Oxygen Poisoning of Copper Surfaces in the Presence of Cesium Ions during Electrochemical Nitrate Reduction to Ammonia

The electrochemical nitrate reduction (NO 3 R) for ammonia synthesis holds promise for utilizing NO 3 – pollutants in water under ambient conditions. In the multielectron transfer process of NO 3 – anions transforming into ammonia, counter-cations play a critical role in influencing the interactions of anions and intermediates. Here, we investigated the impact of Cs + ions on the electropolished flat copper (Cu) (100) surface during NO 3 R. Our results show that the presence of Cs + leads to a significant decline in Cu activity, with an approximately 8-fold decrease in the partial current density for NH 3 and an increase in interfacial resistance compared to using K + . Operando electrochemical Raman spectroscopy revealed the formation of oxygen and hydroxide species adsorbed on the surface (Cu-*O and Cu-*OH, the asterisk symbol indicates surface adsorption), alongside a decrease in the …