Cathode materials for rechargeable aluminum batteries : current status and progress

This work was financially supported by the National Natural Science Foundation of China (No. 21477046, 21277060 and 51361130151), Key Technology R&D Program of Shandong Province (No. 2016ZDJS11A03), Science Development Project of Shandong Province (No. 2014GGX104004) and Natural Science Foundation of Shandong Province (No. ZR2015EM044).Peer reviewedPostprin

Electrochemical impacts of sheet-like hafnium phosphide and hafnium disulfide catalysts bonded with reduced graphene oxide sheets for bifunctional oxygen reactions in alkaline electrolytes

Non-noble metal-based catalysts with efficient catalytic activities for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are critical for energy conversion devices, including fuel cells and metal–air batteries. In this work, novel hafnium phosphide-reduced graphene oxide nanosheets (HfP-rGO NS) and hafnium disulfide-reduced graphene oxide nanosheets (HfS2-rGO NS) were synthesized and investigated as bifunctional electrocatalysts for OER and ORR. The prepared HfP-rGO NS and HfS2-rGO NS catalysts showed nanosheet structures, where the HfP or HfS2 nanosheet was closely packed with rGO. A unique methodology was adopted to lodge the non-metal oxide catalytic sheets (i.e., HfP and HfS2) over the rGO sheets, which positioned the oxide layer on the catalytic sheet surface for instant oxygen evolution. Low intensity X-ray diffraction patterns and Raman spectra confirmed the sheet-like structure of HfP-rGO NS and HfS2-rGO NS. Scanning electron microscope mapping images revealed that all elements (i.e., Hf, P, C and O for HfP-rGO NS and Hf, S, C and O for HfS2-rGO NS) were equally distributed in the synthesized heteroatomic nanosheets. Moreover, both the HfP-rGO NS and HfS2-rGO NS demonstrated excellent durability for both ORR and OER. This outperforms the most state-of-the-art non-precious-metal-based bifunctional catalysts, which is attributed to the synergistic effect of rGO and Hf-based catalysts. The different ORR and OER reaction potentials in HfP-rGO NS and HfS2-rGO NS likely result from the influence of HfP and HfS2

Recent Advance on Polyaniline or Polypyrrole-Derived Electrocatalysts for Oxygen Reduction Reaction

The fuel cell, as one of the most promising electrochemical devices, is sustainable, clean, and environmentally benign. The sluggish oxygen reduction reaction (ORR) is an important fuel cell cathodic reaction that decides the efficiency of the overall energy conversion. In order to improve ORR efficiency, many efficient catalysts have been developed, in which the N-doped material is most popular. Polyaniline and polypyrrole as common aromatic polymers containing nitrogen were widely applied in the N-doped material. The shape-controlled N-doped carbon material can be prepared from the pyrolysis of the polyaniline or polypyrrole, which is effective to catalyze the ORR. This review is focused on the recent advance of polyaniline or polypyrrole-based ORR electrocatalysts

A Hybrid Material Combined Copper Oxide with Graphene for an Oxygen Reduction Reaction in an Alkaline Medium

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 × 10−5 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

Synthesis and Characterizations of Zinc Oxide on Reduced Graphene Oxide for High Performance Electrocatalytic Reduction of Oxygen

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 × 10−5 mA/cm2), positive onset potential (−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

Preparation and Combustion Mechanism of Boron-Based High-Energy Fuels

Due to the characteristics of high energy density and a high calorific value, boron has become a high-energy fuel and shows great potential to be a high-performance candidate for propellants. However, the wide applications of boron are still limited by the characteristics of easy oxidization, ignition difficulty, a long combustion duration, and combustion products that readily adhere to the surface and inhibit full combustion. Therefore, how to overcome the shortcomings and improve the combustion efficiencies of boron-based fuels have become the highlights in exploring novel high-performance energetic materials. In this paper, the prevalent preparation methods and the corresponding combustion mechanisms of boron-based energetic materials are briefly summarized. The results showed that the boron-based energetic materials can be prepared by surface coating, mechanical milling, and ultrasonic mixing methods. At the same time, the corresponding ignition delay and combustion efficiency were also analyzed according to different combustion tests. The results showed that the boron-based composites with different additives had different combustion characteristics. The combustion of boron-based energetic materials can be optimized by removing surface oxide layers, providing extra heat, inhibiting the formation of or the rapid removal of the combustion intermediates, and increasing the diffusion rate of oxygen. With the improvement of the combustion efficiency of boron-based energetic materials, boron-based high-energy fuels will become more and more widely adopted in the future

Constructing Strategies and Applications of Nitrogen-Rich Energetic Metal–Organic Framework Materials

