Coordination between Electron Transfer and Molecule Diffusion through a Bioinspired Amorphous Titania Nanoshell for Photocatalytic Nicotinamide Cofactor Regeneration

In-depth understanding and rational manipulation of the electron transfer process and molecule diffusion process are critical to promote the overall photocatalytic efficiency. In our study, core@shell photocatalysts that embody graphitic carbon nitride (GCN) core and amorphous titania (a-TiO2) nanoshell are prepared to elucidate and coordinate the electron transfer and molecule diffusion for the regeneration of nicotinamide adenine dinucleotide (NADH) with [Cp*Rh(bpy)H2O]2+ as the redox mediator. The GCN core absorbs visible light to generate electron–hole pairs, whereas the a-TiO2 nanoshell facilitates the transfer of photogenerated electrons from GCN to the a-TiO2 surface for NADH regeneration, which also enables the diffusion of electron donor molecules (triethanolamine, TEOA) from the a-TiO2 surface to GCN for consuming the holes left on GCN. The transfer of photogenerated electrons and the diffusion of electron donor molecules are coordinated by finely tuning the thickness of the a-TiO2 nanoshell. Under the optimized nanoshell thickness of ∼2.1 nm, the GCN@a-TiO2 photocatalyst exhibits the highest NADH regeneration yield of 82.1% after a 10 min reaction under LED light (405 nm), over 200% higher than that of the GCN photocatalyst. Combined with the highly controllable and mild features of the bioinspired mineralization method, our study may offer a facile and generic strategy to design high performance photocatalysts through rational coordination of different substances/species transport processes.