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[Display omitted] • The size of MTN were simply controlled. • Monodispersed Ag/bMTN were prepared by a novel in situ method. • PDA/Ag/bMTN exhibited narrowed bandgap and enhanced visible light absorption. • Photocatalytic and antibacterial mechanisms of PDA/Ag/bMTN were suggested. Driven by clean solar energy, photocatalytic technology can effectively degrade organic pollutants and kills pathogenic bacteria. Researchers are always devoted to developing more economical and efficient photocatalysts. In this work, mesoporous TiO 2 nanoparticles (MTN) with controlled diameters (100–200 nm) and large specific surface areas (∼112 m2/g) were prepared via a simple sol–gel method. Then, 10 wt% Ag nanocrystals (∼5 nm) were in situ generated in the MTN via solvothermal process, Ti3+ and oxygen vacancies also been introduced on their surface, thereby leading to a narrowed bandgap (∼2.9 eV) and strong absorption in the visible region. Finally, polydopamine (PDA) was decorated on the surface of Ag/bMTN to further improve their dispersity and photocatalytic activity. The degradation rate of tetracycline and the bactericide rate of E. coli could surpass 90 % and 99 %, which were mainly attributed to the generated O 2 − and the released Ag ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr 2 O 3 as cocatalyst for CO 2 photoreduction was reported for the first time. • The crystal facets engineering and cocatalyst loading maximized the charge transfer. • The photocatalytic CO 2 conversion efficiency of TiO 2 increased by 30-fold. Implanting cocatalysts on semiconductor photocatalysts is considered as an essential strategy to promote reaction activity. However, the development of highly efficient cocatalysts remains challenging. In the present work, we construct independent Cr 2 O 3 as an efficient cocatalyst on the crystal facets engineered TiO 2 for photocatalytic CO 2 reduction for the first time. Moreover, a combined strategy of crystal facets engineering of TiO 2 and loading of Cr 2 O 3 cocatalyst is adopted to further promote the charge carriers' separation/transfer. In comparison with the cocatalyst-free TiO 2 without facets engineering, 2HF-TiO 2 /0.2Cr 2 O 3 exhibits near 30-fold enhancement on the CO 2 conversion efficiency. The enhanced photocatalytic activity is attributed to the maximal synergy of crystal facets engineering and cocatalyst loading for well-matched CO 2 reduction half-reaction and H 2 O oxidation half-reaction. These findings not only provide new insights for understanding the role of Cr 2 O 3 in photocatalytic systems but also may shed light on the design of photocatalysts from the perspective of overall photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]