Guiding Electrochemical Carbon Dioxide Reduction toward Carbonyls Using Copper Silver Thin Films with Interphase Miscibility

Abstract

Steering the selectivity of Cu-based electrochemical CO 2 reduction (CO 2 R) catalysts toward targeted products will serve to improve the technoeconomic outlook of technologies based on this process. Using physical vapor deposition as a tool to overcome thermodynamic miscibility limitations, CuAg thin films with nonequilibrium Cu/Ag alloying were prepared for CO 2 R performance evaluation. In comparison to pure Cu, the CuAg thin films showed significantly higher activity and selectivity toward liquid carbonyl products, including acetaldehyde and acetate. Suppressed activity and selectivity toward hydrocarbons and the competing hydrogen evolution were also demonstrated on CuAg thin films, with a greater degree of suppression observed at increasing nominal Ag compositions. Compositional-dependent CO 2 R trends coupled with physical characterization and density functional theory suggest that significant miscibility of Ag into the Cu-rich phase of the catalyst underpinned the observed CO 2 R trends through tuning of adsorbate and reaction intermediate binding energies on the surface.

Rational Design of Ag‐Based Catalysts for the Electrochemical CO2 Reduction to CO: A Review

“…[122][123][124][125][126] Further studies demonstrated that the selectivity and activity of these bi-metallicA g-Cu electrocatalysts for the ECR to CO were closely relatedt ot he atomic distributions and ratios of Ag and Cu. [121,126,128]…”

“…It was also reported that structure, morphology, size, and composition of the catalyst can lead to adsorption and decoupling site preferences of different adsorbates of C bound on the surface and further result in the breaking of the linear scaling relationships and tuning of the adsorption strength, eventually exerting a dramatic influence on the ECR performance . Indeed, in addition to polycrystalline and single‐crystalline Ag, some new A types have been developed and characterized recently, such as nanostructured Ag with different sizes, supported Ag catalysts with different substrates including C, TiO 2 , Al 2 O 3 , dopant‐aided Ag, oxide‐derived Ag, and surface‐modified Ag …”

“…Interestingly, although CO is the predominant reaction product for Ag–Cu in the selective ECR, which is derived mainly from synergistic reactions rather than pure dilution effects between Ag and Cu, it should be noted that Cu and Cu‐based catalysts including Ag–Cu also have the potential to convert CO 2 to various hydrocarbons such as C 2 H 6 , CH 4 , or/and oxygenates such as C 2 H 5 OH, CH 3 OH, HCHO . Further studies demonstrated that the selectivity and activity of these bimetallic Ag–Cu electrocatalysts for the ECR to CO were closely related to the atomic distributions and ratios of Ag and Cu …”

“…[69,76] It was also reported that structure, morphology,s ize, and compositionoft he catalystcan lead to adsorption and decoupling site preferences of different adsorbates of Cb ound on the surfacea nd further result in the breakingo ft he linear scaling relationships and tuning of the adsorption strength, eventually exertingadramatici nfluence on the ECR performance. [69,77,78] Indeed, in addition to polycrystalline and single-crystalline Ag, some new At ypes have been developed and characterized recently,s uch as nanostructured Ag with different sizes, [79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94] supported Ag catalysts with different substrates including C, TiO 2 ,A l 2 O 3 , [95][96][97] dopant-aided Ag, [98-120, 129, 130] oxide-derived Ag, [121][122][123][124][125][126][127][128] and surface-modified Ag. [131][132][133][134] In principle, the reduction of NP size can enhancet he surface reactivity of nanomaterials by either directly affecting the atomic arrangement, such as ratio of the atoms at the edge, corner, or surface, or amplifying the effects of other structural factors such as defects, resulting in the tuning of BEs of intermediates and transition states on catalyst surfaces.…”

Selective reduction of CO to acetaldehyde with CuAg electrocatalysts

“…In this work, we leveraged insights from the aforementioned strategies that control the intrinsic and extrinsic properties of electrocatalytic systems, with the aim of steering the selectivity of COR toward a single C 2+ oxygenate. To modify the intrinsic electrocatalytic properties of Cu electrodes, we implemented an Ag galvanic exchange process as previous research indicated that CuAg bimetallic electrocatalysts enhance selectivity toward C 2+ oxygenates by suppressing the competing hydrogen evolution reaction (HER) (22,28). In addition, alkaline pH conditions were used for COR based on previous studies that show the energy efficiency and selectivity to C 2+ oxygenates can be improved by governing this extrinsic property around the electrocatalyst (11,51,52).…”