Interfacial-Confined In-Situ growth of NiSe2/CoSe2 nanoparticles on Fluoride-Free Ti3C2Tx for enhanced pseudocapacitive Ion capture

Abstract

Transition metal selenides (TMSs) with high specific capacities are regarded as promising electrode materials for capacitive deionization (CDI), but are hindered by insufficient electronic conductivity and large volume effects. Herein, we propose an interfacial-confined in-situ derivation strategy for constructing fluoride-free Ti₃C₂T_x MXene supported NiSe₂/CoSe₂ nanoparticles hybrids (Ti₃C₂T_x@NiSe₂/CoSe₂), through utilizing the redox reaction products derived from the molten salt etching process as precursors. The robust Ti-O-Ni/Co chemical bonding between Ti₃C₂T_x and NiSe₂/CoSe₂ ensure the ultrasmall nanosized NiSe₂/CoSe₂ particles evenly distributed that leads to expose abundant multi-interface active sites and provides additional pseudocapacitance. Significantly, the fluoride-free Ti₃C₂T_x MXene with superior electrical conductivity, adjustable surface functional groups and multi-channel pathway further promotes the electrochemical reaction kinetics and preserves significant structural integrity of NiSe₂/CoSe₂ nanoparticles via the space confinement effect. Ti₃C₂T_x@NiSe₂/CoSe₂ exhibits exceptional brackish water desalination performance (130.0 mg g⁻¹ at 1.6 V) and superior cycling stability in the hybrid CDI system. The four-cell CDI stack effectively reduces ion levels in brackish and lake waters to meet Chinese drinking water standards (GB 5749–2022), offering a techno-economic benefit with a treatment cost of $ 0.39 m⁻³. The proposed strategy in this work enables the rational use of Lewis acidic etching by-products and paves the way for the preparation of MXene/TMSs compound hybrids as advanced CDI anodes.