understanding the improvement mechanism of plasma etching treatment on oxygen reduction reaction catalysts. Exploration 2024, 4, 20230034. [Google Scholar] [CrossRef]
  4. Ye, P.; Fang, K.; Wang, H.; Wang, Y.; Huang, H.; Mo, C.; Ning, J.; Hu, Y. Lattice oxygen activation and local electric field enhancement by co-doping Fe and F in CoO nanoneedle arrays for industrial electrocatalytic water oxidation. Nat. Commun. 2024, 15, 1012. [Google Scholar] [CrossRef]
  5. Sun, S.; Dang, J.; Pan, Q.; Zhang, C.; Liu, S. pH-responsive flexible copper electrode with switchable wettability for electrocatalytic hydrogen/oxygen evolution reactions and urea oxidation reaction. ACS Appl. Mater. Interfaces 2023, 15, 27357–27368. [Google Scholar] [CrossRef]
  6. Sun, R.; Zhu, M.; Chen, J.; Yan, L.; Bai, L.; Ning, J.; Zhong, Y.; Hu, Y. Tuning the formation kinetics of *OOH intermediate with hollow bowl-like carbon by pulsed electroreduction for enhanced H2O2 Production. ACS Nano 2025, 19, 13414–13426. [Google Scholar] [CrossRef] [PubMed]
  7. Cavaliere, P. Fundamentals of water electrolysis. In Water Electrolysis for Hydrogen Production; Springer International Publishing: Cham, Switzerland, 2023; pp. 1–60. [Google Scholar]
  8. Jia, Y.; Yao, X. Defects in carbon-based materials for electrocatalysis: Synthesis, recognition, and advances. Acc. Chem. Res. 2023, 56, 948–958. [Google Scholar] [CrossRef]
  9. Shi, L.; Zhang, W.; Li, J.; Yan, Q.; Chen, Z.; Zhou, X.; Li, J.; Gao, R.; Wu, Y.; Li, G.D. Recent development of non-iridium-based electrocatalysts for acidic oxygen evolution reaction. Carbon Neutral. 2024, 3, 1101–1130. [Google Scholar] [CrossRef]
  10. Xu, Z.; Chen, J.; Zhang, T.; Lu, H.; Yan, L.; Ning, J.; Hu, Y. Enhancing efficiency and durability of alkaline Zn-Co/air hybrid batteries with self-reconstructed Co/Co2P heterojunctions. Adv. Energy Mater. 2024, 15, 2402839. [Google Scholar] [CrossRef]
  11. Park, M.G.; Hwang, J.; Deng, Y.P.; Lee, D.U.; Fu, J.; Hu, Y.; Jang, M.J.; Choi, S.M.; Feng, R.; Jiang, G.; et al. Longevous cycling of rechargeable Zn-air battery enabled by “raisin-bread” cobalt oxynitride/porous carbon hybrid electrocatalysts. Adv. Mater. 2023, 36, e2311105. [Google Scholar] [CrossRef]
  12. Yan, L.; Xie, B.; Yang, C.; Wang, Y.; Ning, J.; Zhong, Y.; Hu, Y. Engineering self-supported hydrophobic–aerophilic air cathode with CoS/Fe3S4 nanoparticles embedded in S, N co-doped carbon plate arrays for long-life rechargeable Zn–air batteries. Adv. Energy Mater. 2023, 13, 2204245. [Google Scholar] [CrossRef]
  13. Tang, J.; Su, C.; Shao, Z. Advanced membrane-based electrode engineering toward efficient and durable water electrolysis and cost-effective seawater electrolysis in membrane electrolyzers. Exploration 2024, 4, 20220112. [Google Scholar] [CrossRef] [PubMed]
  14. Wang, N.; Ma, S.; Zhang, R.; Wang, L.; Wang, Y.; Yang, L.; Li, J.; Guan, F.; Duan, J.; Hou, B. Regulating N species in N-doped carbon electro-catalysts for high-efficiency synthesis of hydrogen peroxide in simulated seawater. Adv. Sci. 2023, 10, 2302446. [Google Scholar] [CrossRef]
