Search Results (112)

Electrochemical water splitting represents a sustainable approach for hydrogen production, yet efficient hydrogen evolution reaction (HER) catalysts operating in alkaline environments remain critically needed. Herein, we report the fabrication of Co₃O₄–NiS₂ nanocomposites synthesized through a facile coprecipitation and subsequent thermal treatment method. Detailed characterization via physicochemical techniques confirmed the successful formation of a hybrid Co₃O₄–NiS₂ heterostructure with tunable compositional and morphological characteristics. Among the synthesized catalysts (Co–Ni–1, Co–Ni–2, and Co–Ni–3), the Co–Ni–2 sample demonstrated optimal structural integration, displaying interconnected nanosheet morphologies and balanced elemental distribution. Remarkably, Co–Ni–2 achieved exceptional HER performance in 1 M KOH electrolyte, requiring an ultralow overpotential of only 84 mV at 10 mA cm⁻² and exhibiting a favorable Tafel slope of 67.5 mV dec⁻¹. Electrochemical impedance spectroscopy and electrochemical surface area measurements further substantiated the superior electrocatalytic kinetics, rapid charge transport, and abundant active site accessibility in the optimized Co–Ni–2 composite. Additionally, Co–Ni–2 demonstrated outstanding durability with negligible activity decay over 5000 cycles. This study not only highlights the strategic synthesis of Co₃O₄–NiS₂ nanostructures but also provides valuable insights for designing advanced, stable, and efficient non-noble electrocatalysts for sustainable hydrogen generation. Full article

This review article compiled previous reports in the fabrication of hydroquinone (HQ) electrochemical sensors using differently modified electrodes. The electrode materials, which are also called electrocatalysts, play a crucial role in electrochemical detection of biomolecules and toxic substances. Metal oxides, MXenes, carbon-based materials such as reduced graphene oxide (rGO), carbon nanotubes (CNTs), layered double hydroxides (LDH), metal sulfides, and hybrid composites were extensively utilized in the fabrication of HQ sensors. The electrochemical performance, including limit of detection, linearity, sensitivity, selectivity, stability, reproducibility, repeatability, and recovery for real-time sensing of the HQ sensors have been discussed. The limitations, challenges, and future directions are also discussed in the conclusion section. It is believed that the present review article may benefit researchers who are involved in the development of HQ sensors and catalyst preparation for electrochemical sensing of other toxic substances. Full article

The electrocatalytic decomposition of ammonia represents a promising route for sustainable hydrogen production, yet current systems rely heavily on noble metal catalysts with prohibitive costs and limited durability. A critical challenge lies in developing non-noble electrocatalysts that simultaneously achieve high active site exposure, optimized electronic configurations, and robust structural stability. Addressing these requirements, this study strategically engineered Cu-doped ZIF-8 architectures via in situ growth on nickel foam (NF) substrates through a facile room-temperature hydrothermal synthesis approach. Systematic optimization of the Cu/Zn molar ratio revealed that Cu_0.7Zn_0.3-ZIF/NF achieved optimal performance, exhibiting a distinctive nanoflower-like architecture that substantially increased accessible active sites. The hybrid catalyst demonstrated superior electrocatalytic performance with a current density of 124 mA cm⁻² at 1.6 V vs. RHE and a notably low Tafel slope of 30.94 mV dec⁻¹, outperforming both Zn-ZIF/NF (39.45 mV dec⁻¹) and Cu-ZIF/NF (31.39 mV dec⁻¹). Combined XPS and EDS analyses unveiled a synergistic electronic structure modulation between Zn and Cu, which facilitated charge transfer and enhanced catalytic efficiency. A gas chromatography product analysis identified H₂ and N₂ as the primary gaseous products, confirming the predominant occurrence of the ammonia oxidation reaction (AOR). This study not only presents a noble metal-free electrocatalyst with exceptional efficiency and durability for ammonia decomposition but also demonstrates the significant potential of MOF-derived materials in sustainable hydrogen production technologies. Full article

