Perspectives on the Competition between the Electrochemical Water and N₂ Oxidation on a TiO₂(110) Electrode

Abstract

The electrochemical nitrogen oxidation reaction (NOR) has recently drawn attention due to promising experimental and theoretical results. It provides an alternative, environmentally friendly route to directly synthesize nitrate from N 2 (g). There is to date a limited number of investigations focused on the electrochemical NOR. Herein, we present a detailed computational study on the kinetics of both the NOR and the competing oxygen evolution reaction (OER) on the TiO 2 (110) electrode under ambient conditions. The use of grand canonical density functional theory in combination with the linearized Poisson−Boltzmann equation allows a continuous tuning of the explicitly applied electrical potential. We find that the OER may either promote or suppress the NOR on TiO 2 (110) depending on reaction conditions. The detailed atomistic insights provided on the mechanisms of these competing processes make possible further developments toward a direct electrochemical NOR process.

Pulsed Electrocatalysis Enabling High Overall Nitrogen Fixation Performance for Atomically Dispersed Fe on TiO2

“…Electrochemical N 2 fixation, powered by renewable electricity, using water (H 2 O) and N 2 in the atmosphere (78 %), has been demonstrated as a sustainable and promising approach for NH 3 and HNO 3 production [13–18] . While, according to the potential pH advantage diagram of N 2 ‐H 2 O system (Figure S1), the standard electrode potentials of N 2 fixation reaction (NOR: nitrogen oxidation reaction and NRR: nitrogen reduction reaction) and H 2 O decomposition reaction are comparable [19–21] . Despite extensive research efforts, limited achievements have been obtained for the competitive reaction of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in recent years [22–25] .…”

“…The electrochemical nitrogen activation by active intermediates during water decomposition was verified to be a feasible pathway. The electrochemical nitrogen activation could be divided into the electrocatalytic process water‐splitting for active intermediates and non‐electrocatalytic process of nitrogen activation [19–21] . So, appropriate electrochemical regulation may be effective and necessary.…”

“…[13][14][15][16][17][18] While, according to the potential pH advantage diagram of N 2 -H 2 O system (Figure S1), the standard electrode potentials of N 2 fixation reaction (NOR: nitrogen oxidation reaction and NRR: nitrogen reduction reaction) and H 2 O decomposition reaction are comparable. [19][20][21] Despite extensive research efforts, limited achievements have been obtained for the competitive reaction of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in recent years. [22][23][24][25] No satisfying regulating strategy had been reported to restrain the competitive reactions for NOR and NRR, even the overall electrochemical nitrogen fixation yet, previously.…”

“…The electrochemical nitrogen activation could be divided into the electrocatalytic process water-splitting for active intermediates and non-electrocatalytic process of nitrogen activation. [19][20][21] So, appropriate electrochemical regulation may be effective and necessary. Pulsed electrochemical catalysis (PE) was demonstrated as an operable and efficient reaction regulation method in complicated electrocatalytic reactions for its precise control of electron transmission and regulation selectivity in the past years.…”

Limitations of Electrochemical Nitrogen Oxidation toward Nitrate

“…Computationally, beyond-generalized gradient approximation (GGA) approaches such GGA+U or hybrids might be interesting to be utilized to investigate the defect/polaron states in catalysts . In addition, grand canonical DFT − could be further employed in the future to explore other possible reaction pathways and explicit dependence on pH, applied potential, surface coverages, and ions for a more detailed understanding of NOR.…”