Unlocking synergy between multi-valence rhodium species for promoted methanol photoreforming

Abstract

Solar-powered photocatalytic methanol dehydrogenation to produce hydrogen (H2) and formaldehyde provides a promising approach for storable H2 fuel without carbon emissions. However, the different properties of C–H and O–H bonds in methanol molecules make it challenging to cleave both bonds effectively on a single catalytic active site during the methanol dehydrogenation process. This work proposes a strategy that constructs multi-valence metal species in the co-catalyst to address this challenge. In the case study of multi-valence rhodium species (Rh0 and Rh3+) on titanium dioxide (RhOx/TiO2) photocatalysts, an apparent turnover frequency (TOF, the H2 evolution rate as a function of the co-catalyst amount) of 1236 h−1 is achieved, outperforming that of most reported co-catalysts. Detailed investigations unveil that the synergy between Rh0 and Rh3+ not only facilitates the cleavage of both C–H and O–H bonds in methanol molecules but also facilitates the desorption of H2 molecules, leading to improved efficiency. This work showcases an effective strategy for engineering co-catalysts to promote photocatalytic methanol dehydrogenation and provides insights into the mechanism of this reaction catalyzed by heterogeneous photocatalysts.