Spikes Effect: Decoding and Redesigning Pulsed Electrochemical CO2 Reduction for Enhanced C–C Coupling on Oxide-Derived Copper

Pulsed electrolysis has emerged as a highly effective technique for enhancing the selectivity of oxide-derived copper (OD-Cu) catalysts in the electrochemical CO₂ reduction reaction (CO₂RR), particularly toward valuable multicarbon (C₂₊) products. Despite extensive studies, the role of transient current spikes─brief surges in current induced by abrupt potential switching─has remained largely unexplored. In this work, we systematically dissect the contribution of these current spikes using two distinct electrolysis modes: pulsed amperometry (PA) and pulsed potentiometry (PP). By decoupling the effects of current spikes from other pulsing-induced phenomena, we demonstrate that while both methods suppress hydrogen evolution, only PA─defined by sharp, transient current spikes─substantially enhances C₂₊ selectivity. In situ ATR-SEIRAS measurements reveal a marked increase in *CO_atop intermediates under PA conditions, in line with DFT predictions that weakly bound *CO_atop facilitates C–C coupling. Leveraging these mechanistic insights, we developed a double-stage pulse method that strategically amplifies current spikes and is compatible with a gas diffusion electrode (GDE) system. This method achieves a striking 9.36-fold increase in C₂₊/C₁ selectivity at an industrially relevant current density of 450 mA cm^–2. Our findings uncover a previously overlooked yet critical parameter in pulsed electrolysis, and by leveraging this insight, we establish a powerful and scalable method to significantly enhance CO₂-to-C₂₊ conversion for practical applications.