Interfacial proton enrichment enhances proton-coupled electrocatalytic reactions

Abstract

Proton-coupled electrocatalytic reactions, such as the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic media, are very important half-reactions of fuel cells and water electrolysis. Aiming at increasing the interfacial proton concentration to improve the ORR/HER activity, we synthesize PdNi alloy nanostructures (PdNi-ANSs)–polyethyleneimine (PEI) inorganic–organic nanocomposites (PdNi-ANSs@PEI) by a PEI assisted cyanogel-reduction strategy. Various physical characterization techniques show that PdNi-ANSs are successfully functionalized by the PEI polymer during the synthesis of PdNi-ANSs@PEI because of the N–Pd interaction. Thanks to the increased interfacial proton concentration caused by the protonation of amine groups at PEI in acidic media, the molecular weight optimized PdNi-ANSs@PEI exhibit enhanced ORR/HER activity compared to PdNi-ANSs without PEI and commercial electrocatalysts, which indicates that the electrocatalytic activity of metal nanostructures can be remarkably improved by reasonable interface design.