Supercapacitor and Photocurrent Performance of Tunable Reduced Graphene Oxide

Abstract

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 À1 at current density 0.5 A g À1 . It exhibits long cyclic stability (~95% after 10,000 cycles), excellent rate capability (56.5% retention at a current density 20 A g À1 ) and high energy density 10.76 W h kg À1 at power density 125 W kg À1 . 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.

A New Facile Synthesis of Tungsten Oxide from Tungsten Disulfide: Structure Dependent Supercapacitor and Negative Differential Resistance Properties

“…All the electrochemical experiments were carried out at room temperature (25 °C). For comparison of CV curves of the samples for different scan rates, the current ( i , A) was converted for a particular potential into the corresponding specific capacitance ( C s , F g −1 ) using the equation C s = i / mv , where “ m ” is the loading mass of the sample in gram and “ v ” is the applied scan rate in V s −1 . In GCD curves the time ( t , s) is converted to specific charge ( Q s , C g −1 ) using the equation Q s = it / m , where “ i ” is the applied current in ampere (A) and “ m ” is the loading mass of the sample in gm.…”

“…In GCD curves the time ( t , s) is converted to specific charge ( Q s , C g −1 ) using the equation Q s = it / m , where “ i ” is the applied current in ampere (A) and “ m ” is the loading mass of the sample in gm. The specific capacitance ( C s , F g −1 ) of samples were calculated from GCD curves using the following equationwhere Δ Q s is the total discharge specific charge in C g −1 and Δ V is the potential window in volt (V).…”

“…The measurements were performed using Keithley model 2401 source meter at 25 °C. The DC conductivity of the sample was measured by two‐probe method using the following equationwhere “ R ” is the resistance, “ a ” is the effective area of plate, “ d ” is the thickness of the pellet. The current−voltage ( I − V ) cycles were performed at potential window of −5 to +5 V.…”

“…To further investigate the potential application of our prepared WO 3 electrode, an ASC has been fabricated using it as negative electrode and our previously reported potassium iodide (KI) reduced (mildly reduced) graphene oxide (KG) as positive electrode as it is very efficient at the positive domain of voltage. [49] We have used poly(vinyl alcohol) (PVA)/H 2 SO 4 gel as electrolyte and separator. The potential range of the device is estimated from the individual CV curves of the electrode materials measured in three-electrode system in 0.5 m H 2 SO 4 .…”

Quantum‐Dot‐Mediated Controlled Synthesis of Dual Oxides of Molybdenum from MoS2: Quantification of Supercapacitor Efficacy

“…The results in Figure5cc learly demonstrate that, compared with MoO 3 ,t he MoO 2 electrodes are capable of better capacitive contributions and, with increasing mass loading, the capacitive contribution decreases. [36,59] The equivalent series resistance (R e ), which arises from the ionicr esistance of the electrolyte, inherent resistance of electrodem aterials, and contact resistanceatt he active material and current collector interface, is obtainedf rom the intercept at the real part (Z)atvery high frequencies. The decreasei nc apacitance with cycles might be because of dissolution of samples in the aqueous medium.…”