Search Results (166)

Electrocatalytic urea oxidation reaction (UOR) is a promising dual-purpose approach for hydrogen production and wastewater treatment, addressing critical energy and environmental challenges. However, conventional anode materials often suffer from limited active sites and high charge transfer resistance, restricting UOR efficiency. To overcome these issues, a novel NiP@PNC/NF electrocatalyst was developed via a one-step thermal annealing process under nitrogen, integrating nickel phosphide (NiP) with phosphorus and nitrogen co-doped carbon nanotubes (PNCs) on a nickel foam (NF) substrate. This design enhances catalytic activity and charge transfer, achieving current densities of 50 mA cm⁻² at 1.34 V and 100 mA cm⁻² at 1.43 V versus the reversible hydrogen electrode (RHE). The electrode’s high electrochemical surface area (235 cm²) and double-layer capacitance (94.1 mF) reflect abundant active sites, far surpassing NiP/NF (48 cm², 15.8 mF) and PNC/NF (39.5 cm², 12.9 mF). It maintains exceptional stability, with only a 16.3% performance loss after 35 h, as confirmed by HR-TEM showing an intact nanostructure. Our single-step annealing technique provides simplicity, scalability, and efficient integration of NiP nanoparticles inside a PNC matrix on nickel foam. This method enables consistent distribution and robust substrate adhesion, which are difficult to attain with multi-step or more intricate techniques. Full article

The simultaneous generation of hydrogen fuel and wastewater remediation via electrocatalytic urea oxidation has emerged as a promising approach for sustainable energy and environmental solutions. However, the practical application of this process is hindered by the limited active sites and high charge-transfer resistance of conventional anode materials. In this work, we introduce a novel CoP@P, N-CNTs/NF electrocatalyst, fabricated through a facile one-step thermal annealing technique. Comprehensive characterizations confirm the successful integration of CoP nanoparticles and phosphorus/nitrogen co-doped carbon nanotubes (P, N-CNTs) onto nickel foam, yielding a unique hierarchical structure that offers abundant active sites and accelerated electron transport. As a result, the CoP@P, N-CNTs/NF electrode achieves outstanding urea oxidation reaction (UOR) performance, delivering current densities of 158.5 mA cm⁻² at 1.5 V and 232.95 mA cm⁻² at 1.6 V versus RHE, along with exceptional operational stability exceeding 50 h with negligible performance loss. This innovative, multi-element-doped electrode design marks a significant advancement in the field, enabling highly efficient UOR and energy-efficient hydrogen production. Our approach paves the way for scalable, cost-effective solutions that couple renewable energy generation with effective wastewater treatment. Full article

Overuse of tert-butylhydroquinone (TBHQ) as a food antioxidant has the potential to pollute the environment and threaten human health. Therefore, it is imperative to develop precise and rapid methods to detect TBHQ in food products. In this study, Fe- and Mn-doped Prussian blue analogs (FeMn-PBAs) were prepared by co-precipitation, FeMn-PBAs/PAN was prepared by electrostatic spinning, and a novel FeMn@C/CNFs composite was prepared by carbonization in nitrogen. Bimetallic FeMn doping has been shown to reduce vacancy defects and enhance the structural stability of PBA. Furthermore, electrostatic spinning has been demonstrated to reduce the agglomeration of PBA nanoparticles, which are electrode-modifying materials with high stability and good electrical conductivity. The morphological and structural characteristics of the FeMn@C/CNF composites were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical behavior of tert-butyl hydroquinone in FeMn@C/CNFs was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronocoulometry (CC). The results demonstrate that the sensor exhibits excellent repeatability, reproducibility, and anti-interference capabilities. The prepared electrochemical sensor can be effectively utilized for the detection of TBHQ in food samples such as soybean and peanut oil samples, proving its strong potential for practical applications. Full article

The electrocatalytic reduction of nitrate is an efficient and green method for NH₃ production. In this study, a Co-containing MOF with a stable three-dimensional carbon framework that offers abundant metal active sites is prepared as a precursor to a Co-N-C electrocatalyst. Facile pyrolysis of the three-dimensional MOF affords the desired Co-N-C electrocatalyst, which exhibits excellent stability, an NH₃ yield of 1.12 mmol h⁻¹ mg⁻¹, and faradaic efficiency of 86.7% at −0.23 V in a 0.1 M KOH/0.1 M KNO₃. The excellent activity and durability are ascribed to the highly exposed active centres, large surface area, and high porosity structure. N doping allows the electronic properties to be modulated and provides outstanding stability owing to the strong interaction between the nitrogen-doped carbon support and Co nanoparticles. This study presents a simple and efficient synthesis strategy for the production of non-noble-metal electrocatalysts with abundant active sites for the nitrate reduction reaction. Full article

