Synergistic Effect of Cu₂O Mesh Pattern on High‐Facet Cu Surface for Selective CO₂ Electroreduction to Ethanol

Abstract

Although the electroconversion of carbon dioxide (CO2) into ethanol is considered to be one of the most promising ways of using CO2, the ethanol selectivity is less than 50% because of difficulties in designing an optimal catalyst that arise from the complicated pathways for the electroreduction of CO2 to ethanol. Several approaches including the fabrication of oxide‐derived structures, atomic surface control, and the Cu+/Cu interfaces have been primarily used to produce ethanol from CO2. Here, a combined structure with Cu+ and high‐facets as electrocatalysts is constructed by creating high‐facets of wrinkled Cu surrounded by Cu2O mesh patterns. Using chemical vapor deposition graphene growth procedures, the insufficiently grown graphene is used as an oxidation‐masking material, and the high‐facet wrinkled Cu is simultaneously generated during the graphene growth synthesis. The resulting electrocatalyst shows an ethanol selectivity of 43% at −0.8 V versus reversible hydrogen electrode, which is one of the highest ethanol selectivity values reported thus far. This is attributed to the role of Cu+ in enhancing CO binding strength, and the high‐facets, which favor C–C coupling and the ethanol pathway. This method for generating the combined structure can be widely applicable not only for electrochemical catalysts but also in various fields.

Insight Into Heterogeneous Electrocatalyst Design Understanding for the Reduction of Carbon Dioxide

“…Sub-2 nm SnO 2 QWs H-type 0.1 m KHCO 3 −1.156 V@13.7 mA cm −2 FE (HCOO − ) > 80% (−1.21 V) 25 000 s@−0.956 V [26] LiET-Zn H-type 0.1 m KHCO 3 −0.948 V@23 mA cm −2 FE (CO) = 91.1% (−1.17 V) 4 h@−1.17 V [28] CN-H-CNT H-type 0.1 m KHCO 3 N/A FE (CO) = 88% (−0.5 V) 24 000 s@−0.5 V [30] Single-atom Sn δ+ on N-doped graphene H-type 0.25 m KHCO 3 −1.6 V@11.7 mA cm −2 FE (CO) = 74.3% (−1.6 V vs SCE) 200 h@−1.6 V vs SCE [33] Ni SAs/N-C H-type 0.5 m KHCO 3 −0.89 V@10.48 mA cm −2 FE (CO) = 71.9% (−0.89 V) 60 h@−1.0 V [47] CuSAs/TCNFs H-type 0.1 m KHCO 3 −0.9 V@93 mA cm −2 FE (HCH 3 OH) = 44% (−0.9 V vs SCE) 50 h@−93 mA cm −2 [49] Branched CuO NPs H-type 0.5 m KHCO 3 N/A FE (C 2 H 4 ) > 70% (−1.05 V) 12 h@-24 mA cm −2 [75] Graphite/carbon NPs/ Cu/PTFE Flow cell 10 m KHCO 3 −0.67 V@473 mA cm −2 FE (C 2 H 4 ) = 70% (−0.55 V) 150 h@−0.55 V [77] Reconstructed Cu H-type 0.05 m KHCO 3 −1.8 to −2.0 V@17 mA cm −2 FE (C 2+ ) = 73% (−2.0 V) N/A [80] Flow cell 3 m KHCO 3 −0.68 V@336 mA cm −2 FE (C 2+ ) > 84% (−2.0 V) H-CPs H-type 0.5 m KHCO 3 −0.68 V@336 mA cm −2 FE (CO) > 90% (−0.7 to −1.2 V) 40 h@−1.0 V [93] O2P2 H-type 0.1 m CsHCO 3 −1.0 V@45.5 mA cm −2 FE (C 2+ ) ≈ 69% (−1.0 V) 7 h@−1.0 V [96] NiSA/PCFM Flow cell 0.5 m KHCO 3 −1.0 V@308.4 mA cm −2 FE (CO) ≈ 88% (−1.0 V) 120 h@−1.0 V [99] Pd NPs H-type 0.1 m KHCO 3 −0.89 V@23.9 A g Pd FE (HCOO − ) = 64% (−0.89 V) N/A [116] Au NWs H-type 0.5 m KHCO 3 −0.35 V@1.84 A g Au FE (CO) = 94% (−0.35 V) 6 h@−0.35 V [117] Au 25 H-type 0.1 m KHCO 3 −0.35 V@1.84 A g Au FE (CO) ≈ 100% (−1.0 V) N/A [118] Cu cubes H-type 0.1 m KHCO 3 N/A FE (C 2 H 4 ) = 41% (−1.1 V) N/A [119] ZnO-Ag@UC H-type 0.5 m KHCO 3 N/A FE (CO) ≈ 94.1% (−0.93 V) 150 h@−0.93 V [123] CuZn-Ni aerogel H-type 1.0 m KOH −1.0 V@145 mA cm −2 FE (CO) = 80% (−0.85 V) 5 h@−1.35 V [125] Cu nanocube H-type 0.1 m KHCO 3 N/A FE (C 2+ ) = 73% (−1.0 V) N/A [127] A-CuNWs H-type 0.1 m KHCO 3 −1.01 V@17.3 mA cm −2 FE (C 2 H 4 ) = 77.4% (−0.75 to −1.1 V) > 200 h@−0.93 V [131] Pd NP H-type 0.5 m KHCO 3 −0.2 V@22 mA cm −2 FE (HCOO − ) = 97% (−0.2 V) 350 min@−0.2 V [133] Tri-Ag-NPs H-type 0.1 m KHCO 3 −0.856 V@1.25 mA cm −2 FE (CO) = 96.8% (−0.85 V) 7 days@−0.856 V [134] Cu + /hf-Cu H-type 0.1 m KCl N/A FE (C 2+ ) ≈ 32% (−0.8 V) 5 h@−0.9 V [140] SnO x /AgO x H-type 0.1 m KHCO 3 N/A FE (CO) = 43% (−0.8 V) 20 h@−0.8 V [...…”

Structure‐Function Correlation and Dynamic Restructuring of Cu for Highly Efficient Electrochemical CO2 Conversion

“…For instance, ethanol is theoretically confirmed more thermodynamically favored on the Cu facet consisting of n(100) × m( 110), due to a lower energy barrier along the reaction way *COCHO + H + + e À !*CHOCHO. [40] To this end, Cu electrocatalysts having rich Cu(310) and ( 210) facets, such as Cu(OH) 2 /Cu [40] and wrinkled Cu film, [41,42] were rationally designed to achieve a higher ethanol production (Figure 5a,b). Notably, the synergistic interaction between Cu- (110) and Cu(100) played a key role.…”

Boosting electrocatalytic CO2–to–ethanol production via asymmetric C–C coupling

“…Clark et al hypothesized that the boosted EtOH selectivity results from Ag-induced strain effects of Cu surfaces that modulate EtOH production and suppresses the hydrogen evolution reaction (HER) 26 . Despite significant progress, the advances of reported bimetallic catalysts for FE of EtOH (FE EtOH ) remain limited, especially the production and output efficiency for EtOH is far from the current target for practical application 29 – 38 (i.e., partial current density > 300 mA cm −2 and half-cell cathodic energy efficiencies (EE HC ) > 20%). In addition, the key impact of modified components on intrinsic kinetics of reported Cu-based bimetallic catalysts for CO 2 RR at high conversion rates is unclear, which significantly hinders understanding of the mechanism and catalyst design 3 , 14 .…”