Dimensional engineering of 2D rGO and 3D carbon-supported Fe, Co, Ni, and Cu sulfide nanocomposites for high-performance pseudocapacitive energy storage

Official URL: https://dx.doi.org/10.1016/j.est.2026.121042

In the pursuit of high-performance electrochemical energy storage, this manuscript presents a systematic investigation of nanocomposites comprising transition metal sulfides, iron sulfide, cobalt sulfide, nickel sulfide, and copper sulfide, integrated with three-dimensional carbon spheres and two-dimensional reduced graphene oxide. A total of twenty-four distinct thin film electrodes were synthesized via a controlled hydrothermal route using variable metal loadings of 20%, 30%, and 50%, followed by extensive structural, morphological, optical, and electrochemical characterization using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, cyclic voltammetry, galvanostatic charge-discharge analysis, and electrochemical impedance spectroscopy. A direct comparison between carbon sphere-based and reduced graphene oxide-based architectures reveals pronounced differences in electrochemical behavior. Notably, the reduced graphene oxide-supported iron sulfide electrode with 50% loading delivers an exceptional specific capacitance of 476 Fg−1 at 0.5 Ag−1 after 100 cyclic voltammetry cycles, significantly surpassing its carbon sphere counterpart, which achieves 253 Fg−1. Similarly, reduced graphene oxide-based cobalt, copper, and nickel sulfide electrodes exhibit high capacitance values of 329 Fg−1, 197 Fg−1, and 127 Fg−1, respectively. The superior performance is attributed to the high electrical conductivity, π-π interaction mediated anchoring, and structural robustness of reduced graphene oxide, which effectively mitigates electrochemical degradation during prolonged cycling. This study establishes two-dimensional reduced graphene oxide as a superior carbon matrix over three-dimensional carbon spheres and provides a decisive framework for designing durable, high capacitance pseudocapacitor electrodes.