Spin state engineering of spinel oxides by integration of Cr doping and a p-n junction for water oxidation.

Spinel Co 3 O 4 has emerged as a promising electrocatalyst towards alkaline water oxidation, but its activity is restricted by the undesirable electronic configuration of the octahedral Co 3+ site. Herein, we simultaneously manipulate Cr doping and p-n junction engineering on Co 3 O 4 nanorods, which contributes to the formation of Co 2+ and Ni 3+ octahedral sites with optimal e g fillings, thus achieving a superior OER performance.