Sub-50 nm perovskite-type tantalum-based oxynitride single crystals with enhanced photoactivity for water splitting

A long-standing trade-off exists between improving crystallinity and minimizing particle size in the synthesis of perovskite-type transition-metal oxynitride photocatalysts via the thermal nitridation of commonly used metal oxide and carbonate precursors. Here, we overcome this limitation to fabricate ATaO2N (A = Sr, Ca, Ba) single nanocrystals with particle sizes of several tens of nanometers, excellent crystallinity and tunable long-wavelength response via thermal nitridation of mixtures of tantalum disulfide, metal hydroxides (A(OH)2), and molten-salt fluxes (e.g., SrCl2) as precursors. The SrTaO2N nanocrystals modified with a tailored Ir-Pt alloy@Cr2O3 cocatalyst evolved H2 around two orders of magnitude more efficiently than the previously reported SrTaO2N photocatalysts, with a record solar-to-hydrogen energy conversion efficiency of 0.15% for SrTaO2N in Z-scheme water splitting. Our findings enable the synthesis of perovskite-type transition-metal oxynitride nanocrystals by thermal nitridation and pave the way for manufacturing advanced long-wavelength-responsive particulate photocatalysts for efficient solar energy conversion. A trade-off exists between improving crystallinity and minimizing particle size in the synthesis of perovskite-type transition-metal oxynitrides. The authors break this limitation to fabricate sub-50 nm ATaO2N (A = Sr, Ca, Ba) single nanocrystals exhibiting improved photocatalytic water-splitting performance

Automated summary

There is a trade-off between improving crystallinity and minimizing particle size in the synthesis of perovskite-type transition-metal oxynitrides. In this study, the researchers overcome this limitation by using thermal nitridation to fabricate sub-50 nm ATaO2N (A = Sr, Ca, Ba) single nanocrystals with excellent crystallinity and tunable long-wavelength response. The SrTaO2N nanocrystals modified with a tailored Ir-Pt alloy@Cr2O3 cocatalyst showed significantly improved efficiency in hydrogen evolution compared to previously reported SrTaO2N photocatalysts, achieving a record solar-to-hydrogen energy conversion efficiency of 0.15% in Z-scheme water splitting. These findings enable the synthesis of perovskite-type transition-metal oxynitride nanocrystals and pave the way for the manufacturing of advanced long-wavelength-responsive particulate photocatalysts for efficient solar energy conversion.