Physico-chemical principles of AC electrosynthesis

Electrolysis integrates renewable energy into chemical manufacturing and is key towards sustainable chemistry. Controlling the waveform beyond direct current addresses the long-standing obstacle of chemoselectivity, yet it also expands the parameter set to optimise, creating a demand for theoretical predictions. Here, we report the first analytical theory for predicting chemoselectivity in alternating current electrosynthesis. The mechanism is a selective reversal of the unwanted redox reaction during periods of opposite polarity. Notably, we find regimes within which a square waveform can not only bias but also reverse the chemoselectivity compared to direct current approaches, favouring overoxidation/overreduction. Sinusoidal waves exhibit the opposite effect. These trends are consistent with existing experimental works. Therefore, we find alternating current to be a promising avenue for achieving the ultimate control over reaction pathways.