Work function: a determining factor of the photodegradation rate of methyl orange via hollow octadecahedron CuO crystals.

Currently, photocatalytic degradation of methyl orange by Cu2O nanocrystals with different morphologies is mainly attributed to their narrow bandgap (Eg) and highly active lattice facets. Herein, three different sizes of hollow octadecahedron Cu2O crystals, with different degrees of exposed {110} facets, were developed and exhibited excellent, stable photocatalytic degradation performances. This study has shown that the intermediates in the photocatalytic degradation process are mainly peroxy radicals from the reaction of excited electrons in the Cu2O conduction band with oxygen molecules adsorbed on the surface. In the photodegradation process of the hollow octadecahedron (HO) Cu2O crystals, the excited-state electrons must break away from the work function restriction before participating in the reaction. HO-2 has achieved the best photocatalytic properties due to its smallest work function as a determining factor affecting the photocatalytic activity.