The rapid growth in population and industrialization have significantly increased global energy demand, placing immense pressure on finite and environmentally harmful conventional fossil fuel-based energy sources. In this context, the development of hybrid electrocatalysts presents a crucial solution for energy conversion and storage, addressing environmental challenges while meeting rising energy needs. In this study, the fabrication of a novel bifunctional catalyst, copper nickel aluminum spinel (Cu_0.5Ni_0.5Al₂O₄) supported on graphitic carbon nitride (GCN), using a solid-state synthesis process is reported. Because of its effective interface design and spinel cubic structure, the Cu_0.5Ni_0.5Al₂O₄/GCN nanocomposite, as synthesized, performs exceptionally well in electrochemical energy conversion, such as the oxygen evolution reaction (OER), the hydrogen evolution reaction (HER), and energy storage. In particular, compared to noble metals, Pt/C- and IrO₂-based water-splitting cells require higher voltages (1.70 V), while for the Cu_0.5Ni_0.5Al₂O₄/GCN nanocomposite, a voltage of 1.49 V is sufficient to generate a current density of 10 mA cm⁻² in an alkaline solution. When used as supercapacitor electrode materials, Cu_0.5Ni_0.5Al₂O₄/GCN nanocomposites show a specific capacitance of 1290 F g⁻¹ at a current density of 1 A g⁻¹ and maintain a specific capacitance of 609 F g⁻¹ even at a higher current density of 5 A g⁻¹, suggesting exceptional rate performance and charge storage capacity. The electrode’s exceptional capacitive properties were further confirmed through the determination of the roughness factor (Rf), which represents surface heterogeneity and active area enhancement, with a value of 345.5. These distinctive characteristics render the Cu_0.5Ni_0.5Al₂O₄/GCN composite a compelling alternative to fossil fuels in the ongoing quest for a viable replacement. Undoubtedly, the creation of the Cu_0.5Ni_0.5Al₂O₄/GCN composite represents a significant breakthrough in addressing the energy crisis and environmental concerns. Owing to its unique composition and electrocatalytic characteristics, it is considered a feasible choice in the pursuit of ecologically sustainable alternatives to fossil fuels. Full article

Zinc–air batteries (ZABs) are crucial for renewable energy conversion and storage due to their cost-effectiveness, excellent safety, and superior cycling stability. However, developing efficient and affordable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the air cathode remains a significant challenge. Manganese (Mn)-based materials, known for their tunable oxidation states, adaptable crystal structures, and environmental friendliness, are regarded as the most promising candidates. This review systematically summarizes recent advances in Mn-based bifunctional catalysts, concentrating on four primary categories: Mn–N–C electrocatalysts, manganese oxides, manganates, and other Mn-based compounds. By examining the intrinsic merits and limitations of each category, we provide a comprehensive discussion of optimization strategies, which include morphological modulation, structural engineering, carbon hybridization, heterointerface construction, heteroatom doping, and defect engineering, aimed at enhancing catalytic performance. Additionally, we critically address existing challenges and propose future research directions for Mn-based materials in rechargeable ZABs, offering theoretical insights and design principles to advance the development of next-generation energy storage systems. Full article

A “thermal-annealing vacancy-filling” synthesis strategy was developed to engineer cobalt single-atom catalysts (Co-MoS₂/RGO) for exceptional hydrogen evolution reaction (HER) performance. By anchoring atomic Co onto Frenkel defect-engineered MoS₂ nanosheets supported by reduced graphene oxide (RGO), we achieved simultaneous optimization of catalytic stability, electrical conductivity, and active site accessibility. The optimized Co₃-MoS₂/RGO hybrid demonstrates remarkable alkaline HER activity, requiring only 94.0 mV overpotential to achieve 10 mA cm⁻² current density while maintaining excellent durability over extended operation. The atomically dispersed Co promoted HER kinetics through electronic structure modulation of MoS₂ basal planes, creation of catalytic active centers, and defect-mediated synergies. The RGO further contributed to performance enhancement by preventing nanosheet aggregation, facilitating charge transfer, and exposing active sites. This defect engineering strategy provides a facile method for developing cost-effective, stable, and high-performance electrocatalysts for sustainable hydrogen production. 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

This paper presents the kinetic study of titanium carbide (TiC)-supported, platinum-doped tetrahedral amorphous carbon (taC:Pt) referred to as TiC-taC, for the hydrogen evolution reaction (HER). This study employs the Volmer–Heyrovsky–Tafel (VHT) mechanism. A theoretical approach was utilized to investigate the kinetic properties of these materials for an HER in 0.5 M H₂SO₄. TiC-taC exhibited Volmer-dominated reactions with a Tafel slope of 40 mV/dec and the overpotential at 10 mA/cm² was 185 mV. In contrast, isolated TiC and taC:Pt recorded significantly higher Tafel slopes with 60–110 mV/dec and overpotentials of 871 mV and 1009 mV, respectively. The developed model was tested in one dimension (1D) for individual TiC and taC:Pt. The simulated kinetics parameters were determined for both TiC and taC:Pt, revealing that TiC follows the VHT steps, while taC:Pt follows the VH steps. The simulation results show excellent coherence with the experimental results. Further simulation of the hybrid TiC-taC electrocatalyst was conducted considering surface diffusion and edge effects in two (2D) and three dimensions (3D). To the best of our knowledge, this FEM simulation approach is the first to be reported due to the unique geometry of the TiC-taC catalyst enabling the assumption of surface diffusion and edge effect. The introduction of edge effects on the taC:Pt side of the TiC support significantly enhanced the current output, aligning closely with experimental results. The edge exhibited distinct kinetic properties compared to both TiC and taC:Pt. The kinetic parameters determined from the simulation demonstrated strong agreement with experimental findings. Adding the edge effects was essential to explaining the higher current output from the TiC-taC electrode. It exhibited unique kinetic properties not observed in either TiC or taC:Pt alone, acting as a pump where it absorbs c_Hs from neighbouring sites due to surface diffusivity and releases H2 via the Heyrovsky reaction. While surface diffusion had a lesser effect, the simulation indicated its positive influence on the HER. Full article

