“Hole” traps promoting direct nitrate synthesis within flux controlled N2-rich circumstance

Electrooxidation of nitrogen to nitrate is a promising alternative to the energy-intensive process for industrially manufacturing nitrate product. However, nitrogen oxidation reaction (NOR) is still severely restricted by the adsorption and activation of nitrogen. Herein, a catalyst of Fe-doped CeO2 nanorods with “hole” traps promoting activity is designed and made full use of by constructing a flux controlled N2-rich circumstance. Density functional theory (DFT) calculations indicate that due to the narrower band gap and lower Bader charge induced by Fe-doping, the Fe-CeO2 possesses unique enhanced Ce active sites as “hole” traps to capture “hole” (lose electron) for effectively adsorbing N2 and destabilizing NN bond. Subsequently, the active sites trap external “holes” and transfer to the vulnerable activated intermediates under electrooxidation, accompanied by the transfer of electrons from intermediates through active sites, then to external circuit. This gives rise to the lower energy barriers of nitrogen oxidation for the Fe-CeO2. The electrochemical performance of Fe-CeO2 catalyst is experimentally confirmed and is further boosted by constructing a flux controlled N2-rich circumstance. As expected, a considerable nitrate Faradaic efficiency of 43.9 % and a superior nitrate yield rate of 17.41 µg h−1 mg−1 are achieved in this proof-of-concept system.