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In this work, efficient NiO nanoparticles/TiO 2 nanorods p-n heterojunction structure photocatalyst is constructed by reasonable design of two-step calcination technology and examined for hydrogen production activity from methanol-water mixture. In the NiO/TiO 2 heterojunction structure small NiO nanoparticles are evenly distributed on the surface of TiO 2 and tightly connected together with TiO 2 , as it was determined by microscope characterization techniques, which conducive to the interface transport of photogenerated carriers. The novelty of this paper is the detailed characterization of NiO/TiO 2 photocatalysts by electrochemical technics as Transient photocurrent response, Mott-Schottky plots, linear sweep voltammograms and Electrochemical impedance spectroscopy and their correlation with photoactivity. The rationally designed NiO/TiO 2 p-n heterojunction promotes the transfer of photogenerated electrons and inhibits carrier recombination. The highest hydrogen production was exhibited in the presence of the 2-NiO/TiO 2 composite during 3 h of UV irradiation (701 μmol/g cat.), which exceeded the activity of pure TiO 2 by more than 1.3 times. The loss of photocatalytic hydrogen yield is negligible after repeating cycle reactions. Finally, a possible p-n heterojunction photocatalytic reduction mechanism has been discussed and apparent quantum yield was calculated. [Display omitted] • NiO nanoparticles/TiO 2 nanorods p-n heterojunction photocatalyst was constructed. • NiO/TiO 2 exhibited higher photoactivity for H 2 production in comparison with TiO 2. • Correlation of photoelectrochemical measurements with photoactivity of NiO/TiO 2. • NiO/TiO 2 p-n heterojunction inhibits carrier recombination. • Apparent Quantum Yields were calculated. [ABSTRACT FROM AUTHOR]

In this study, we investigated different synthesis methods (template-free and template-based) using copolymers of poly(ethylene oxide) and poly(propylene oxide) to enhance the CO 2 reduction activity of mesoporous TiO 2. Our main goal was to identify key factors affecting photocatalyst efficiency and selectivity. We compared the newly synthesized TiO 2 photocatalysts with the commercial photocatalyst P25. Among the materials studied, TiO 2 -P123 in its pure anatase form demonstrated the highest photoreduction efficiency and CO 2 selectivity. In contrast, TiO 2 -EG, TiO 2 -F127, and P25, which contained both rutile and anatase phases, exhibited decreased photoactivity due to the formation of a type II heterojunction between the phases and higher oxygen adsorption on rutile's surface. Additionally, we observed that the choice of chemicals for photocatalyst preparation significantly influenced the specific surface area. TiO 2 -P123, the most active photocatalyst, had the highest specific surface area, providing more reactive sites for improved light absorption efficiency and prolonged electron-hole pair lifetimes, resulting in enhanced photocatalytic activity. We also calculated apparent quantum yields to support our findings. [ABSTRACT FROM AUTHOR]