Selective Electrodeposition of Tantalum(V) Oxide Electrodes

Thin films of TaO_xH_y were cathodically electrodeposited from an aqueous solution containing Ta-IPA precursor and KNO₃ as a sacrificial agent. It was shown that the deposition resulted from a precipitation reaction triggered by the local change of pH at the surface of working electrode. Combined structural and compositional analysis revealed that during the electrodeposition the oxidation state of tantalum remained constant, Ta(V). The as-deposited films are mesoporous amorphous tantalum oxide hydrate films, which can be converted to either pure Ta₂O₅ or Ta₃N₅ by high-temperature annealing in either air (or Ar) or ammonia, respectively. The Ta₃N₅ electrodes exhibited promising PEC activity for water oxidation. These results open the door for the reduced temperature synthesis of Ta₃N₅ electrodes on TCO substrates which would allow for efficient overall solar water splitting.