Gaddam Rajeshkhanna

Ni- and Fe-based dual MOF-derived trifunctional core–shell Ni ₂ P@Fe ₂ P/NF is developed enabling the fabrication of a methanol-assisted hybrid electrolyzer for low-cost H ₂ generation at cathode and subsequent methanol-to-formate valorization at anode.

Due to the exhaustion of fossil fuels and rising concerns about environmental pollution, direct methanol fuel cells (DMFCs) have emerged as one of the prominent green energy solutions in recent decades. However, the commercialization of DMFCs faces a significant challenge due to the dependence on expensive noble-metal-based electrode materials and the issue of methanol crossover. Therefore, there has been growing interest in developing cost-effective, high-performance anode catalysts to enhance the methanol oxidation reaction (MOR). In this work, unexplored non-noble transition metal oxide materials, such as metal-organic framework (MOF)-derived ZnO, ZnCo₂O₄, and Zn₂CoO₄, were directly synthesized on Ni foam using a simple solvothermal method, followed by calcination. The MOR activity of all the materials was tested in a 0.5 M methanol solution under alkaline conditions. Due to the synergetic effect of combined metallic composition, mixed metal oxides exhibited superior performance. The order of MOR activity was measured to be ZnO < Zn₂CoO₄ < ZnCo₂O₄. Particularly, ZnCo₂O₄ exhibited the highest mass activity (42.64 mA mg^-1) and geometric current density (166.28 mA cm^-2), outperforming Zn₂CoO₄ (27.44 mA mg^-1) and ZnO (12.72 mA mg^-1). It also demonstrated the lowest onset potential of 1.32 V (vs RHE) compared to Zn₂CoO₄ (1.35 V) and ZnO (1.39 V) and maintained excellent long-term stability for 12 h at 1.5 V (vs RHE). Additionally, to determine the optimal methanol concentration, all electrocatalysts were tested across a range of methanol concentrations from 0.1 to 1 M, showing 0.5 M methanol as the most suitable concentration. This study aims to develop cost-effective MOF-derived electrode materials and optimize methanol concentration to maximize catalytic activity. Furthermore, it establishes a foundation for the development of various MOF-derived electrocatalysts and the advancement of DMFC technology.

Efficient overall water electrolysis of fabricated symmetrical alkaline electrolyzers for H ₂ production using Cu, Co and Mo-based bifunctional electrocatalysts as anodes and cathodes.

Finding inexpensive and efficient anode materials is crucial for the oxidation of methanol in the direct methanol fuel cell (DMFC), which is the key electrode reaction. Herein, we report metal-organic framework (MOF)-derived Co₃O₄, NiO, and Ni_xCo_3-xO₄ (where x = 1.5, 1, and 0.6) materials deposited on nickel foam as efficient anode material for methanol oxidation. Among them, NiCo₂O₄ exhibited the highest methanol oxidation activity, owing to its lowest charge-transfer resistance (0.097 Ω) and high electrochemically active surface area (1950 cm²), resulting in the lowest onset potential of 0.35 V vs Hg/HgO. The optimized Ni-to-Co ratio and synergistic effect between Ni and Co metals enable NiCo₂O₄ to achieve the highest mass activity of 151 mA mg^-1 and geometric current density of 288 mA cm^-2, demonstrating excellent durability over 14 h at 0.6 V. In addition, to optimize methanol concentration, all the electrocatalysts were tested in a range of methanol concentrations, showing 0.5 M methanol as the optimal concentration. This study focuses on optimizing the metal ratio and methanol concentration to achieve the highest catalytic activity. Additionally, this lays the foundation for developing diverse MOF-derived electrocatalysts and advancing DMFCs.

The exceptional bifunctional catalytic activity of Co@Fe-based core@shell materials, when Co₂P@Fe₂P/NF was used as both the anode and cathode, achieving outstanding performance in alkaline water splitting, excelling in both the OER and the HER.

This study introduces two efficient electrode materials, NF@ZIF-67@NiCo₂S₄ and NF@Co–N–C@NiCo₂S₄, for H₂ production, achieving excellent OER, HER and overall water splitting activities with remarkable durability in an alkaline electrolyzer.

Three alkaline electrolyzers with Co ₃ O ₄ @NF and Co ₃ S ₄ @NF were fabricated for sustainable green H ₂ production. The electrode materials demonstrated excellent performance in the OER, HER, and overall water splitting, coupled with robust durability.

MXenes, a novel family of 2D transition metal carbide, nitride and carbonitride materials, have been gaining tremendous interest in recent days as potential electrocatalysts for various electrochemical reactions, including hydrogen evolution reaction (HER). MXenes are characterized by their etchable metal layers, excellent structural stability, versatility for heteroatoms doping, excellent electronic conductivity, unique surface functional groups and admirable surface area, suitable for the role of electrocatalyst/support in electrochemical reactions, such as HER. In this review article, we summarized recent developments in MXene-based electrocatalysts synthesis and HER performance in terms of the theoretical and experimental point of view. We systematically evaluated the superiority of the MXene-based catalysts over traditional Pt/C catalysts in terms of HER kinetics, Tafel slope, overpotential and stability, both in acidic and alkaline electrolytic environments. We also pointed out the motives behind the electro catalytic enhancements, the effect of synthesis conditions, heteroatom doping, the effect of surface terminations on the electrocatalytic active sites of various MXenes families. At the end, various possible approaches were recommended for a deeper understanding of the active sites and catalytic improvement of MXenes catalysts for HER.