Enhanced electrochemical hydrogen peroxide production from surface state modified mesoporous tin oxide catalysts

Electrochemical hydrogen peroxide (H₂O₂) production via the two-electron oxygen reduction reaction (ORR) has received much consideration as a substitute to the well-known industrial anthraquinone method. The present challenge in this area is developing appropriate cost-efficient materials with excellent electrocatalytic properties, durability, and product selectivity. This study examined electrocatalytic performance and selectivity toward H₂O₂ production of mesoporous SnO₂ (meso-SnO₂) electrodes prepared using a tunable hydrothermal process. After evaluating the effects of different NaCl concentrations and annealing conditions in the hydrothermal method, an electrode was developed with a significantly improved H₂O₂ production rate than the pristine material. Vacuum annealing led to materials with more surface defects. Meso-SnO₂ annealed under vacuum exhibits distinctive electrochemical properties of two well-separated 2e⁻ O₂ reduction peaks to produce H₂O₂ as the main product compared to meso-SnO₂ annealed in air. Most importantly, the introduction of surface oxygen vacancies into the meso-SnO₂ crystal structure was determined to be a prominent approach to enhance its ORR performance in producing H₂O₂, showing great selectivity of above 85% at an onset potential of ∼0.6 V_RHE. The vacancy-rich meso-SnO₂ reveals enhanced electrocatalytic performance with ORR peak potential to be 0.6 V_RHE, and the number of electron transfer numbers is 2.5, but greater durability in alkaline solutions. Thus, this work presents an innovative route for designing, synthesizing, and mechanistic examining enhanced SnO₂-based catalytic materials for H₂O₂ production.