Superbase and Hydrophobic Ionic Liquid Confined within Ni Foams as a Free-Standing Catalyst for CO2 Electroreduction

Access to high-performance and cost-effective catalyst materials is one of the crucial preconditions for the industrial application of electrochemical CO2 reduction (ECR). In this work, a facile and simple strategy is proposed for the construction of a free-standing electrocatalyst via confining a superbase and hydrophobic ionic liquid (IL, [P-66614][triz]) into Ni foam pores, denoted as [P-66614][triz]@Ni foam. These ILs can modulate the surface of Ni foam and create a microenvironment with high CO2 concentration around the electrode/electrolyte interface, which successfully suppresses the hydrogen evolution reaction (HER) of Ni foam. Consequently, the synthesized [P-66614][triz]@Ni foam sample can obtain a CO product with 63% Faradaic efficiency from the ECR procedure, while no detectable CO can be found on pristine Ni foam. Owing to the superbase IL, the valency of Ni species retains Ni(I)/Ni(0) during electrolysis. Furthermore, the strikingly high CO2 capacity by [P-66614][Triz] (0.91 mol CO2 per mole of IL) offers a high CO2 local concentration in the reaction region. Theoretical calculations indicated that the neutral CO2 molecule turned to be negatively charged with -0.546 e and changed into a bent geometry, thus rendering CO2 activation and reduction in a low-energy pathway. This study provides a new method of electrode interface modification for the design of efficient ECR catalysts.