In the “dual carbon” objective, the preparation of non-precious metal catalysts with low cost and high activity is essential for the study of hydrogen evolution reactions (HERs). This study employed biomass pomelo peel powder as the carbon source and ammonium metatungstate (AMT) as the tungsten source and, through a facile one-step method in molten salt, fabricated a biomass carbon-based nanocatalyst featuring carbon flakes adorned with tungsten carbide (WC) nanoparticles. Dicyandiamide and cysteine were introduced as nitrogen and sulfur sources, respectively, to explore the impacts of N-S elemental doping on the structure, composition, and HER performance of the WC/C catalyst. The experimental results showed that N-S doping changed the electronic structure of WC and increased the electrochemically active surface area, resulting in a significant increase in the HER activity of WC/C@N-S catalysts. The WC/C@N-S catalyst was evaluated with hydrogen evolution performance in a 0.5 mol/L H₂SO₄ solution. When the cathodic current density reached 10 mA/cm², the overpotential was 158 mV, and the Tafel slope was 68 mV/dec, underscoring its excellent HER performance. The outcomes offer novel insights into the high-value utilization of agricultural biomass resources, and pave the way for the development of cost-effective, innovative hydrogen evolution catalysts. Full article

This report introduces a high-performance bimetallic electrocatalyst for the oxygen reduction reaction (ORR) featuring a 20 wt.% platinum content. The PtCu-based catalyst combines de-alloyed nanoparticles (NPs) supported on nitrogen-doped carbon. Enhanced uniformity in NP distribution significantly boosts the catalyst performance. Nitrogen-doped carbon provides active centers for NP deposition, which is confirmed by HAADF-STEM and EDX. The PtCu/CN catalyst achieves over 5.6 times the ORR mass activity and two times the stability under pulse cycling compared to commercial Pt/C. Uniquely, the study examines bimetallic NPs and local nano-sites before and after stress testing using IL-TEM. In situ analysis of PtCu/CN microstructure revealed two primary degradation mechanisms, (i) partial dissolution of NPs and (ii) NP agglomeration, with the C–N support significantly mitigating these effects through strong NP–support interactions. The findings underscore the prospects of bimetallic PtCu catalysts with nitrogen-doped support by showcasing exceptional ORR activity and durability. Full article

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. Full article

Catalytic hydrogenolysis of lignin to produce high-value monophenols has emerged as a pivotal strategy in modern biorefineries. In this study, we synthesized spherical nitrogen-doped porous carbon (SNCB) materials by using Al/Co-BTC as a precursor, introducing melamine as a supplementary carbon and nitrogen source, and activating the material with NaOH solution. The SNCB framework was decorated with Cu-Pd bimetallic nanoparticles, exhibiting outstanding catalytic activity in the hydrogenolytic depolymerization of organosolv lignin. The Cu-Pd@SNCB catalyst exhibited remarkable activity, attributed to the hierarchical porous structure of SNCB that facilitated metal nanoparticle dispersion and reactant accessibility. The synergistic effect between Cu as the reactive site for reactant adsorption and Pd as the reactive site for H₂ adsorption enhanced the catalytic activity of the catalyst. Systematically optimized conditions (2 MPa H₂, 270 °C, 3 h) yielded 43.02 wt% phenolic monomers, with 4-(3-hydroxypropyl)-2,6-dimethoxyphenol dominating the product profile at 46.3% selectivity. The catalyst and its reaction products were analyzed using advanced characterization techniques, including XPS, XRD, TEM, SEM, BET, GC-MS, GPC, 2D HSQC NMR, and FT-IR, to elucidate the reaction mechanism. The mechanism proceeds through: (1) nucleophilic substitution of the β-O-4 hydroxyl group by MeOH, followed by (2) simultaneous hydrogenolytic cleavage of C_β-O and C_α-O bonds mediated by Cu-Pd@SNCB under H₂ atmosphere, which selectively produces 4-(3-hydroxypropyl)-2,6-dimethoxyphenol and 4-propyl-2,6-dimethoxyphenol. This study proposes a bimetallic synergistic mechanism, offering a general blueprint for developing selective lignin valorization catalysts. Full article