  15. Guo, J.; Zheng, Y.; Hu, Z.; Zheng, C.; Mao, J.; Du, K.; Jaroniec, M.; Qiao, S.Z.; Ling, T. Direct seawater electrolysis by adjusting the local reaction environment of a catalyst. Nat. Energy 2023, 8, 264–272. [Google Scholar] [CrossRef]
  16. Fan, J.G.; Pan, J.M.; Wang, H.; Liu, S.; Zhan, Y.; Yan, X. Research and progress in mitigating carbon oxidation in air electrodes. Adv. Funct. Mater. 2025, 35, 2417580. [Google Scholar] [CrossRef]
  17. Sun, Y.; Wang, L.; Li, H.; Zeng, S.; Li, R.; Yao, Q.; Chen, H.; Qu, K. N, S codoped porous carbon with trace single-atom Fe for enhanced oxygen reduction with robust poison resistance and efficient rechargeable zinc–air battery. Carbon Neutral. 2025, 4, e196. [Google Scholar] [CrossRef]
  18. Huang, C.; Wang, F.; Chen, X.; Li, J.; Shao, M.; Wei, Z. Innovative strategies for designing and constructing efficient fuel cell electrocatalysts. Chem. Commun. 2025, 61, 2658–2683. [Google Scholar] [CrossRef]
  19. Ma, Y.; Chen, D.; Li, W.; Zheng, Y.; Wang, L.; Shao, G.; Liu, Q.; Yang, W. Highly dispersive Co@N-C catalyst as freestanding bifunctional cathode for flexible and rechargeable zinc–air batteries. Energy Environ. Mater. 2022, 5, 543–554. [Google Scholar] [CrossRef]
  20. Wang, S.; Liu, S.; Chen, W.; Hu, Y.; Chen, D.; He, M.; Zhou, M.; Lei, T.; Zhang, Y.; Xiong, J. Designing reliable cathode system for high-performance inorganic solid-state pouch cells. Adv. Sci. 2024, 11, 2401889. [Google Scholar] [CrossRef]
  21. Abu Nayem, S.M.; Hardianto, Y.P.; Shuaibu, A.D.; Shah, S.S.; Islam, S.; Jafar Mazumder, M.A.; Aziz, M.A.; Saleh Ahammad, A.J. Biomass derived amino acid assisted synthesis of FeNi layered double hydroxide for efficient oxygen evolution reaction. Inorg. Chem. Commun. 2025, 171, 113574. [Google Scholar] [CrossRef]
  22. Li, W.; Liu, Y.; Azam, A.; Liu, Y.; Yang, J.; Wang, D.; Sorrell, C.C.; Zhao, C.; Li, S. Unlocking efficiency: Minimizing energy loss in electrocatalysts for water splitting. Adv. Mater. 2024, 36, 2404658. [Google Scholar] [CrossRef] [PubMed]
  23. Zhang, Y.; Zhang, T.; Huang, Z.; Yang, J. A new class of electronic devices based on flexible porous substrates. Adv. Sci. 2022, 9, e2105084. [Google Scholar] [CrossRef]
  24. Li, D.; Li, Z.; Chen, Z.; Shi, G.; Wang, L.; Chen, Z.; Tu, W.; Xia, R.; Iwuoha, E.I.; Liu, C.; et al. Wood-derived, monolithic chainmail electrocatalyst for biomass-assisted hydrogen production. Adv. Energy Mater. 2023, 13, 2300427. [Google Scholar] [CrossRef]
  25. Zhu, Z.; Ma, S.; He, S.; Song, M.; Xia, B.Y.; You, B. Heterogeneous electrocatalysts from nanostructures to single atoms for biomass-derived feedstocks upgrading. Coord. Chem. Rev. 2025, 527, 216399. [Google Scholar] [CrossRef]
  26. Qiu, C.; Zhang, L.; Wang, B.; Yang, G.; Lucia, L.; Li, F.; Chen, J. Wood based quasi-solid-state Zn-air battery with dual honeycomb-like porous carbon and cationic nanocellulose film. Ind. Crop. Prod. 2022, 186, 115242. [Google Scholar] [CrossRef]
