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Sulfur-doped two-dimensional (2D) graphitic carbon nitride nanosheets (2D-SCN) with efficient photocatalytic activity were synthesized via (1) polycondensation of thiourea to form bulk sulfur-doped graphitic carbon nitride (SCN) and (2) followed by thermal oxidative treatment of the prepared SCN via an etching strategy to form 2D-SCN. Sulfur was doped in situ into SCN by using thiourea as the precursor, and the 2D nanosheet structure was obtained during the thermal oxidative etching process. The structural, morphological, and optical properties of the 2D-SCN sample were investigated in detail. Herein, it is shown that the thermal oxidative etching treatment and sulfur doping induced a 2D nanosheet structure (2D-SCN-3h) with a thickness of about 4.0 nm and exposure of more sulfur elements on the surface. The surface area increased from 16.6 m2/g for SCN to 226.9 m2/g. Compared to bulk SCN, a blue shift of the absorption peaks was observed for the obtained 2D-SCN-3h photocatalyst, and the absorption intensity was higher than that of the sulfur-free counterpart (2D-CN). The successful in situ doping of S element into SCN or 2D-SCN-3h samples is beneficial to the introduction of surface N defects and O species. 2D-SCN-3h indicated higher efficiency in photogenerated charge carrier separation and showed the highest reductive activity in photocatalytic splitting of water at a rate of 127.4 μmol/h under simulated solar light irradiation, which was 250 times and 3 times higher than that of SCN and 2D-CN photocatalysts, respectively. The apparent quantum efficiency was estimated to be 8.35% at 420 nm irradiation. The S–C–N bond formed by sulfur doping was beneficial to the charge-transfer process, and this led to higher photocatalytic activity according to partial density of state analysis computed by first-principles methods.

Photocatalytic hydrogen evolution is an attractive field for future environment-friendly energy. However, fast recombination of photogenerated charges severely inhibits hydrogen efficiency. Single-atom cocatalysts such as Pt have emerged as an effective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment. Herein, we demonstrated a new strategy to develop a highly active Pd single atom in carbon-deficient g-C3N4 with a unique coordination. The single-atom Pd–N3 sites constructed by oil bath heating and photoreduction process were confirmed by HADDF-STEM and XPS measurements. Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers, leading to a longer lifespan for consequent reactions. The obtained single-atom Pd loaded on the carbon-deficient g–C3N4 showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g–C3N4 and nano-sized Pd on the same support, respectively. This work provides a new insight on the design of single-atom catalyst.

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The abuse of tetracycline antibiotics (TCs) has imposed great threats to both human bodies and the ecosystem. Therefore, developing efficient technologies to remediate these contaminants is of significant and practical...

In this study, nanocrystalline-assembled mesoporous CuO microspheres (MCMs) with enhanced visible-light driven photocatalytic activity were synthesized by a facile one-step hydrothermal method. MCMs exhibit excellent visible-light driven photocatalytic activity with 85% removal of methyl orange (MO) (60% removal of total organic carbon (TOC)) in 40 min. The excellent photocatalytic performance is dependent on the specific morphology and excellent visible-light absorption ability. Interestingly, MCMs can efficiently remove MO with or without light. The amount and categories of active species were determined by electron paramagnetic resonance and photoluminance (PL). Reactive oxygen species (ROS) (mainly ·[Formula: see text] and HO) and Cu (I) radicals are important in fading and further mineralization of MO. With the assistance of gas chromatography-mass spectrometer , TOC and x-ray photoelectron spectroscopy, the degradation pathways in light and dark conditions were analyzed. It has been proven that MO could be efficiently mineralized by ROS generated in light, while reaction in dark condition was more likely to be an efficient fading process.