Hydrous RuO2 film synthesized in an alkali-assisted steam thermal reactor: Low temperature synthesis and pseudocapacitance

Abstract

The method of preparing RuO2 thin film by decomposing RuCl3 precursor in steam has shown a potential of having lower temperature and higher capacitance in our previous research work. We have further improved the method of thermal decomposition in steam in our previous work and proposed the alkali-assisted steam thermal reactor (AASTR) method, which has achieved the synthesis of RuO2 thin film with a capacitance of 514 F·g−1 at a low temperature of 150 °C. In the AASTR method, a concentrated sodium hydroxide solution is chosen and placed at the bottom of the reactor. The Ti foil substrates are placed in the vapor phase and do not contact the sodium hydroxide solution. The sodium hydroxide solution is employed to absorb hydrogen chloride generated in the hydrolysis process of RuCl3 and thus promotes the hydrolysis process. As a result, thermal decomposition at a lower temperature (around 150 °C, the critical crystallization temperature) becomes possible due to the modified hydrolysis process. The film exhibits an almost ideal surface controlled pseudocapacitive performance due to its low charge transfer resistance in the charge/discharge process. Therefore, the AASTR method has promising applications in low-temperature synthesis of other hydrous metallic oxides.