The synthesis of energetic metal–organic frameworks (EMOFs) with one-dimensional, two-dimensional and three-dimensional structures is an effective strategy for developing new-generation high-energy-density and insensitive materials. The basic properties, models, synthetic strategies and applications of EMOF materials with nitrogen-rich energetic groups as ligands are reviewed. In contrast with traditional energetic materials, EMOFs exhibit some interesting characteristics, like tunable structure, diverse pores, high-density, high-detonation heat and so on. The traditional strategies to design EMOF materials with ideal properties are just to change the types and the size of energetic ligands and to select different metal ions. Recently, some new design concepts have come forth to produce more EMOFs materials with excellent properties, by modifying the energetic groups on the ligands and introducing highly energetic anion into skeleton, encapsulating metastable anions, introducing templates and so on. The paper points out that appropriate constructing strategy should be adopted according to the inherent characteristics of different EMOFs, by combining with functional requirements and considering the difficulties and the cost of production. To promote the development and application of EMOF materials, the more accurate and comprehensive synthesis, systematic performance measurement methods, theoretical calculation and structure simulation should be reinforced

Reduced graphene oxide intercalated co2c or co4n nanoparticles as efficient and durable fuel cell catalyst for oxygen reduction

Research on catalysis for fuel cells is extremely important to enhance the sluggish oxygen reduction reaction (ORR) using heterogeneous catalyst materials. In this work, cobalt carbide (Co<small>2</small>C) and cobalt nitride (Co<small>4</small>N) nanoparticles were intercalated with reduced graphene oxide (rGO) sheets through heteroatom doping and utilized for the ORR in alkaline fuel cells, in which rGO acted as a catalyst support. Cyclic voltammetry results indicated that the ORR half-wave potentials of Co<small>2</small>C/rGO and Co<small>4</small>N/rGO were found to be −0.095 V and −0.118 V, respectively. Chronoamperometric studies revealed the excellent catalytic stability of the prepared catalysts. The reaction kinetics study showed that Co<small>2</small>C/rGO and Co<small>4</small>N/rGO pursued a 4e<small>−</small> (four electron) oxygen reduction process. The catalytic activity and stability in alkaline electrolyte indicated that Co<small>2</small>C/rGO and Co<small>4</small>N/rGO have great potential as alternatives to precious metal-based catalysts

Catalytic Performances of NiCuP@rGO and NiCuN@rGO for Oxygen Reduction and Oxygen Evolution Reactions in Alkaline Electrolyte

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim In this paper, the reduced graphene oxide (rGO) supported nickel-copper phosphide (NiCuP@rGO) nanotube and nickel-copper nitride (NiCuN@rGO) nano-rods were synthesized and the catalytic performances of them for oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in alkaline electrolyte were reported. Structure investigations show that the NiCuP@rGO has a nanotube structure, whereas NiCuN@rGO has aggregated nanorods structure. The catalytic performance of NiCuP@rGO and NiCuN@rGO for ORR and OER were investigated by cyclic voltammetry (CV), Tafel, rotating disc electrode (RDE) and rotating ring disc electrode (RRDE) tests and other methodologies. Results showed that both NiCuP@rGO and NiCuN@rGO had good catalytic performance for ORR, which major happened through 4-electron pathway. Thus, the catalytic performance of NiCuP@rGO for OER was much higher than that of NiCuN@rGO. The great difference in the catalytic performance should be attributed to the different electronegativity of nitrogen and phosphorus. The higher negativity of nitrogen facilitates the electron transfer from catalyst to oxygen molecules but inhibits the acceptance of electron from hydroxide ions in the alkaline electrolyte. On the other hand, the nanotube structure of NiCuP@rGO with superior electron conductivity facilitates the OER reaction on the catalyst surface. This paper provides a reference for the design of novel catalysts for ORR and OER

Study on Thermal Decomposition Behavior, Gaseous Products, and Kinetic Analysis of Bis-(Dimethylglyoximato) Nickel(II) Complex Using TG-DSC-FTIR-MS Technique

The fiber-like bis-(dimethylglyoximato) nickel(II) complex, Ni(DMG)2 was successfully synthesized. The obtained samples were characterized by SEM-EDS, FT-IR, XRD, and XPS. The TG-DSC-FTIR-MS coupling technique was used to characterize the thermal decomposition behavior and evolved gas analysis of Ni(DMG)2. The non-isothermal decomposition reaction kinetic parameters were obtained by both combined kinetic analysis and isoconversional Vyazovkin methods. It was found that Ni(DMG)2 begins to decompose at around 280 &deg;C, and a sharp exothermic peak is observed in the DSC curve at about 308.2 &deg;C at a heating rate of 10 &deg;C&middot;min&minus;1. The main gaseous products are H2O, NH3, N2O, CO, and HCN, and the content of H2O is significantly higher than that of the others. The activation energy obtained by the combined kinetic analysis method is 170.61 &plusmn; 0.65 kJ&middot;mol&minus;1. The decomposition process can be described by the random nucleation and growth of the nuclei model. However, it was challenging to attempt to evaluate the reaction mechanism precisely by one ideal kinetic model