Triphenylamine-triazine polymer materials obtained by electrochemical polymerization: Electrochemistry stability, anions trapping behavior and electrochromic-supercapacitor application

Electrochemical energy-saving and storage applications such as electrochromism and supercapacitor were always accompanied by the ions exchange between electrolytes and electrode materials. The repeated ions exchange may cause ions trapping behavior. However, the ions trapping mechanism is still not fully understood, especially for conjugated organic/polymer films. Here we report two triphenylamine-triazine/ditrazine polymers obtained by electrochemical polymerization, namely pTPATz and pTPADTz. During the spectroelectrochemical experimental process, severe loss of charge capacity and optical contrast for both two polymer films were observed after long-term cycling under higher applied potential (1.4 V vs Ag/AgCl) in the electrolyte containing ClO4−. The XPS and FTIR results certificated the ClO4− anions trapping and the formation of weak O···N+ bond similar to hydrogen bond between triphenylamine and ClO4− anions, corresponding to a new binding energy of 402.1 eV of N+ in polymer films after cycling. The repeated ions exchange in the electrochemical charge/discharge process caused the continuous accumulation of O···N+-(C)3 group to form the irreversible anion trapping and charge doping effect, which surely induce the severe electrochemical instability of polymer films pTPATz and pTPADTz. After replacing ClO4−with BF4− anions, the electrochemical or cycling stability can be significantly improved based on two polymer films and their electrochromic-supercapacitor devices. This work provides an in-depth insight into the degradation phenomenon taking place in conjugated organic/polymer films from the viewpoint of ion trapping.