  27. Alemu, M.A.; Assegie, A.A.; Ilbas, M.; Al Afif, R.; Getie, M.Z. Biomass-derived metal-free nanostructured carbon electrocatalysts for high-performance rechargeable zinc–air batteries. Adv. Energy Sust. Res. 2025, 6, 2400414. [Google Scholar] [CrossRef]
  28. Zhou, G.; Li, M.C.; Liu, C.; Chen, W.; Yu, G.; Zhang, D.; Li, Z.; Mei, C. A flexible Zn-ion capacitor based on wood derived porous carbon and polyacrylamide/cellulose nanofiber hydrogel. Ind. Crop. Prod. 2023, 193, 116216. [Google Scholar] [CrossRef]
  29. Yu, L.; Shang, Z.; Lin, X.; Li, M.; Liu, Y.; Ren, L.; Deng, S.; Zhang, F.; Luo, L.; Duan, H.; et al. Bio-derived wood-based gas diffusion electrode for high-performance aluminum–air batteries: Insights into pore structure. Adv. Mater. Interfaces 2023, 11, 2300355. [Google Scholar] [CrossRef]
  30. Zhu, H.; Luo, W.; Ciesielski, P.N.; Fang, Z.; Zhu, J.; Henriksson, G.; Himmel, M.E.; Hu, L. Wood-derived materials for green electronics, biological devices, and energy applications. Chem. Rev. 2016, 116, 9305–9374. [Google Scholar] [CrossRef]
  31. Shrivastava, K.; Gill, F.S.; Juyal, S.; Lal, M.; Jain, A. Green carbon for clean energy: Biomass-derived hierarchical structures in energy storage. WIREs Energy Environ. 2025, 14, e70007. [Google Scholar] [CrossRef]
  32. Segmehl, J.S.; Studer, V.; Keplinger, T.; Burgert, I. Characterization of wood derived hierarchical cellulose scaffolds for multifunctional applications. Materials 2018, 11, 517. [Google Scholar] [CrossRef] [PubMed]
  33. Nie, Z.; Liu, Y.; Yang, L.; Wang, X.; Xu, C.; Wang, C. Engineering biomass into advanced carbon-based materials for Zn-air batteries. Sci. China Mater. 2025, 68, 1509–1529. [Google Scholar] [CrossRef]
  34. Yan, L.; Xu, Z.Y.; Hu, W.K.; Ning, J.Q.; Zhong, Y.J.; Hu, Y. Formation of sandwiched leaf-like CNTs-Co/ZnCo2O4@NC-CNTs nanohybrids for high-power-density rechargeable Zn-air batteries. Nano Energy 2021, 82, 105710. [Google Scholar] [CrossRef]
  35. Luo, J.; Zhou, K.; Tu, B.; Shi, Y.; Lu, K.; Qian, X.; Shi, C. Fire-retardant, smoke-suppressive and sustainable diatomite-based auxiliaries for highly fire-resistant epoxy resin. Adv. Powder Technol. 2024, 35, 104639. [Google Scholar] [CrossRef]
  36. Yan, L.; Xu, Z.; Liu, X.; Mahmood, S.; Shen, J.; Ning, J.; Li, S.; Zhong, Y.; Hu, Y. Integrating trifunctional Co@NC-CNTs@NiFe-LDH electrocatalysts with arrays of porous triangle carbon plates for high-power-density rechargeable Zn-air batteries and self-powered water splitting. Chem. Eng. J. 2022, 446, 137049. [Google Scholar] [CrossRef]
  37. Zhang, Y.; Pan, H.; Murugananthan, M.; Sun, P.; Dionysiou, D.D.; Zhang, K.; Khan, A.; Zhang, Y. Glucose and melamine derived nitrogen-doped carbonaceous catalyst for nonradical peroxymonosulfate activation. Carbon 2020, 156, 399–409. [Google Scholar] [CrossRef]
  38. Wang, Y.; Shang, Y.; Cao, Z.; Zeng, K.; Xie, Y.; Li, J.; Yao, Y.; Gan, W. Highly efficient, field-assisted water splitting enabled by a bifunctional Ni3Fe magnetized wood carbon. Chem. Eng. J. 2022, 439, 135722. [Google Scholar] [CrossRef]
