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Tuning the activity and selectivity of electroreduction of CO₂ to synthesis gas using bimetallic catalysts.

ABSTRACT: The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H₂ ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption strength of *H than *HOCO, with the free energies between these two key intermediates (i.e., ?G(*H)-?G(*HOCO)) correlating well with the carbon dioxide reduction reaction activity and selectivity observed in the experiments, and thus can be used as a descriptor to search for other bimetallic catalysts. The results also demonstrate the possibility of alloying Pd with non-precious transition metals to promote the electrochemical conversion of CO₂ to syngas.

SUBMITTER: Lee JH

PROVIDER: S-EPMC6700200 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Tuning the activity and selectivity of electroreduction of CO<sub>2</sub> to synthesis gas using bimetallic catalysts.

Lee Ji Hoon JH Kattel Shyam S Jiang Zhao Z Xie Zhenhua Z Yao Siyu S Tackett Brian M BM Xu Wenqian W Marinkovic Nebojsa S NS Chen Jingguang G JG

Nature communications 20190819 1

The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H<sub>2</sub> ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption stren ...[more]

PMID: 31427576

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Project description:Among metals used for CO2 electroreduction in water, Cu appears to be unique in its ability to produce C2+ products like ethylene. Bimetallic combinations of Cu with other metals have been investigated with the goal of steering selectivity via creating a tandem pathway through the CO intermediate or by changing the surface electronic structure. Here, we demonstrate a facile cation exchange method to synthesize Ag/Cu electrocatalysts for CO2 reduction using Cu sulfides as a growth template. Beginning with Cu2-x S nanosheets (C-nano-0, 100 nm lateral dimension, 14 nm thick), varying the Ag+ concentration in the exchange solution produces a gradual change in crystal structure from Cu7S4 to Ag2S, as the Ag/Cu mass ratio varies from 0.3 to 25 (CA-nano-x, x indicating increasing Ag fraction). After cation exchange, the nanosheet morphology remains but with increased shape distortion as the Ag fraction is increased. Interestingly, the control (C-nano-0) and cation exchanged nanosheets have very high faradaic efficiency for producing formate at low overpotential (-0.2 V vs. RHE). The primary effect of Ag incorporation is increased production of C2+ products at -1.0 V vs. RHE compared with C-nano-0, which primarily produces formate. Cation exchange can also be used to modify the surface of Cu foils. A two-step electro-oxidation/sulfurization process was used to form Cu sulfides on Cu foil (C-foil-x) to a depth of a few 10 s of microns. With lower Ag+ concentrations, cation exchange produces uniformly dispersed Ag; however, at higher concentrations, Ag particles nucleate on the surface. During CO2 electroreduction testing, the product distribution for Ag/Cu sulfides on Cu foil (CA-foil-x-y) changes in time with an initial increase in ethylene and methane production followed by a decrease as more H2 is produced. The catalysts undergo a morphology evolution towards a nest-like structure which could be responsible for the change in selectivity. For cation-exchanged nanosheets (CA-nano-x), pre-reduction at negative potentials increases the CO2 reduction selectivity compared to tests of as-synthesized material, although this led to the aggregation of nanosheets into filaments. Both types of bimetallic catalysts are capable of selective reduction of CO2 to multi-carbon products, although the optimal configurations appear to be metastable.

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Tuning the activity and selectivity of electroreduction of CO₂ to synthesis gas using bimetallic catalysts.

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Tuning the activity and selectivity of electroreduction of CO<sub>2</sub> to synthesis gas using bimetallic catalysts.

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Tuning the activity and selectivity of electroreduction of CO2 to synthesis gas using bimetallic catalysts.

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Tuning the activity and selectivity of electroreduction of CO<sub>2</sub> to synthesis gas using bimetallic catalysts.

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OmicsDI is part of the ELIXIR infrastructure

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Tuning the activity and selectivity of electroreduction of CO₂ to synthesis gas using bimetallic catalysts.