Sketch representing that the remaining sol gel adsorbate (ethanol) showed pronounced effects on catalytic evaluation under controlled environment and offered electrons for the reprecipitation of leached copper.

Abstract

This study examines how synthesis routes and storage conditions affect the reliability of photocatalytic data for SnO₂/Cu catalysts. Our findings show that nanoparticle stability and photocatalytic performance are significantly influenced by adsorbed ethanol from synthesis—a factor often overlooked in soft-chemistry methods. Ethanol adsorbates show strong stability, resisting standard removal techniques, and directly affecting photocatalytic results. Over two weeks, these adsorbates persisted under controlled storage, particularly in samples with higher copper content, highlighting strong copper-ethanol interactions. Post-reaction analysis also revealed copper phase transitions during photocatalytic CO₂ reduction (CO₂RR). In uncontrolled storage, Cu⁰ oxidizes to CuO; however, photocatalysis promotes a shift to Cu₂O, driven by ethanol oxidation. Furthermore, leached copper reduction on SnO₂ in water suggests a potential light-induced synthesis route for Cu-based wide band gap semiconductors and supports Cu redox cycling on the catalyst. These results confirm that adsorbed ethanol acts as an electron donor, actively participating in the photocatalytic process. This study emphasizes the importance of accounting for synthesis-derived adsorbates to ensure accurate and reliable photocatalytic data.