Oxygen Vacancy-Rich Amorphous Copper Oxide Enables Highly Selective Electroreduction of Carbon Dioxide to Ethylene

Abstract

The ever-increasing carbon dioxide (CO2) emissions caused by excessive fossil fuel consumption induce environmental issues such as global warming. To overcome this, the electrocatalytic CO2 reduction (ECR) under ambient conditions offers an appealing approach for converting CO2 to value-added chemicals and realizing a closed carbon loop. Among the ECR products, ethylene (C2H4), an important building block for plastics and other chemicals, has attracted considerable attention owing to its compatibility with existing infrastructure and the promising substitution of industrial steam cracking. In recent years, numerous efforts have been devoted to developing highly active and selective catalysts for converting CO2 to C2H4, with most studies having focused on Cu-based materials. Despite the significant advancements made to date, the development of the ECR-to-C2H4 process is still hindered by the lack of suitable catalysts that can effectively activate CO2 and strengthen the surface binding of *CO and *COH species. In this study, an amorphous copper oxide (CuOx) nanofilm that is rich in oxygen vacancies was prepared via a facile vacuum evaporation method for the efficient electrocatalytic conversion of CO2 to C2H4. It was expected that the nano-scale electrode thickness would greatly accelerate charge-and mass-transfer during CO2 electrolysis. Moreover, the introduction of oxygen vacancies favored the adsorption of CO2 and intermediates. As a result, in a typical H-cell, the synthesized defective catalyst delivered a maximum Faradaic efficiency of 85 ± 3% at −1.3 V versus the reversible hydrogen electrode and maintained a stable C2H4 selectivity over 48 h in a 0.1 M potassium bicarbonate solution. Interestingly, the performance observed with the synthesized electrocatalyst in this study is comparable with that of state-of-the-art Cu-based ECR catalysts. Additional structural and chemical characterizations confirmed the robust nature of the as-prepared catalyst. Moreover, when the catalyst was utilized in a membrane electrode assembly cell, it achieved a maximum C2H4 partial current density of approximately 115.4 mA•cm 2 at a cell voltage of −1.95 V and Faradaic efficiency of 78 ± 2% at a cell voltage of −1.75 V. Furthermore, theoretical and experimental analyses revealed that oxygen defects not only favored CO2 adsorption but also enabled strong affinities for *CO and *COH intermediates, which synergistically contributed to a high selectivity for C2H4 formation. We believe that our present work will motivate the exploration of amorphous Cu-based materials for achieving efficient CO2-to-C2H4 electrolysis and be a guide towards fundamentally understanding the mechanism of catalytic CO2 reduction.

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Highly dispersed Ru clusters toward an efficient and durable hydrogen oxidation reaction

“…[1][2][3][4][5] Indeed, some transition metal-based materials have been proven to activate oxygen reduction comparable to the commercial Pt/C for the AEMFC cathode. [6][7][8][9] But, for the AEMFC anode, it should be noted that the hydrogen oxidation reaction (HOR) kinetic rate of Pt in alkaline media is about two to three orders of magnitude slower than that in acidic electrolyte, 10-12 which consequently requires much higher Pt loading. 13,14 Therefore, it is imperative to design Pt-free and efficient HOR catalysts under alkaline conditions to realize the implementation of AEMFCs.Since then, various strategies have emerged to develop highperformance HOR catalysts, such as engineering the crystalline phase, 14 tuning the composition of alloy particles, 15,16 designing a core-shell structure, 17-22 constructing a hierarchical structure, 23 and so on.…”

“…1–5 Indeed, some transition metal-based materials have been proven to activate oxygen reduction comparable to the commercial Pt/C for the AEMFC cathode. 6–9 But, for the AEMFC anode, it should be noted that the hydrogen oxidation reaction (HOR) kinetic rate of Pt in alkaline media is about two to three orders of magnitude slower than that in acidic electrolyte, 10–12 which consequently requires much higher Pt loading. 13,14 Therefore, it is imperative to design Pt-free and efficient HOR catalysts under alkaline conditions to realize the implementation of AEMFCs.…”