In this work, the effect of copper addition on NiMo coating is evaluated in regard to the hydrogen evolution reaction (HER). NiMo and NiMo–NiCu composites are prepared by a simple coelectrodeposition process. The effect of Cu on deposit characters were tested by varying it in the range of 0.06–0.20 molar ratio. Copper addition promotes the growth of a new crystalline phase: NiCu. Also, the copper addition changed the composite surface. NiMo–NiCu0.12 shows a surface roughness 30 times higher than the NiMo material. NiMo–NiCu materials present higher activity toward HER, larger electroactive area, and higher stability in continuous water electrolysis than NiMo catalysts, as demonstrated by Tafel curves, electrochemical impedance spectroscopy measurements, and polarization tests. The combination of the large electroactive area due to the copper addition, the synergism between Ni–Mo, and the presence of Ni and Mo oxides on the surface results in catalyst with excellent features for HER application.

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Lanthanum‐based perovskites have been gaining attention in recent years as cost‐attractive and efficient catalysts for the oxygen evolution reaction (OER). Showing a simplified LaBO3 stoichiometry (B=transition metal cation), the structure and composition of the perovskites play key roles in their electrocatalytic performance. This paper aims to review the physicochemical concepts, structures, and recent advances on kinetic parameters for lanthanum‐based perovskites for catalytic OER. First, advances on mechanisms and descriptors that govern general perovskites will be discussed in detail. Next, the current results for lanthanum cobaltite (LaCoO3), nickelate (LaNiO3), ferrite (LaFeO3), manganite (LaMnO3), and their derivations will be provided. Moreover, the existing results on less explored lanthanum perovskites for catalytic OER (LaCrO3, LaCuO3, LaVO3, and LaTiO3) will be also presented. The impacts of structural defects, orbital occupancy, materials morphology, and composition on the perovskite electrocatalytic performance will be assessed for each case. Finally, emerging trends for lanthanum‐based perovskites will be provided.

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Amorphous molybdenum sulfide (MoSx) is a promising material for hydrogen evolution reaction (HER) due to its nearly zero hydrogen adsorption free energy at the sulfur (S) edge-sites. To prepare more efficient MoSx-based electrocatalysts, new attempts are required to increase the exposure of the MoSx lateral size and, therefore, increase the S atom's contents. The majority of studies reported in the literature investigate MoSx over conductive substrates. However, MoSx can be electrodeposited over inexpensive and chemically stable platforms, such as semiconductors. This work presents the semiconductor substrate morphology effect for prepared sulfur-rich MoSx for electrochemical hydrogen evolution reaction. The electrodes are prepared by cyclic voltammetry with 25 cycles over TiO2 film and TiO2 nanotubes (TiO2NT) substrates. The MoSx deposit on TiO2NT presents an increase S atoms contents and exhibits excellent HER activity with a low overpotential of -93±7.5 mV to reach -10 mA cm-2 and a higher exchange current density equal to 91 µA cm-2, and a smaller Tafel slope of 43 mV dec-1.

Solar radiation is a renewable and clean energy source used in photoelectrochemical cells (PEC) to produce hydrogen gas as a powerful alternative to carbon-based fuels. Semiconductors play a vital role in this approach, absorbing the incident solar photons and converting them into electrons and holes. The hydrogen evolution reaction (HER) occurs in the interface of the p-type semiconductor that works as a photocathode in the PEC. Cu-chalcopyrites such as Cu(In, Ga)(Se,S) 2 (CIGS) and CuIn(Se,S) 2 (CIS) present excellent semiconductor characteristics for this purpose, but drawbacks as charge recombination, deficient chemical stability, and slow charge transfer kinetics, demanding improvements like the use of n-type buffer layer, a protective layer, and a cocatalyst material. Concerning the last one, platinum (Pt) is the most efficient and stable material, but the high price due to its scarcity imposes the search for inexpensive and abundant alternative cocatalyst. The present Minireview highlighted the use of metal alloys, transition metal chalcogenides, and inorganic carbon-based nanostructures as efficient alternative cocatalysts for HER in PEC.