Electrochemical Fragmentation of Cu₂O Nanoparticles Enhancing Selective C–C Coupling from CO₂ Reduction Reaction

Abstract

In this study, we demonstrate that the initial morphology of nanoparticles can be transformed into small fragmented nanoparticles, which were densely contacted to each other, during electrochemical CO 2 reduction reaction (CO 2 RR). Cu-based nanoparticles were directly grown on a carbon support by using cysteamine immobilization agent, and the synthesized nanoparticle catalyst showed increasing activity during initial CO 2 RR, doubling Faradaic efficiency of C 2 H 4 production from 27% to 57.3%. The increased C 2 H 4 production activity was related to the morphological transformation over reaction time. Twenty nm cubic Cu 2 O crystalline particles gradually experienced in situ electrochemical fragmentation into 2−4 nm small particles under the negative potential, and the fragmentation was found to be initiated from the surface of the nanocrystal. Compared to Cu@CuO nanoparticle/C or bulk Cu foil, the fragmented Cu-based NP/C catalyst achieved enhanced C 2+ production selectivity, accounting 87% of the total CO 2 RR products, and suppressed H 2 production. In-situ X-ray absorption near edge structure studies showed metallic Cu 0 state was observed under CO 2 RR, but the fragmented nanoparticles were more readily reoxidized at open circuit potential inside of the electrolyte, allowing labile Cu states. The unique morphology, small nanoparticles stacked upon on another, is proposed to promote C−C coupling reaction selectivity from CO 2 RR by suppressing HER.

Strategies in catalysts and electrolyzer design for electrochemical CO2reduction toward C2+products

“…In stark contrast, electrochemical CO 2 reduction using renewable energy provides a cleaner and more sustainable route. Great effort has been made to develop efficient electrocatalysts toward C 2+ hydrocarbons (32,33,(65)(66)(67)(68)(69)(70).…”

“…4E). To date, the active sites on copper have been identified as Cu 0 , Cu + , and/or their interface for ECR in different studies (39,41,42,81,82). However, what is the active site is still being debated.…”

Potential Link between Cu Surface and Selective CO2 Electroreduction: Perspective on Future Electrocatalyst Designs

“…Later, Jung et al performed CO 2 RR studies with shape‐controlled Cu 2 O nanoparticles, and monitored the transformation of the catalyst. [ 75 ] HRTEM analyses showed that the Cu 2 O NPs with an initial particle size of 20 nm were slowly fragmented into 2–4 nm sized particles after 10 h of continuous CO 2 RR, and the CO 2 RR activity is highly related with the morphological changes. HRTEM images of catalysts at different elapsed time of CO 2 RR show that Cu 2 O catalysts collapsed and were fragmented into smaller sizes with compact arrangement and deformed crystal plane, as shown in Figure 4h,i.…”

Strategies for Designing Nanoparticles for Electro‐ and Photocatalytic CO2 Reduction

“…[15b] The designo fC u-based catalysts for practical and efficient CO 2 RR is still an ongoing issue. Recent advances in artificial rereduction from polluting Cu surfaces, including CuO, [32] Cu 2 O, [29,33] Cu 2 (OH) 3 Cl, [15c] CuO Cl , [15a] and boron dopedC u [15b] showed excellent C 2 + selectivity.A pplying these techniquest o well-defined Cu nanostructures, combined with variouso xidants for polluting Cu surfaces would be ap otential option to enhanceC 2 selectivity.T he monitoring of electrochemical CO 2 RR is also essential. Cu + residues during the electrochemical CO 2 RR promote C 2 + production, and factors such as the density of defects, the types of dopants, and the surface morphologies are strongly correlated with the maintenance of Cu + species.H owever,t he precise state of Cu + species and the mechanism of CÀCc ouplingo nC u + surfaceh ave not been resolved yet.…”

“…The resulting catalyst showed al arge increaseo fe thylene Faradaic efficiency,u pt o5 4% after 6h at À1.1 V(vs. RHE). [33] Although the FEs for C 2 chemicals in electrochemical CO 2 RR were highlye nhanced by various types of catalyst design, the exact formation mechanism is still unclear.Ah igh local pH is one of the reasons for high Fes because it promotes the CÀC coupling reaction. However,a no verly-high pH condition hasa negative effect of reducing CO 2 solubility in electrolytes.…”