The atomic ensemble effect will affect the catalysis on catalyst surfaces and determine the selectivity of multielectron reactions, which is an effective potential strategy to modulate the oxygen reduction reaction (ORR) selectivity for hydrogen peroxide (H2O2) production. Here, we reported the investigation of the ensemble effect on Pt/Pd chalcogenides for the two-electron ORR. A series of Pt/Pd chalcogenides were synthesized via introducing chalcogens into Pt/Pd, resulting in catalysts with isolated Pt/Pd active site. X-ray adsorption spectroscopy reveals the change of the electronic structure. Their ORR selectivity transformed from a four-electron process to a two-electron one, which was attributed to the isolated active sites changing the adsorption mode and the tunable electronic property weakening the adsorption energy. Density functional theory calculations revealed that Pt/Pd chalcogenides possessed a lower binding energy of OOH* and inhibited the breakage of the O-O bond, and PtSe2/C with an optimal adsorption energy of OOH* showed 91% selectivity toward H2O2 production. This work provides a design principle for synthesizing highly selective Pt group catalysts for H2O2 production.
Keywords: Pt/Pd chalcogenides; electrocatalysis; hydrogen peroxide; oxygen reduction reaction.