Unlocking the Critical Role of Noncovalent Interactions Between Alkali Metal Cations and Nitrate in Promoting the
Shuai Qi1, Xinbao Chen1, Huan He1
1College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P.R. China.
Abstract:
The electrochemical nitrate reduction reaction (NO3 -RR) is widely investigated for sustainable ammonia (NH3) production from NO3 - pollutants. Alkali metal cations (AM+) in the electrolyte often greatly impact electrocatalytic performance; however, the role of AM+ in the NO3 -RR remains unclear. Here, we first investigate the influence of AM+ on the Cu-catalyzed NO3 -RR, revealing an activity increase trend of Li+ < Cs+ < Na+ < K+, which is inconsistent with the local electric field and proton transfer rate increase trend of Li+ < Na+ < K+ < Cs+, hinting that the presence of other important factors governs the NO3 -RR activity. Intriguingly, Ab initio molecular dynamic (AIMD) simulations uncover that Na+, K+, and Cs+ with relatively soft solvation shells could be partially desolvated and then coordinate with NO3 - via a short-range electrostatic interaction, thereby boosting the rate determining step (RDS), that is the conversion of NO3 - to NO2 -. Notably, K+ with suitable NO3 - interaction strength has higher ability to boost the RDS than Na+ and Cs+ with too weak and strong strength, respectively. Our results highlight that the short-range electrostatic interaction strength of AM+/NO3 - is a crucial factor to determine the NO3 -RR activity.
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