Ordered mesoporous carbon decorated with metal oxides: a comparison of amorphous and crystalline WO3 for energy storage applications

The sustained growth rate of renewable energy sources and widespread utilization of portable electronic devices have underlined the demands for efficient portable energy storage with high rate capability and large specific capacity. Subsequently, electrochemical energy storage (EES) is considered a cut-edging technology in energy applications, as it accounts for providing high specific power and capacity in addition to low cost and long cycling stability. Tungsten oxide and mesoporous carbon structure have both caused attraction due to their long life cycle and less environmental impact, in addition to the high theoretical capacity of the former and high specific surface area of the latter material. In this project, a hybrid material, produced from ordered mesoporous carbon and WO3 (OMC-WO3), is investigated as the active material of half electrochemical cells. The storage properties are highly dependent on the nature of the carbonaceous material (providing a high surface area with low electrical resistance) and the investigated metal oxide structures (WO3) (e.g., phases and degree of crystallinity). Both OMC-WO3 and OMC are tested in water-based (0.5 M H2SO4) cells and aprotic-based coin cells (1 M LiPF6 in EC:DMC). OMC is obtained by the hard-template method through the carbonization of sucrose into the mesopores of the SBA-15 silica. The hybrid powder is synthesized by impregnation of phosphotungstic acid into OMC, followed by thermal decomposition in N2 atmosphere in three different temperatures, including 300, 400, 600 C, providing three different samples. Regarding the XRD and FE-SEM observations, the first two hybrid materials are amorphous while the crystalline structure appears after the thermal annealing at 600 C. Evidently, the OMC-WO3-400 aqueous cell and OMC-WO3-600 aprotic coin cell exhibit the highest specific energies with 732 mAh/g (scan rate = 5 mV/s after 5000 cycles) and 114 mAh/g (current density = 560 mA/g after 1600 cycles), respectively. Therefore, as the future reference in the design of high-performance EES devices, the hybrid material can be considered as anode and pristine OMC can be a possible choice for the cathode.