In situ growth of CaMoO4 on electropolymerized PANI as a hybrid electrocatalyst for enhanced oxygen evolution

Electrochemical water splitting stands as a promising avenue for sustainable hydrogen production, with the oxygen evolution reaction (OER) playing a pivotal role. Efficient and durable electrocatalysts are crucial for expediting the sluggish kinetics of OER. In this work, we investigate the synthesis and performance of a novel CaMoO4/polyaniline (CaMoO4/PANI) composite catalyst for OER. In situ growth of CaMoO4 has been done after the electropolymerization of polyaniline on nickel foam (NF), offering advantages such as improved structural integrity, increased surface area, and enhanced electroconductivity. Electrochemical characterization reveals that CaMoO4/PANI exhibits superior catalytic activity, with an overpotential of 233 mV at 10 mA cm-2, outperforming pristine CaMoO4, PANI, and certain current similar non-noble-metal electrocatalysts. Electrochemical studies reveal that the exceptional activity can be attributed to reduced charge transfer resistance, underscoring the catalyst's enhanced efficiency. Furthermore, multistep chronopotentiometry confirms excellent robustness of the catalyst electrode as well as its excellent mass transportation. This work highlights the potential of inorganic oxide/conductive polymer composites as efficient catalysts for OER, offering insights for future developments in sustainable energy technologies.

Metal-Oxides- and Metal-Oxyhydroxides-Based Nanocomposites for Water Splitting: An Overview

Water electrolysis is an important alternative technology for large-scale hydrogen production to facilitate the development of green energy technology. As such, many efforts have been devoted over the past three decades to producing novel electrocatalysis with strong electrochemical (EC) performance using inexpensive electrocatalysts. Transition metal oxyhydroxide (OxH)-based electrocatalysts have received substantial interest, and prominent results have been achieved for the hydrogen evolution reaction (HER) under alkaline conditions. Herein, the extensive research focusing on the discussion of OxH-based electrocatalysts is comprehensively highlighted. The general forms of the water-splitting mechanism are described to provide a profound understanding of the mechanism, and their scaling relation activities for OxH electrode materials are given. This paper summarizes the current developments on the EC performance of transition metal OxHs, rare metal OxHs, polymers, and MXene-supported OxH-based electrocatalysts. Additionally, an outline of the suggested HER, OER, and water-splitting processes on transition metal OxH-based electrocatalysts, their primary applications, existing problems, and their EC performance prospects are discussed. Furthermore, this review article discusses the production of energy sources from the proton and electron transfer processes. The highlighted electrocatalysts have received substantial interest to boost the synergetic electrochemical effects to improve the economy of the use of hydrogen, which is one of best ways to fulfill the global energy requirements and address environmental crises. This article also provides useful information regarding the development of OxH electrodes with a hierarchical nanostructure for the water-splitting reaction. Finally, the challenges with the reaction and perspectives for the future development of OxH are elaborated.

Tunable d-band center of a NiFeMo alloy with enlarged lattice strain enhancing the intrinsic catalytic activity for overall water-splitting

Developing efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) under alkaline conditions is prospective for reducing energy consumption during water electrolysis. In this work, we successfully synthesized nanocluster structure composites composed of NiFeMo alloys with controllable lattice strain by the electrodeposition method at room temperature. The unique structure of NiFeMo/SSM (stainless steel mesh) facilitates the exposure of abundant active sites and promotes mass transfer and gas exportation. The NiFeMo/SSM electrode exhibits a low overpotential of 86 mV at 10 mA cm^-2 for the HER and 318 mV at 50 mA cm^-2 for the OER, and the assembled device reveals a low voltage of 1.764 V at 50 mA cm^-2. Moreover, both the experimental results and theoretical calculations reveal that the dual doping of Mo and Fe can induce the tunable lattice strain of nickel, which in turn changes the d-band center and electronic interaction of the catalytically active site, and finally enhances the HER and OER catalytic activity. This work may provide more options for the design and preparation of bifunctional catalysts based on non-noble metals.