Particle Size Effects in the Catalytic Electroreduction of CO₂ on Cu Nanoparticles

Abstract

A study of particle size effects during the catalytic CO2 electroreduction on size-controlled Cu nanoparticles (NPs) is presented. Cu NP catalysts in the 2-15 nm mean size range were prepared, and their catalytic activity and selectivity during CO2 electroreduction were analyzed and compared to a bulk Cu electrode. A dramatic increase in the catalytic activity and selectivity for H2 and CO was observed with decreasing Cu particle size, in particular, for NPs below 5 nm. Hydrocarbon (methane and ethylene) selectivity was increasingly suppressed for nanoscale Cu surfaces. The size dependence of the surface atomic coordination of model spherical Cu particles was used to rationalize the experimental results. Changes in the population of low-coordinated surface sites and their stronger chemisorption were linked to surging H2 and CO selectivities, higher catalytic activity, and smaller hydrocarbon selectivity. The presented activity-selectivity-size relations provide novel insights in the CO2 electroreduction reaction on nanoscale surfaces. Our smallest nanoparticles (~2 nm) enter the ab initio computationally accessible size regime, and therefore, the results obtained lend themselves well to density functional theory (DFT) evaluation and reaction mechanism verification.

CO2 Reduction: From the Electrochemical to Photochemical Approach

“…Particle size dependence of b) current density and c) Faradaic efficiency for different CO 2 RR products on Cu NPs; d) population of surface atoms with certain coordination number (CN) as a function of particle diameter. Reproduced with permission 54. Copyright 2014, American Chemical Society.…”

“…Strasser and co‐workers discovered that Cu nanoparticles (NPs) exhibited dramatically enhanced total current density and higher selectivity toward CO and H 2 as their particle size was decreased, particularly for those under 5 nm, while hydrocarbon selectivity was increasingly suppressed (Figure 5b–d) 54. This experimental observation was rationalized by DFT calculations, which showed that smaller Cu NPs could provide more undercoordinated atoms as strong binding sites to key intermediates such as H and COOH, thus accelerating HER and the reduction of CO 2 to CO while decreasing further recombination reaction to hydrocarbons.…”

Enhanced Electrochemical Methanation of Carbon Dioxide with a Dispersible Nanoscale Copper Catalyst

“…This possibly explains why previous studies of dense films of copper nanoparticles have not observed enhanced methanation yields. (26)(27)(28) A systematic study of single-crystal electrodes for CO 2 reduction has put forth the possibility that the introduction of a particular step-edge present on a (210) single crystal can enhance methanation yields. (20) This suggests that more isolated nanoparticles expose catalytic sites that are more effective for methanation, which are lost as they fuse to form dense aggregates.…”

RETRACTED ARTICLE: An overview of CO2 electroreduction into hydrocarbons and liquid fuels on nanostructured copper catalysts

“…Nanostructured copper has been reported as an exclusive novel material for the electrochemical reduction of CO 2 into hydrocarbons with high Faraday efficiency and selectivity (33,34,42,(49)(50)(51)(52)(53). The onset potential for the reduction of CO 2 at porous copper foam was −1.0 V vs. Ag/AgCl with the formation of formic acid (HCOOH) initially ( Figure 1).…”

“…Their presented activity-selectivity-size relationships could provide novel insights into the CO 2 electroreduction reactions on nanoscale surfaces. Figure 3 describes the dependence of overall catalytic activity of CO 2 reduction on particle size at two different electrode potentials, E = −1.1 V/RHE and E = −1.0 V/RHE (51). The graphs compare the overall activity of bulk Cu and Cu NPs down to about 5 nm, after which a dramatic trend toward higher catalytic activity with smaller Cu NPs size becomes evident.…”