Modulating Electron Density of Ce Site via a Ce–O–Bi configuration on Ce-BiOX (X = Cl, Br, I) to Boost Hydrogen Peroxide Electrosynthesis

The selectivity of two-electron oxygen reduction reaction (2e - ORR) is predominantly determined by the adsorption strength of the key intermediate *OOH on the catalyst active sites, which has often been tuned by 3d transition-metal doping. Herein, we fabricate rare earth Ce doped bismuth oxyhalide (BiOX, X = Cl, Br, I) catalysts. The built in Ce–O–Bi local configuration triggers efficient charge rearrangement and tunes the surface electron density of Ce active centers. Meanwhile, the differences in ionic radius and electronegativity among halogen species can modulate the symmetry of the Bi–O lattice, thereby forming a typical volcano-type correlation between the bond length and 2e - ORR catalytic performance. The synergistic effect of Ce doping and halogen modulation endows the 2.5%Ce-BOB catalyst with optimal 2e - ORR performance. It delivers a H 2 O 2 selectivity of over 90% within the potential range of 0.2-0.6 V and achieves a H 2 O 2 production rate of 2631.4 mmol g -1 h -1 at 0.1 V. Furthermore, this optimized catalyst demonstrates potential application in organic wastewater treatment, where the degradation efficiency of methylene blue (MB) reaches approximately 95% in 40 min and that of rhodamine B (RhB) approaches 99% in 15 min. This work provides new insights into the rational design of electrocatalysts and environmental applications of electrosynthesized H 2 O 2 via the synergistic regulation of rare-earth metal doping and halogen modulation.