Regulating the oxidation state of nanomaterials for electrocatalytic CO2 reduction

Wu, Zhe; Gao, Fei‐Yue; Gao, Min‐Rui

doi:10.1039/d0ee02747b

“…The oxidation state in pure Cu catalysts during CO2ER electrolysis has been widely investigated and remains a topic of debate. 48 Some studies have found evidence of persistence of surface or subsurface oxide 37,38,49,50 while our after chronopotentiometry activation at -2 mA cm -2 up to -0.5 V, after 2 h CO2ER electrolysis at -0.7 V and -0.9 V, and after exposure to air. Spectra are presented with a vertical offset to facilitate comparison.…”

Section: Quasi In Situ Xpsmentioning

confidence: 84%

Tracking Structure and Composition Changes in Oxide Derived Cu-Sn Catalysts During CO2 Electroreduction Using X-Ray Spectroscopy

L¹,

Arndt²,

Stojkovikj³

et al. 2021

Preprint

0

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<div> In the field of electrochemical CO2 conversion, the development of earth-abundant catalysts which are selective for a single product is a central challenge. Cu-Sn bimetallic catalysts have been reported to yield selective CO2 reduction towards either carbon monoxide or formate. To advance the understanding of possible synergetic effects between Cu and Sn which direct product selectivity, a thorough investigation of the catalyst structure and composition in its active state is desired. We present an X-ray spectroscopy investigation of oxide-derived Cu-Sn catalysts prepared by functionalization of Cu(OH)2 nanowire arrays with ultrathin SnO2 overlayers. This method allows precisely tunable Sn composition, which enables synthesis of composite catalysts with high selectivity toward either CO or formate. Under CO2 reduction conditions, the materials undergo significant transformations before reaching their catalytically active forms. Complementary information on the electrocatalysts’ dynamic bulk and surface structure was revealed via correlating observations from multiple X-ray spectroscopy methods. In situ investigations of Cu K-edge revealed that in the bulk Cu is fully reduced from Cu2+ to Cu° after a pre reduction step. Quasi in situ XPS demonstrated that, at the catalyst surface, Cu is also present exclusively as Cu°, whereas significant differences in Sn quantification and speciation were observed between the CO- and formate-selective catalysts. After CO<a>2</a> electrolysis, CO-selective catalysts exhibited a surface Sn content of 13 at. % predominantly present as Sn oxide, while the formate-selective catalysts had a Sn content of ~70 at. % consisting of both metallic Sn° and Sn oxide species. Our study reveals the complex dependence of catalyst structure, composition, and speciation with applied electrochemical bias in Sn-functionalized nanostructured Cu catalysts.</div>

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“…Furthermore, Bader charge analysis suggests that Ni and Cu atoms transfers 0.49 e − and 0.37 e − electronic charge respectively, which is lower than that of Co atoms (0.80 e − ). Thus, in these complexes, Cobalt atom acquires more positive charge leading to more unoccupied 3d orbitals which in turn enhances the adsorption and thus reduction of CO molecule [27] …”

Section: Resultsmentioning

confidence: 99%

A Highly Efficient Conjoined‐twin Porphyrin‐based Complex for the Electrochemical Reduction of CO to Ethanol

Kour

¹

,

Du

²

2021

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Electrochemical conversion of carbon monoxide, a major one‐carbon product of carbon dioxide reduction, into high‐value multi‐carbon products is one of the promising strategies to address the overall energy demands and climate change. A lot of efforts have been devoted to the exploration of highly efficient catalysts for the formation of single carbon products. However, further reduction to more reduced products is hampered by high energy barriers for C−C bond formation and low selectivity of the products. Herein, the potential of homo‐bimetallic and hetero‐bimetallic complexes of previously established expanded twin porphyrin (H4L) ligand, also known as conjoined‐twin porphyrin (CTP) ligand, towards the reduction of CO to valued commodity chemicals is systematically investigated by using density functional theory (DFT) computations. In these complexes, the presence of two metal atoms in the N4 pockets enhances the chances of coupling of two adsorbed CO molecules, thus facilitating the formation of C−C bond formation. The results reveal that both the dicobalt and cobalt nickel complex of conjoined‐twin porphyrin ligand show high activity and selectivity towards the conversion of CO to ethanol with a limiting potential of only −0.59 V and −0.61 V, respectively. The narrow band gap and shallower d band centre could be attributed to the potential cause for the enhanced activity of Co containing complexes. Moreover, these complexes displayed high thermal stability, thus acts as potential candidates for experimental exploration. Our results offer a promising alternative to traditional Cu‐based electrocatalysts for the formation of C2 products.

