Evaluating the Utility of Thin Film Electrocatalysts for Heterogeneous CO2 Reduction

Abstract

The success of various bimetallic thin film electrocatalysts for heterogeneous CO2 reduction motivates researching unexplored bimetallic catalysts as well as combinations of known catalysts. The effects of the solid support used encourages exploring known catalysts on new substrates. Various thin film catalysts were synthesized on glassy carbon, Ti, and Ta substrates. Their activity was evaluated through bulk electrolysis of CO2. SEM, EDX, and XRD were used to determine the morphology and composition of the thin films and substrates. Catalysts containing Zr and Zn species on glassy carbon promoted the reduction of CO2 to CO with Faradaic efficiencies as high as 20%, displaying moderate utility as CO2 electrocatalysts. Ni-Al 3:1 and Ga thin films juxtaposed on a single piece of glassy carbon did not produce CO2 reduction products with Faradaic efficiencies greater than 3%. These multiple catalyst electrodes (MCEs) were shown to be less effective than their single-catalyst counterparts. Ni-Al and Ni-Ga 3:1 thin films were synthesized on Ti and Ta substrates, but these catalysts proved to be much less active towards CO2 reduction than the same thin films on glassy carbon. It was also found that catalyst utility was affected by the glassy carbon’s level of usage, so IR measurements were performed to investigate structural changes in glassy carbon from usage effects.