Monolithic Low-tortuous Copper(I) Phosphide Nanorod Arrays for Exceptional Areal Performance in Electrochemical Chloride Ion Removal

Abstract

Copper(I) phosphide (Cu₃P) with high theoretical capacity and metalloid characteristics performs great potential as chloride ion (Cl⁻) storage electrodes in chloride-ion batteries and deionization. However, the unsatisfactory electrochemical performance of Cu₃P due to the sluggish rate and poor stability severely limited the development of practical application in electrochemical Cl⁻ removal. Herein, monolithic low-tortuous Cu₃P nanorod arrays (mCu₃P NA) have been fabricated through sacrificial template array engineering combined with the controlled phosphating strategy. Benefiting from the low-tortuous array structural advantages involving rapid charge transfer and plentiful active sites, the resultant mCu₃P NA electrode exhibited excellent areal deionization capacity (2.21 mg-Cl⁻ cm⁻² at 1.6 V) and corresponding fabulous rate (0.074 mg-Cl⁻ cm⁻² min⁻¹), which was superior to previously reported electrodes in electrochemical deionization. Furthermore, the phosphating degree could adjust array architecture and component of Cu₃P/Cu heterostructure, thus affecting areal deionization performance. In addition, the mechanism of Cl⁻ capture by Cu₃P was first elucidated, related to the redox of P³⁻/P⁰ and the formation of CuCl. These findings unlock the potential and elucidate the mechanism of Cu₃P for electrochemical Cl⁻ removal, as well as provide a new idea for rational design of high-performance array electrodes for environmental applications.