Hollow porous Cu particles from silica-encapsulated Cu₂O nanoparticle aggregates effectively catalyze 4-nitrophenol...

A hollow metal micro/nanomaterial with a porous wall is one of the most attractive structures for catalysts. The synthesis of hollow porous Cu particles remains a challenge due to their air-sensitive characteristics. In this study, we report a facile and scalable method for the preparation of high-quality hollow porous Cu particles in the range of 500 nm-1.5 μm with a well-defined structure from Cu₂O nanoparticle aggregates (NPAs). The synthetic procedure involves the silica-encapsulation and depth-controlled reduction of Cu₂O NPAs followed by heat-treatment in air and selective removal of the encapsulating layer. The catalytic performance of the hollow porous Cu particles was evaluated through the catalytic reduction of 4-nitrophenol with NaBH₄ as a model reaction. The hollow porous Cu particles exhibited a high activity factor, K = 186 s^-1 g^-1, which is the highest K value obtained among the unsupported Cu catalysts to date. And the K value is better than that of some noble metal catalysts, such as Au, Ag, and Pd. In addition, the catalyst could be easily separated from the reaction system and still possessed high activity as well as stability in recycled reactions.