The core of realizing the effective CO 2 conversion by solar energy is to develop a stable photocatalyst with high CO 2 adsorption capacity and high charge separation efficiency. In this work, a hollow spherical Z-scheme SnS 2 /g-C 3 N 4 /C (SCC) photocatalyst is successfully constructed by a morphology-inherited strategy. Biomass mabospores are utilized as both the precursor for formation of hollow spherical structure and carbon source, and the g-C 3 N 4 and SnS 2 nanosheets tightly anchor on the surface of mabospores-derived carbon spheres. The Z-scheme SCC heterostructure exhibits 5.5 times activity enhancement on CO 2 photoreduction to CO with a high evolution rate up to 40.86 μmol∙g −1 ∙h −1 . Examined by various photoelectrochemical analysis, the boosted photocatalytic activity originates mainly from the construction of hollow spherical Z-scheme heterojunction, providing the more preferable basic sites for CO 2 adsorption, promoting the separation efficiency of electron-hole pairs, as well as increasing the reductionability of electrons in conduction band of g-C 3 N 4 . The formed internal electric fields between the g-C 3 N 4 and SnS 2 can also further reinforce the spatial separation of photogenerated charge carriers. Theoretical calculations further verify that the SCC Z-scheme heterostructure can effectively decrease the energy barriers of formed intermediates, especially the crucial COOH*, and thus leading to the facile conversion of CO 2 -to-CO. This work induces a new strategy to construct g-C 3 N 4 -based Z-scheme heterojunction assisted by versatile biomasses with optimized structure and enhanced photoelectrochemical merits for efficient CO 2 conversion into chemical fuels.
Tin disulfide is a promising anode material for Li-ion batteries (LIB) owing to its high theoretical capacity and the abundance of its composing elements. However, bare SnS 2 suffers from low electrical conductivity and large volume expansion, which results in poor rate performance and cycling stability. Herein, we present a solution-based strategy to grow SnS 2 nanostructures within a matrix of porous g-C 3 N 4 (CN) and high electrical conductivity graphite plates (GPs). We test the resulting nanocomposite as anode in LIBs. First, SnS 2 nanostructures with different geometries are tested, to find out that thin SnS 2 nanoplates (SnS 2 -NPLs) provide the highest performances. Such SnS 2 -NPLs, incorporated into hierarchical SnS 2 /CN/GP nanocomposites, display excellent rate capabilities (536.5 mA h g −1 at 2.0 A g −1 ) and an outstanding stability (∼99.7% retention after 400 cycles), which are partially associated with a high pseudocapacitance contribution (88.8% at 1.0 mV s −1 ). The excellent electrochemical properties of these nanocomposites are ascribed to the synergy created between the three nanocomposite components: i) thin SnS 2 -NPLs provide a large surface for rapid Li-ion intercalation and a proper geometry to stand volume expansions during lithiation/delithiation cycles; ii) porous CN prevents SnS 2 -NPLs aggregation, habilitates efficient channels for Li-ion diffusion and buffer stresses associated to SnS 2 volume changes; and iii) conductive GPs allow an efficient charge transport.
Zhongwei Fan,Jingfei Luan,Changqing Zhu,Fuqiang Liu
The novel Z-scheme heterojunction photocatalyst g-C 3 N 4 /Ag 2 S/SnS 2 with Ag 2 S quantum dots as electron mediators was successfully synthesized by in-situ ion exchange reaction and self-peeling of g-C 3 N 4 . Compared with g-C 3 N 4 , SnS 2 or g-C 3 N 4 /SnS 2 , the photocatalyst g-C 3 N 4 /Ag 2 S/SnS 2 exhibited more excellent photocatalytic performance under visible light irradiation. The removal rate of methyl orange was 96.8% after 30 minutes visible light irradiation and the reaction rate constant reached 0.10225 min -1 . The enhanced photocatalytic activity could be attributed to the formation of Z-scheme heterojunction structure and the 2D layered structure. The electrochemical and photoelectric performance tests showed that the separation and transfer efficiency of the photogenic electron-hole pairs as well as the redox potential were significantly improved. Additionally, the quenching experiments showed that the superoxide radicals and holes were the primarily active species. Combined with other characterizations, the reaction mechanism of the g-C 3 N 4 /Ag 2 S/SnS 2 for degrading the target pollutant methyl orange under visible light irradiation was proposed.
Yi Peng,Juntao Wang,Ying Yan,Wenlei Wang,Hongbo Xiao
In this work, a high content of pyrrole nitrogen carbon nitride (HPCN)-SnS 2 has been successfully constructed with −C═Sn− chemical bond as the interface framework. The charge state of Sn species was adjusted by β particles to obtain controllable sulfur defects onto the HPCN-SnS 2 through electron beam irradiation (EBI). The composites exhibited excellent photocatalytic oxidation capacity of As(Ⅲ) and adsorption capacity of As(Ⅴ). It is confirmed that the optimized HPCN-SnS 1.38 can remove the total As concentrations below 0.40 mg/L within 80 min. Additionally, the effect of various conditions (pH value and type of anions) was evaluated using degradation experiments, and HPCN-SnS 1.38 could be reused at least 5 times without an obvious reduction in the photocatalysis and adsorption performances. Based on the experimental results, the photocatalytic mechanism of As(Ⅲ) by HPCN-SnS 2 after electron beam irradiation was studied. Free radical quenching experiments and electron paramagnetic resonance (EPR) showed that the oxidation of As(III) under visible light is mainly controlled by •O 2 − and •OH, and •OH is converted from •O 2 − under acidic conditions.
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