Accelerated Proton-Coupled Electron Transfer via Engineering Palladium Sub-Nanoclusters for Scalable Electrosynthesis...

Electrosynthesis of H₂O₂ from oxygen reduction reaction via a two-electron pathway is vital as an alternative for the energy-intensive anthraquinone process. However, this process is largely hindered in neutral and alkaline conditions due to sluggish kinetics associated with the transformation of intermediate O₂* into OOH* via proton-coupled electron transfer sourced from slow water dissociation. Herein, we developed Pd sub-nanoclusters on the nickel ditelluride nanosheets (Pd SNCs/NiTe₂) to enhance the performance of H₂O₂ electrosynthesis. The newly-developed Pd SNCs/NiTe₂ exhibited a H₂O₂ selectivity of as high as 99 % and a positive shift of onset potential up to 0.81 V. Combined theoretical calculations and experimental studies (e.g., X-ray absorption and attenuated total reflectance-Fourier transform infrared spectra measurements) revealed that the Pd sub-nanoclusters supported by NiTe₂ nanosheets efficiently reduced the energy barrier of water dissociation to generate more protons, facilitating the proton feeding kinetics. When used in a flow cell, Pd SNCs/NiTe₂ cathode efficiently produced H₂O₂ with a maximum yield rate of 1.75 mmol h^-1 cm^-2 and a current efficiency of 95 % at 100 mA cm^-2. Further, an accumulated H₂O₂ concentration of 1.43 mol L^-1 was reached after 10 hours of continuous electrolysis, showing the potential for practical H₂O₂ electrosynthesis.