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Development of highly efficient and low-cost electrocatalysts for oxygen reaction is of high importance for the commercialization of fuel cells. In the present study, we synthesized the hybrid of reduced graphene oxide (rGO) supported NiZnO2 nanoparticles (NPs) as highly efficient non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). The NiZnO2 NPs composed of ∼8 nm being relatively well distributed and strongly anchored on rGO. Electrochemical test reveals that the NiZnO2/rGO exhibits excellent electrocatalytic activity towards ORR, in terms of positive onset potential (0.80 V), high cathode current density (3.49 × 10−4), and low H2O2 yield (about 2%). The mechanism analysis shows that it favors the 4-electron pathway for the reduction of oxygen. Furthermore, the NiZnO2/rGO exhibits excellent electrochemical performance in term of durability.

In this feature article, Cu0.31Ni0.69O nanoparticles were assembled on reduced graphene nanosheets (Cu0.31Ni0.69O/rGO) by a simple hydrothermal method. The structural characterizations confirm that the synthesized nanoparticles with an average size around 9 nm are densely and uniformly assembled on the reduced graphene oxide (rGO) nanosheets. The electrochemical measurements demonstrate that the as-synthesized Cu0.31Ni0.69O/rGO catalyst exhibits excellent catalytic performance for oxygen reduction reaction with high cathodic current density (2.08 × 10−4 mA/cm2), positive onset potential (−0.21 V), low H2O2 yielding rate (less than 2.5%) and long-term running stability. The rotating disk and rotating ring-disk electrode measurements proved that the oxygen reduction reaction occurs on Cu0.31Ni0.69O/rGO through a high efficient four-electron pathway. The Cu0.31Ni0.69O/rGO nanoparticles shows great potential to be promising noble metal-free catalyst for cathodes of alkaline fuel cells.

The oxygen reduction reaction (ORR) is a key reaction for fuel cells and metal–air batteries. In this work, zinc sulfide (ZnS) nanoparticles were supported by reduced graphene oxide (rGO) and utilized for the ORR. Scanning electron microscopy and transmission electron microscopy profiles reveal that the ZnS nanoparticles are uniformly distributed on the rGO. Cyclic voltammograms, rotating disk electrode and rotating ring disk electrode measurements demonstrated that the hierarchical ZnS/rGO sheets exhibited excellent electrocatalytic activity for the ORR in an alkaline medium, which was evidenced by their high cathodic current density, positive onset potential, low H2O2 yield, and high electron transfer number. Chronoamperometric studies revealed the excellent catalytic stability of the prepared catalyst. The catalytic activity and stability in the alkaline electrolyte indicated that ZnS/rGO sheets have great potential as alternatives to precious metal-based catalysts.

The vapor–liquid equilibrium (VLE) data of the ethanol + sec-butyl acetate, 1-propanol + sec-butyl acetate, and 2-propanol + sec-butyl acetate mixtures were determined at 101.3 kPa. The first principle quantum chemistry calculation method, which focuses on the hydrogen bond and interaction energies, is used to give insight into interactions at the molecular level. The experimental VLE data passed the thermodynamic consistency test. The data were regressed using Wilson, nonrandom two liquids, and universal quasi-chemical equations. The 1-propanol + sec-butyl acetate mixture forms a minimum temperature azeotropic mixture. The azeotropic temperature is 370.01 K, and the composition of 1-propanol is 89.2 mol % when calculated with the Wilson model.

In this work, an electrode material based on CuO nanoparticles (NPs)/graphene (G) is developed for ORR in alkaline medium. According to the characterization of scanning electron microscope and transmission electron microscope, CuO NPs are uniformly distributed on the wrinkled G sheets. The X-ray diffraction test reveals that the phase of CuO is monoclinic. The CuO/G hybrid electrode exhibits a positive onset potential (0.8 V), high cathodic current density (3.79 &times, 10&minus, 5 mA/cm2) and high electron transfer number (four-electron from O2 to H2O) for ORR in alkaline media. Compared with commercial Pt/C electrocatalyst, the CuO/G electrode also shows superior fuel durability. The high electrocatalytic activity and durability are attribute to the strong coupling between CuO NPs and G nanosheets.

Electrocatalysts for the oxygen reduction (ORR) reaction play an important role in renewable energy technologies, including fuel cells and metal-air batteries. However, development of cost effective catalyst with high activity remains a great challenge. In this feature article, a hybrid material combining ZnO nanoparticles (NPs) with reduced graphene oxide (rGO) is applied as an efficient oxygen reduction electrocatalyst. It is fabricated through a facile one-step hydrothermal method, in which the formation of ZnO NPs and the reduction of graphene oxide are accomplished simultaneously. Transmission electron microscopy and scanning electron microscopy profiles reveal the uniform distribution of ZnO NPs on rGO sheets. Cyclic voltammograms, rotating disk electrode and rotating ring disk electrode measurements demonstrate that the hierarchical ZnO/rGO hybrid nanomaterial exhibits excellent electrocatalytic activity for ORR in alkaline medium, due to the high cathodic current density (9.21 &times, 10&minus, 5 mA/cm2), positive onset potential (&minus, 0.22 V), low H2O2 yield (less than 3%), and high electron transfer numbers (4e from O2 to H2O). The proposed catalyst is also compared with commercial Pt/C catalyst, comparable catalytic performance and better stability are obtained. It is expected that the ZnO/rGO hybrid could be used as promising non-precious metal cathode in alkaline fuel cells.

The development of sustainable enantioselective olefin epoxidation and alkane oxidation reactions under environmentally friendly conditions is an ultimate goal that has long been pursued in chemistry. Excellent examples are naturally occurring monooxygenases, which are able to catalyze a variety of biological oxidation reactions using molecular oxygen (O2) that afford high chemo-, regio-, and/or stereoselectivities. Inspired by the oxidation reactions of iron-containing monooxygenases, substantial efforts have been made towards the development of efficient catalysis for the enantioselective oxidation of hydrocarbons using bioinspired nonheme iron and manganese catalysts under mild conditions. In this review, we describe synthetic models that functionally mimic these monooxygenases. There are a large number of nonheme iron and manganese complexes that can epoxidize olefins with high enantioselectivities, whereas only a few examples are reported for nonheme iron- and manganese-catalyzed enantioselective oxidation of inert C(sp3)–H bonds. In addition to its great achievement for synthetic applications, mechanistic studies in biomimetic oxidation systems have also been intensively investigated, providing important insights into the understanding of the nature of active oxidants and the formation of the intermediates via O O bond activation and the design of more elegant biomimetic oxidation catalysts. Thus, these bioinspired nonheme iron and manganese complexes used as catalysts in the enantioselective C C epoxidation and aliphatic C(sp3)–H oxidation are the focus of discussion in this review.

The isobaric vapor–liquid equilibrium (VLE) data of methyl ethyl ketone (MEK) + sec-butyl acetate (SBAC), 2-methoxyethanol + SBAC, and 1, 2-dimethoxyethane (DME) + SBAC were determined at 101.3 kPa by using an Ellis vapor–liquid equilibrium still. The experimental data passed the thermodynamic consistency test by Herington method and Wisniak test. The VLE values were correlated by the nonrandom two-liquid (NRTL), universal quasichemical activity coefficience (UNIQUAC), and Wilson activity-coefficient models. The results indicated that the three models had good agreement with the experimental data. The 2-methoxyethanol + SBAC system forms a minimum temperature binary azeotrope at 101.3 kPa. The azeotropic temperature is 383.86 K, and the composition of SBAC is 85.1 mol %.