Jin Sen,Jing Huijuan,Wang Libo,Hu Qianku,Zhou Aiguo
Nowadays, photocatalytic technologies are regarded as promising strategies to solve energy problems, and various photocatalysts have been synthesized and explored. In this paper, a novel CdS/MoO 2 @Mo 2 C-MXene photocatalyst for H 2 production was constructed by a two-step hydrothermal method, where MoO 2 @Mo 2 C-MXene acted as a binary co-catalyst. In the first hydrothermal step, MoO 2 crystals with an egged shape grew on the surface of two-dimensional (2D) Mo 2 C MXene via an oxidation process in HCl aqueous solution. In the second hydrothermal step, CdS nanorods were uniformly assembled on the surface of MoO 2 @Mo 2 C-MXene in ethylenediamine with an inorganic cadmium source and organic sulfur source. The CdS/MoO 2 @Mo 2 C-MXene composite with MoO 2 @Mo 2 C-MXene of 5 wt% exhibits an ultrahigh visible-light photocatalytic H 2 production activity of 22,672 µmol/(g·h), which is ∼21% higher than that of CdS/Mo 2 C-MXene. In the CdS/MoO 2 @Mo 2 C-MXene composite, the MoO 2 with metallic nature separates CdS and Mo 2 C MXene, which acts as an electron-transport bridge between CdS and Mo 2 C MXene to accelerate the photoinduced electron transferring. Moreover, the energy band structure of CdS was changed by MoO 2 @Mo 2 C-MXene to suppress the recombination of photogenerated carriers. This novel compound delivers upgraded photocatalytic H 2 evolution performance and a new pathway of preparing the low-cost photocatalyst to solve energy problems in the future.
Meng Chen,Huawei Fang,Chao Wang,Jixiang Xu,Lei Wang
Background Solar-driven water splitting is regarded as one promising green way to produce H 2 . Photo-reduction of hexavalent chromium (Cr(Ⅵ)) to hypotoxic Cr(III) can control the Cr(VI)-induced pollution. A key in these processes is to develop a photocatalyst with high specific surface area, good light absorption and efficient charge carrier separation. Methods A Co-encapsulated N-doped carbon (Co@NC) was prepared by pyrolysis ZIF-8@ZIF-67 precursor to modify CdSe quantum dots (QDs). The obtained catalyst was used to reduce Cr(Ⅵ) and split water under visible light irradiation. Significant findings Modification CdSe with Co@NC made obtained Co@NC/CdSe possessing enhanced visible-light absorption and photoexcited charge separation. The optimal 2%Co@NC/CdSe exhibited the excellent Cr(Ⅵ) reduction performance with a rate constant of 0.28 min –1 in the absence of sacrificial agent, as well as high H 2 evolution rate of 6.48 mmol g –1 h –1 in 10% lactic acid solution. The H 2 O 2 and electrons were the active species to reduce Cr(VI). This work gives a beneficial insight for improving the photocatalytic activity of QDs.
Caihong Fang,Ran Li,Xin Wang,Fei Duan,Junfeng Lin,Yunqin Hu,Zhiqing Cui
The heterogeneous nanoparticles−nanorod Ni−NiMoO 4 nanostructures grown in situ on nickel foam (Ni−NiMoO 4 /NF) were rationally engineered as efficient electrocatalysts. The morphological and compositional features cooperatively propel high-performance electrocatalysis to hydrogen evolution reaction (η 10 , η 100 , and η 200 values are 26/84/113 mV in fresh water and 27/101/132 mV in seawater), urea oxidation reaction (η 10 , η 100 , and η 200 values are 1.321/1.340/1.356 and 1.329/1.344/1.361 V in fresh/seawater). The Ni−NiMoO 4 /NF nanostructures therefore perform a low cell voltage of 1.506/1.509@10 mA cm −2 in fresh/sea water. Specifically, the record cell voltage even drops to as low as 1.339/1.361 V in fresh/sea water for overall urea splitting (OUS) reaction with a long-term stability for 240 h@100 mA cm −2 toward OUS in seawater. More importantly, to realize a green manner, we also evaluated a solar-driven H 2 production. Even in seawater, H 2 gas was collected in high speed under solar illumination on a commercial solar panel.
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