Chunhu Li

High performance heterojunction photocatalytic membranes formed by embedding Cu2O and TiO2 nanowires in reduced graphene oxide

A heterojunction photocatalytic membrane consisting of Cu2O and TiO2 nanowires between reduced graphene oxide (rGO) sheets was fabricated using a facile process from a colloidal suspension. The resultant membrane exhibits significantly enhanced activity in the UV-vis range, surpassing nanowire dispersions, owing to the heterojunction formation and concurrent electron and hole transfer on rGO sheets. The membrane also possesses increased permeability and photocorrosion resistance. Such a design and fabrication method of an rGO-facilitated heterojunction photocatalytic membrane can be extended to a broad range of energy and environmental applications.

Fatty acid decarboxylation reaction kinetics and pathway of co-conversion with amino acid on supported iron oxide catalysts

Fe2O3/Al-MCM-41 nanocomposite catalysts were designed and fabricated to upgrade microalgae hydrothermal liquefaction (HTL)-derived biocrude and its model compounds (palmitic acid and glutamic acid) in the absence of hydrogen. The Fe2O3/Al-MCM-41 catalysts were prepared by encapsulating Fe2O3 particles on highly stable pure silica MCM-41 and Al-MCM-41. XRD, TEM, N2 adsorption isotherms, XPS, and UV-Vis characterizations of the catalysts revealed that 10–30 nm γ-Fe2O3 particles were well dispersed on the mesoporous support. In the range of 320–350 °C and under subcritical water, palmitic acid conversion was improved by 43–54% by the Fe2O3/Al-MCM-41 catalyst. The overall reaction rate was first order to palmitic acid for non-catalytic and catalytic conversions, and the activation energy was 336.76 kJ mol−1 for Fe2O3/Al-MCM-41. In situ DRIFTS reaction test demonstrated that the initiation temperature for the catalytic decarboxylation of palmitic acid was decreased to 195 °C, and desorption of the produced CO2 occurred at 255 °C. Based on the GC-MS results of the HTL products, the reaction pathway of the binary mixture of palmitic acid and glutamic acid was elucidated, and the chemical origins of amide, pyrrolidinone, hydroxy-butanoic acid, and pentadecane were proposed.

The growth mechanism of calcareous deposits under various hydrostatic pressures during the cathodic protection of carbon steel in seawater

A galvanostatic method was used to study the influence of hydrostatic pressure on the cathodic protection of carbon steel in seawater. The polarization and electrochemical behavior of Q235 carbon steel was studied after being covered with calcareous deposits. Surface analysis was performed to investigate the growth mechanism of the calcareous deposits under various hydrostatic pressures. Although there was no obvious effect of the hydrostatic pressure on the polarization potential decay, the protectiveness of calcareous deposits showed significant variation under the different pressures. The results of electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) indicate that the electrochemical reaction resistance Rct on the polarized metal surface initially increased with the increasing pressure and then decreased, with a maximum value at 2 MPa. The protection factor Fp of the deposits decreased when the pressure was higher than 2 MPa. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses illustrated that parts of the calcium lattice positions were substituted by magnesium ions in the initial crystallization of calcium carbonate under 5 MPa pressure or even higher, which resulted in a crystal structure transformation from aragonite to dolomite. The order degree δ of dolomite decreased under high pressure due to the low free energy of the lattice.

Visible Light Driven photocatalyst BiVO4 for photocatalytic removal of NO

BiVO4 nanoparticles were synthesized through hydrothermal method, and characterized by XRD, SEM, FTIR and UV-Vis. The BiVO4 were pure monoclinic scheelite type, with particle size around 300-500nm and band gaps around 2.34-2.45ev. The photocatalytic activity was evaluated by oxidation of NO under visible light irradiation. The hydrothermal temperature of 200 °C induced the best photocatalytic activity due to the fine crystalline phase, flower-like morphology and the stronger visible light absorbance.

Microalgae hydrothermal liquefaction and derived biocrude upgrading with modified SBA-15 catalysts

In this study, a novel route was proposed for microalgae biofuel production by catalytic upgrading of Chlorella hydrothermal liquefaction (HTL) derived biocrude. Al-SBA-15, CuO/Al-SBA-15, ZuO/Al-SBA-15, and CuO-ZnO/Al-SBA-15 catalysts were synthesized in a facile, one-pot way, and tested for methyl palmitate decarboxylation and biocrude upgrading without H2 addition. These modified SBA-15 catalysts enhanced alkane selectivity of methyl palmitate decarboxylation from 7.6 wt% up to 79.6 wt% at 340-350 °C. FT-IR, TG and GC-MS characterizations were employed to identify the composition and properties of the upgraded bio-oils. Compared with thermal upgrading, modified SBA-15 catalysts enriched the yield of low boiling point compounds, and the content of heavy bio-oil (>400 °C) declined from 9.57 wt% to 1.89 wt%. Hydrocarbon yield was greatly enriched on the catalysts, and aromatics predominant on Al-SBA-15 while aliphatics abundant on metal oxide(s) supported catalysts. The hydrocarbon yield was increased from 25.1 wt% (thermal) to 65.7 wt% on the CuO/Al-SBA-15.