Designing Ru-doped Zn3V3O8 bifunctional OER and HER catalysts through a unified computational and experimental approach.

Abstract

Developing stable and cost-effective catalysts is the key to the next-generation renewable energy conversion technology. Here we unify computational and experimental approaches to use the Zn3V3O8 (001) surface supporting noble metal Ru as a bifunctional catalyst for the OER and HER in alkaline media. In particular, different reaction sites have been studied at four surface terminations along the [001] orientation: the A-layer with V atoms at octahedral sites, the C-layer with V and Zn atoms at octahedral sites, and with additional Zn atoms at tetrahedral sites (B-layer and D-layer, respectively). The first-principles density functional theory (DFT) results indicate that the B-layer termination with V and tetrahedrally coordinated Zn on the top showed the best OER catalytic effect, while the HER favored the D-layer termination with extra Zn atoms at the octahedral sites on the top layer. Our DFT results also suggest that Ru doping by substituting V and Zn atoms at the octahedral site could dramatically enhance the catalytic activities for the OER and HER, respectively. In particular, compared to undoped Zn3V3O8, Ru doping could reduce the calculated OER overpotential from 0.58 V to 0.30 V, which has been confirmed by our experimental results that the OER overpotential decreased from 480 mV to 260 mV at a current density of 10 mA cm-o. Moreover, the experimental results show that Ru doping could reduce the HER overpotential from 152 mV to 70 mV at a current density of 10 mA cm-r. The new insights into the underlying catalytic mechanisms may be further extended to many similar electrocatalytic processes.