Surface electronic states mediate concerted electron and proton transfer at metal nanoscale interfaces for catalytic hydride reduction of -NO to -NH

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 23; pp. 1295 - 12957
• Main Authors: Shan, Bing-Qian, Zhou, Jia-Feng, Ding, Meng, Hu, Xiao-Dan, Zhang, Kun
• Format: Journal Article
• Published: 16.06.2021
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d1cp01792f

Concerted electron and proton transfer is a key step for the reversible conversion of molecular hydrogen in both heterogeneous nanocatalysis and metalloenzyme catalysis. However, its activation mechanism involving electron and proton transfer kinetics remains elusive. With the most widely used catalytic hydride reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction, we evaluate the catalytic activity of noble metal nanoparticles (NPs) trapped in porous silica in aqueous NaBH 4 solution. By virtue of a novel combination of catalyst design, reaction kinetics, isotope labeling, and multiple spectroscopic techniques, the real catalytic site for the conversion of -NO 2 to -NH 2 is identified to be the water-hydroxyl transition metal complex, which could further react with NaBH 4 to form a new triangular configuration metal complex of H 3 B-water-hydroxyl with dynamic features. It yields an ensemble of surface electronic states (SESs) though space overlapping of p orbitals of one B and several O atoms (including the O atoms of 4-NP), which could act as an alternative channel for concerted electron and proton transfer. This work highlights the critical role of the conceptual SESs model in heterogeneous catalysis to tune the chemical reactivity and also sheds light on the intricate working of the [FeFe]-hydrogenases. Surface electronic states mediate concerted electron and proton transfer at metal nanoscale interfaces for catalytic hydride reduction of -NO 2 to -NH 2 , beyond the conventional metal centered d-band theory