Porous hexagonal nanoplate cobalt oxide derived from a coordination polymer as an effective catalyst for activating...

As cobalt (Co) represents an effective transition metal for activating Oxone to degrade contaminants, tricobalt tetraoxide (Co₃O₄) is extensively employed as a heterogeneous phase of Co for Oxone activation. Since Co₃O₄ can be manipulated to exhibit various shapes, 2-dimensional plate-like morphology of Co₃O₄ can offer large contact surfaces. If the large plate-like surfaces can be even porous, forming porous nanoplate Co₃O₄ (PNC), such a PNC should be a promising catalyst for Oxone activation. Therefore, a facile but straightforward method is proposed to prepare such a PNC for activating Oxone to degrade pollutants. In particular, a cobaltic coordination polymer with a morphology of hexagonal nanoplate, which is synthesized through coordination between Co²⁺ and thiocyanuric acid (TCA), is adopted as a precursor. Through calcination, CoTCA could be transformed into hexagonal nanoplate-like Co₃O₄ with pores to become PNC. This PNC also shows different characteristics from the commercial Co₃O₄ nanoparticle (NP) in terms of surficial reactivity and textural properties. Thus, PNC exhibits a much higher catalytic activity than the commercial Co₃O₄ NP towards activation of Oxone to degrade a model contaminant, salicylic acid (SA). Specifically, SA was 100% degraded by PNC activating Oxone within 120 min, and the E_a of SA degradation by PNC-activated Oxone is 70.2 kJ/mol. PNC can also remain stable and effective for SA degradation even in the presence of other anions, and PNC could be reused over multiple cycles without significant loss of catalytic activity. These features validate that PNC is a promising and useful Co-based catalyst for Oxone activation.