B-Site Engineering in Ruddlesden–Popper Perovskites (A ₂ BO ₄ ) for H ₂ O ₂ Production with 4.85% of Solar-to-Chemical Efficiency

The electrochemical synthesis of hydrogen peroxide (H₂O₂) via the oxygen reduction reaction (ORR) offers a promising alternative to the anthraquinone process, addressing environmental concerns without requiring expensive hydrogen. However, developing catalysts that selectively promote the two-electron ORR pathway while maintaining stability remains challenging. Here, we report Ruddlesden-Popper (RP) perovskite oxides as efficient catalysts for selective H₂O₂ production. Among the tested LaSrBO₄ compositions (B = Ni, Co, Fe, Mn), LaSrNiO₄ (LSN) showed the best two-electron ORR selectivity (∼87%) and activity. Integrated into a photovoltaic-electrochemical system, LSN achieved a solar-to-chemical conversion efficiency of 4.85%, producing a H₂O₂ production rate of 149.2 μmol cm^-2 h^-1 with good stability over 50 h. Density functional theory calculations attributed this performance to favorable H₂O₂ formation and desorption kinetics at the Ni B-site. Overall, RP perovskites offer earth-abundant, efficient, and sustainable catalysts for electrochemical H₂O₂ generation, providing an alternative to carbon- or noble-metal-based systems.