UV‐Initiated Synthesis of Electroactive High Surface Area Ta and Ti Mesoporous Oxides Composites with Polypyrrole Nanowires within the Pores

Abstract

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.

Low‐Temperature Synthesis and Electrochemical Properties of Mesoporous Titanium Oxysulfides

“…All samples demonstrate that the materials remain predominantly amorphous with a disordered wormhole pore structure. These observations are in close agreement with what has been reported previously for this class of materials …”

“…Mesoporous transition‐metal oxides typically show an initial endothermic weight loss up to 200 °C, caused by the loss of residual solvents present within the sample. After a temperature of 250 °C is reached, all materials show a sharp increase towards positive values in the DTA plot, typically indicating the start of the exothermic process in these samples . The weight loss between 0 and 250 °C can be used to determine the desorption of residual solvent within the samples.…”

“…After at emperature of 250 8Ci s reached, all materials show as harpi ncrease towards positive values in the DTAp lot, typically indicating the start of the exothermicp rocess in these samples. [19,20] The weight loss between 0a nd 250 8Cc an be used to determine the desorption of residual solvent within the samples. These losses in this temperature range were 9, 2, and 10 wt %f or samples made by using 1.5, 2.5, and 3.5 mL of HMDST, respectively.A st hese values correspond to loss of solvent, the unusually low value of 2wt% for the 2.5 mL sample may be attributedt ou neven drying between the three samples of different surfacea reas and porosity characteristics.T he second regiono ft he plot between 250 and 700 8Cc orresponds to the combustion of the organic content within the main sample, producing al arge exothermic peak as seen in our previous work.…”

“…These observations are in close agreement with what has been reported previously for this class of materials. [20]…”

“…[19] However,c ycling performance was still insufficient relative to competitive battery materials. Most recentlyi no ur group, similar methodologies were employed by using photopolymerization in place of ac hemical oxidanti nt he hope that improving the interface between the host and threaded polymer nanowires would further improve the conductivity and capacity; [20] however,s imilar results were observed, with polymer loadings of 5% being optimal.…”