Hydrogen and carbon monoxide generation from laser-induced graphitized nanodiamonds in water

Abstract

Nanodiamonds (ND) were found to generate hydrogen (H₂) and carbon monoxide (CO) from water at a remarkable rate under pulsed laser (532 nm) irradiation. The transformation of diamond structure into graphitic layers takes place to form an onion-like carbon structure. The CO generation suggests the oxidative degradation reaction of graphitic layers, C + H₂O → CO + 2H⁺ + 2e⁻, which produced a unique laser-induced reaction: C + H₂O → CO + H₂. Au, Pt, Pd, Ag, and Cu nanoparticles on the ND enhance both gas evolution rates (∼2 times for Au) and graphitization and, specifically, Au was found to be the most efficient amongst other nanoparticles. The enhancement effect was ascribed to effective charge separation between the metal nanoparticles and ND. The Au–ND hybrid on the reduced graphene oxide produced consistently a greater photocurrent than the ND upon visible light irradiation.