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“…The oxidation state in pure Cu catalysts during CO2ER electrolysis has been widely investigated and remains a topic of debate. 48 Some studies have found evidence of persistence of surface or subsurface oxide 37,38,49,50 while our after chronopotentiometry activation at -2 mA cm -2 up to -0.5 V, after 2 h CO2ER electrolysis at -0.7 V and -0.9 V, and after exposure to air. Spectra are presented with a vertical offset to facilitate comparison.…”

Section: Quasi In Situ Xpsmentioning

confidence: 90%

Tracking Structure and Composition Changes in Oxide Derived Cu-Sn Catalysts During CO2 Electroreduction Using X-Ray Spectroscopy

Pérez¹,

Arndt²,

Stojkovikj³

et al. 2021

Preprint

0

View full text Add to dashboard Cite

<div> In the field of electrochemical CO2 conversion, the development of earth-abundant catalysts which are selective for a single product is a central challenge. Cu-Sn bimetallic catalysts have been reported to yield selective CO2 reduction towards either carbon monoxide or formate. To advance the understanding of possible synergetic effects between Cu and Sn which direct product selectivity, a thorough investigation of the catalyst structure and composition in its active state is desired. We present an X-ray spectroscopy investigation of oxide-derived Cu-Sn catalysts prepared by functionalization of Cu(OH)2 nanowire arrays with ultrathin SnO2 overlayers. This method allows precisely tunable Sn composition, which enables synthesis of composite catalysts with high selectivity toward either CO or formate. Under CO2 reduction conditions, the materials undergo significant transformations before reaching their catalytically active forms. Complementary information on the electrocatalysts’ dynamic bulk and surface structure was revealed via correlating observations from multiple X-ray spectroscopy methods. In situ investigations of Cu K-edge revealed that in the bulk Cu is fully reduced from Cu2+ to Cu° after a pre reduction step. Quasi in situ XPS demonstrated that, at the catalyst surface, Cu is also present exclusively as Cu°, whereas significant differences in Sn quantification and speciation were observed between the CO- and formate-selective catalysts. After CO<a>2</a> electrolysis, CO-selective catalysts exhibited a surface Sn content of 13 at. % predominantly present as Sn oxide, while the formate-selective catalysts had a Sn content of ~70 at. % consisting of both metallic Sn° and Sn oxide species. Our study reveals the complex dependence of catalyst structure, composition, and speciation with applied electrochemical bias in Sn-functionalized nanostructured Cu catalysts.</div>

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Regulating the oxidation state of nanomaterials for electrocatalytic CO₂ reduction

Abstract: The electrochemical carbon dioxide reduction reaction (CO2RR) converts CO2 into value-added chemicals and fuels to realize the carbon recycling is a means to solve the problem of renewable energy shortage...

Cited by 200 publications

References 92 publications

Tracking Structure and Composition Changes in Oxide Derived Cu-Sn Catalysts During CO2 Electroreduction Using X-Ray Spectroscopy

Tracking Structure and Composition Changes in Oxide Derived Cu-Sn Catalysts During CO2 Electroreduction Using X-Ray Spectroscopy

A Highly Efficient Conjoined‐twin Porphyrin‐based Complex for the Electrochemical Reduction of CO to Ethanol

Tracking Structure and Composition Changes in Oxide Derived Cu-Sn Catalysts During CO2 Electroreduction Using X-Ray Spectroscopy

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