Spent Coffee Grounds Derived Carbon Loading C, N Doped TiO 2 for Photocatalytic Degradation of Organic Dyes.

Titanium dioxide (TiO 2 ) is an ideal photocatalyst candidate due to its high activity, low toxicity and cost, and high chemical stability. However, its practical application in photocatalysis is seriously hindered by the wide band gap energy of TiO 2 and the prone recombination of electron-hole pairs. In this study, C, N doped TiO 2 were supported on spent coffee grounds-derived carbon (ACG) via in situ formation, which was denoted as C, N-TiO 2 @ACG. The obtained C, N-TiO 2 @ACG exhibits increased light absorption efficiency with the band gap energy decreasing from 3.31 eV of TiO 2 to 2.34 eV, a higher specific surface area of 145.8 m 2 /g, and reduced recombination rates attributed to the synergistic effect of a spent coffee grounds-derived carbon substrate and C, N doping. Consequently, the optimal 1:1 C, N-TiO 2 @ACG delivers considerable photocatalytic activity with degradation efficiencies for methylene blue (MB) reaching 96.9% within 45 min, as well as a high reaction rate of 0.06348 min -1 , approximately 4.66 times that of TiO 2 (0.01361 min -1 ). Furthermore, it also demonstrated greatly enhanced photocatalytic efficiency towards methyl orange (MO) in the presence of MB compared with a single MO solution. This work provides a feasible and universal strategy of synchronous introducing nonmetal doping and biomass-derived carbon substrates to promote the photocatalytic performance of TiO 2 for the degradation of organic dyes.