Abstract:

Electric fields play a pivotal role in renewable energy technologies and are essential for enabling a sustainable future. However, the regulation of macroscale catalytic behavior by electric fields has not been well digitally understood yet, as conventional computational models rely on reaction energy profiles that overlook the nonlinear effects of electric fields on elementary reaction steps. Here, we use advanced constant-potential microkinetic simulations to revisit the electrochemical nitrogen reduction reaction (eNRR) under operating conditions, which makes it possible to explicitly integrate both electrochemical and chemical steps and quantitatively predict the effects of electric fields on eNRR macroscale performance. The theoretical activity trends for different metals were successfully reproduced with our model, which are in good qualitative agreement with experimental observations. Furthermore, we propose a new theoretical protocol for eNRR catalyst screening, where an optimal catalyst should exhibit overwhelming N₂ adsorption ability over a wide potential range to sufficiently facilitate eNRR at high potentials. Interestingly, the rate-determining step undergoes dynamic evolution with potential variations, with chemical steps imposing fundamental constraints on practical ammonia (NH₃) electrosynthesis. Microkinetic simulations demonstrate that incorporating ^*NH₃ desorption steps can alter reaction rates by orders of magnitude, highlighting their critical yet often overlooked role. This work establishes a quantitative framework for achieving accurate, physically realistic theoretical simulations in heterogeneous electrochemistry.

Key words: Electrochemistry, Non-electrochemical steps, Constant potential model, Potential-dependent free energy, Microkinetic modeling