PROTON INSERTION INTO THIN-FILMS OF AMORPHOUS WO3 - THERMODYNAMIC STUDY

The electrochemical incorporation of protons at ambient temperature into thin films of amorphous tungsten trioxide has been thermodynamically studied. The variation of the chemical potential of the inserted species in WO3 has been measured using an electrochemical method. The reduction of the amorphous oxide proceeds in a homogeneous phase, as shown by the shape of the E vs. x curve. A theoretical treatment of the E vs. x curve allows us to determine the repulsive interaction between the inserted species as insertion occurs and the influence of the electronic term on the potential. The Gibb's free energy of the insertion reaction: x/2 H-2(g) + WO3(s) --> HxWO3(s), and the corresponding Gibb's free of the inserted sites are determined from the E vs. x data. The results are compared with those obtained with crystalline oxides.