Photocatalytic Upcycling of Toxic Glyphosate Waste Into Compound Fertilizer for Corn Growth.

Abstract

Glyphosate (GP), the most widely used herbicide worldwide, poses serious ecological and health risks due to its persistence and toxic degradation intermediates. Although semiconductor photocatalysis offers a promising remediation pathway, the interplay between degradation selectivity, the secondary utilization of products, and environmental sustainability remains poorly understood. Here, we present a facet-dependent photocatalytic degradation of GP using bismuth oxybromide (BiOBr) nanosheets with dominant (001), (010), and (102) facets. Spectroscopic and theoretical analyses reveal that BiOBr-(010) and BiOBr-(102) achieve faster GP degradation via enhanced charge separation and dual adsorption of carboxyl and phosphate groups. However, they predominantly yield and accumulate aminomethylphosphonic acid (AMPA), a toxic and recalcitrant intermediate. In contrast, the (001) facet selectively cleaves the C─N bond in GP via stronger hole accumulation and higher AMPA affinity, producing NH₄ ⁺, NO₃ ^-, PO₄ ^3-, and CH₃COOH. Importantly, the final products act as a compound fertilizer that can directly promote corn growth. These findings highlight the need to consider more than just degradation efficiency when designing photocatalysts, establishing a structure-function framework that prioritizes kinetic performance and crop growth-promoting potential.