Hydrogenated Ti2O3: A semiconducting, optically active electrode for planar microsupercapacitors

Hydrogenated titanium sesquioxide (H:Ti 2 O 3 ) is exploited for a new class of semiconducting electrode for microsupercapacitor (MSC). The surface hydroxyl groups and oxygen related defect states of Ti 2 O 3 were altered by hydrogenation that effectively participate in protons exchange process attributing to pseudocapacitive response in energy storage. A remarkable enhancement (∼2.3 times) of the energy storage activity is measured as compared to the pristine counterpart with the specific capacitance of 82.6 mF/cm 2 at the scan rate of 1 mV/s. A planar MSC is fabricated using the intrinsic narrow bandgap (∼0.1 eV) character and efficient energy storage activity of the H:Ti 2 O 3 that exhibits the specific capacitance of 13.5 mF/cm 2 , which is ∼7 times higher compared to MSCs based on carbon materials at 5 mV/s. The large capacitance of MSC is attributed to the efficient redox-active sites of H:Ti 2 O 3 , faster electrolyte ions diffusion in nanoparticles electrodes and complete utilization of electrochemically active surfaces. Furthermore, owing to the ultra-narrow bandgap, the MSC shows infrared light sensitive response, where an efficient enhancement (∼58%) in the energy storage response was observed under light illumination as compared to the absence of light because of the photothermal effect in H:Ti 2 O 3 .