  39. Yan, L.; Wang, H.Y.; Shen, J.L.; Ning, J.Q.; Zhong, Y.J.; Hu, Y. Formation of mesoporous Co/CoS/Metal-N-C@S, N-codoped hairy carbon polyhedrons as an efficient trifunctional electrocatalyst for Zn-air batteries and water splitting. Chem. Eng. J. 2021, 403, 126385. [Google Scholar] [CrossRef]
  40. Jing, L.; Tian, Q.; Li, X.; Sun, J.; Wang, W.; Yang, H.; Chai, X.; Hu, Q.; He, C. Dual-engineering of porous structure and carbon edge enables highly selective H2O2 electrosynthesis. Adv. Funct. Mater. 2023, 33, 2305795. [Google Scholar] [CrossRef]
  41. Gan, W.; Wu, L.; Wang, Y.; Gao, H.; Gao, L.; Xiao, S.; Liu, J.; Xie, Y.; Li, T.; Li, J. Carbonized wood decorated with cobalt-nickel binary nanoparticles as a low-cost and efficient electrode for water splitting. Adv. Funct. Mater. 2021, 31, 2010951. [Google Scholar] [CrossRef]
  42. Douka, A.I.; Xu, Y.; Yang, H.; Zaman, S.; Yan, Y.; Liu, H.; Salam, M.A.; Xia, B.Y. A Zeolitic-imidazole frameworks-derived interconnected macroporous carbon matrix for efficient oxygen electrocatalysis in rechargeable zinc-air batteries. Adv. Mater. 2020, 32, e2002170. [Google Scholar] [CrossRef] [PubMed]
  43. Yang, Q.; Jia, Y.; Wei, F.; Zhuang, L.; Yang, D.; Liu, J.; Wang, X.; Lin, S.; Yuan, P.; Yao, X. Understanding the activity of Co-N4-xCx in atomic metal catalysts for oxygen reduction catalysis. Angew. Chem. Int. Ed. 2020, 59, 6122–6127. [Google Scholar] [CrossRef]
  44. Yan, L.; Sun, R.; Mahmood, S.; Bai, L.; Zhong, Y.; Ning, J.; Hu, Y. Facilitating reactant accessibility to heterometallic phosphide with superhydrophilic interfaces for efficient electrochemical production of ammonia and lactic acid. Appl. Catal. B Environ. 2024, 358, 124390. [Google Scholar] [CrossRef]
  45. Yang, J.Y.; Ahn, J.G.; Ko, B.; Park, T.; Hong, S.J.; Han, D.K.; Lee, D.; Li, C.A.; Song, S.H. Green and sustainable bifunctional carbonized wood electrodes decorated with controlled nickel/α(β)-nickel(ii) hydroxide to boost overall water splitting. J. Mater. Chem. A 2023, 11, 26672–26680. [Google Scholar] [CrossRef]
  46. Cui, X.; Liu, Y.; Han, G.; Cao, M.; Han, L.; Zhou, B.; Mehdi, S.; Wu, X.; Li, B.; Jiang, J. Wood-derived integral air electrode for enhanced interfacial electrocatalysis in rechargeable zinc–air battery. Small 2021, 17, 2101607. [Google Scholar] [CrossRef]
  47. Mao, C.; Shi, Z.; Peng, J.; Ou, L.; Chen, Y.; Huang, J. Hierarchically porous carbonized wood decorated with MoNi4-embedded MoO2 nanosheets: An efficient electrocatalyst for water splitting. Adv. Funct. Mater. 2024, 34, 2308337. [Google Scholar] [CrossRef]
  48. Chen, Z.; Chen, H.; Li, T.; Tian, X.; Zhang, K.; Miao, Y.; Xia, C.; Cai, L.; Hui, B.; Chen, C. Defective wood-based chainmail electrocatalysts boost performances of seawater-medium Zn-air batteries. J. Energy Chem. 2025, 102, 134–143. [Google Scholar] [CrossRef]
  49. Zhong, L.; Jiang, C.; Zheng, M.; Peng, X.; Liu, T.; Xi, S.; Chi, X.; Zhang, Q.; Gu, L.; Zhang, S. Wood carbon based single-atom catalyst for rechargeable Zn–air batteries. ACS Energy Lett. 2021, 6, 3624–3633. [Google Scholar] [CrossRef]
