The modulated oxygen evolution reaction performance in La2/3Sr1/3CoO3 by a design of stoichiometry offset

The OER performance of La0.67Sr0.33CoO3-σ compared to the La0.67Sr0.33CoO3 gets a great enhancement via the Co3+/Co4+ ratio tune via stoichiometry break. [Display omitted] •The electronic state of Co in La2/3Sr1/3CoO3 to the OER performance was examined.•The Co valance state of La2/3Sr1/3CoO3 was well controlled by growth oxygen pressure.•The Co4+ ion of La2/3Sr1/3CoO3 was confirmed as the active sites. The accurate stoichiometry control of single-crystalline transition metal oxide thin film and the electrochemical performance such as in oxygen evolution reaction (OER) offer a useful pathway towards the mechanism understanding and the strategy of improving electrochemical activity at the atomic level. As a stable, low cost, and high active OER catalyst, La2/3Sr1/3CoO3 (LSCO) has drawn substantial attention recently. Here we report a modulated OER performance of LSCO by different stoichiometry offsets, an overall ∼2074.63% tunability can be seen. Meanwhile, the overpotential of LSCO exhibits a volcano trend as a function of oxygen concentration. These phenomena can be understood on the competition of double- and super-exchanges in Co3+/Co4+ with the help of the overlap of O 2p and Co 3d orbits. Our investigation provides an effective platform for obtaining a narrow window of improved electrochemical activity in correlated transition metal oxides.