Single-step two-electron transfer mechanism in semiconductor photocatalysts discovered by DAL

Single-step two-electron transfer mechanism in semiconductor photocatalysts discovered by DAL

Recently, Li Can's team at the National Key Laboratory of Catalysis and the National Laboratory of Clean Energy (DLP16) of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, revealed for the first time two electrons between a semiconductor and a hydrogen-producing hydrogen catalyst under strong alkali conditions. Mechanisms of metastasis, related research results were published in the form of communication in the "Yuxing Xu, Hongxian Han & Can Li etc.J.Am.Chem.Soc.2016, DOI:101021/jacs.6b04080).

The research team has been engaged in the research of coupling systems of semiconductors and molecular catalysts (metal complex molecules) for many years, aiming at the use of broad spectrum absorption of semiconductors and high activity of molecular hydrogen production (or oxygen generation) catalysts to construct highly efficient photocatalytic decomposition. Aquatic Hydrogen Systems (J. Catal., 2011, 281, 318; ChemSusChem, 2012, 5, 849; Chem. Commun., 2012, 48, 988; Acc. Chem. Res., 2013, 46, 2355; J. Catal ., 2016, 338, 168).

Photocatalytic water splitting by solar energy is a photochemical reaction process involving multiple electron transfer. For many photocatalytic systems, the charge transfer mechanism between the semiconductor and the catalyst is not clear. Researchers through the electron transfer thermodynamic and kinetic analysis of the CoPy/CdS system, combined with electron spin resonance and UV-Vis absorption on the cobalt species intermediate species found: when pH = 13.5, if the electrons from CdS to Co ( III) Py transfer proceeds via a two-step single electron transfer process, Co(III)Py-Co(II)Py-Co(I)Py, and a second photogenerated electron is transferred from CdS to Co(II)Py to generate a catalytic proton The reduced thermodynamic driving force of Co(I)Py, an inevitable intermediate for hydrogen production, is insufficient to explain the experimental results of hydrogen production observed under strong alkali conditions; and the single-step two-electron transfer pathway, Co(III)Py— Co(I)Py makes it possible to produce Co(I)Py, and finally realize catalytic reduction of hydrogen by protons. This discovery not only reveals the possible multiple electron transfer process between semiconductors and molecular catalysts, but also provides new research ideas for the construction of high-efficiency photocatalytic systems based on multi-electron transfer mechanisms.

The work was funded by the "973" project of the Ministry of Science and Technology, the National Natural Science Foundation, and the iChEM.

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