Improved supercapacitor and oxygen evolution reaction performances of morphology-controlled cobalt molybdate

Abstract

Herein, various morphologies (Bundle of rods, rods, nanoparticles, and umbra) of cobalt molybdate (CoMoO4) were obtained by changing the pH (6, 7, 8, and 9) of the solutions during hydrothermal synthesis. The evolution mechanism of different morphologies was explained. These samples were used for supercapacitors and oxygen evolution reaction (OER) catalysts. The higher double-layer capacitance (464 mF cm−2) was observed in CoMoO4 nanoparticles. It demonstrated high specific capacitance (191 F/g at a current density of 1 A/g) and excellent cyclic stability performance (98 % retention capability after 2000 cycles) in the 3 M KOH solution. Furthermore, CoMoO4 nanoparticles showed the lowest overpotential (200 mV at 10 mA/cm2) and onset potential in linear sweep voltammetry polarization curves, superior turnover frequency (0.0095 s−1), and low Tafel slopes (149 mV/dec) compared to other morphologies. According to chronoamperometry test, good electrochemical stability was noted in nanoparticles for 10 h towards OER. The higher energy storage and OER performances of CoMoO4 nanoparticles were related to excellent oxidation/reduction/electron transfer abilities, great surface area, and rich active sites. Thus, these findings suggest that morphology controlled CoMoO4 could be a great candidate for efficient supercapacitor electrode materials and OER catalysts.