A recrystallization-assisted way was developed to create Z-scheme Cu2O nanoparticle/g-C3N4 nanosheet layered heterostructures using melamine and copper salts by a two-step polymerization procedure. The recrystallization of melamine was carried out by adding different Cu salts. These copper salts not only influenced the recrystallization process of melamine but also resulted in the introduction of a little amount of Cu ions in the melamine crystals. The two-step polymerization procedure at 650 and 700 °C produces superior thin Cu2O/g-C3N4 nanosheets. The decrease of the thickness of the nanosheets increased specific surface areas. Cu2+ ions were reduced into Cu2O after heat treatment. Cu2O/g-C3N4 nanosheets revealed expanded visible light absorption and a decreased band gap. Cu2O/g-C3N4 nanosheets prepared by optimized preparation conditions (sample 650-700-Cu2O/RCNs) exhibited the best H2 generation of 5776.4 μmol/g/h with 3 wt % Pt as a cocatalyst and triethanolamine (TEOA) as a sacrificial reagent, which was about 3 times that of pure g-C3N4 nanosheets (sample 650-700-CN, 1912.6 μmol/g/h). Without the Pt cocatalyst, the photocatalytic H2 evolution of the sample 650-700-Cu2O/RCNs was 266.3 μmol/g/h, which was ∼18 times that of the sample 650-700-CN. The excellent performance is ascribed to the formation of Z-scheme heterostructures. This work provides a strategy to prepare highly efficient photocatalysts.

The conversion of nitrogen oxide (NO) by photocatalysis is promising to solve the increasingly serious air pollution. Herein, raspberry-like TiO2 hollow spheres consisted of small nanocrystals (less than 10 nm)...

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Cobalt ions were introduced during thermal polymerization at high temperature to prepare graphic carbon nitride (g-C3N4) and Co composites. The interface engineering induced by Co ions resulted in the variation of morphology as well as photo- and electro-chemical performance of the composite samples. Co-g-C3N4 composite samples revealed superior thin-nanosheet and nanotube morphologies at 680 and 750 °C, respectively. As separation centers, Co–N bonds at the interface promoted the transfer of charges and improved photocatalytic properties. Thus, the Co-g-C3N4 composite nanosheets revealed the best photocatalytic performance, in which the maximum degradation rate constant of rhodamine B reached to 0.126 min–1, which was 9.7 times of that of pure g-C3N4 nanosheets. In contrast, the Co-g-C3N4 composite nanotubes with Co nanoparticles effectively enhanced the hydrogen evolution reaction. In the case of a current density of 10 mA cm–2, the overpotential of the Co-g-C3N4 composite nanotubes was 249 mV and the Tafel slope was 80 mV dec–1. In addition, the Co-g-C3N4 composite nanotubes revealed high charge–discharge capacity as a supercapacitor. This result provided a method for building g-C3N4-based photo- and electro-catalysts for various photo- and electro-chemical applications including photocatalytic degradation of organic pollutants, electrocatalytic hydrogen evolution reaction, and supercapacitors.