FeMoO4 nanoparticles as functional negative electrode material for high performance supercapacitor devices over a wide pH range

Rational design of functional negative electrode materials with wide potential window, high capacitance, high rate capability, cost-effectiveness, and durability in various electrolytes is a grand challenge to realize the fabrication of high-performance supercapacitor devices. We report the successful synthesis of β-FeMoO4 nanoparticles and their utilization as a negative electrode in supercapacitor devices over a wide pH range. The morphology, elemental, and surface analysis of the fabricated β-FeMoO4 are characterized via FESEM, EDS, and the N2-adsorption/desorption techniques. Moreover, the elemental composition and the crystal structure of the fabricated FeMoO4 are elucidated using XPS and XRD analyses. Upon analyzing its electrochemical performance as a supercapacitor electrode in 2 M KOH, the fabricated β-FeMoO4 reveals remarkable specific capacitance of 600 F g−1 at 1 A g−1. The charge storage mechanism is elucidated in detail, revealing mixed surface capacitive-pseudocapacitive mechanism. Besides, the assembled asymmetric supercapacitor device utilizing Ni-Cu-P as the cathode (positive pole) and β-FeMoO4 as the anode (negative pole) displays superior specific energy and specific power of 40.75 Wh Kg−1 and 850 W kg−1, respectively.