Oxygen-bridge-mediated control of selectivity in the transition from four-electron to two-electron oxygen reduction.

Abstract

The electrochemical synthesis of hydrogen peroxide via the two-electron oxygen reduction and water oxidation pathways offers a sustainable alternative to the energy-intensive anthraquinone process. However, developing bifunctional catalysts capable of suppressing the competitive four-electron pathway remains a significant challenge. Herein, we conduct a systematic density functional theory (DFT) study of 184 axial oxygen-bridged heterostructures (M-O-M') constructed by coupling metal phthalocyanine materials (M-Pc) with transition metal nitrogen-doped carbon (M'-N-C). Through a rigorous multi-step screening encompassing thermodynamic stability, electrochemical dissolution potential, and selectivity descriptors, nine promising candidates were identified. Notably, the Co-O-V system emerges as a highly efficient bifunctional electrocatalyst for both 2e- ORR and 2e- WOR, the performance of which was further validated under operationally relevant electrochemical conditions via the constant potential method. The axial oxygen-bridge facilitates a strong exchange interaction, triggering a spin-state transition at the active Co center; this electronic modulation optimizes the adsorption energetics of OOH⁎ and OH⁎, effectively preventing OO bond cleavage. Furthermore, machine learning analysis was performed to elucidate the activity origins, identifying the d-band center and Bader charge as key descriptors governing the reaction energetics. This work not only identifies efficient bifunctional catalysts but also establishes a fundamental understanding of spin-regulated catalysis under realistic electrochemical conditions.