Binder-free cobalt molybdate nanoflakes grown on nickel foam as a hybrid supercapacitor and electrocatalyst for methanol oxidation reaction

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2024-01, Vol.299, p.116972, Article 116972
• Main Authors: Muthu, Dinesh, Sadhasivam, T., Hwan Oh, Tae
• Format: Article
• Language: English
• Subjects: Binary metal oxide; Cobalt molybdate; Electrocatalyst; Energy storage; Methanol oxidation; Supercapacitor
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2023.116972

Schematic CoMoO4 before and after a long cycle. [Display omitted] •Cobalt molybdate nanoflakes with a thickness of ∼91 nm were grown on nickel foam.•CoMoO4/NF exhibited a capacitance (capacity) of 359.8 F g−1 (215.88 C g−1).•After 9500 cycle, the nanoflake size decreased to 53.34 nm from 91 nm.•CoMoO4/NF showed good oxidation properties towards methanol to carbon dioxide.•After 1000 cycles, the methanol oxidation peak shifted to −0.052 V from −0.00884 V. In this work, Cobalt molybdate nanoflakes were grown on nickel foam which is used as an electrode for the supercapacitor and electrocatalyst for the methanol oxidation reaction. XRD, Raman, and XPS analysis further confirm the formation of CoMoO4. FESEM image shows that the CoMoO4 nanoflakes with a thickness of ∼91 nm and diameter of ∼1 µm were formed. In a three-electrode system, CoMoO4/NF exhibited a capacitance (capacity) of 359.8 F g−1 (215.88 Cg−1). CoMoO4/NF retained 73.8 % of capacitance after 9500 cycles with 89.4 % of coulombic efficiency. After a long cycle, the electrode undergoes XPS and FESEM analysis. From XPS, its major oxidation state was changed from 2+ to 3+ and Mo was leached out from the electrode. FESEM analysis showed that nanoflake size decreased to 53.34 nm from 91 nm. The aqueous hybrid supercapacitor (HSC) exhibited a capacitance of 86 F g−1 at 1 A g−1. Aqueous HSC exhibited an energy density of 17.5 Wh Kg−1 and a power density of 2970 W Kg−1. CoMoO4/NF showed good oxidation properties towards methanol to carbon dioxide. After the 1000 cycles, the forward oxidation peak shifted to −0.052 V from −0.00884 V vs Hg/HgO. After the 1000 cycles, a 46 % decrease in methanol oxidation current is observed.