Composite catalysts combining a metal–organic framework (MOF) with its derivatives have attracted significant attention in electrocatalysis due to their unique properties. In this study, we report the synthesis of a Ni-doped Co-1,4-benzenedicarboxylate (defined as Co₃Ni₁BDC) metal–organic framework via a straightforward solvothermal method, aiming to enhance oxygen evolution reaction (OER) activity. The introduction of Ni modulated the electronic structure, yielding high catalytic activity with an overpotential (η₁₀₀) of 300 mV and excellent stability for the OER. The Co₃Ni₁BDC material was further encapsulated with Co₂P nanoparticles via a controlled phosphating annealing process, forming a hybrid electrocatalyst (Co₃Ni₁BDC@Co₂P) to boost hydrogen evolution reaction (HER) performance. The Co₃Ni₁BDC@ Co₂P catalysts exhibited superior HER performance with low overpotentials of η₁₀ = 20 mV and η₁₀₀ = 127 mV, outperforming the Co₃Ni₁BDC precursor. An alkaline electrolyzer assembled with Co₃Ni₁BDC//Co₃Ni₁BDC@Co₂P achieved a cell voltage of 1.70 V at a current density of 20 mA cm⁻². This work provides a valuable idea for designing efficient electrocatalysts for overall water splitting. Full article

Developing cost-effective and high-performance non-precious metal-based electrocatalysts for hydrogen evolution reaction is of crucial importance toward sustainable hydrogen energy systems. Herein, we prepare a novel hybrid electrode featuring intermetallic Fe₂Mo nanoparticles anchored on the hierarchical nanoporous copper skeleton as robust hydrogen evolution electrocatalyst by simple and scalable alloying and dealloying methods. By virtue of the highly active intermetallic Fe₂Mo nanoparticles and unique bicontinuous nanoporous copper skeleton facilitating ion/molecule transportation, nanoporous Fe₂Mo/Cu electrode shows excellent hydrogen evolution reaction electrocatalysis, with a low Tafel slope (~71 mV dec⁻¹) to realize ampere-level current density of 1 A cm⁻² at a low overpotential of ~200 mV in 1 M KOH electrolyte. Furthermore, nanoporous Fe₂Mo/Cu electrode exhibits long−term stability exceeding 400 h to maintain ~250 mA cm⁻² at an overpotential of 150 mV. Such outstanding electrocatalytic performance enables the nanoporous Fe₂Mo/Cu electrode to be an attractive hydrogen evolution reaction catalyst for water splitting in the hydrogen economy. Full article

The electrocatalysts of heteroatom-doped non-precious metal oxide materials are of great significance for efficient and low-cost electrochemical water-splitting systems. Herein, an innovative Fe-doped Co₃O₄ nanoflake (Fe-Co₃O₄/NF) on nickel foam has been developed, which exhibits excellent electrocatalytic activity for both hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Benefiting from the synergy of the charge redistribution and d-band center shift caused by doping engineering, the as-obtained Fe-Co₃O₄/NF shows both excellent HER (η₁₀ = 196 mV) and OER (η₁₀ = 290 mV) activities with low Tafel slopes (109 mV dec⁻¹ for HER and 49 mV dec⁻¹ for OER, respectively) and excellent stability. This work provides an effective method for designing and synthesizing bifunctional electrocatalysts with high activity and stability of metal oxide hybrids for the HER/OER. Full article

