Novel monoclinic ABO4 oxide with single-crystal structure as next generation electrocatalyst for oxygen evolution reaction

Designing highly active and stable electrocatalysts to efficiently catalyze oxygen evolution reaction (OER) plays a crucial role in hydrogen production from water splitting. Here, we develop a novel monoclinic ABO4-type metal oxide as versatile candidate for high performance OER catalysis. It has a flexible multi-metal composition and tunable structure which can rationally optimize the OER catalytic activities of ABO4-type oxide. Remarkably, the obtained single-crystal Fe0.4Co0.6W0.4Mo0.6O4 shows an excellent OER catalytic activity with an overpotential of 276.4 mV at 10 mA cm−2, as well as an ultra-low Tafel slope of 30.9 mV decade−1, which outperforms that of the state-of-the-art RuO2 electrocatalyst. Mechanism analysis by density functional theory calculations confirms that the octahedral A sites with low valence state can serve as the active sites in ABO4-type oxide for OER. In addition, faster charge transfer occurs in the low spin state of Co2+ sites (LS: t2g6eg1), in which the formation of O* from OH* as the rate-determining step in OER can be accelerated for favorable OER. More importantly, the new monoclinic ABO4-type material presented in this work is significantly different from the known spinel and perovskite oxides and may pioneer a new wave of research as efficient electrocatalysts and energy materials.