Simultaneous Hydrogen Production and Dye Decomposition in Alkaline Photocatalytic Process Using Calcined Xerogels of CuO-TiO2

Research on hydrogen (H₂) production has been intensively investigated due to the critical need for transitioning from fossil fuels to cleaner energy sources. This study demonstrates a dual-purpose approach where water pollutant degradation and H₂ production occur simultaneously, eliminating the need for sacrificial materials and reducing costs. CuO-TiO₂ calcined xerogels were employed in solutions containing NaOH and acid black dye 1 (AB1). The CuO-TiO₂/AB1/NaOH system successfully degraded recalcitrant pollutants while producing H₂ under optimized conditions. H₂ evolution occurred at the photocatalyst holes due to AB1's lower potential compared to water, while AB1 decomposition proceeded via O2^•- radical formation. X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analyses showed sponge-like structures with 20 nm crystals. Polarization curves confirmed H₂ generation in the cathodic region. Bode diagrams of the CuO-TiO₂/AB1/NaOH system (0.3 M NaOH and 60 mg/L AB1) exhibited noble/passive behavior, consistent with the polarization curve data. Using 0.3-0.4 M NaOH and 60 mg/L AB1, 636-647 ppb H₂/g_catalyst was produced in 60 min, and only 0.07 mg/L AB1 was left as indicated by absorbance measurements at 618 nm. H₂ evolution decreased as dye degradation increased. The best system for dye degradation has a k constant of 0.066 min^-1 and R² of 0.99, contains 40 mg/L AB1, and runs at 40 °C, whereas the maximum dual performance required 0.5 M NaOH, yielding 5050 ppb H₂/g_catalyst.