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Electrodeposited NiCoCr ternary alloy is explored as a cost‐effective and Earth‐abundant alternative electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions. Different metal salt concentrations (between 10 and 100 mM) and cathodic current densities (between 75 and 225 mA cm−2) are tested to prepare an optimized material exhibiting both the best electrocatalytic efficiency and robustness for water splitting. Combining electrochemistry with complementary physicochemical characterizations (scanning electron microscopy, energy‐dispersive X‐ray spectroscopy analysis, and X‐ray photoelectron spectroscopy) has enabled to gain a deep knowledge of the composition, morphology, and catalytic activity before and after long‐term electrolytic tests. Compared with the related NiCo and NiCr binary alloys, NiCoCr shows catalytic performance for HER similar to NiCr and higher than that of NiCo. In contrast, its catalytic activity for OER is quite comparable to that of NiCo and higher than that of NiCr. Importantly, the presence of Cr is found to be beneficial to increase the oxidation resistance of the ternary alloy. This work provides a scalable way to produce bifunctional and robust electrode materials. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate how the classical concept of band gap engineering usually used in III–V semiconductor devices can be extended to the engineering of the band lineup between semiconducting photoelectrodes and electrolytes. The performances of photoelectrodes made of GaP1−xAsx epilayers in the full compositional range and grown on low-cost Si substrates were studied and compared with those of photoelectrodes grown on GaAs and GaP substrates. We first show that the changes of incident photon to current conversion efficiency (IPCE) with the As content in GaP1−xAsx alloys are related to the band gap nature (direct or indirect) and band gap energy variations. Then, from flat band potential measurements during Mott–Schottky experiments, valence and conduction band energies of GaP1−xAsx alloys are positioned versus the reversible hydrogen potential. A weak change of conduction band energies and a large evolution of valence band energies are obtained, in good agreement with expected theoretical trends. Such results show that both band gaps and semiconductor/electrolyte band lineups can be engineered through alloying of III–V semiconductors deposited on silicon substrates. This band lineup engineering strategy is expected to be of great interest to address specific redox reactions in the electrolyte, provided that suitable protecting or passivating layers can be used to limit surface/interface recombinations. [ABSTRACT FROM AUTHOR]