Electrochemical reduction-induced oxygen vacancies and in-situ selenization strategies synergistically construct...

Supercapacitors encounter difficulties in terms of slow kinetics. The development of supercapacitors with fast reaction kinetics is a significant challenge. This work presents the synthesis ofnickel foam (NF)-supported CoMn layered double hydroxides (CoMn-LDH) and CoSe₂ composites (O_V-CoMn-LDH@CoSe₂/NF) were synthesized using electrochemical reduction-induced oxygen vacancy (O_V) and in situ selenization strategies. The resultant electrode materials exhibited a core-shell heterostructure encapsulated by defective nanosheets, and the abundant oxygen defects and heterostructures provided a substantial number of active sites while facilitating electron transfer during electrochemical processes. The capacitance of the prepared electrode materials was found to be 2673.3F g^-1 (1 A g^-1), with a capacity retention of 89.03 % (10 A g^-1, 10,000 cycles). This represents a substantial enhancement in electrochemical performance when compared to other materials. Furthermore, the hybrid supercapacitor consisting of O_V-CM@CS/NF and activated carbon (O_V-CM@CS/NF//AC) has a capacitance retention of 86 % (10 A g^-1, 10,000 cycles) and an energy density of 95 Wh kg^-1 (750 W kg^-1). Morphological characterization and density functional theory (DFT) calculations demonstrate that heterogeneous interfaces and defect structures can fundamentally alter the electronic structure of the materials and rationally explain the affinity relationship between O_V-CoMn-LDH@CoSe₂/NF and OH^- adsorption energy. This suggests that the material facilitates the reversible adsorption and desorption processes during electrode reactions. This study proposes a method to improve the electrochemical performance of cathode materials for supercapacitors.