Fluorescent carbon dots are nontoxic nanoparticles composed of carbon, exhibiting advantageous properties for applications in bioimaging and functional materials. We present a methodology for synthesizing fluorescent nitrogen-doped carbon dots (N-CDs) using starch, a biopolymer, and urea as the sources of nitrogen, via the microwave-assisted hydrothermal method. Furthermore, the dependence of the fluorescence spectra and fluorescence quantum yield of N-CDs on the initial concentration of urea in the reactant solution was examined, thereby providing a comprehensive understanding of the influence of nitrogen doping on the CDs. The fluorescence of N-CDs was tunable by varying the excitation wavelength. Stronger fluorescence intensity was observed for a moist phosphate salt/N-CD composite, in contrast to the weaker fluorescence exhibited by a dried one. Fluorescence lifetime measurements revealed that the change in fluorescence intensity can be attributed to the suppression of the non-radiative deactivation process. This observation highlights the critical importance of the interaction between water molecules and surface functional groups in controlling the photophysics of the excited state of N-CDs. Full article

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was also synthesized. Extensive characterization, including SEM, Raman spectroscopy, XPS, and XRD revealed the catalysts’ microstructure and properties. Electrochemical testing demonstrated that the AWC-Ni-N catalyst significantly enhanced the efficiency of the hydrazine oxidation reaction. In addition, direct N₂H₄-H₂O₂ single-fuel-cell tests were conducted using the prepared AWC-N and AWC-Ni-N catalysts as the anodes and cathodes. Peak power densities of up to 10.8 mW cm⁻² were achieved at 25 °C, corresponding to a current density of 27 mA cm⁻² and a cell voltage of 0.4 V when the AWC-Ni-N catalyst was used as both the anode and cathode. Furthermore, the peak power density increased by approximately 1.6 and 2.9 times, respectively, when the operating temperature was raised from 25 °C to 55 °C for the AWC-N and AWC-Ni-N catalysts. Overall, the AWC-N and AWC-Ni-N catalysts demonstrated significant potential as anode and cathode materials in direct N₂H₄-H₂O₂ fuel cells. Full article

In this study, a novel, highly efficient, environment friendly, and low-cost nanocatalyst, denoted as Ni(x)@Co−N−C, was successfully developed by encapsulating Ni nanoparticles into N-doped porous carbon derived from ZIF-67. A variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption/desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrometer (XPS) were used to characterize the prepared materials. The TEM images reveal that the nanoparticles were distributed homogeneously in the carbon support. The N atoms in the carbon support serve as the sites for the nucleation and uniform growth of Ni nanoparticles. The catalyst was used for the degradation of environmentally harmful 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among all the catalysts investigated, Ni(10)@Co-N-C exhibited the highest catalytic activity for the hydrogenation of 4-NP, with a specific reaction rate of 6.1 × 10⁻³ s⁻¹, activity parameter of 31 s⁻¹g⁻¹, and turn over frequency (TOF) of 1.78 × 10¹⁹ molecules g_metal⁻¹s⁻¹. On the other hand, the specific reaction rate and TOF value were 1.7 × 10⁻³ s⁻¹ and 6.96 × 10¹⁸ molecules g_metal⁻¹s⁻¹, respectively, for Co−N−C. This suggests that Ni(10)@Co−N−C is about three times more catalytically active than the Co−N−C catalyst. The superb activity of Ni(10)@Co−N−C in comparison to Co−N−C can be ascribed to the homogeneous dispersion of small-sized Ni nanoparticles, the interconnected three-dimensional porous arrangement of the support Co−N−C, the presence of N atoms in the carbon framework that stabilize metal nanoparticles, and the synergistic electronic effect between Ni and Co. The Ni(10)@Co−N−C catalyst maintained consistent catalytic activity over multiple cycles, which suggests that porous N-containing carbon support can effectively prevent aggregation and leaching of metal nanoparticles. The ICP-AES analysis of the recycled Ni(10)@Co−N−C revealed a slight reduction in metal content compared to the fresh sample, suggesting almost negligible leaching of metal nanoparticles. Full article

Developing efficient bifunctional oxygen reduction (ORR) and oxygen evolution (OER) electrocatalysts is critical for renewable energy technologies. Noble metal catalysts face limitations in cost, scarcity, and bifunctional compatibility. Herein, we report the synthesis of nickel nanoparticles encapsulated in nitrogen-doped carbon nanosheets (Ni@NC-T) via a solvothermal polymerization and pyrolysis process using a Ni-hexamine coordination framework (NiHMT) as a precursor. The Ni@NC-900 catalyst exhibits superior ORR and OER activity under alkaline conditions, with an ORR performance (half-wave potential = 0.86 V) comparable to commercial Pt/C and an OER overpotential of only 430 mV at 10 mA cm⁻². Structural analysis indicates that the hierarchical porous structure and high specific surface area (409 m² g⁻¹) of Ni@NC-900 facilitate the exposure of active sites and enhance mass transport. The surface-doped nitrogen species, predominantly in the form of pyridinic N and graphitic N, promote electron transfer during the ORR. Furthermore, its application as a bifunctional cathode in rechargeable zinc-air batteries results in a high power density of 137 mW cm⁻², surpassing the performance levels of many existing carbon-based bifunctional catalysts. This work highlights a facile strategy for the fabrication of transition metal-based catalysts encapsulated in MOF-derived carbon matrices, with promising potential for energy storage and conversion devices. Full article

