Excellent degradation performance towards organic pollutants of 3D hierarchical nanoporous structures of Copper

Advanced oxidation process provides a promising way to the degradation of organic pollutants in wastewater, where in developing highly efficient catalyst is of paramount importance. Herein, a three-dimensional (3D) hierarchical nanoporous structures of Cu catalyst with desirable geometries were synthesized by laser 3D printing combined with chemical dealloying. The resulting 3D nanoporous Cu (3D NP-Cu) exhibited 660-fold larger specific surface area than conventional 2D ribbon or powder catalysts. The 3D NP-Cu catalysts exhibited high degradation efficiency towards azo dyes with a kinetic reaction constant of 0.147 min-1, which is 14 times higher than the commercial catalyst of Cu2+ and 4 times higher than Cu0 powders. Impressively, the 3D NP-Cu exhibited a fairly good reusability and excellent versatility, as indicated by fast degradation of the mixture of complex dyes and reduction of the chemical oxygen demand (COD). The extraordinary catalytic activities of the 3D NP-Cu catalyst originated from the unique 3D hierarchical mill/nano-porous structures with large surface areas and numerous active atomic steps on Cu ligaments, which generate abundant active species and accelerate the transport of reactants. In addition, the presence of a small amount of Cu+ active specie in the as-prepared 3D NP-Cu catalyst also played a critical role in promoting the degradation process, leading to decomposition of azo dyes even in the absence of H2O2. Moreover, two possible pathways of degradation towards azo dyes were proposed based on liquid chromatograph-mass spectrometry analysis, i.e. reduction of azo bond and demethylation of MO. The current work may inspire the development of new types of 3D nanostructured metal catalysts for remediation of wastewater.