Perovskite-based nanocubes with simultaneously improved visible-light absorption and charge separation enabling efficient photocatalytic CO₂ reduction

Highlights: • Nitrogen and oxygen-vacancy confined in Perovskite tantalate was achieved. • V_o-NaTaON endows band absorption from UV to visible regime beyond 600 nm. • Novel heterojunctions present superior broad spectrum CO₂ photoreduction. • Efficient light-absorption and charge separation have been confirmed. • Mechanism for efficient photocatalytic CO₂ reduction is proposed. Finding an ideal model to disclose the role upon tuning band structure and charge separation of wide-bandgap perovskite semiconductors by introducing suitable heteroatoms remains a huge challenge in photocatalysis. Herein, we propose an efficient pathway to increase the light absorption and charge separation for nitrogen and oxygen-vacancy confined in sodium tantalate nanocubes (V_o-NaTaON) and nitrogen-doped graphene quantum dots (N-GQDs) grafted V_o-NaTaON nanocubes by solution-etching-induced phase-transition and in-situ reduction strategies. First-principles calculations demonstrate that the simultaneous incorporation of nitrogen and oxygen-vacancy in sodium tantalate can effectively regulate the electronic structure of sodium tantalate. The analysis of UV–vis spectra and electron paramagnetic resonance reveal that the synergistic contribution of nitrogen and oxygen-vacancy endows the wide-bandgap perovskites tuning the band absorption region from UV (315 nm) to visible regime beyond 600 nm. As expected, an optimized V_o-NaTaON catalyst was developed, exhibiting superior broad spectrum photochemical reduction of CO₂ to fuels. Moreover, N-GQDs/V_o-NaTaON heterojunctions further improve the broad spectrum CO₂ photoreduction due to the synergetic catalytic effect of simultaneously improved light-absorption and charge separation. This work may open up more opportunities in the design of efficient photocatalysts for applications in solar photochemical conversion.