Cobalt substitution impact on structural modifications and capacitive contributions of BiVO4 nanorods for promising pseudocapacitors electrode applications

Abstract

Morphology tuning at the nanoscale, along with crystal imperfections introduced by ion doping, plays a crucial role in enhancing electrochemical performance. Here, pristine and cobalt (Co) doped bismuth vanadate (Co-BiVO₄) elongated nanorods were synthesized and optimized by varying Co-ion concentrations (0 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%) for potential applications as pseudocapacitor electrode materials. The aim was to investigate the structural and capacitive contributions of Co substitution. The pristine BiVO₄ exhibited a spherical nanoparticle morphology and a specific capacitance of 676F/g after 5000 GCD cycles. In contrast, the 6 wt% Co-doped BiVO₄, which exhibited an elongated nanorod morphology, demonstrated significant improvements in nanostructure and electrochemical performance, achieving an impressive specific capacitance of 1472F/g at 1 A/g, with excellent stability and 89 % retention over 5000 GCD cycles. Power law analysis (b = 0.81) and the Dunn method (58.22 % capacitive contribution at 75 mV/s) confirmed its suitability for pseudocapacitor applications. Low R_s values from EIS and high specific capacitance position Co-BiVO₄ nanorods as promising candidates for addressing energy storage demands in supercapacitors.