Liqing He

Facile synthesis of anhydrous alkaline earth metal dodecaborates MB12H12 (M = Mg, Ca) from M(BH4)2.

Metal dodecaborates M2/nB12H12 are among the dehydrogenation intermediates of metal borohydrides M(BH4)n with a high hydrogen density of approximately 10 mass%, the latter is a potential hydrogen storage material. There is therefore a great need to synthesize anhydrous M2/nB12H12 in order to investigate the thermal decomposition of M2/nB12H12 and to understand its role in the dehydrogenation and rehydrogenation of M(BH4)n. In this work, anhydrous alkaline earth metal dodecaborates MB12H12 (M = Mg, Ca) have been successfully synthesized by sintering M(BH4)2 (M = Mg, Ca) and B10H14 in a stoichiometric molar ratio of 1 : 1. Thermal decomposition of MB12H12 shows multistep pathways with the formation of H-deficient monomers MB12H12-x containing icosahedral B12 skeletons and is followed by the formation of (MByHz)n polymers. Comparison of the thermal decomposition of MB12H12 and M(BH4)2 suggests different behaviours of the anhydrous MB12H12 and those formed from the decomposition of M(BH4)n.

Understanding and suppressing side reactions in Li–air batteries

Li–air batteries have attracted intensive recent research attention owing to their extremely high energy density that is ten times that of the conventional Li-ion batteries; however, achieving this energy capability in practical Li–air batteries has been proven to be difficult. A lot of effort has been devoted to improving their stability, energy efficiency and cycle life with a better understanding of the reaction mechanisms. The electrochemical processes associated with the reversible formation/decomposition of Li2O2 are affected by the surrounding conditions, which often involve several side reactions. In this review, we summarize recent progress in Li–air batteries, especially in the side reactions taking place in the electrochemical process, including carbon corrosion in the cathodes, electrolyte degradation, and the shuttle effect of redox mediators in the electrolytes as well as contaminants from the air (CO2, H2O, and N2). The main strategies for suppressing or making full use of these side reactions for enhancing the performance of Li–air batteries are presented. Meanwhile, we also provide perspectives on the development of Li–air batteries.

Advanced SEM and TEM Techniques Applied in Mg-Based Hydrogen Storage Research

Mg-based materials are regarded as one of the most promising candidates for hydrogen storage. In order to clarify the relationship between the structures and properties as well as to understand the reaction and formation mechanisms, it is beneficial to obtain useful information about the size, morphology, and microstructure of the studied materials. Herein, the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques for the representation of Mg-based hydrogen storage materials is described. The basic principles of SEM and TEM are presented and the characterizations of the size, morphology observation, phase and composition determination, and formation and reaction mechanisms clarification of Mg-based hydrogen storage materials are discussed. The applications of advanced SEM and TEM play significant roles in the research and development of the next-generation hydrogen storage materials.

Evaluation of A-Site Ba2

Exploring earth-abundant and cost-effective catalysts with high activity and stability for a hydrogen evolution reaction (HER) is of great importance to practical applications of alkaline water electrolysis. Here, we report on A-site Ba2+-deficiency doping as an effective strategy to enhance the electrochemical activity of BaCo0.4Fe0.4Zr0.1Y0.1O3−δ for HER, which is related to the formation of oxygen vacancies around active Co/Fe ions. By comparison with the benchmarking Ba0.5Sr0.5Co0.8Fe0.2O3−δ, one of the most spotlighted perovskite oxides, the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ oxide has lower overpotential and smaller Tafel slope. Furthermore, the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ catalyst is ultrastable in an alkaline solution. The enhanced HER performance originated from the increased active atoms adjacent to oxygen vacancies on the surface of the Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ catalyst induced by Ba2+-deficiency doping. The low-coordinated active atoms and adjacent oxygen ions may play the role of heterojunctions that synergistically facilitate the Volmer process and thus render stimulated HER catalytic activity. The preliminary results suggest that Ba2+-deficiency doping is a feasible method to tailor the physical and electrochemical properties of perovskite, and that Ba0.95Co0.4Fe0.4Zr0.1Y0.1O3−δ is a potential catalyst for HER.