Thin-film approach for scalability and enhancement of solar hydrogen production with CNT integrated Ce-doped-TiO2 composite in direct sunlight

Solar hydrogen production by photocatalysis has long been considered as an important energy option. Whichever photocatalyst succeeds, methods should be available to scale-up in a most sustainable and cost-effective manner, and the present work addresses this specific issue. In the present study, Ce-doped in the TiO 2 lattice (Ce-TiO 2 ) and the same integrated with CNT (CNT-Ce-TiO 2 ; (CCT)) composite was synthesized and characterized. Current study demonstrates the synergistic integration of Ce-TiO₂ as a light absorber and charge generator with CNTs as efficient charge separation at heterojunctions as well as charge transporter in a thin-film configuration (lab-scale (4.7 cm 2 ), bench-scale (500 cm 2 )). Improved H 2 generation under direct sunlight demonstrated in thin film form, than in particulate suspension, is attributed to efficient light absorption, particularly for electron-hole pair separation and their dispersion to redox sites. Additionally, the role of the binder is highlighted for improving H 2 yield and the sustainability of the thin-film form of photocatalyst. ∼200 mg (1 g) CCT coated over 500 cm 2 (2500 cm 2 ) photocatalyst produced 21.6 mmol/h (102 mmol/h) H 2 in sunlight. Present results provides a proof of concept that the thin film form of photocatalyst displays, at least 10 times, higher H 2 yield than its powder counterpart, depending on the measurement conditions. A non-linear enhancement in H 2 yield with small and large area thin-film indicates complex underlying factors and highlights the scope for further improvements.