Modulation of Lewis and Brønsted acid centers with oxygen vacancies for Nb2O5 electrocatalysts: Towards highly efficient simultaneously electrochemical ozone and hydrogen peroxide production

Assembling two desirable half-reactions of green oxidants hydrogen peroxide (H2O2) and ozone (O3) into efficient paired electrolysis is highly valuable in terms of efficiency and environmental-friendliness. However, rational design and construction of electrocatalysts with regulable active sites for the paired electrosynthesis of green oxidants of H2O2 and O3 remain a significant challenge. Herein, A new strategy was developed for tunning the active sites of pseudo-hexagonal centers (TT, Lewis acid sites) and orthogonal centers (T, Brønsted acid sites) in Mxene layered structure niobium pentoxide (Nb2O5) with abundant oxygen vacancy (OV) for the paired electrolysis of 2e- oxygen reduction reaction (ORR) and electrochemical ozone production (EOP). The TT-300 and T-400 electrocatalysts exhibited outstanding electrochemical activity of 2e- ORR (H2O2 selectively of 92% at 0.4 VRHE) and EOP (gaseous ozone FE of 13% at 50 mA cm−2), respectively. The excellent performance was mainly attributed to the TT-300 (Lewis acid sites) and T-400 (Brønsted acid sites) with abundant OV that improve the oxygen-containing intermediates formation of OOH* and deprotonation of water. In addition, the in-situ electro-degradation of organic compounds experiments indicated that the synergistic degradation of O3 and H2O2 possessed a faster kinetic constant compared with a single electrolysis system of O3 and H2O2. The work provides meaningful insights into the rational design and construction of advanced solid acid electrocatalysts for efficient simultaneously electrocatalytic hydrogenation and oxidation to produce green oxidants of O3 and H2O2.