Atividade e seletividade de eletrocatalisadores de Au para a eletrorredução de dióxido de carbono em eletrólito ácido de estado sólido
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Data
2025-04-01
Autores
Marconsini, Lília Togneri
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Universidade Federal do Espírito Santo
Resumo
Gold-based electrocatalysts are well known for their activity in the electrochemical reduction of CO2 (CO2RR) to CO in aqueous solution. However, under such experimental conditions, water electrolysis emerges as a competing reaction, reducing selectivity, and both size and dispersion of Au particles directly influence the catalytic performance of the electrodes. In this context, studies in the field of electrocatalysis have proposed gold-based electrocatalysts in gas diffusion electrodes (GDEs) towards mitigating mass transport limitations, enhancing CO2 solubility, and and suppressing the hydrogen evolution reaction (HER). Evidence has shown CO2RR in acidic media and in presence of alkali metal cations can inhibit the migration of undesirable species between the cell compartments and reduce carbonation. This study investigates CO2RR in H2SO4 and K2SO4 using Au-based electrocatalysts in GDEs. Such materials were synthesized via chemical reduction with NaBH4 and sputtering deposition. Structural and morphological characterization was performed by X-Ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X Ray Spectroscopy (EDX) and Transmission Electron Microscopy (TEM) for providing detailed information on the properties of the GDE componentes and electrochemical experiments were conducted in zero-gap cell, where CO2 was supplied from the rear side of the GDE directly at the interface between the cathode and the Nafion membrane. Finally, electrochemical mass spectrometry (EC-MS) and gas chromatography (GC) assessed product distribution and quantification. The results showed electrocatalyst performance is strongly influenced by morphology and Au-Citrate catalyst achieved higher faradaic efficiency (FE) for CO, reaching values above 90%. In contrast, Au-sputtering formed a dense and homogeneous film, resulting in a lower number of active sites (specifically fewer low-coordination Au atoms), hence, reduced FE (maximum of 57%) and increased HER competition. A TEM analysis revealed structural modifications in Au-Citrate nanoparticles after electrolysis experiments, suggesting a coalescence process that, while potentially reducing the active surface area, may also expose new catalytically active sites, thereby enhancing CO2RR efficiency
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Palavras-chave
Eletrorredução de CO2 , Meio ácido , Cátions de metais alcalinos , Célula zero-gap , Ouro , CO2 electroreduction , Acidic medium , Alkali metal cations , Zero-gap cell; , Gold