  50. Huang, J. Diffusion impedance of electroactive materials, electrolytic solutions and porous electrodes: Warburg impedance and beyond. Electrochim. Acta 2018, 281, 170–188. [Google Scholar] [CrossRef]
  51. Yang, Y.; Chen, D.; Wang, H.; Ye, P.; Ping, Z.; Ning, J.; Zhong, Y.; Hu, Y. Two-step nitrogen and sulfur doping in porous carbon dodecahedra for Zn-ion hybrid supercapacitors with long term stability. Chem. Eng. J. 2022, 431, 133250. [Google Scholar] [CrossRef]
  52. Zhu, Y.; Jiang, Y.; Li, H.; Zhang, D.; Tao, L.; Fu, X.Z.; Liu, M.; Wang, S. Tip-like Fe-N4 sites induced surface microenvironments regulation boosts the oxygen reduction reaction. Angew. Chem. Int. Ed. 2024, 63, e202319370. [Google Scholar] [CrossRef] [PubMed]
  53. Pal, S.; Shimizu, K.; Khatun, S.; Singha, S.; Watanabe, S.; Roy, P. Electrolyte engineering for effective seawater splitting based on manganese iron chromium layered triple hydroxides as novel bifunctional electrocatalysts. J. Mater. Chem. A 2023, 11, 12151–12163. [Google Scholar] [CrossRef]
  54. Lu, S.Y.; Dou, W.; Wu, C.; Zhang, J.; Wang, L.; Hu, T.; Wang, R.; Liu, Y.; Yang, Q.; Jin, M. Strong electronic interaction in chromium-molybdenum dual incorporated few-layer cobalt sulfide nanosheets with lattice distortion for efficient bifunctional water splitting. Fuel 2024, 377, 132780. [Google Scholar] [CrossRef]
  55. Zhang, Z.; Ma, X.; Tang, J. Porous NiMoO4−x/MoO2 hybrids as highly effective electrocatalysts for the water splitting reaction. J. Mater. Chem. A 2018, 6, 12361–12369. [Google Scholar] [CrossRef]
  56. Zhao, X.; Pachfule, P.; Li, S.; Simke, J.R.J.; Schmidt, J.; Thomas, A. Bifunctional electrocatalysts for overall water splitting from an iron/nickel-based bimetallic metal–organic framework/dicyandiamide composite. Angew. Chem. Int. Ed. 2018, 57, 8921–8926. [Google Scholar] [CrossRef]
  57. Nairan, A.; Zou, P.; Liang, C.; Liu, J.; Wu, D.; Liu, P.; Yang, C. NiMo solid solution nanowire array electrodes for highly efficient hydrogen evolution reaction. Adv. Funct. Mater. 2019, 29, 1903747. [Google Scholar] [CrossRef]
  58. Zhang, Y.; Si, J.; Chen, Z.; Zhao, L.; Qiu, F.; Li, W.; Zhang, W.; Miao, S. High crystalline MxSby (M=Fe, Co, and Ni) nanocrystals tuned by antimony for boosting overall water splitting catalysis. Adv. Energy Mater. 2025, 65, 2405275. [Google Scholar] [CrossRef]
  59. Sang, Y.; Li, G.; Xue, J.; Hu, J.; Tong, Y.; Liang, B.; Li, L. Engineering of metal Co/Ni-CoO nanoparticles embedded in N-doped unclosed hollow carbon nanoboxes as a highly efficient bifunctional electrocatalyst for overall water splitting. Surf. Interfaces 2024, 44, 103729. [Google Scholar] [CrossRef]
  60. Yang, R.; Zhou, Y.; Xing, Y.; Li, D.; Jiang, D.; Chen, M.; Shi, W.; Yuan, S. Synergistic coupling of CoFe-LDH arrays with NiFe-LDH nanosheet for highly efficient overall water splitting in alkaline media. Appl. Catal. B Environ. 2019, 253, 131–139. [Google Scholar] [CrossRef]
Catalysts 15 00503 g001
Figure 1. Schematic diagram of the synthesis of the wood-derived, monolithic electrode (Co@NC/CW).
