Stirring effects on AC-induced chemoselectivity in reversible electrochemical reactions

Bulk electrolysis presents a sustainable alternative to heat-driven chemical synthesis and modulating the applied potential across time, a process known as alternating current (AC) electrosynthesis, adds the possibility of chemoselectivity control. However, finding the optimal AC waveform requires scanning over a huge parameter space, a problem better tackled from a theoretical front. To this end, we recently developed the first analytical theory for chemoselectivity prediction in AC electrolysis by considering the diffusion dynamics near the electrode surface. In this follow-up study, we introduce approximations to the aforesaid model that provide valuable new insights to the problem. We also tackle a key limitation from before – the absence of stirring effects. Our analytical results suggest that stirring accelerates the reaction's approach towards its long-time steady-state outcome at a characteristic rate of D/Lx_d, where D is the molecular diffusivity, L is the electrolytic cell width, and x_d is the diffusion layer thickness. For AC frequencies faster than this rate, i.e. for ν >> D/Lx_d, the steady-state reaction outcome reached in the long time limit is the same as our previous work, which was conducted without any stirring. Therefore, given that most electrosynthetic setups employ fast AC frequencies beyond D/Lx_d, we expect our earlier predictions to be relevant to realistic scenarios.