Copper-modified g-C$_3$N$_4$/TiO$_2$ nanostructured photocatalysts for H$_2$ evolution from glucose aqueous solution

Two strategies for synthesis of copper-modified composite photocatalysts based on graphitic carbon nitride and titanium dioxide for hydrogen evolution reaction are presented. The first one is based on the mechanical dispersion of separately prepared g-C$_3$N$_4$ and commercial TiO$_2$ (Evonik P25), modified with copper. Another approach is co-calcination of melamine and commercial TiO$_2$ with subsequent modification by copper. The samples were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The synthesized photocatalysts were tested in hydrogen evolution from glucose aqueous solution under visible light irradiation (440 nm). The largest photocatalytic activities met 235 and 259 $\mu$mol $\cdot$ g$^{-1}$ $\cdot$ h$^{-1}$, corresponding to the first and the second photocatalyst series, respectively. The most active photocatalyst from the first series 1 wt.% g-C$_3$N$_4$/1 wt.% CuO$_n$/TiO$_2$ maintained its hydrogen production rate during a 6-hour cyclic stability test.