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

Spinel Co₃O₄ has emerged as a promising electrocatalyst towards alkaline water oxidation, but its activity is restricted by the undesirable electronic configuration of the octahedral Co³⁺ site. Herein, we simultaneously manipulate Cr doping and p-n junction engineering on Co₃O₄ nanorods, which contributes to the formation of Co²⁺ and Ni³⁺ octahedral sites with optimal e(g) fillings, thus achieving a superior OER performance.