Robust Co-catalytic performance of nanodiamonds loaded on WO₃ for the decomposition of volatile organic compounds under visible light

Proper co-catalysts (usually noble metals), combined with semiconductor materials, are commonly needed to maximize the efficiency of photocatalysis. Search for cost-effective and practical alternatives for noble-metal co-catalysts is under intense investigation. In this work, nanodiamond (ND), which is a carbon nanomaterial with a unique sp³(core)/sp²(shell) structure, was combined with WO₃ (as an alternative co-catalyst for Pt) and applied for the degradation of volatile organic compounds under visible light. NDs-loaded WO₃ showed a highly enhanced photocatalytic activity for the degradation of acetaldehyde (∼17 times higher than bare WO) which is more efficient than other well-known co-catalysts (Ag, Pd, Au, and CuO) loaded onto WO₃ and comparable to Pt-loaded WO₃. Various surface modifications of ND and photoelectochemical measurements revealed that the graphitic carbon shell (sp²) on the diamond core (sp³) plays a crucial role in charge separation and the subsequent interfacial charge transfer. As a result, ND/WO₃ showed much higher production of OH radicals than bare WO₃ under visible light. Since ND has a highly transparent characteristic, the light shielding that is often problematic with other carbon-based co-catalysts was considerably lower with NDs-loaded WO₃. As a result, the photocatalytic activity of NDs/WO₃ was higher than that of WO₃ loaded with other carbon-based co-catalysts (graphene oxide or reduced graphene oxide). A range of spectroscopic and photo(electro)chemical techniques were systematically employed to investigate the properties of NDs-loaded WO₃. ND is proposed as a cost-effective and practical nanomaterial to replace expensive noble-metal co-catalysts.