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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO₂ reduction.

ABSTRACT: Copper electrocatalysts have been shown to selectively reduce carbon dioxide to hydrocarbons. Nevertheless, the absence of a systematic study based on time-resolved spectroscopy renders the functional agent-either metallic or oxidative Copper-for the selectivity still undecidable. Herein, we develop an operando seconds-resolved X-ray absorption spectroscopy to uncover the chemical state evolution of working catalysts. An oxide-derived Copper electrocatalyst is employed as a model catalyst to offer scientific insights into the roles metal states serve in carbon dioxide reduction reaction (CO₂RR). Using a potential switching approach, the model catalyst can achieve a steady chemical state of half-Cu(0)-and-half-Cu(I) and selectively produce asymmetric C₂ products - C₂H₅OH. Furthermore, a theoretical analysis reveals that a surface composed of Cu-Cu(I) ensembles can have dual carbon monoxide molecules coupled asymmetrically, which potentially enhances the catalyst's CO₂RR product selectivity toward C₂ products. Our results offer understandings of the fundamental chemical states and insights to the establishment of selective CO₂RR.

SUBMITTER: Lin SC

PROVIDER: S-EPMC7360608 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO<sub>2</sub> reduction.

Lin Sheng-Chih SC Chang Chun-Chih CC Chiu Shih-Yun SY Pai Hsiao-Tien HT Liao Tzu-Yu TY Hsu Chia-Shuo CS Chiang Wei-Hung WH Tsai Ming-Kang MK Chen Hao Ming HM Chen Hao Ming HM

Nature communications 20200714 1

Copper electrocatalysts have been shown to selectively reduce carbon dioxide to hydrocarbons. Nevertheless, the absence of a systematic study based on time-resolved spectroscopy renders the functional agent-either metallic or oxidative Copper-for the selectivity still undecidable. Herein, we develop an operando seconds-resolved X-ray absorption spectroscopy to uncover the chemical state evolution of working catalysts. An oxide-derived Copper electrocatalyst is employed as a model catalyst to off ...[more]

PMID: 32665607

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Project description:Copper-based catalysts are established catalytic systems for the electrocatalytic CO2 reduction reaction (CO2RR), where the greenhouse gas CO2 is converted into valuable industrial chemicals, such as energy-dense C2+ products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions, is needed to expedite the economic viability of the CO2RR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for the CO2RR. Nevertheless, the synergy between copper and the selected secondary metal species, the evolution of the bimetallic structural motifs under working conditions and the effect of the secondary metal on the kinetics of the Cu redox behavior require careful investigation. Here, we employ operando quick X-ray absorption fine structure (QXAFS) spectroscopy coupled with machine-learning based data analysis and surface-enhanced Raman spectroscopy (SERS) to investigate the time-dependent chemical and structural changes in catalysts derived from shape-selected ZnO/Cu2O nanocubes under CO2RR conditions at current densities up to -500 mA cm-2. We furthermore relate the catalyst transformations observed under working conditions to the catalytic activity and selectivity and correlate potential-dependent surface and subsurface processes. We report that the addition of Zn to a Cu-based catalyst has a crucial impact on the kinetics of subsurface processes, while redox processes of the Cu surface layer remain largely unaffected. Interestingly, the presence of Zn was found to contribute to the stabilization of cationic Cu(i) species, which is of catalytic relevance since Cu(0)/Cu(i) interfaces have been reported to be beneficial for efficient electrocatalytic CO2 conversion to complex multicarbon products. At the same time, we attribute the increase of the C2+ product selectivity to the formation of Cu-rich CuZn alloys in samples with low Zn content, while Zn-rich alloy phases result in an increased formation of CO paralleled by an increase of the parasitic hydrogen evolution reaction.

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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO₂ reduction.

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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO<sub>2</sub> reduction.

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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO2 reduction.

Publications

Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO<sub>2</sub> reduction.

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OmicsDI is part of the ELIXIR infrastructure

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Operando time-resolved X-ray absorption spectroscopy reveals the chemical nature enabling highly selective CO₂ reduction.