Upcycling Spent Lithium Iron Phosphate Battery Into Fe-CN₃P Single Atom Catalyst for Environmental Remediation

Increasing environmental pollution and shortage of critical resources call for technologies capable of achieving total resource recovery from waste materials. In this study, high leaching rates of 99.16% for lithium and 97.37% for iron were obtained from spent lithium iron phosphate (LFP) batteries through electrochemical (EC) advanced oxidation processes (EAOPs), and associated leaching mechanism was subsequently investigated. Moreover, residual C, Fe, and P elements in leach residue were directly converted into a P, N-doped asymmetric single-atom Fe catalyst (Fe-CN₃P), enabled by well-dispersion of Fe elements and removal of surface passivation layers during leaching. When activated with peroxymonosulfate (PMS), Fe-CN₃P catalyst exhibited a pseudo-first-order kinetic rate of 10.768 min^-1 for bisphenol A (BPA) degradation, which is approximately 2-10 times higher than those of conventional single-atom catalysts. Based upon experimental and theoretical investigation, the presence of P in the local coordination environment was found to substantially enhance catalytic activity of Fe sites. P incorporation alters the adsorption mode of HSO₅ ^- on Fe active centres and increases Bader charges in the Fe^IV═O reactive intermediate, thereby improving the capability of Fe to withdraw electrons from the BPA molecules. This study offers new perspectives for synergistically advancing "comprehensive resources recovery" and "waste to treat waste."