Nitrogen reduction utilizing solvated electrons produced by thermal excitation of trapped electrons in reduced titanium oxide

Abstract

Heterogeneous catalytic dinitrogen reduction to produce ammonia at ambient pressure and temperature is a challenging task when attempting to mimic the natural dinitrogen fixation process because the N₂ molecule hardly binds with solid catalytic materials and the generation of high energy intermediates is required. Energetic solvated electrons, as highly reactive species, can directly react in solution and thus can overcome such limitations in ammonia synthesis. Although solvated electrons are commonly generated by high energy radiation, a facile approach for generation of solvated electrons is of increasing importance. Previous literature reported that photo-illuminated hydrogen-terminated diamond yields solvated electrons for reduction of N₂. In this study, the solvated electrons were produced by direct emission of stabilized electrons from heavily reduced TiO₂ into water under thermal or infrared light excitation. The structural change of the reduced TiO₂ was characterized to understand the process of stabilization and release of excess electrons. Furthermore, the conversion of N₂ into NH₃ at different conditions under thermal excitation was tested to evaluate the reduction activity of solvated electrons. The thermal energy-controlled electron emission from the reduced TiO₂ particles into solution has great application potentials in areas of energy conversion, chemical synthesis, and medical treatment.