fig1

Figure 1. Schematic of the top-down reconstruction strategy for upcycling Spent LiFePO₄ (S-LFP) slags into electrocatalysts. Lithium extraction from S-LFP cathodes yields a solid slag that is conventionally discarded. Through acid-leaching-induced structural reconstruction, this low-value slag is transformed into a disordered Fe-P-O matrix (denoted HS-LFP) that serves as an efficient catalyst for electrocatalytic nitrate reduction to ammonia. The proposed local structural model of HS-LFP contains highly dispersed Fe-O_x species, neighboring Fe-O coordination motifs, and short-range ordered FePO₄-related domains within a reconstructed Fe-P-O matrix. LFP: LiFePO₄. HS-LFP: the S-LFP-derived slag.