Carbon-based electrocatalysts decorated with Pt and Ni nanoparticles were introduced herein to increase the efficiency of the water splitting process and thus reduce the price of the produced green hydrogen. The materials were prepared by innovative direct carbonization of ionic liquids containing the corresponding metal, thereby eliminating the need for additional solutions and templates. The structural integrity of the materials was validated through X-ray diffraction analysis and Fourier-transform infrared spectroscopy. The electrochemical performance of these materials in catalyzing hydrogen (HER) and oxygen (OER) evolution reactions was evaluated using voltammetry and electrochemical impedance spectroscopy, uncovering distinct behaviors and highlighting the role of ionic liquid in tailoring materials’ properties and performance. Specifically, the presence of Ni was observed to enhance the catalytic performance towards the HERs due to the interaction of Ni nanoparticles and a higher amount of sp²-hybridized carbon present. In contrast, incorporating Pt into the carbon matrix was found to augment the catalytic activity for OERs with a Tafel slope of 129 mV dec⁻¹ and a current density of 10 mA cm⁻² reached at a potential of 1.67 V. Moreover, chronoamperometric measurements evidenced materials’ steady performance under both HER and OER conditions. These findings of good activity and stability showed that the introduced approach of synthesis of carbon electrocatalysts decorated with heteroatoms by direct carbonization of ionic liquids holds great promise for the synthesis of efficient and affordable electrocatalysts for green hydrogen production. Full article

The increasing energy demand for and fast depletion of fossil fuels have driven the need to explore renewable and clean energy sources. Hydrogen production via water electrocatalysis is considered a promising green fuel technology for addressing global energy and environmental challenges while supporting sustainable development. Molybdenum disulfide (MoS₂) has emerged as a potential electrocatalyst for hydrogen evolution reactions (HERs) and super-capacitor (SC) applications due to its high electrochemical activity, low cost, and abundance. However, compared to noble metals like platinum (Pt), MoS₂ exhibit lower HER activity in water electrocatalysis. Therefore, further modification is needed to enhance its catalytic performance. To address this, MoS₂ has been effectively modified with materials such as reduced graphene oxide (rGO), carbon nanotubes (CNTs), polymers, metal oxides, and MXenes. These modifications significantly improve the electrochemical properties of MoS₂, enhancing its performance in HER and SC applications. In this review article, we have compiled recent reports on the fabrication of MoS₂-based hybrid materials for HER and SC applications. The challenges, advantages, and future perspectives of MoS₂-based materials for HERs and SCs have been discussed. It is believed that readers may benefit from the recent updates on the fabrication of MoS₂-based hybrid materials for HER and SC applications. Full article

The pursuit of efficient and economical catalysts for water splitting, a critical step in hydrogen production, has gained momentum with the increasing demand for sustainable energy. Among the various electrocatalysts developed to date, cobalt oxide (Co₃O₄) has emerged as a promising candidate owing to its availability, stability, and catalytic activity. However, intrinsic limitations, including low catalytic activity and poor electrical conductivity, often hinder its effectiveness in electrocatalytic water splitting. To overcome these challenges, substantial efforts have focused on enhancing the electrocatalytic performance of Co₃O₄ by synthesizing composites with conductive materials, transition metals, carbon-based nanomaterials, and metal–organic frameworks. This review explores the recent advancements in Co₃O₄-based composites for the oxygen evolution reaction and the hydrogen evolution reaction, emphasizing strategies such as nanostructuring, doping, hybridization, and surface modification to improve catalytic performance. Additionally, it examines the mechanisms driving the enhanced activity and stability of these composites while also discussing the future potential of Co₃O₄-based electrocatalysts for large-scale water-splitting applications. Full article

Electrochemical biosensors have emerged as predominant devices for sensitive, rapid, and specific sensing of biomolecules, with significant applications in clinical diagnostics, environmental observation, and food processing. The improvement of inventive materials, especially carbon-based materials, and metal/metal oxide nanoparticles (M/MONPs), has changed the impact of biosensing, improving the performance and flexibility of electrochemical biosensors. Carbon-based materials, such as graphene, carbon nanotubes, and carbon nanofibers, have excellent electrical conductivity, a high surface area, large pore size, and good biocompatibility, making them ideal electrocatalysts for biosensor applications. Furthermore, M and MONPs have highly effective synergistic, electronic, and optical properties that influence signal transduction, selectivity, and sensitivity. This study completely explored continuous progressions and upgrades in carbonaceous materials (CBN materials) and M/MONPs for electrochemical biosensor applications. It analyzed the synergistic effects of hybrid nanocomposites that combine carbon materials with metal nanoparticles (MNPs) and their part in upgrading sensor performance. The paper likewise incorporated the surface alteration procedures and integration of these materials into biosensor models. The study examined difficulties, requirements, and possibilities for executing these innovative materials in practical contexts. This overview aimed to provide specialists with insights into the most recent patterns in the materials study of electrochemical biosensors and advance further progressions in this dynamic sector. Full article