Balancing selectivity retention and catalyst restructuring in pulsed CO2 electroreduction on silver.

Pulsed electrochemical CO2 reduction has emerged as a strategy to extend electrolyzer lifetime by periodically interrupting reductive operation with short oxidative pulses. Here we investigate the effect of oxidative pulse potential, pulse frequency, and pulse duration on the selectivity and structural integrity of electrospun polymer-based silver gas diffusion electrodes over extended periods of operation. We show that the threshold potential for anodic dissolution of silver at 0.55 V vs. SHE defines an upper boundary for the pulse potential: pulses with a potential below this threshold enable periodic local acidification of the electrolyte in the vicinity of the catalyst promoting partial dissolution of (bi)carbonate precipitates, while pulses with a potential above the threshold drive a silver dissolution-redeposition cycle that restructures the catalyst into silver clusters promoting the hydrogen evolution reaction. Systematic exploration of the pulse parameter space identifies an optimal protocol consisting of 10-seconds-long oxidative pulses applied every 30 minutes, yielding a duty cycle exceeding 99%. Under these conditions, carbon product faradaic efficiency is maintained in the range of 70-80% over 100 hours of operation, representing a five-fold improvement in selectivity relative to continuous electrolysis. Our results demonstrate the potential of pulsed electrolysis to maintain high CO selectivity over long operational periods, thus representing an important step towards the industrialization of CO2 electrolysis.