A bifunctional CoP/N-doped porous carbon composite derived from a single source precursor for bisphenol A removal

Abstract

Transition metal phosphides are promising materials for catalysis and their synthesis procedures commonly require costly or hazardous reagents. Herein, we adopted a yeast-extracted nucleic acid as an environmentally benign non-metal source to develop bifunctional cobalt phosphide/nitrogen-doped porous carbon composites. The single source precursor, i.e., a Co²⁺–nucleic acid complex was formed by coordination and could be converted to cobalt phosphide/carbon by pyrolysis with the assistance of a molten salt. Material characterization confirmed the formation of a well-crystallized CoP phase, N-doped carbon and hierarchical porous structure. In situ generated reducing gases (CO, H₂, PH₃, etc.) from the nucleic acid were detected by thermogravimetry-mass spectrometry (TG-MS) and thermogravimetry-infrared spectroscopy (TG-IR); also, they were suggested to be responsible for the transformation of phosphate in the precursor to phosphide in CoP. When applied for model pollutant (bisphenol A, BPA) removal, the developed composite not only exhibited considerable adsorption capability, but also performed well for peroxymonosulfate activation in an advanced oxidation process (AOP). In a two-step removal procedure, 75.5% of BPA was adsorbed in 60 min and the residual 24.5% of BPA could be degraded in 2 min by AOP. Further investigations verified that sulfate radicals, hydroxyl radicals and singlet oxygen were all involved in AOP for catalytic BPA degradation. The exhausted sample could also be regenerated by a facile thermal treatment approach. In this study, we have provided a facile strategy of utilizing inherent biomass components to construct an advanced metal phosphide-containing composite, which may open a new route for the value-added conversion of biomass.