Surface engineering at the interface of core/shell nanoparticles promotes hydrogen peroxide generation

Hydrogen peroxide (H₂O₂), an environmentally friendly oxidant, has already been widely used in many chemical synthesis and industrials as an alternative to replace traditional oxidants including chlorinated oxidizers and strong acids. However, the conventional synthesis method confronts intense energy cost, tedious separation procedures and high cost, which is not competitive with traditional oxidants. Although directH₂O₂ synthesis fromH₂ and O₂ is a green and atomically economic reaction, satisfactory activity and desirable selectivity still remain formidable challenges. Herein, for the first time, a class of Pd@NiO-x nanoparticles (NPs) (x=1, 2, 3 and 4) with a unique core@shell interface structure has been created to achieve high activity, selectivity and stability for the direct H₂O₂ synthesis. A precise thermal annealing on Pd@Ni-x NPs revealed that the resulting Pd@NiO-x NPs exhibited the volcano-like activity toward direct H₂O₂ synthesis as a function of annealing temperature and time. By tuning the composition of Pd@NiO-x NPs and the reaction condition, the efficiency of H₂O₂ synthesis could be well optimized with 5 wt% Pd@NiO-3/TiO₂ exhibiting the highest productivity (89 mol/(kg_cat h)) and selectivity (91%) to H₂O₂ as well as excellent stability, making it one of the best catalysts for direct H₂O₂ synthesis reported to date.