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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Hydrogen is seen as a future energy carrier that will assist the global energy fuel demand. However, it is still necessary to study efficient and inexpensive catalysts that can be used on a large scale to make this technology practical. In this paper the electrodeposition of molybdenum disulfide (MoS 2) film on titanium (Ti) substrate was performed by cyclic voltammetry and the film was evaluated for hydrogen evolution reaction (HER). The deposition optimized conditions was 25 cycles and 4 mmol L-1 (NH 4) 2 [MoS 4 ] in 0.1 mol L-1 NaClO 4 solution. The film was characterized from X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and they showed an amorphous structure and high catalytic activity for HER. The Tafel slope was 85 mV dec-1 and overpotential at −10 mA cm-2 was −139 mV showing that Ti substrate compared with fluorine-tin doped oxide (FTO) substrate favored the HER and electroactivity of MoS 2 films.

Sb 2 Se 3 is considered a promising photocathode material for hydrogen production via solar water splitting. Nevertheless, losses caused by photocorrosion and slow charge transfer at the semiconductor/electrolyte interface require the presence of a cocatalyst to improve the kinetic factors. In this work, the activity of all-electrochemically grown Sb 2 Se 3 /amorphous-MoS x photocathodes was studied in function of the number of cocatalyst deposition cycles. MoS x , a noble-metal-free electrocatalyst, has shown high activity toward the hydrogen evolution reaction. It promoted an ∼70-time higher improvement in the photocurrent of the Sb 2 Se 3 -absorber. An antagonistic effect was observed as the number of cycles increased: thin MoS x layers promoted the maximum enhancement in photocurrent and the decrease in surface recombination, but the photocorrosion inhibition was compromised. In the counterpart, thick MoS x layers allowed the material to be less susceptible to photocorrosion, but the photocurrent was inhibited. Therefore, the relationship between cocatalyst thickness and photocurrent enhancement/inhibition, variation in surface recombination, and photocorrosion stability was evaluated.