Tuning the Wettability of Vertically Aligned CNT-TiO2 Hybrid Electrodes for Enhanced Supercapacitor Performance

Boosting the energy density of carbon-based materials is of great importance for developing supercapacitors with high cyclic stability. Chemical vapor deposition (CVD) growth of vertically aligned carbon nanotube (VACNT) forest is reported with millimeter height on Si/SiO2 substrate and engineer its microstructure and wettability for remarkable supercapacitor performance. A simple method to alter the microstructure of VACNT forest by adding small amount of ethanol in KOH electrolyte is demonstrated. The modified electrolyte facilitates the formation of pores and channels in CNT forest and leads to increased active surface area. Microstructure-engineered CNT forest is further coated conformally with 3 nm of TiO2 using atomic layer deposition. The developed VACNT-TiO2 hybrid shows 102-fold increase in energy density, 20-fold increase in specific capacitance, and 13-fold increase in power density along with high capacitive retention as compared to bare VACNT in KOH. This improved performance is correlated to formation of micro channels that enable more accessible surface area for electrolytic ions. The demonstrated simple electrolyte engineering approach with increased energy density of aligned CNT-TiO2 hybrid is relevant for portable energy storage applications.