Atomically isolated Pd sites within Pd-S nanocrystals enable trifunctional catalysis for direct, electrocatalytic and photocatalytic syntheses of H2O2

Although high-efficiency production of hydrogen peroxide (H2O2) can be realized separately by means of direct, electrochemical, and photocatalytic synthesis, developing versatile catalysts is particularly challenging yet desirable. Herein, for the first time we reported that palladium-sulphur nanocrystals (Pd-S NCs) can be adopted as robust and universal catalysts, which can realize the efficient O2 conversion by three methods. As a result, Pd-S NCs exhibit an excellent selectivity (89.5%) to H2O2 with high productivity (133.6 mol·kgcat−1h−1) in the direct synthesis, along with the significantly enhanced H2O2 production activity and stability via electrocatalytic and photocatalytic syntheses. It is demonstrated that the isolated Pd sites can enhance the adsorption of O2 and inhibit its O-O bond dissociation, improving H2O2 selectivity and reducing H2O2 degradation. Further study confirms that the difference in surface atom composition and arrangement is the key factor for different ORR mechanisms on Pd NCs and Pd-S NCs.