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Black phosphorus (BP) has recently emerged as a versatile photocatalyst owing to its unique photophysical properties and tunable bandgap. Nonetheless, the rapid recombination of the photogenerated charges of pristine BP samples has significantly hindered its practical applications in photocatalysis. Herein, we report, for the first time, the effect of transition metal nanoparticles (Ni and Co) as co-catalysts on the photocatalytic activity of BP/tungsten disulfide (WS2) binary heterojunctions (BP/WS2-TM (TM: Ni, Co)) in the hydrogen evolution reaction (HER) under visible light irradiation (λ > 420 nm). Ternary heterojunctions named BP/WS2-TM (TM: Ni, Co) were synthesized via a chemical reduction method, leading to the formation of an S-scheme heterojunction, in which BP acts as a reduction catalyst and WS2 serves as an oxidation catalyst. BP/WS2-Ni and BP/WS2-Co performed substantial amounts of hydrogen generation of 9.53 mmol h−1g−1 and 12.13 mmol h−1g−1, respectively. Moreover, BP/WS2-Co exhibited about 5 and 15 times higher photocatalytic activity compared to the binary BP/WS2 heterojunctions and pristine BP, respectively. The enhanced photocatalytic activity of the heterojunction catalysts is attributed to the extended light absorption ability, enhanced charge separation, and larger active sites. This study is the first example of photocatalytic hydrogen evolution from water by using Ni- and Co-doped binary BP/WS2 heterojunctions. [ABSTRACT FROM AUTHOR]

To activate dimethyl sulfoxide (DMSO, CH3SOCH3) as a methylation agent in the C–H functionalization of (iso)quinoliniums (1), a heterogeneous photo-Fenton-like method involving the in situ generation of hydroxyl radicals by a gCN/MnO/MnO(OH) photocatalyst under visible light irradiation was realized for the first time. In the developed methodology, only a small amount of gCN/MnO/MnO(OH) photocatalysts (15 mg) was needed for the methylation of (iso)quinoliniums (1.0 mmol-scale of 1) to achieve moderate to good yields of the expected methylated-products (2) under ambient conditions. Mechanistically, hydroxyl radicals (˙OH) are produced when the gCN/MnO/MnO(OH) photocatalyst reacts with H2O and O2 under visible light illumination, and then they are added to DMSO, where they subsequently fragment into ˙CH3 radicals. The product is generated via the nucleophilic attack of the ˙CH3 radical at the most electron-deficient position of 1, followed by deprotonation reaction. The same procedure could also be used to create trideuteromethylated (iso)quinolines (3) when DMSO-d6 (CD3SOCD3) was used in place of DMSO. The presented novel strategy for DMSO or DMSO-d6 activation herein is more practical, cost-effective, and risk-free compared to the conventional Fenton reagent (H2O2 and Fe2+/Fe3+) systems available in the literature. Additionally, the gCN/MnO/MnO(OH) photocatalyst is easy to prepare, practical and economical together with being easy recoverable and reusable for several runs without considerable loss in its initial activity. [ABSTRACT FROM AUTHOR]

Summary: New photocatalysts comprising the 2D/2D heterojunction of graphitic carbon nitride (gCN) and molybdenum disulfide (MoS2) semiconductors doped with nickel (Ni) or cobalt (Co), denoted as gCN/MoS2‐M (M: Ni, Co), were fabricated for the photocatalytic hydrogen evolution reaction (HER) under visible light illumination. First, the binary gCN/MoS2 heterojunctions were fabricated by using an in‐situ solvothermal method and then they were doped with Ni or Co via a chemical reduction method. The photocatalytic HER experiments revealed that the prepared gCN/MoS2‐M (M: Ni, Co) photocatalysts showed enhanced HER activities and stabilities compared to pristine gCN and binary gCN/MoS2 heterojunctions. Total H2 productions of 5924 μmol gcat−1 and 5159 μmol gcat−1 in 8 hours were provided by using gCN/MoS2‐Ni and gCN/MoS2‐Co photocatalysts, respectively, under visible light illumination. The detailed structural characterization and examination of optical properties of gCN/MoS2‐M (M: Ni, Co) photocatalysts revealed that their enhanced photocatalytic activities were attributed to the formation of 'type‐I' 2D/2D heterojunction between gCN and MoS2 semiconductors and the creation of S‐deficient MoS2 nanostructures after Ni or Co doping, which promoted the separation of the photogenerated electron‐hole pairs, the charge mobility, and the visible light absorption. [ABSTRACT FROM AUTHOR]