thermodynamic equilibrium potential, as shown in Figure 1. The HER process involves electro chemical H + adsorption and electrochemical/chemical desorption of H 2 , which is a two-electron transport process to generate a single H 2 molecule. By contrast, OER undergoes a four-electron transport coupled with the breaking of the OH bond, and the formation of the OO bond; therefore, for a kinetically hindered process, a high potential is needed to overcome the kinetic energy barriers. [12] To date, the OER remains a bottleneck in water splitting. Therefore, enormous efforts have been devoted to design and discover novel OER catalysts to satisfy the economic production of hydrogen from water splitting.Thus far, the benchmarks of OER catalysts in acidic solution are RuO 2 and IrO 2 , which are located on top of the volcanoplot, and express a relatively low overpotential (η), high current density, small Tafel slope, and high durability. [13,14] However, the wide utilization of RuO 2 or IrO 2 is hindered by high cost and insufficient reserves in the earth. Moreover, the aforementioned noble metal oxides are not the best OER electrocatalysts under alkaline conditions anymore. Their OER performances have been exceeded by several first-row transition metal based compounds (FTMCs). [15][16][17][18][19][20][21] Therefore, considerable attention has been focused on cost-effective alternatives that feature high electrocatalytic activity and life span. However, a relatively high overpotential (>300 mV) is still required by these nonprecious catalysts to reach a current density of 10 mA cm −2 , a widely used figure of merit that is equivalent to 12% solar-to-hydrogen efficiency. Thus, improving OER performance based on FTMCs is of great significance.Previous discoveries demonstrated that elemental doping is effective to boost the performance of FTMCs, given that the electronic structure of the catalysts can be tuned by dopants. [12,15] A well-known example is iron-doped nickel compounds, with trace amounts of iron-doped nickel hydroxides possibly enhancing the catalytic activity of OER significantly. [21][22][23] Thus, considerable efforts have been focused on optimizing elemental doping species and concentration and identifying the active sites of the catalysts. In addition to elemental doping, several novel and advantageous strategies have been developed Owing to its abundance, high gravimetric energy density, and environmental friendliness, hydrogen is a promising renewable energy to replace fossil fuels. One of the most prominent routes toward hydrogen acquisition is water splitting, which is currently bottlenecked by the sluggish kinetics of oxygen evolution reaction (OER). Numerous of electrocatalysts have been developed in the past decades to accelerate the OER process. Up to now, the first-row transition metal based compounds are in pole position under alkaline conditions, which have become subjects of extensive studies. Recently, significant advances in providing compelling catalytic performance as well as exploring t...

Highly hierarchical platelike FeWO(4) microcrystals have been synthesized by a simple solvothermal route using FeCl(3) x 6 H(2)O and Na(2)WO(4) x 2 H(2)O as precursors, where ethylene glycol (EG) plays an important role as a capping agent in directing growth and self-assembly of such unique structures. In addition, a certain amount of CH(3)COONa (NaAc) was necessary for the formation of such unique FeWO(4) microstructures. The photocatalytic property of as-synthesized hierarchical FeWO(4) microcrystals has been first studied, which shows excellent photocatalytic activity for the degradation of rhodamine B (RhB) under UV and visible light irradiation (modeling sunlight). Moreover, magnetic measurement indicates that hexangular FeWO(4) platelike microcrystals show a small ferromagnetic ordering at low temperature because of spin-canting of antiferromagnetic materials and surface spins of FeWO(4) nanoparticles.

A simple solvothermal route in a binary solution of triethylenetetramine (TETA) and deionized water (DIW) has been used to synthesize hierarchical hollow Co(9)S(8) microspheres with high surface area (80.38 m(2) g(-1)). An appropriate volume ratio of TETA:DIW has been found to be essential for the formation of hollow Co(9)S(8) microspheres. The magnetic study indicated that the Co(9)S(8) hollow microspheres are paramagnetic at high temperature and antiferromagnetic at low temperature. The oxygen reduction reaction experiments demonstrated that the onset potential of the Co(9)S(8) sample is 0.88 V, which is comparable to the value predicted for Co(9)S(8) (0.74 V) from the theoretical simulation. The discharge capability of Co(9)S(8) hollow microspheres as cathode materials for lithium ion batteries and their electrocatalytic activity for the oxygen reduction reaction (ORR) have been studied.