Guanidinium Formate Decomposition on the (101) TiO2-Anatase Surface: Combined Minimum Energy Reaction Pathway Calculations and Temperature-Programmed Decomposition Experiments

Abstract

Local minima, saddle points, and connecting intrinsic reaction paths for the decomposition of guanidinium formate (GuFo) on a (101) TiO2-anatase surface and in the gas phase have been studied on the basis of density functional theory (DFT) energy surfaces. We are aware of only one preceding electronic structure theory study of reaction barriers at a slab surface model. The formation of ammonia and carbon dioxide as final products of the GuFo decomposition is proposed to proceed in three principal stages: first, the decomposition of GuFo to guanidine and formic acid, then the hydrolysis or decomposition of guanidine to ammonia and carbon dioxide via urea and isocyanic acid intermediates, and, in parallel to the latter, the decomposition of formic acid to water and carbon monoxide or to hydrogen and carbon dioxide. The moment in which water enters the decomposition of guanidine is crucial and determines its course. Temperature-programmed decomposition experiments propose a decomposition of guanidine to urea...