Controllable Integration of Binary Functional Species\nEndows Directionally Optimized Kinetics for CoNiSe<sub>2</sub>‑Based\nHigh-Performance Supercapacitors

Side reactions of water decomposition and capacitive reactions\noccur concomitantly in aqueous supercapacitors. To improve the energy\ndensity, integrated design modifications to address the impact of\nthese two aspects on the reaction kinetics are theoretically effective.\nHerein, a two-step modification strategy for introducing binary functional\nspecies is designed to regulate the chemical environment and electronic\nstructure of the metal active sites and further optimize the electrochemical\nkinetics comprehensively. For promoting the capacitive reactions,\nAg nanoparticles were loaded to decrease the corresponding energy\nbarriers. For suppressing the oxygen evolution side reaction, preintercalation\nof K<sup>+</sup> ions was realized to increase the corresponding energy\nbarriers. The assembled supercapacitor device shows an ultrahigh energy\ndensity of 143.2 Wh kg<sup>–1</sup>. Uniquely, in situ techniques,\nDFT calculations, and overpotential tests are combined to verify the\nsuppression mechanism. This work provides valuable guidance for coordinating\ndesigns and studies on the electrochemical kinetics of transition-metal-based\nelectrode materials.