Formation of RuO2 thin film using dopamine as a reducing, chelating, and adhesive agent simultaneously

We demonstrate a facile and seedless wet chemical process to deposit RuO2 thin film on a glass slide. The process entails the use of dopamine and its oxidized form, polydopamine (PDA), as the reducing and chelating agent, as well as the adhesive agent bonding the RuO2 and glass slide. The formula starts with the oxidation of K2RuCl5 to prepare RuO4 solution, followed by its reduction by dopamine to form chelated RuO2 colloids for the deposition of amorphous RuO2 thin film containing 26.5 at% hydrous RuO2 and 73.5 at% RuO2. After a mild Ar annealing, the RuO2 thin film exhibits a rutile phase with (110) preferred orientation. Elemental analysis indicates incomplete pyrolysis of PDA. Results from X-ray absorption spectroscopy confirm the presence of RuO4 and its transformation to RuO2. Electrochemical analysis of the adsorbed dopamine molecules on an ITO substrate validates the oxidative behavior of dopamine. The bonding strength of RuO2 thin film is determined by a tape-peeling test in which both the as-deposited and annealed RuO2 thin films show robust adhesion to the glass substrate. (C) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.