Open AccessWhat Is the Role of Pyridinium in Pyridine-Catalyzed CO2 Reduction on p-GaP Photocathodes?
Author(s) -
Martina Lessio,
Emily A. Carter
Publication year - 2015
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.5b08639
Subject(s) - pyridinium , chemistry , adsorption , pyridine , electron transfer , pyridinium compounds , catalysis , reduction (mathematics) , photochemistry , band gap , inorganic chemistry , photocatalysis , computational chemistry , medicinal chemistry , organic chemistry , optoelectronics , physics , geometry , mathematics
Experimental evidence suggests that pyridinium plays an important role in photocatalytic CO2 reduction on p-GaP photoelectrodes. Pyridinium reduction to pyridinyl has been previously proposed as an essential mechanistic step for this reaction. However, theoretical calculations suggest that this step is not feasible in solution. Here, cluster models and accurate periodic boundary condition calculations are used to determine whether such a reduction step could occur by transfer of photoexcited electrons from the p-GaP photocathode and whether this transfer could be catalyzed by pyridinium adsorption on the p-GaP surface. It is found that both the transfer of photoexcited electrons to pyridinium and pyridinium adsorption are not energetically favored, thus making very unlikely pyridinium reduction to the pyridinyl radical and the proposed mechanisms requiring this reduction step. Given this conclusion, an alternative and energetically viable pathway for pyridinium reduction on p-GaP photoelectrodes is proposed. This pathway leads to the formation of adsorbed species that could react to form adsorbed dihydropyridine, which was proposed previously to play the role of the active catalyst in this system.