Spontaneous Generation of HO and Hydroxyl Radical through O Reduction on Copper Phosphide under Ambient Aqueous Condition.

Copper phosphide (Cu P) was synthesized and tested for its reactivity for generating HO through spontaneous reduction of dioxygen under ambient aqueous condition. The in situ generated HO was subsequently decomposed to generate OH radicals, which enabled the degradation of organic compounds in water. The oxygen reduction reaction proceeded along with the concurrent oxidation of phosphide to phosphate, then copper ions and phosphate ions were dissolved out during the reaction. The reactivity of Cu P was gradually reduced during 10 cycles with consuming 8.7 mg of Cu P for the successive removal of 17 μmol 4-chlorophenol. CoP which was compared as a control sample under the same experimental condition also produced HO through activating dioxygen but did not degrade organic compounds at all. The electrochemical analysis for the electron transfers on Cu P and CoP showed that the number of electrons transferred to O is 3 and 2, respectively, which explains why OH radical is generated on Cu P, not on CoP. The Cu species generated on the Cu P surface can participate in Fenton-like reaction with in situ generated HO. Cu P is proposed as a solid reagent that can activate dioxygen to generate reactive oxygen species in ambient aqueous condition, which is more facile to handle and store than liquid/gas reagents (e.g., HO, Cl, O).