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Impact of pH on CuO/SnO2 nanomaterials synthesis in electrochemical reduction of CO2 to produce C1/C2 carboxylic acids
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Date
2025-08-01
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Abstract
The electrochemical reduction of carbon dioxide into value-added chemicals is a promising solution to mitigate greenhouse gas emissions while producing sustainable fuels. In this study, CuO/SnO2 nanomaterials (NM) were synthesized using the sol-gel technique under varying pH conditions in acidic and alkaline to investigate their impact on material properties and electrochemical performance for CO2 reduction. The synthesized CuO/SnO2 NM were characterized using XRD, TEM, SEM, XPS, and FTIR to analyze their morphology, crystallinity, and surface properties. Results revealed that CuO/SnO2 NM prepared in alkaline media exhibited superior homogeneity, stability, and reduced particle size compared to acidic conditions, as confirmed by surface analysis. Electrochemical studies conducted in a two-compartment cell with a Ni foam cathode coated with CuO/SnO2 (1:1) demonstrated higher activity and selectivity in alkaline-prepared NM. Specifically, the alkaline-synthesized nanomaterials achieved a Faradaic efficiency (FE) of 87% for the overall of formic acid and oxalic acid at -1.4 V in a 0.5 M KHCO3 electrolyte, producing a maximum formic acid concentration of 1186 mg/L after 3 h. In contrast, materials synthesized in acidic media displayed agglomeration and reduced stability, leading to lower FE and current efficiency. XPS analysis confirmed the partial reduction of Cu2+ to Cu+ in alkaline-prepared nanomaterials during CO2 electrochemical reduction, highlighting their enhanced catalytic activity and stability. The study highlights the critical role of pH in controlling the morphology and electronic properties of CuO/SnO2 nanomaterials synthesized via the sol-gel method. The enhanced CO2 reduction performance in alkaline-prepared nanomaterials is attributed to their higher surface area, uniform distribution, and improved electron transfer characteristics. This work provides a cost-effective strategy for fabricating efficient electrocatalysts for CO2 reduction, particularly targeting C1/C2 carboxylic acids production.