Constructing a Dynamic Interface via Thermoresponsive Polymers to Promote CO2 Electroreduction in a Strongly Acidic Electrolyte

Abstract The electrochemical CO2 reduction (CO2RR) in acidic electrolytes enhances carbon utilization but suffers from a severe competing hydrogen evolution reaction (HER). This study proposes, for the first time, a dynamic interface strategy for enhancing the CO2RR in an acidic electrolyte. Specifically, a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), is grafted onto an Au cathode via stable Au–S bonds. Above its lower critical solution temperature (LCST), PNIPAM chains collapse into a compact molecular modification layer, which creates a hydrophobic layer on the Au surface and significantly suppresses HER. Below the LCST, the stretched PNIPAM chains can ensure sufficient mass transport channels for both inward CO2 diffusion to Au active sites and outward CO diffusion to the electrolyte. By applying temperature pulses during electrolysis, the dynamic interface can balance the suppression of HER and the maintenance of mass transfer channels. Consequently, this dynamic system achieves a high Faradaic efficiency of 96.3% for CO in a strongly acidic electrolyte (pH = 1) with exceptional stability for over 210 h. In situ spectroscopic and theoretical studies further confirm the advantage of the dynamic interface compared with a static interface. This work pioneers a dynamic interface strategy for acidic CO2RR, offering valuable insights for other electrocatalytic systems.