Sn-doped TiO₂–carbon composites were identified as promising multifunctional supports for Pt electrocatalysts, in which the oxide component enhances resistance against corrosion and strong metal–support interactions at the Pt-oxide boundary ensure high stability for the Pt nanoparticles. This work is devoted to the study of the influence of preliminary functionalization of the carbon on the properties of Pt/Ti_0.9Sn_0.1O₂–C catalysts. The structural, compositional and morphological differences between the samples prepared using functionalized or unmodified carbon, as well as the effect of carbon pre-modification on the electrocatalytic behavior of the synthesized Pt catalysts, were investigated using TEM, XRD, XPS, nitrogen adsorption and electrochemical measurements. The presence of oxygen-containing functional groups on carbon treated with HNO₃ and glucose leads to the formation of a homogeneous coating of the carbon with dispersed crystallites of mixed oxide. Elemental mapping revealed the proximity of Sn species with highly dispersed (2–3 nm) Pt particles. Notably, the electrochemical results indicated enhanced activity in CO electrooxidation for both functionalized and unmodified carbon-containing catalysts. An improvement in the 10,000-cycle long-term stability of the catalyst prepared using functionalized carbon was evident compared to the catalyst with untreated carbon or reference Pt/C. Full article

Nitrogen-doped graphene-coated Fe nanoparticles (EC@N₆Fe_0.6-700) were synthesized through the pyrolysis of a durian peel-supported urea ferric salt mixture. These materials were subsequently utilized to activate peroxymonosulfate (PMS) for oxidation of terramycin (TEC). The incorporation of an optimal amount of urea and ferric nitrate during the synthesis of materials significantly improves the catalytic activity of the resulting catalysts after pyrolysis. Using EC@N₆Fe_0.6-700 catalyst at a concentration of 0.10 g L⁻¹, 98.55% oxidation of 20 mg L⁻¹ TEC is achieved within 60 min. Additionally, EC@N₆Fe_0.6-700 exhibits exceptionally low metal leaching, with levels remaining below 0.25 mg L⁻¹. The EC@N₆Fe_0.6-700 shows remarkable stability during oxidation and effectively resists interference, reusability, and robust stability throughout the oxidation process. The mechanism of the EC@N₆Fe_0.6-700/PMS/TEC system is determined, and the ¹O₂ is the main reactive oxygen species (ROSs). The XPS analysis confirms that the primary active sites are Fe⁰, as well as nitrogen-doped regions within the carbon matrix. This research demonstrates that by integrating iron and nitrogen with durian peel, it is possible to develop a PMS activator with satisfactory oxidation performance for the degradation of environmental pollutants. Full article

Ionic porous polymers have been widely utilized efficiently to anchor various metal atoms for the preparation of metal-embedded heteroatom-doped porous carbon composites as the active materials for electrocatalytic applications. However, the rational design of the heteroatom and metal elements in HPC-based composites remains a significant challenge, due to the tendency of the aggregation of metal nanoparticles during pyrolysis. In this study, a nitrogen (N)- and sulfur (S)-enriched ionic covalent organic framework (iCOF) incorporating viologen and thieno[3,4-b] thiophene (TbT) was constructed via Zincke-type polycondensation. The synthesized iCOF possesses a crystalline porous structure with a pore size of 3.05 nm, a low optical band gap of 1.88 eV, and superior ionic conductivity of 10^−2.672 S cm⁻¹ at 333 K, confirming the ionic and conjugated nature of our novel iCOF. By applying the iCOF as the precursor, a ruthenium and ruthenium(IV) oxide (Ru/RuO₂) nanoparticle-embedded N/S-co-doped porous carbon composite (NSPC-Ru) was prepared by using a two-step sequence of anion-exchange and pyrolysis processes. In the electrochemical nitrogen reduction reaction (eNRR) application, the NSPC-Ru achieves an impressive NH₃ yield rate of 32.0 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 13.2% at −0.34 V vs. RHE. Thus, this innovative approach proposes a new route for the design of iCOF-derived metal-embedded porous carbon composites for enhanced NRR performance. Full article