Figure 1. Schematic diagram of the synthesis of the wood-derived, monolithic electrode (Co@NC/CW).
Catalysts 15 00503 g001
Catalysts 15 00503 g002
Figure 2. (a,b) SEM images of Co@NC/CW for (a) vertical view and (b) parallel view. (c) SEM image of Co@NC/CW at higher magnification. (d) TEM image and (e–g) energy-dispersive X-ray (EDX) elemental images of Co@NC/CW. (h) XRD patterns of Co@NC/CW and CW. (i) High-solution Co 2p spectrum and (j) N 1s spectrum of Co@NC/CW. (k) Water contact angles of Co@NC/CW and CW. (l) O2 bubbles adhesion behavior evolution on the surfaces of Co@NC/CW.
Figure 2. (a,b) SEM images of Co@NC/CW for (a) vertical view and (b) parallel view. (c) SEM image of Co@NC/CW at higher magnification. (d) TEM image and (e–g) energy-dispersive X-ray (EDX) elemental images of Co@NC/CW. (h) XRD patterns of Co@NC/CW and CW. (i) High-solution Co 2p spectrum and (j) N 1s spectrum of Co@NC/CW. (k) Water contact angles of Co@NC/CW and CW. (l) O2 bubbles adhesion behavior evolution on the surfaces of Co@NC/CW.
Catalysts 15 00503 g002
Catalysts 15 00503 g003
Figure 3. (a) Polarization curves for OERs on Co@NC/CW, Co/CW, CW, and RuO2 under 1 M KOH. (b) Corresponding overpotentials at different current densities. (c) OER Tafel plots of Co@NC/CW, Co/CW, and CW. (d) Comparison of overpotential at a current density of 50 mA cm−2 with other wood-based catalysts reported in the literature. (e) ECSA values of the Co@NC/CW, Co/CW, and CW electrocatalysts. (f) EIS plot of the Co@NC/CW, Co/CW, and CW electrocatalysts. (g) The relationship between the real part of impedance and low frequencies of the three samples. (h) A 180 h chronoamperometric test for OERs.
Figure 3. (a) Polarization curves for OERs on Co@NC/CW, Co/CW, CW, and RuO2 under 1 M KOH. (b) Corresponding overpotentials at different current densities. (c) OER Tafel plots of Co@NC/CW, Co/CW, and CW. (d) Comparison of overpotential at a current density of 50 mA cm−2 with other wood-based catalysts reported in the literature. (e) ECSA values of the Co@NC/CW, Co/CW, and CW electrocatalysts. (f) EIS plot of the Co@NC/CW, Co/CW, and CW electrocatalysts. (g) The relationship between the real part of impedance and low frequencies of the three samples. (h) A 180 h chronoamperometric test for OERs.
Catalysts 15 00503 g003
Catalysts 15 00503 g004
Figure 4. (a–c) Nyquist plots of electrochemical impedance data obtained at different potentials during the OER for Co@NC/CW, Co/CW, and CW. (d) The equivalent circuits fitting model. (e) Rct plotted as a function of applied potentials for Co@NC/CW, Co/CW, and CW. (f) Rmt plotted as a function of applied potentials for Co@NC/CW, Co/CW, and CW.
