Integrating RuO2@TiO2 catalyzed electrochemical chlorine evolution with a NO oxidation reaction for nitrate synthesis

Abstract

We report a cascade chlorine evolution–nitric oxide (NO) oxidation system for the homogeneous synthesis of nitrate, in which NO can be efficiently converted to nitrate by reacting with the active chlorine species. This highly efficient nitrate synthesis system was demonstrated by using a RuO₂ nanoparticle-decorated TiO₂ nanobelt array on a titanium plate (RuO₂@TiO₂/TP) under ambient conditions, capable of attaining a high nitrate yield of 95.22 mg cm⁻² h⁻¹ at 2.1 V versus the reversible hydrogen electrode in NO-saturated 0.5 M NaCl + 0.01 M HClO₄. Electrochemical in situ Raman spectroscopy studies reveal the adsorption of Cl–O species on the electrode surface and the key role of high-valence Ru^x+ (x > 4) at high potentials. The electron paramagnetic resonance results confirmed the existence of chlorine radicals and hydroxyl radicals generated by RuO₂@TiO₂/TP in the electrolyte.