Mo2B2 MBene-supported single-atom catalysts as bifunctional HER/OER and OER/ORR electrocatalysts

Abstract

Searching for highly efficient and cost-effective bifunctional electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), which can be applied to water splitting, fuel cells and metal–air batteries, is critical for developing clean and renewable energies. Yet it remains a great challenge. By means of first-principles calculations, we have studied the OER, ORR and HER catalytic activity of Mo₂B₂ MBene-supported single-atom catalysts (SACs) by embedding a series of transition metal atoms in the Mo vacancy (TM@Mo₂B₂, TM = Ti, V, Cr, Mn, Fe, Co, Ni and Cu) as electrocatalysts. All TM@Mo₂B₂ SACs show excellent metallic conductivity, which would be favorable for the charge transfer in electrocatalytic reactions. Importantly, Ni@Mo₂B₂ can be used as a HER/OER bifunctional electrocatalyst with a lower |ΔG_H| (−0.09 eV) for the HER under 1/4H coverage and a lower overpotential (η_OER = 0.52 V) than that of IrO₂ (η_OER = 0.56 V) for the OER, while Cu@Mo₂B₂ can be used as an OER/ORR bifunctional electrocatalyst with a lower overpotential (η_OER = 0.31 V) than that of IrO₂ (η_OER = 0.56 V) and RuO₂ (η_OER = 0.42 V) for the OER and a lower overpotential of 0.34 V than that of Pt (η_ORR = 0.45 V) for the ORR, for both of which the transition metal atoms serve as the active sites. This work could open up an avenue for the development of non-noble-metal-based bifunctional MBene electrocatalysts.