Graphitic carbon nitride (g-C 3 N 4 ), a polymeric semiconductor, has become a rising star for photocatalytic energy conversion because of its facile accessibility, metal-free nature, low cost, and environmentally benign properties. This work reviews the latest progress of g-C 3 N 4 -based materials in visible-light-driven water splitting to hydrogen. It begins with a brief history of g-C 3 N 4 , followed by various engineering strategies of g-C 3 N 4 , such as elemental doping, copolymerization, crystalline tailoring, surface engineering, and single-atom modification, for elevated photocatalytic water decomposition. In addition, the synthesis of g-C 3 N 4 in different dimensions (0D, 1D, 2D, and 3D) and configurations of a series of g-C 3 N 4based heterojunctions (type II, Z-scheme, S-scheme, g-C 3 N 4 /metal, and g-C 3 N 4 /carbon heterojunctions) were also discussed for their improvement in photocatalytic hydrogen production. Lastly, the challenges and opportunities of g-C 3 N 4 -based nanomaterials are provided. It is anticipated that this review will promote the further development of the emerging g-C 3 N 4 -based materials for more efficiency in photocatalytic water splitting to hydrogen.

This work is mainly focused on the investigation of the influence of the amount of a few CeO2 on the physicochemical and catalytic properties of CeO2-doped TiO2 catalysts for NO reduction by a CO model reaction. The obtained samples were characterized by means of XRD, N2-physisorption (BET), LRS, UV-vis DRS, XPS, (O2, CO, and NO)-TPD, H2-TPR, in situ FT-IR, and a NO + CO model reaction. These results indicate that a small quantity of CeO2 doping into the TiO2 support will cause an obvious change in the properties of the catalyst and the TC-60 : 1 (the TiO2/CeO2 molar ratio is 60 : 1) support exhibits the most extent of lattice expansion, which indicates that the band lengths of Ce-O-Ti are longer than other TC (the solid solution of TiO2 and CeO2) samples, probably contributing to larger structural distortion and disorder, more defects and oxygen vacancies. Copper oxide species supported on TC supports are much easier to be reduced than those supported on the pure TiO2 and CeO2 surface-modified TiO2 supports. Furthermore, the Cu/TC-60 : 1 catalyst shows the highest activity and selectivity due to more oxygen vacancies, higher mobility of surface and lattice oxygen at lower temperature (which contributes to the regeneration of oxygen vacancies, and the best reducing ability), the most content of Cu(+), and the strongest synergistic effect between Ti(3+), Ce(3+) and Cu(+). On the other hand, the CeO2 doping into TiO2 promotes the formation of a Cu(+)/Cu(0) redox cycle at high temperatures, which has a crucial effect on N2O reduction. Finally, in order to further understand the nature of the catalytic performances of these samples, taking the Cu/TC-60 : 1 catalyst as an example, a possible reaction mechanism is tentatively proposed.

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Monometallic and bimetallic MOF-74-M (M = Mn, Co, Ni, Zn, MnCo, MnNi, and MnZn) catalysts were prepared by the solvothermal method for NH 3 -SCR. XRD, BET, SEM, and EDS-mapping tests indicate the successful synthesis of the MOF-74-M catalyst with uniform distribution of metal elements and large specific surface area, and the morphology is almost hexagonal. Adding Mn element to a single-metal catalyst can enhance activity, which is mainly because of the existence of various valence states of Mn so that it has excellent redox properties; the catalytic activity of water and sulfur resistance tests showed that the catalytic activity of MOF-74-M increases after adding a proper amount of SO 2 , mainly because of the increase in acidic sites. In situ DRIFTS results indicate that the low-temperature range of MOF-74-MnCo and MOF-74-Mn is dominated by the E−R mechanism and the high-temperature range is dominated by the L−H mechanism. The entire temperature range of MOF-74-Zn is dominated by the L−H mechanism. KEYWORDS: MOF-74, in situ DRIFTS, NH 3 -SCR, resistance of H 2 O and SO 2 , mechanism

This paper aims to catch the influence of various operating conditions and catalyst addition on the property of gas product and tar evolution. The gasification of three local biomass samples (sawdust, peanut shell, and wheat straw) was performed using a fluidized bed gasification reactor, and the gas product and liquid tar were analyzed with gas chromatography (GC). First, the influence of biomass property, gasification temperature, and air equivalence ratio was investigated. The biomass feeding rate was set at ∼2.37 kg/h; the furnace temperature variant was between 750 and 850 °C; and the equivalence ratio (ER) was 0.15−0.35. It can be observed that a lower heating value (LHV) of gas product from sawdust is higher than peanut shell and straw, while the tar content is also much higher than the other two samples, which might be attributed to the high volatile content. At 800 °C, with the increase of ER, the gas yield increased rapidly from 1.14 to 1.93 m3/kg, while the LHV decreased from 7.09 to 3.26 MJ/m3. Meanwhile, the variation of ER also showed a great effect on tar species. With the increase in temperature, combustible gas content, gas yield, and LHV all increased significantly, while the tar content decreased sharply from 13.24 to 6.53 g/m3, which indicated that high temperature was favorable for biomass gasification. Then, three additives (dolomite, magnesite, and olivine) were introduced into the gasification process as catalyst for tar cracking. It is great for the upgrading of gas product quality, and tar removal efficiencies are all above 50%. It is significant for the development of biomass gasification technology.