The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (eTiO2-) has been studied under anaerobic conditions. TiO2 was loaded with 10-130 electrons per particle using γ-irradiation of acidic TiO2 colloid solutions containing 2-propanol. The study is based on time-resolved kinetics and reactants and products analysis. The reduction of NO by eTiO2- is interpreted in terms of competition between a reaction path leading to formation of NH3 and a path leading to N2O and N2. The proposed mechanism involves consecutive one-electron transfers of NO, and its reduction intermediates HNO, NH2O•, and NH2OH. The results show that eTiO2- does not reduce N2O and N2. Second-order rate constants of eTiO2- reactions with NO (740 ± 30 M-1 s-1) and NH2OH (270 ± 30 M-1 s-1) have been determined employing the rapid-mixing stopped-flow technique and that with HNO (>1.3 × 106 M-1 s-1) was derived from fitting the kinetic traces to the suggested reaction mechanism, which is discussed in detail.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry