Penghui Shi

Influence of calcination temperature on the catalytic performance of Co3O4/GO nanocomposites for Orange II degradation

In this study, graphene oxide-supported cobalt oxide catalysts (Co3O4/GO), which are used to degrade Orange II from water via advanced oxidation processes based on sulfate radicals, are synthesized in situ as heterogeneous catalysts via a solvothermal method. The catalysts were calcined at different temperatures of 300 °C, 500 °C, 700 °C, and 900 °C for 2 h in N2 atmosphere. The catalytic activities of both uncalcined and calcined catalysts were studied at the same time. The results show that all the formed catalysts exhibit high catalytic activity, and the catalysts calcined at 900 °C have the best activity for the degradation of Orange II. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) are employed to study the mechanism behind the change in catalytic activity. The analysis indicates that the change in the quantity of hydroxylated cobalt (Co–OH), the valence state of cobalt oxide and the reduction degree of graphene oxide (GO), which are all caused by calcination, are responsible for the change in catalytic activity.

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.

Simple method to construct three-dimensional porous carbon for electrochemical energy storage

A 3D porous carbon matrix with a high nitrogen content has been synthesized by employing particles of a nitrogen-enriched superabsorbent polymer (SAP) from the waste diapers of newborn babies. The derived material exhibits an ultrathin layered structure with interconnected pores and a large specific surface area. As it inherits the unique skeleton of the functional polymer from waste diapers, the resulting material (NSAPC-W) has been assessed as an inserting host anode with excellent ultralong cycling performance, as well as steady rate capability for both Li+ and Na+ ions in half cells. Furthermore, the unique structure imparts intimate structural interconnectivity, wide open channels for ion diffusion, and a large accessible surface area, as well as high structural stability, and opens up a wide horizon for electrochemical applications.

Recycling application of waste Li–MnO2 batteries as efficient catalysts based on electrochemical lithiation to improve catalytic activity

The ever-increasing consumption of tons of lithium batteries, for example, Li–MnO2 batteries, has generated great concern regarding their recycling. Currently, the developed or proposed cathode recycling processes often suffer from complex recycling procedures, potential secondary pollution, high operating costs, or thermal reprocessing. The discharge of Li–MnO2 batteries involves electrochemical lithiation, which is simultaneously accompanied by the transition from Mn(IV) to Mn(III). Studies on manganese-containing catalysts have experimentally and theoretically emphasized the role of Mn(III) as an important intermediate state for enabling catalytic reactions. We present herein a simple washing-recycling process for efficiently recycling the MnO2-based cathode materials as catalysts from depleted lithium batteries. The multiple important properties of the lithiated MnO2, including phase structure, oxidation state, surface oxygen species, and structural factors, were investigated in detail. Correspondingly, the effect of the degree of electrochemical lithiation on the catalytic activity of recycled MnO2 was observed to be continuously tuned. Compared with pristine MnO2, the recycled MnO2 exhibited remarkably enhanced catalytic activity for activating PMS to decompose contaminants. The catalytic activity was correlated with the composition of LixMnO2 generated in situ in Li–MnO2 batteries owing to the tuning of the Mn valence and structural factors. This study provides an attractive method for converting the depleted electrode materials of lithium batteries into catalysts to enhance their recycling efficiency.