Unravelling the Chemistry of Catalyst Surface and Solvent towards C-C Bond Formation through Activation and Electrochemical Conversion of CO2 into Hydrocarbons over Micro-structured Dendritic Copper

Herein, we report the results from our study towards understanding the role of electrocatalyst surfaces and solvent (aqueous versus wet organic medium) on C-C bond formation over microstructrured spheres, polygons, aggregates and dendrites of copper, which is a crucial aspect for the selective and sustainable conversion of CO2 into high energy density hydrocarbons like ethylene. Our results establish that apart from morphology, the crystal orientations and characteristic electrode/electrolyte interfacial physico-chemical aspects significantly affect the electrochemical carbon dioxide reduction reaction (ECR) activity and selectivity of copper electrocatalysts. Moreover, we report that an appropriate combination of catalyst properties and solvent/electrode interface ensures selective electroreduction of CO2 into C1 and C2 hydrocarbons, especially ethylene, over dendritic copper electrocatalysts. It was found that given a particular solvent, the morphology was the sole determitant of the observed catalyst activity, wherea an elaborate dendritic shape enhanced the ECR reaction irrespective of the solvent used. A detailed account of the electrocatalytic performance, product selectivity, and Faradaic efficiency of Cu-electrodeposits for ECR in aqueous medium and wet-organic (DMSO) electrolyte is presented. In aqueous 0.2 M KHCO3 solution, the catalyst exhibit Faradaic efficiency of 43% for ethylene production at -1.0 V vs RHE and a selectivity of 74% among the total hydrocarbon products. Importantly, the Cu-based electrocatalysts fabricated for the present study inhibit parasitic hydrogen evolution reactions and production of parallel products viz. CO, CH4, C2H6 during the ECR. Our results further establish that C-C coupling for the formation of ethylene is affected by the nano-morphology of the electrocatalyst and the composition of the electrolyte system employed for the electroreduction.