General Synthesis of Tube-like Nanostructured Perovskite Oxides with Tunable Transition Metal-Oxygen Covalency for Efficient Water Electrooxidation in Neutral Media.

Hydrogen production from water electrolysis in neutral-pH electrolytes can not only avoid the corrosion and safety issues and expand the catalyst option but also potentially integrate with artificial photosynthesis and bioelectrocatalysis. However, heterogeneous catalysts that can efficiently negotiate the sluggish oxygen evolution reaction (OER) in neutral solutions are considerably lacking. Herein, we report a template-assisted strategy for the synthesis of 13 kinds of tube-like nanostructured perovskite oxides (TNPOs) with markedly high Brunauer-Emmett-Teller surface areas. By systematic examination of these TNPOs, we found that the OER activity of TNPOs in neutral solution exhibits a volcano shape as a function of the covalency of transition metal-oxygen bonds. Consequently, our designed Sm-doped LaCoO catalyst yields a geometric current density of 8.5 mA cm at 1.75 V versus the reversible hydrogen electrode in 1 M phosphate buffer solution (pH 7) due to the optimized covalency of Co 3d and O 2p states, representing the most active noble-metal-free OER catalyst in neutral electrolytes reported as yet.