Modulation of Protons and Cations at the electrode-electrolyte interface for Effective Selectivity of Ammonia Production during Electrochemical Nitrate Reduction Reaction
Jou-Chun Lin, Meng-Chi, Hsieh, Lo-Yu Lee, Yi-Cheng Su, Yi-Chia Chen, Yung-Yi Huang, Cheng-Chi Xiao, Chueh-Cheng Yang, Chun-Chih Chang*, Chia-Hsin Wang* and Di-Yan Wang*
This study systematically investigates the competitive interactions between sodium ions (Na+) and protons (H+) and their specific influence on the electrochemical nitrate reduction reaction (NO3RR). Copper nanodendrites (Cu NDs) served as the catalysts, evaluated via chronoamperometry within NaNO3, HNO3, and equimolar mixed electrolytes at 0.1 M and 0.01 M concentrations. To elucidate complex interfacial processes, in-situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and molecular dynamics (MD) simulations were conducted. Findings reveal that in pure NaNO3, competitive adsorption of Na+ on the catalyst surface effectively suppresses NO3– binding, increasing overpotential and favoring nitrite (NO2–) formation between +0.2 V and -0.2 V (vs. RHE). Conversely, the presence of H+ promotes NO3– adsorption and significantly enhances ammonia production. These results clarify the origin of high overpotentials in neutral media and highlight how alkali cations and protons govern NO3RR selectivity. This work offers fundamental insights for designing efficient, sustainable, and electrocatalytic ammonia synthesis systems.