Ta2O5-graphene Schottky heterojunction composite symmetric supercapacitor with ultrahigh energy density for self-powered pulse sensor driven by green long afterglow phosphor-enhanced solar cell

Abstract

Ta2O5 has received great attention in high-energy supercapacitors because of biocompatibility, multielectron redox and wide voltage window, but poor electronic conductivity limits its practical applications. The study reports synthesis of Ta2O5-graphene composite (G-Ta2O5) mediated by salicylic acid ionic liquid. The synthesis strategy realizes three-dimensional structure, excellent dispersion, small size of G-Ta2O5 nanorods and Schottky heterojunction. The unique structure improves the electronic conductivity and expands voltage window to 2 V. The G-Ta2O5 symmetrical supercapacitors exhibits ultrahigh specific capacitance of 554.7F g−1 at 1 A g−1, rate-capacity of 227.7F g−1 at 50 A g−1, capacity retention of 99.6% after 10,000 cycles at 1 A g−1 and energy density of 77.04 W h Kg−1 at 503.52 W kg−1. The supercapacitors was integrated with green long afterglow phosphor-enhanced solar cell and pulse device to construct wearable self-powered pulse sensor system. The introduction of phosphor brings an increases of 5.14% in the photocurrent during day time and an additional electric energy required for the sensor to work for more than 3 h at night. The sensor system can work for a long time no need of any additional power supply and shows one broad application prospect in disease diagnosis and monitoring health.