RESUMO
The Co3O4 nanoparticle-modified indium tin oxide-coated glass slide (ITO) electrodes are successfully prepared using dicarboxylic acid as the self-assembled monolayer through a surface esterification reaction. The ITO-SAM-Co3O4 (SAM = dicarboxylic acid) are active to electrochemically catalyze oxygen evolution reaction (OER) in acid. The most active assembly, with Co loading at 3.31 × 10-8 mol cm-2, exhibits 374 mV onset overpotential and 497 mV overpotential to reach 1 mA cm-2 OER current in 0.1 M HClO4. The electron transfer rate constant (k) is acquired using Laviron's approach, and the results show that k is not affected by the carbon chain lengths of the SAM (up to 18 -CH2 groups) and that an increase in the average diameter of Co3O4 nanoparticles enhances the k. In addition, shorter carbon chains and smaller Co3O4 nanoparticles can increase the turn-over frequency (TOF) of Co sites toward OER. The Co3O4 nanoparticles tethered to the ITO surface show both a higher number of electrochemically active Co sites and a higher TOF of OER than the Co3O4 nanoparticles bound to ITO using Nafion.
RESUMO
Transition-metal selenides are regarded as promising electrode materials due to their superior electrochemical performances for supercapacitors. In this study, a nanorod-like hybrid of Ni0.85Se@Cu2-xSe on a Ni-foam substrate is successfully synthesized via a facile one-step route. The Ni0.85Se@Cu2-xSe nanorods are found to be deposited uniformly on the Ni-form substrates. When used as a battery-type electrode in a supercapacitor, the as-deposited Ni0.85Se@Cu2-xSe electrode exhibits a high specific capacity of 1831 F g-1 at 1 A g-1 and 78.4% of capacitance retention after 8000 cycles at 10 A g-1. Moreover, the assembled Ni0.85Se@Cu2-xSe//AC asymmetric supercapacitor (ASC) exhibits an energy density of 63.2 W h kg-1 at a power density of 800.1 W kg-1, as well as good cycling stability (92.1% capacitance retention after 5000 cycles).
