This paper describes the synthesis and characterisation of high‐surface‐area mesoporous titanium oxides with polypyrrole nanowires within the pores, and the subsequent variation of synthesis parameters such as polymer‐loading level and pore size to improve performance. These modifications are employed to improve the electron conductivity of the amorphous host and exploit the high internal surface areas of over 800 m2g−1 for potential use as a lithium battery cathode material, once fully optimised, with fast charge‐transfer kinetics expected from the proximity of the vast majority of the redox sites at, or near, the surface of the inner pore walls. A full structural characterisation, in addition to electrochemical assessments, of the composite materials is presented and compared to the pristine mesoporous titanium oxide hosts. The best synthesis conditions were achieved with 5 % polymer loading and the largest pore sized host materials. Excessive polymer loading and smaller pore sizes lead to decreased performance, possibly due to inhibition of Li+ transport. The C18 templated TiO2 composite produced the best capacity retention at 58 % retention, and the C12 composite produced the highest initial capacity of 170 mAh g−1 by using a current density of 1 mAcm−2.

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ABSTRACT:A vanadium aryl hydride gel was prepared by thermal decomposition and subsequent hydrogenation of tetraphenyl vanadium and evaluated for electrochemical and hydrogen storage performance. Characterization by IR, XRD, XPS, nitrogen adsorption, and TGA suggests that the material consists predominantly of a mixture of vanadium centers in oxidation states of II-IV bound together by bridging hydride and phenyl groups. Electrochemical properties were explored to probe the reversible oxidation state behavior and possible applications to Li batteries, with the hypothesis that the low mass of the hydride ligand may lead to superior gravimetric performance relative to heavier vanadium oxides and phosphates. The material shows reversible redox activity and has a promising peak capacity of 131 mAhg -1 , at a discharge rate of 1 mAcm -2 , comparable to bulk VO2 samples also tested in this study. After repeated charge discharge cycling for 50 cycles, the material retained 36% of its capacity. The material also shows improved hydrogen storage performance relative to previously synthesized VH3-based gels, reaching a reversible gravimetric storage capacity of 5.8 wt% at 130 bar and 25 °C. Based on the measured density, this corresponds to a volumetric capacity of 79.77 kgH2 m -3 , demonstrating that the 2017 US DOE system goals of 5.5 wt% and 40 kg H2 m -3 may be achievable upon containment in a Type 1 tank and coupling to a fuel cell.

This paper describes the synthesis and characterization of high surface area mesoporous Ti and Ta oxides with polypyrrole nanowires in the pores. The incorporation of polymer was used to improve the electron conductivity into the channels inside these high surface area (400–1000 m2 g−1) materials in order to exploit surface redox sites for possible pseudocapacitive Li storage. Synthesis was achieved using catalyst‐free UV‐initiated polymerization of vapor‐loaded pyrrole monomer. The best materials showed improved conductivity for both the Ti and Ta oxides as well as improved Li capacity (190 mA h g−1) relative to the pristine material (128 mA h g−1) and superior capacity retention (49 % as compared to 22 %) for the Ti composites. The retention in surface area was also 87 % compared to 49 % reported previously for analogous materials synthesized by catalyst‐initiated methods, which only yielded Li capacities of 170 mA h g−1, further highlighting the superiority of this new photochemical approach.

This paper describes the synthesis and electrochemical properties of mesoporous titanium oxysulfides prepared through the chemical treatment of pristine mesoporous titanium oxide under various synthesis conditions. The materials were doped with sulfur by using hexamethyldisilathiane (HMDST), a strategy that was developed to improve the conductivity of the material, whilst also retaining the porosity and thermal stability. Varying amounts of HMDST and different synthesis temperatures were tested to optimize the surface area and electrochemical performance. Lower temperatures generally yielded materials with superior properties and, even though the conductivity was improved by using higher loading levels of HMDST, it also led to a drop in initial capacity at the highest synthesis temperature of 200 °C (137–41 mAh g−1). The best performing material was, thus, synthesized by using the highest level of HMDST (3.5 mL) at lower heating temperatures (100–150 °C). This set of conditions maximizes the combination of surface area, initial capacity, conductivity, and capacity retention, the latter of which was notably superior to that of the pristine material (81 vs. 35 %), emphasizing the overall success of this doping strategy in improving the electrochemical properties of these otherwise insulating materials.