Insight into synergistic enhancement of photothermal catalytic hydrogen production by plasmonic Au-NP/TiO2 in the presence of glycerol

Using glycerol that is by-product in biodiesel production for hydrogen production represents a promising way to utilize solar energy to recycle energy contained in waste resources. In this work, Au nanoparticles are synthesized on TiO2 nanoparticles (Au-NP/TiO2) for photothermal catalytic hydrogen production in the presence of glycerol. Particular attention is paid to the enhancement mechanism of the loaded plasmonic Au nanoparticles and their synergistic effect on hydrogen evolution. It is demonstrated that the local electromagnetic field at the contact interface between Au and TiO2 in relation to radiative relaxation of local surface plasmon resonance (LSPR) is greatly enhanced for efficient separation of electrons and holes. The thermal effect caused by non-radiative relaxation of LSPR not only enhances intermolecular collisions between reactant molecules through thermolization, but also increases the carrier concentration to generate more free radicals. The apparent activation energy also dramatically decreases. Because of these synergistic effects, the photothermal catalytic hydrogen production rate is greatly improved. This work not only deepens the understanding of the LSPR contribution to photothermal catalytic hydrogen production, but also demonstrates the promising potential in recycling the by-product from biodiesel industries to produce hydrogen.