Potential of Tandem Catalysts for Excellent H

Direct electrosynthesis of hydrogen peroxide (H2O2) serves as an innovative and less-energy-demanding alternative to the conventional anthraquinone process. As the process involves active hydrogen (*H) production and hydrogenation of oxygen-containing intermediates, catalysts containing dual functional sites for *H and *OOH intermediate generation might boost the H2O2 electrosynthesis activity. Here, we report a tandem catalyst with a uniform distribution of single-atom Al sites around Al2O3 species, constituting the adjacent catalytic centers (Al2O3/Al1-O-C). The Al2O3/Al1-O-C catalysts exhibit high H2O2 selectivity in alkaline conditions and achieve a yield rate of 39.4 mol gcat.-1 h-1 with a favorable stability of over 100 h in the flow cell. The direct output concentration of H2O2 can reach 1659.2 mmol L-1 (5.61 wt %) at 400 mA cm-2. The in situ measurements and simulated calculations reveal that the Al2O3 sites catalyze the Volmer step in water decomposition to generate *H, which significantly promotes the *OOH generation from the reduction of *O2 on single-atom Al sites, thus promoting H2O2 electrosynthesis at high current densities. This tandem design enables industrially relevant H2O2 electrosynthesis, demonstrating the potential for practical applications in the future.