Weifeng Yao

Cobalt super-microparticles anchored on nitrogen-doped graphene for aniline oxidation based on sulfate radicals

Cobalt super-microparticles anchored on nitrogen-doped graphene (Co-NG) were prepared using an inexpensive method and were tested for heterogeneous oxidation of aniline with peroxymonosulfate (PMS) in aqueous solutions. The crystal structure, morphology, and textural properties of Co-NG hybrids were investigated by various characterization techniques, such as X-ray diffraction, Raman spectroscopy, dark-field scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Electron paramagnetic resonance and classical quenching tests were conducted to investigate the mechanism of PMS activation and aniline oxidation. The catalyst Co-NG exhibits an unexpectedly high catalytic activity in the degradation of aniline in water by advanced oxidation technology based on sulfate radicals (SO4-), and 100% decomposition can be achieved in 10min. This paper offers new insights on heterogeneous catalysis.

High efficiency and stable tungsten phosphide cocatalysts for photocatalytic hydrogen production

Research and development of high efficiency non-noble metal cocatalysts for solar photocatalytic hydrogen production have been aiming at a long-term goal of a renewable hydrogen economy. This research reports an active and stable tungsten phosphide (WP) cocatalyst as a potential replacement for Pt and Pd noble metal cocatalysts. WP nanoparticles are synthesized via a simple wet chemical process using less expensive and earth abundant materials. The synthesized WP cocatalyst nanoparticles are ball-milled and loaded onto the surface of a CdS photocatalyst, forming a WP/CdS composite. During visible light photocatalytic hydrogen production via the photocatalytic oxidation of an aqueous ammonium sulfite solution, the WP/CdS has shown high photocatalytic activity and stability in comparison with Pt and Pd noble metal cocatalysts. It is found that the 4.0 wt% WP loaded CdS photocatalyst can achieve as high as a 155.2 μmol h−1 hydrogen evolution rate, which is 11.67 times higher than that of the pure CdS photocatalyst and at about 1/3 of the hydrogen production rate (510.4 μmol h−1) of 0.5 wt% Pt loaded Pt/CdS. Electrochemical characterizations of the WP cocatalyst indicate that WP has high electrocatalytic activity and an efficient charge transfer rate between CdS and WP nanocrystals. These are the key factors responsible for the enhanced photocatalytic activity of the WP/CdS photocatalyst.

Cost effective Mo rich Mo2C electrocatalysts for the hydrogen evolution reaction

Cost-effective electrocatalysts for the hydrogen evolution reaction (HER) are attractive for energy conversion and storage processes. Despite high efficiency for the HER, noble metal electrocatalysts are not cost-effective for hydrogen production due to their high cost and low abundance. This paper reports a new and efficient non-noble HER electrocatalyst based on molybdenum rich Mo2C (Mo–Mo2C). The results show that the onset overpotential of Mo–Mo2C is only 67 mV and its Tafel slope is as low as 55 mV dec−1. To obtain a 10 mA cm−2 cathodic current density, the Mo–Mo2C catalyst requires only a 150 mV overpotential. In an acidic electrolyte, the Mo–Mo2C catalyst can achieve 0.019 mA cm−2 exchange current density. The electrocatalyst also demonstrates an excellent long-term durability of more than 12 hours at a current density of 20 mA cm−2. Characterization of the Mo–Mo2C catalyst indicates that its superior HER activities can be attributed to the electrode conductivity improvement for the charge transfer. This study shows that molybdenum rich Mo2C is potentially a highly active non-noble metal electrocatalyst for hydrogen production via water electrolysis.