LAUSR

Abstract Large-scale electrochemical water splitting for hydrogen generation requires cost-effective and efficient catalysts to boost the sluggish kinetics associated with the oxygen evolution reaction (OER). The transition metal oxides hold promise as catalysts for the replacement of noble-metal catalysts with high activity for OER. One of the challenges is how to finely design and tune the micro-structure of the kind of catalysts with enhanced electrochemical activities. Herein, we report on the tuned synthesis of ultrathin nanosheets made of amorphous cobalt manganese oxide (A-CoMnO) with an average thickness of ca. 0.69 nm, and the unique superiority and potential in the OER has also been demonstrated. The results indicate that it is the Co ion-intercalation effects that help to tailor the structure of the amorphous ultrathin A-CoMnO nanosheets at the atomic- and nano-scale, resulting in an enhanced activity for OER due to the active sites that are highly exposed and easily accessible to electrolyte ions. Benefiting from these combined characteristics, the A-CoMnO nanosheets catalyst exhibits highly catalytic activity and stability in water oxidation, outperforming the corresponding noble-metal and high-crystalline catalysts under similar conditions, which is capable of delivering a current density of ca. 498 mA cm -2 at overpotential of 500 mV with a catalyst loading of 0.2 mg cm -2 .