Unleashing Photocarrier Transport in Mesoporous Single-Crystalline LaTiO2N for High-Efficiency Photocatalytic Water Splitting

LaTiO2N is a promising narrow-bandgap semiconductor photocatalyst that shows great promise for water redox reactions. However, its performance is often hindered by fast photocarrier recombination events. Herein, LaTiO2N mesoporous single crystals (MSCs) are successfully fabricated via a topotactic conversion route by using the Ruddlesden-Popper compound NaLaTiO4 as the precursor. The LaTiO2N MSCs are characterized by high crystallinity, abundant mesopores, no grain boundaries (GBs), and exposure of (010) and (101) crystal facets. A facet-assisted photocarrier separation mechanism is identified for these LaTiO2N MSCs which contributes to the much better photocarrier separation than conventional counterparts. By loading proper cocatalysts, LaTiO2N MSCs serve as an efficient photocatalyst for water-splitting half-reactions and are capable of photocatalyzing overall water-splitting reactions, delivering an impressive apparent quantum efficiency (AQE) as high as 65.07% at 420 +/- 20 nm for O-2-evolution and a solar-to-hydrogen (STH) efficiency as high as 0.012% for solar-driven overall water splitting. These findings not only highlight the grain-boundary-free MSCs with peculiar crystal-facet exposure as highly active photocatalysts for particulate photocatalysis but also provide a rational design approach for developing efficient photocatalysts.