High Surface Area Assemblies of Gold Nanoparticles on Hydrophilic Carbon Fiber Paper with Ionomer Overlayers for Aqueous CO2 Reduction Electrocatalysis to Clean Syngas

We report a universal approach for the utilization of nanoparticles on inexpensive, high surface area carbon substrates in aqueous applications. We immobilized gold nanoparticles from aqueous colloid on hydrophilic carbon fiber paper and assessed this electrode assembly in aqueous carbon dioxide reduction electrocatalysis. Uniform distributions of gold nanoparticles on carbon fibers and stable electrocatalytic current generation indicated that immobilization of gold nanoparticles on hydrophilic carbon fiber paper was successful. Surface analysis before and after electroreduction revealed that the detachment of citrate capping ligands enhanced the amount of exposed surface gold and concomitantly increased the CO-to-H 2 ratio in subsequent CO 2 reduction electrocatalysis. Systematic variations of ionomer overlayers controlled the ratio of produced CO and H 2 towards useful syngas compositions and revealed mechanistic insights into catalyst microenvironments, to enhance CO selectivity. Our results demonstrate that hydrophilic carbon fiber paper is an excellent high surface area electrode substrate for the utilization of nanoparticulate electrocatalysts in aqueous electrolyte.