Nitric oxide reduction to ammonia by TiO₂ electrons in colloid solution via consecutive one-electron transfer steps.
The reaction mechanism of nitric oxide (NO) reduction by excess electrons on TiO2 nanoparticles (e(TiO2)(-)) 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 e(TiO2)(-) 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 e(TiO2)(-) does not reduce N2O and N2. Second-order rate constants of e(TiO2)(-) 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 × 10(6) M(-1) s(-1)) was derived from fitting the kinetic traces to the suggested reaction mechanism, which is discussed in detail.
†Institute of Chemistry and the Accelerator Laboratory, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Sara
S
Goldstein
†Institute of Chemistry and the Accelerator Laboratory, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
David
D
Behar
‡Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Tijana
T
Rajh
†Institute of Chemistry and the Accelerator Laboratory, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Joseph
J
Rabani