Ru-O-Cu center constructed by catalytic growth of Ru for efficient hydrogen evolution

Abstract

Ru has been demonstrated as one of the most potential catalysts for hydrogen evolution reaction because of its high activity and low price. The efficient Ru-based catalysts are normally achieved through controlled alloying, structure design, phase exploration, and carbon support modulation strategies. Herein, a stepped annealing approach is employed for Ru active site building. Under the auxiliary reduction of Cu2O intermediate, Ru nanocrystals are in-situ formed on CuO surface during the first stage of low-temperature annealing, generating strong interaction at the interface. In the second annealing stage at a higher temperature, the majority of Ru nanocrystals are removed by forming soluble K2RuO3, leaving rich Ru-O-Cu centers and oxygen vacancies exposed. The resulted sample (Ru-CuO-SA) presents an overpotential= 12.9 mV to reach 10 mA cm−2 current density, Tafel slope= 27.9 mV decade−1 and turnover frequency= 3.034 H2 s−1, exceeding most reported Ru-based materials and commercial Pt/C catalyst. Combined experiments and simulations disclose the creation of Ru-O-Cu bond reinforces surface oxophilicity to promote water adsorption and dissociation (Volmer step), and simultaneously provides a moderate hydrogen binding to accelerate the hydrogen desorption procedure (Tafel step). As such, the stepped annealed Ru-CuO-SA catalyst exhibits booted hydrogen production efficiency from alkaline electrolyte, neutral freshwater, and lake water.