Fe2O3/P-doped CoMoO4 electrocatalyst delivers efficient overall water splitting in alkaline media

Phosphorization of molybdates has been shown to promote hydrogen evolution reaction (HER) activity but is usually detrimental to oxygen evolution reaction (OER) activity, frustrating efforts to create bifunctional HER/OER electrocatalysts. Herein, we show that Fe2O3-modulated P-doped CoMoO4 on nickel foam (Fe-P-CMO) is an excellent bifunctional HER/OER electrocatalyst in alkaline media, with the adverse effect of phosphorization on the OER activity of CoMoO4 being countered via Fe2O3 introduction. An alkaline splitting electrolyser assembled directly using the self-supporting Fe-P-CMO electrode possessed outstanding long-term durability with ultralow cell voltages of 1.48 and 1.59 V required to achieve current densities of 10 and 100 mA cm−2, respectively. Detailed experimental investigations showed that during HER, P-doped CoMoO4 in Fe-P-CMO underwent surface reconstruction with the in-situ formation of Co(OH)2 on the P-CoMoO4 (Co(OH)2/P-CoMoO4). During OER, P-doped CoMoO4 was deeply reconstructed to CoOOH with the complete dissolution of Mo, leading to the in-situ formation of Fe2O3/CoOOH heterojunctions. [Display omitted] •A heterostructured Fe2O3/P-CoMoO4 catalyst on Ni foam (Fe-P-CMO) was prepared.•Fe-P-CMO is a state-of-the-art bifunctional catalyst for overall water splitting.•Only 1.59 V is needed for Fe-P-CMO to drive 100 mA cm−2 for overall water splitting.•The reconstruction processes of Fe-P-CMO during HER and OER were revealed.