Visible-light-driven methanol photo-reforming over cobalt oxides nanofibers: Insights into synthesis, bandgap engineering, and catalytic efficiency

Photocatalytic methanol photo-reforming stands as a promising avenue for sustainable hydrogen production, with potential applications in clean energy generation. In this study, we investigate the utilization of CoO/Co₃O₄ nanofibers as a photocatalyst for methanol photo-reforming, evaluating its performance under different reaction conditions. The synthesized nanofibers are employed with both pure methanol and methanol/water mixtures and compared against TiO₂ nanoparticles for reference. Gas evolution rates and composition are analyzed to elucidate the catalytic behavior of the nanofibers. Results reveal that the CoO/Co₃O₄ nanofibers exhibit superior catalytic activity, yielding high gas evolution rates with pure methanol; 600 mmol/g_cat·s. However, the addition of water leads to a sharp decrease in gas production rate (66.9 mmol/g_cat.s), attributed to competitive water adsorption on the catalyst surface and drastic change in the reaction kinetics. Gas analysis demonstrates the predominant production of carbon monoxide and hydrogen with pure methanol, while carbon dioxide is detected in the presence of water. In contrast, TiO₂ nanoparticles primarily yield carbon dioxide and hydrogen, with no carbon monoxide detected. These findings provide valuable insights into the catalytic mechanisms and selectivity of nanofiber-based catalysts for methanol photo-reforming, paving the way for the development of efficient and selective photocatalytic systems for sustainable energy production.