▎ 摘　　要

We have tuned reduction of graphene oxide (GO) using KI in water (KG) and in acidic medium of different strengths for better supercapacitor and photocurrent performance. FTIR, Raman, WAXS and XPS results indicate that KI in water acts as mild reducing agent, better than thermal reduction but weaker from that in acidic medium. KG exhibits dc-conductivity 0.18 mS/cm and specific capacitance 414 F g(-1) at current density 0.5 A g(-1). It exhibits long cyclic stability (similar to 95% after 10,000 cycles), excellent rate capability (56.5% retention at a current density 20 A g(-1)) and high energy density 10.76 W h kg(-1) at power density 125 W kg(-1). The supercapacitor performance of KG is attributed to both electrical double layer and pseudocapacitances. On irradiation with light KG exhibits highest photocurrent with a 72% increase from its dark current showing good cyclic stability. The results are explained from band gap values. Absence of photocurrent at highly reduced GO suggests that oxygenated groups at an optimum concentration is necessary for good photoresponse property. So reduction of GO using KI in water is suitable both for better supercapacitor and photocurrent performances.