Synergistic energy storage of cobalt manganese oxide/vanadium carbide MXene with graphene quantum dots hybrid composite for electrochemical and hydrogen evolution reaction applications

The research and development of heterostructure materials have received significant consideration because of their superior possessions relative to conventional semiconductor materials. The heterostructure of cobalt manganese oxide (CoMn₂O₄) and vanadium carbide (V₂CT_x) with graphene quantum dots (GQDs) nanocomposite was manufactured by the hydrothermal method. CoMn₂O₄/V₂CT_x@GQDs nanocomposite was characterized by XRD, FTIR, and XPS analysis. SEM investigation revealed that in CoMn₂O₄/V₂CT_x@GQDs composite, CoMn₂O₄, V₂CT_x particles were involved in the surface of GQDs nanosheets. The synthesized composite verified an exceptional energy density (E_d) of 86 Wh kg⁻¹ and a power density (P_d) of 1230 W kg⁻¹. It had a coulombic efficiency of 97.8%, while capacity retention was at 90.2%. CoMn₂O₄/V₂CT_x@GQDs demonstrated exceptional stability for up to 12,000 cycles. Moreover, CoMn₂O₄/V₂CT_x@GQDs nanocomposite exhibited outstanding electrochemical performance for HER. The electrochemical findings indicated a low overpotential of 111 mV, a Tafel slope of 58.72 mV dec⁻¹, and sustained long-term stability. This nanocomposite emerges as a strong candidate for electrochemical and photocatalytic applications, paving the way for the advanced development of composite materials. The novelty of this work lies in the rational integration of CoMn₂O₄, V₂C MXene, and GQDs to construct a unique hybrid architecture. This design provides superior electrical conductivity, abundant active sites, and remarkable improvements in electrochemical and HER performance compared to previously reported materials.