Photocatalytic hydrogen production from water-methanol and -glycerol mixtures using Pd/TiO2(-WO3) catalysts and validation in a solar pilot plant

• Published in: International journal of hydrogen energy 2021-10, Vol.46 (73), p.36152-36166
• Main Authors: Toledo-Camacho, S.Y., Rey, A., Maldonado, M.I., Llorca, J., Contreras, S., Medina, F.
• Format: Article
• Language: English
• Subjects: Hydrogen; Photocatalysis; Photodeposition; Quantum efficiency; Sacrificial agents
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.08.141

This paper is focused on the photocatalytic hydrogen production on Pd/TiO2(-WO3) catalysts from water-methanol and water-glycerol mixtures under UVA and solar irradiation. The photodeposition method for Pd was studied varying conditions such as Pd amount, catalyst concentration and methanol concentration. The catalysts were tested at lab scale under simulated solar light and UVA radiation and also at large scale (25 L) under solar energy using a pilot-scale solar Compound Parabolic Collector (CPC). The catalysts characterization was performed by means of ICP-OES, N2 adsorption–desorption isotherms, XRD, HR-TEM, XPS and DR–UV–Vis spectroscopy. Hydrogen evolution was monitored by on-line gas chromatography.From results it was found the Pd photodeposition method plays a key role to increase the hydrogen evolution, affecting parameters like the Pd amount deposited, the Pd nanoparticles size and dispersion. The highest quantum efficiency (ϕ) obtained in this study was 11.8% and 41.2% under simulated solar and UVA irradiation, respectively, using Pd(0.24 wt%)/P25 in an aqueous solution of methanol (50 vol%). In the pilot-scale solar CPC, for Pd(0.24 wt%)//P25 catalysts in 5 vol% of methanol or glycerol as sacrificial agents, the quantum yield were 2.1 and 2.2%, respectively. When the concentration of the sacrificial agents decreased to 0.37 vol%, the quantum yields were 1.3 and 2.4% for methanol and glycerol, respectively. Compared to literature, the low noble metal content of these catalysts (0.25 wt%) seems to be a competitive factor considering their high price. •Efficient catalysts for H2 generation under solar radiation obtained by Pd photodeposition over TiO2 and WO3 supports.•Pd photodeposition method plays a key role in the hydrogen evolution, affecting parameters such as the nanoparticles size.•Low H2 evolution with municipal wastewater demonstrates the challenges to overcome the photocatalytic H2 generation.