Electronic structure regulation via heterojunction engineering for enhanced oxygen reduction reaction

Transition metal catalysts have promising applications as potential alternatives to platinum-based catalysts in oxygen reduction reactions (ORR), and fine-tuning their local electronic structure is an essential strategy to boost the intrinsic activity. Herein, a Zr–Cu heterojunction catalyst was synthesized by combining ZrO2/C and Cu2(OH)2CO3/C using a simple sol-gel synthesis method. The Zr–Cu heterojunction synergistically achieved high ORR performance with a noticeable half-wave potential of 0.827 V, comparable to commercial Pt/C, along with superior stability and methanol tolerance in alkaline solution. X-ray absorption near-edge spectroscopy (XANES) demonstrated that the interfacial electronic interaction between Zr and Cu species in Zr–Cu heterojunction was enhanced, leading to the enhanced ORR activity. Combined with density functional theory calculations, the Cu atoms located at the interface of Zr–Cu heterojunction were identified as the ORR active sites, while the Zr atoms served as an electronic regulator to induce the electron redistribution by facilitating electron transfer from Zr species and Cu active sites. Therefore, the engineering of Zr–Cu heterojunction catalyst greatly optimized the adsorption strength of O2 as well as reduced the energy barrier of *O2 → *OOH intermediate, ultimately resulting in the promoted ORR performance. The findings of this study suggest a valuable strategy for manipulating heterojunction to optimize the electronic structure of catalytic active sites and improve electrocatalytic reactions.