Face-to-face interfacial assembly of TiO2-g-C3N4 hybrid (2D TCN-A) is developed by surfactant-assisted hydrothermal treatment forming a sandwich structure of anatase TiO2 nanosheets (TiO2-A, 5–6 monolayers) and g-C3N4 nanosheets (∼3 monolayers). Post air-annealing is found effective for insertion of oxygen to the hybrid, which remedies the oxygen vacancies of TiO2 (B) nanosheets and converts it to anatase nanosheets. The enhanced light adsorption, increased donor density, and prolonged life of charge carries are achieved by variation of bandgap and the formation of heterojuction between the two kinds of nanosheets, facilitating separation and transfer of charge carriers. The 2D TCN-A-70 nanosheets show a high photodegradation rate of methyl orange (kapp ≈ 0.189 min–1) and photocatalytic evolution rate of hydrogen (18200 μmol g–1 h–1). This 2D nanosheets hybrid is potentially useful in alleviating environmental and energy issues.Keywords: g-C3N4; photocatalysis; TiO2; two dimension; ultrathin nanosheet;

•Fresh HV and dried HV were used for deoxy-liquefaction under different conditions.•Effect of temperature or residence time on yield and compositions of HCF was greater.•The fuels possessed high HHVs (>41.92 MJ/kg) and low oxygen contents (<4.63 wt.%).•Deoxy-liquefaction of fresh HV could save energy and time for water plants.Fresh Hydrilla verticillata (HV) and air-dried HV were chosen to be deoxy-liquefied in an airtight vessel reactor for high calorific fuel (HCF) production. The influence of temperature (250–450 °C), residence time (4–30 min), catalyst content (0.1–5 wt.%) on the yields and compositions of HCFs were investigated. Results showed that the HCFs obtained at 350 °C with residence time of 15 min possessed the highest HHVs (>44.06 MJ/kg) and lowest oxygen contents (<3.46 wt.%). The HCF contained benzenes, phenols, and long-chain alkanes as main components, with small proportion of non-phenolic oxy-compounds and nitro-compounds. Preliminary analysis of mechanisms indicated that high temperature or long residence time leaded to a deeper cracking of chemical bonds, which was less affected by the addition of catalyst. Experiments also suggested fresh HV rather than air-dried HV were more suitable for preparing high-quality HCF with highest yield of 18.05 wt.%. So, for water plants containing large amounts of water, deoxy-liquefaction under fresh state would be a better choice which could save a lot of energy and time consumed during drying process.

Four different biomass raw materials (corn stalk, reed, tobacco stalk, and banana leaves) were chosen to be deoxy-liquefied in an airtight vessel reactor for high-caloric fuel (HCF) production. The influence of temperature (573−723 K) on the product yields and chemical compositions of HCF from the four samples via deoxy-liquefaction were investigated. It was significant to find that the maximum content of alkanes was obtained at 673 K for corn stalk (35.98 mol %) and tobacco stalk (7.43 mol %), and 623 K for reed (32.56 mol %) and banana leaves (67.79 mol %), which was consistent with the optimum temperature for the highest yield of every sample. HCF from tobacco stalk (HCFt) was rich in phenolics and poor in hydrocarbons, whereas HCF from banana leaves (HCFb) was rich in hydrocarbon (alkanes: C7−C29; benzene derivatives) and poor in phenolics. The HCF from corn stalk and reed (HCFc and HCFr, respectively) were moderate. The composition of HCF had a great relationship with the holocellulose, lignin, and extractives content in the raw materials. Gas chromatography/mass spectrometry (GC/MS) and gas chromatography with a TCD detector (GC122) were used to determine the composition in HCF and in gaseous products, respectively.