Study of self-heating phenomenon and its resultant effect on ultrafast gasochromic coloration of Pt-WO3 nanowire films

We report here the resultant effect of self-heating phenomenon on gasochromic coloration of WO3 nanowire films covered by Pt nanoparticles (Pt-WO3). Ultrafast coloration of Pt-WO3 nanowire films on millisecond scale (less than 10 ms), which is the fastest coloration process of tungsten oxide, is observed. We have found that a unique self-heating is the major cause for speeding up the coloration process. Such self-heating occurs after several cycles of coloration and bleaching in air, without extra heater, and as a result the temperature of nanowire film can increase to above 200 degrees C from room temperature. The characteristics and the underlying mechanism of the self-heating have been studied in depth. It is proposed that persistent and rapid catalytic reaction between H-2 and O-2 causes heating of Pt-WO3 nanowire. The relation between the maximum temperature of the sample reached by exposure to H-2 gas and the gas concentration can be described by a simple kinetic model, and it predicts that the down scaling of the nanowire diameter may enhance self-heating. (C) 2012 Elsevier B.V. All rights reserved.