Engineering of Coordination Environment and Multiscale Structure in Single-Site Copper Catalyst for Superior Electrocatalytic Oxygen Reduction

Herein, we report efficient single copper atom catalysts that consist of dense atomic Cu sites dispersed on a three-dimensional carbon matrix with highly enhanced mesoporous structures and improved active site accessibility (Cu-SA/NC(meso)). The ratio of +1 to +2 oxidation state of the Cu sites in the Cu-SA/NC(meso) catalysts can be controlled by varying the urea content in the adsorption precursor, and the activity for ORR increases with the addition of Cu¹⁺ sites. The optimal Cu¹⁺-SA/NC(meso)-7 catalyst with highly accessible Cu¹⁺ sites exhibits superior ORR activity in alkaline media with a half-wave potential (E_1/2) of 0.898 V vs RHE, significantly exceeding the commercial Pt/C, along with high durability and enhanced methanol tolerance. Control experiments and theoretical calculations demonstrate that the superior ORR catalytic performance of Cu¹⁺-SA/NC(meso)-7 catalyst is attributed to the atomically dispersed Cu¹⁺ sites in catalyzing the reaction and the advantage of the introduced mesoporous structure in enhancing the mass transport.