Electrodeposited Copper Nanocatalysts for CO2 Electroreduction: Effect of Electrodeposition Conditions on Catalysts’ Morphology and Selectivity

Abstract

Catalytic electroreduction of carbon dioxide represents a promising technology both to reduce CO2 emissions and to store electrical energy from discontinuous sources. In this work, electrochemical deposition of copper on to a gas-diffusion support was tested as a scalable and versatile nanosynthesis technique for the production of catalytic electrodes for CO2 electroreduction. The effect of deposition current density and additives (DAT, DTAB, PEG) on the catalysts’ structure was evaluated. The selectivity of the synthesized catalysts towards the production of CO was evaluated by analyzing the gaseous products obtained using the catalysts as cathodes in electroreduction tests. Catalyst morphology was deeply influenced by the deposition additives. Copper nanospheres, hemispherical microaggregates of nanowires, and shapeless structures were electrodeposited in the presence of dodecyltrimethylammonium bromide (DTAB), 3,5-diamino-1,2,4-triazole (DAT) and polyethylene glycol (PEG), respectively. The effect of the deposition current density on catalyst morphology was also observed and it was found to be additive-specific. DTAB nanostructured electrodes showed the highest selectivity towards CO production, probably attributable to a higher specific surface area. EDX and XPS analysis disclosed the presence of residual DAT and DTAB uniformly distributed onto the catalysts structure. No significant effects of electrodeposition current density and Cu(I)/Cu(II) ratio on the selectivity towards CO were found. In particular, DTAB and DAT electrodes yielded comparable selectivity, although they were characterized by the highest and lowest Cu(I)/Cu(II) ratio, respectively.

Tuning the Selectivity of Electrocatalytic CO2 Reduction Reaction via Anion-driven Nanostructuring of Copper Electrodeposits

“…Electrodeposition is one such simple and effective synthesis method with reasonable control over the physicochemical properties of Cu nano-electrocatalysts for desired applications. 13,19 The properties of the electrodeposits are tuneable with the constituents of the electrolytic bath, 20 precursors concentration, 21 applied current, 22 and deposition time. 23 Several researchers have electro-synthesized well-defined Cunanoarchitectures and have studied the effect of electrodeposition parameters on the physicochemical properties (morphology, composition, and crystal facets) and ECR activity of Cu-electrodeposits.…”

“…23 Several researchers have electro-synthesized well-defined Cunanoarchitectures and have studied the effect of electrodeposition parameters on the physicochemical properties (morphology, composition, and crystal facets) and ECR activity of Cu-electrodeposits. 19,22,24 Cook et al noted the profound impact of supporting electrolytes used for CO 2 electrolysis on the ECR activity of the in situ electrodeposited Cu-nanostructures from CuSO 4 solution. 25 The nature of anions in the supporting electrolyte (catholyte for ECR) has also been reported to influence the ECR product distribution.…”