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Graphical abstract Highlights • A hollow NiS/CdS/TiO 2 photocatalyst was prepared by a hydrolysis process. • Photocatalytic activity of TiO 2 was improved by anchoring CdS and NiS. • The synergistic effect of the heterojunction and cocatalyst promote H 2 production. Abstract Noble-metal-free hollow NiS/CdS/TiO 2 (NS/CT) nanohybrid photocatalyst was prepared by a facile hydrolysis combining sulfidation process using metal–organic framework (MOF) as a template. The as-prepared composites were characterized by SEM, TEM, XRD, XPS, UV–vis, and photoelectrochemical techniques. It is found that NS/CT composites with porous hollow structure show significantly enhanced photocatalytic efficiency compare to TiO 2 , or CdS/TiO 2 , or even Pt decorated CdS/TiO 2 photocatalysts, for hydrogen evolution from water upon visible light irradiation. Significantly, NS/CT composite with optimum amount of 30% CdS and 0.3% NiS exhibits the highest photoactivity, with H 2 production rate of 2149.15 µmol·g−1·h−1, which is 23.9 and 2.3 times higher than that of the pure CdS particles and the CdS/TiO 2 nanocomposites, respectively. The superiority of the composites arises from the synergistic effect of the heterojunction for rapid charge separation and the NiS cocatalyst for accelerated surface redox reaction. [ABSTRACT FROM AUTHOR]

• Solvothermal processed melem is crucial for tailoring carbon nitride structure. • Nitrogen defects and few-layer nanosheet are simultaneously formed in carbon nitride. • DCNS-120 has optimal properties by combining nitrogen defect and nanosheet structure. • DCNS-120 shows 33-folds increase compared to BCN for photocatalytic H 2 production. Carbon nitride nanosheets have shown a great promise for photocatalytic water splitting among numerous photocatalysts due to the versatile advantages. The crucial issues of the weak visible-light absorption and the separation of photo-generated carrier remain a matter of serious concern. Herein, we report a facile calcination-solvothermal-calcination method to prepare nitrogen-deficient carbon nitride nanosheets (DCNS) for the first time, which leads to the simultaneous introduction of nitrogen defects and formation of a fragmented few-layer nanosheet structure. The fragmented few-layer nanosheet structure is known to possess a high specific surface area and abundant interfacial reaction sites, contributing to the rapid consumption of photo-generated carrier. The nitrogen defects are responsible for further boosting the photocatalytic performance by regulating the band structure and optical properties as well as improving the separation efficiency of photo-generated carrier. The optimized DCNS-120 delivers a superior H 2 production rate of 5375 μmol·g−1·h−1, considerably higher than that of bulk carbon nitride (164 μmol·g−1·h−1). We anticipate that this work may pave a new pathway to engineering carbon nitride with a matched structure to achieve the desired efficient photocatalytic H 2 production under visible-light irradiation. [ABSTRACT FROM AUTHOR]

Methane conversion into ethanol and associated derivates under mild reaction conditions is of great significance, yet remains a challenge to date. Herein, we report efficient photocatalytic methane conversion into C2-hydrocarbons by using CO 2 as a soft oxidant over a series of Zn-doped g-C 3 N 4 composites. The results indicate that Zn atoms enter the lattice of g-C 3 N 4 and are chemically coordinated therein in the form of Zn N bonds. The integration of Zn, on one hand, could increase the specific surface area thus surface alkaline sites, and broaden the light response ability as well, promoting the dehydrogenation of methane into methyl. One the other hand, it is found that the Zn N bonds could serve as electron channels, accelerating the charge separation inside g-C 3 N 4 and enabling rapid electron transfer from g-C 3 N 4 to surface photodeposited Ru cocatalyst. This unique behavior changes the photocatalytic pathway and promotes the formation of CH 3 CHO and CH 3 CH 2 OH, as demonstrated by our in-situ infrared spectroscopy. Our photocatalytic tests indicate that the 0.5% Ru/Zn-g-C 3 N 4 -1/20 composite possesses the best activity, with the yields of CO, CH 3 CHO, and CH 3 CH 2 OH up to 865.25, 330.38, and 1442.88 μmol/g in 3 h, respectively. A proposed reaction mechanism based on the experimental results and above characterizations was finally deliberated. Unlabelled Image • Zn doped g-C 3 N 4 samples are prepared by a one-step calcination method. • Zn in the lattice matrix is coordinated in the form of Zn N bond. • Zn N bonds significantly accelerate the charge separation and CO 2 adsorption. • The catalyst can efficiently convert CO 2 and CH 4 into ethanol and acetaldehyde. [ABSTRACT FROM AUTHOR]