Pyrolyzing soft template-containing poly(ionic liquid) into hierarchical N-doped porous carbon for electroreduction of carbon dioxide

Abstract

• Soft template-containing poly(ionic liquid) was pyrolyzed to N-doped carbon. • Porosity and N species were modulated by controlling pyrolysis temperatures. • The resultant carbon featured hierarchically small-/ultra-microporous structure. • High-proportioned surface Grap-N species served as the major active sites. • Hierarchical small-/ultra-micropores accounted for the electrocatalysis activity. Heteroatom-doped carbon materials have demonstrated great potential in the electrochemical reduction reaction of CO 2 (CO 2 RR) due to their versatile structure and function. However, rational structure control remains one challenge. In this work, we reported a unique carbon precursor of soft template-containing porous poly(ionic liquid) (PIL) that was directly synthesized via free-radical self-polymerization of ionic liquid monomer in a soft template route. Variation of the carbonization temperature in a direct pyrolysis process without any additive yielded a series of carbon materials with facile adjustable textural properties and N species. Significantly, the integration of soft-template in the PIL precursor led to the formation of hierarchical porous carbon material with a higher surface area and larger pore size than that from the template-free precursor. In CO 2 RR to CO, the champion catalyst gave a Faraday efficiency of 83.0% and a current density of 1.79 mA∙cm −2 at −0.9 V vs. reversible hydrogen electrode ( vs. RHE). The abundant graphite N species and hierarchical pore structure, especially the unique hierarchical small-/ultra-micropores were revealed to enable better CO 2 RR performance.