Designing Ru-doped Zn ₃ V ₃ O ₈ bifunctional OER and HER catalysts through a unified computational and experimental approach

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.