A general strategy for Ni0–NiOOH hybrid catalyst of high hydrogen evolution activity

Abstract

Ni-based hybrid catalysts consisting of different components in variant valence state have the synergistic effect on boosting hydrogen evolution reaction (HER) activity. A general strategy is developed to achieve a Ni0–NiOOH HER hybrid catalyst, which needs to produce metal Ni0 and Ni(OH)2 concurrently. The strategy is demonstrated by two approaches, both of which include two electrochemical steps. To regular the content of the components in the hybrid catalyst, l-histidine and nitrate ions are introduced to the electrolyte in order to controlling the generation rate of Ni0 and Ni(OH)2. In terms of the two-step electrochemical technology, the pre-catalyst Ni0–Ni(OH)2 is electrochemically deposited firstly, and then electrochemical oxidized to Ni0–NiOOH, wherein Ni0 and NiOOH in different valence act as *H and *OH absorption sites, respectively. The XRD, TEM and XPS results demonstrate the coexistence of Ni0 and Ni(OH)2 in the pre-catalyst and the conversion of Ni(OH)2 to NiOOH in the final catalyst. Electrochemical tests show that the Ni0–NiOOH hybrid catalysts exhibit excellent HER activity. The overpotentials at 10 and 50 mA cm−2 are 39 mV and 88 mV, respectively, and the catalyst keeps a durable stability at 50 mA cm−2 for over 100 h. The present results suggest that the structure-performance correlations of the Ni0–NiOOH hybrid catalyst could be manipulated implementing this general deposition strategy.