No abstract

The development of non-precious metal catalysts for efficient oxygen reduction is of significance for many advanced electrochemical devices such as fuel cells and metal-air batteries. Herein, we develop a graphene-directed assembly route to synthesize hierarchically nanoporous Co-Nx/C materials with a macro/meso/microporous structure, high specific surface area (i.e. 512 m 2 /g) and excellent conductivity using graphene oxide (GO) supported zeolitic imidazolate frameworks nanocrystal arrays as a catalyst precursor, followed by carbonization and acid leaching process. In this route, GO acts as a structure-directing agent to construct ZIF nanocrystal arrays supported on GO nanosheets. During the carbonization process, the resulting reduced graphene oxide functions as a binder and electrical conductor to connect individual ZIFderived carbon nanoparticles into the macroporous structure and increase the overal conductivity. ZIF nanocrystals themselves are also converted into meso/microporous carbon nanoparticles without using any other template. The hierarchically porous Co-Nx/C materials exhibit high ORR catalytic activity, superior stability and good methanol tolerance in both alkaline and acidic conditions.

Nanoporous titania nanoparticles (NTNs) were synthesized and used as an additive at a low concentration of 0.1−1 wt % in the fabrication of poly(ethersulfone) (PES) ultrafiltration membranes via non-solvent-induced phase separation. The structure and properties of nanoparticles were characterized using nitrogen sorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The NTNs have a size distribution with a particle size of mainly <100 nm and have a Brunauer, Emmett, and Teller surface area of ∼100 m 2 g −1 . The modified membranes were fabricated and investigated in terms of their pure water flux, solute rejection, and fouling resistance. The water permeability and molecular weight cutoffs (MWCOs) of membranes were determined under constant-pressure filtration in dead-end mode at 100 kPa. The membrane fouling resistance was characterized under constant flux operation using bovine serum albumin as a model foulant. The membranes were characterized in terms of morphology, porosity, pore size distribution, energy-dispersive X-ray spectroscopy, contact angle goniometry, surface free energy, and viscosity of the dope solution. Overall, the modified membrane showed increased wettability and reduced surface free energy and pore size. The modified UF membrane with 0.5 wt % NTN loading exhibited improved fouling resistance (fouling rate of 0.58 kPa/min compared to a rate of 0.70 kPa/min for the control membrane) with ∼80% water flux recovery. The same membrane showed an ∼20% increase in water flux, an improvement in MWCO, and a narrower pore size distribution.

Highlights Ni(OH)2 were decorated on coral-like TiO2 particles by a precipitation method. Ni(OH)2 decorated TiO2 showed improved activity under visible light. Ni(OH)2 decorated TiO2 performed better than P25 in tetracycline removal. Micro-sized Ni(OH)2 decorated TiO2 could be easily recovered from water.

Abstract-The present study introduced the potential used of Garcinia Mangostana Linn. seeds as feedstock for bio-diesel production. The preparation of biodiesel by two-phase solvent extraction (TSE) and alkali-catalyzed transesterification was studied. The important factors including catalyst concentration, ratio of methanol to oil and temperature on conversion FAME were examined respectively by experiments. The results of two-step transesterification showed that the optimal conversion of Garcinia Mangostana Linn. seeds into fatty acid methyl ester (FAME) were at condition of 4:1 methanol/oil volume ratio, 50 o C reaction temperature, 0.5% ( catalyst / oil weight ratio w/w) solid base catalyst amount and at 5 minutes reaction time.