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The kinetics of hydrogen evolution and hydrogen oxidation reactions (HER/HOR) in alkaline electrolyte on Pt/C and a Pt/C/Ni(OH)2 bi-functional electrocatalyst were studied. The objective was to investigate the enhancement of hydrogen evolution activity of Pt in alkaline environments in presence of transition metal hydroxides, and to determine the optimum concentration of Ni(OH)2 to be added to maximize catalytic activity. The catalysts were prepared by mixing colloidal dispersions of nanosized Ni(OH)2 with a commercially-sourced Pt/C catalyst dispersed in water. Rotating disk electrode (RDE) measurements were performed in 0.1 M KOH at temperatures ranging from 273.15 K to 303.15 K, and the HOR/HER kinetic currents, obtained after IR and mass transport corrections, were fitted using the Butler-Volmer equation to estimate the exchange current densities at each temperature. Arrhenius plots showed very similar activation energies for Pt/C (35 ± 6 kJ/mol) and the bi-functional catalysts (38 ± 6 kJ/mol) –Pt/C/X%Ni(OH)2. The maximum exchange current density (2.44 ± 0.07 mA cm−2Pt at 303.15 K) was obtained with the catalyst containing 10 wt% Ni(OH)2, and was 2.4 times higher than for Pt/C (1.03 ± 0.07 mA cm−2Pt at 303.15 K). The bi-functional catalysts were evaluated in a hydroxide-exchange membrane water electrolyzer operated with ultrapure water, and outperformed Pt/C by about 0.15 V across the entire current density range.
Wang et al. (Sun,) studied this question.
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