Figure 4. (a–c) Nyquist plots of electrochemical impedance data obtained at different potentials during the OER for Co@NC/CW, Co/CW, and CW. (d) The equivalent circuits fitting model. (e) Rct plotted as a function of applied potentials for Co@NC/CW, Co/CW, and CW. (f) Rmt plotted as a function of applied potentials for Co@NC/CW, Co/CW, and CW.
Catalysts 15 00503 g004
Catalysts 15 00503 g005
Figure 5. (a) Polarization curves for HERs on Co@NC/CW, Co/CW, CW, and Pt/C under 1 M KOH. (b) Corresponding overpotentials at different current densities. (c) A 180 h chronoamperometric test for HERs. (d) Schematic illustration of overall water splitting configuration. (e) Two-electrode polarization curves of the Co@NC/CW electrode for water splitting. (f) Comparison of cell voltages at a current density of 50 mA cm−2 with other catalysts reported in the literature. (g) Long-term stability test of Co@NC/CW for overall water splitting. (h) The amounts of gases versus time. (i) Photographs of the gas volume measurement by inverted centrifuge tubes.
Figure 5. (a) Polarization curves for HERs on Co@NC/CW, Co/CW, CW, and Pt/C under 1 M KOH. (b) Corresponding overpotentials at different current densities. (c) A 180 h chronoamperometric test for HERs. (d) Schematic illustration of overall water splitting configuration. (e) Two-electrode polarization curves of the Co@NC/CW electrode for water splitting. (f) Comparison of cell voltages at a current density of 50 mA cm−2 with other catalysts reported in the literature. (g) Long-term stability test of Co@NC/CW for overall water splitting. (h) The amounts of gases versus time. (i) Photographs of the gas volume measurement by inverted centrifuge tubes.
Catalysts 15 00503 g005
Catalysts 15 00503 g006
Figure 6. Polarization curves for the (a) OER and (b) HER on Co@NC/CW under 1 M KOH and 0.5 M NaCl. (c) Long-term stability test of the Co@NC/CW for the OER and HER. (d) Two-electrode polarization curves of overall seawater splitting. (e) Chronopotentiometric curves of seawater electrolysis for 120 h at 50 mA cm−2 in 1 M KOH and 0.5 M NaCl.
Figure 6. Polarization curves for the (a) OER and (b) HER on Co@NC/CW under 1 M KOH and 0.5 M NaCl. (c) Long-term stability test of the Co@NC/CW for the OER and HER. (d) Two-electrode polarization curves of overall seawater splitting. (e) Chronopotentiometric curves of seawater electrolysis for 120 h at 50 mA cm−2 in 1 M KOH and 0.5 M NaCl.
Catalysts 15 00503 g006
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Cheng, Z.; Li, Z.; Huang, S.; Pan, J.; Mei, J.; Zhang, S.; Peng, X.; Lu, W.; Yan, L. Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting. Catalysts 2025, 15, 503. https://doi.org/10.3390/catal15050503

AMA Style

Cheng Z, Li Z, Huang S, Pan J, Mei J, Zhang S, Peng X, Lu W, Yan L. Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting. Catalysts. 2025; 15(5):503. https://doi.org/10.3390/catal15050503

Chicago/Turabian Style

Cheng, Zichen, Zekun Li, Shou Huang, Junfan Pan, Jiaxian Mei, Siqi Zhang, Xingyu Peng, Wen Lu, and Lei Yan. 2025. "Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting" Catalysts 15, no. 5: 503. https://doi.org/10.3390/catal15050503

APA Style

Cheng, Z., Li, Z., Huang, S., Pan, J., Mei, J., Zhang, S., Peng, X., Lu, W., & Yan, L. (2025). Cobalt-Decorated Carbonized Wood as an Efficient Electrocatalyst for Water Splitting. Catalysts, 15(5), 503. https://doi.org/10.3390/catal15050503

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop