Oxygen vacancy-engineered BaTiO₃/g-C₃N₄ nanocomposites for highly selective and efficient photocatalytic CO₂ reduction to CH₄

Achieving high selectivity and high conversion in the photocatalytic reduction of CO₂ to a single fuel remains a significant challenge, primarily due to the multitude of potential products and their similar reduction potentials. Herein, we design a photocatalyst composed of g-C₃N₄-supported BaTiO₃ (BTO) nanoparticles coated with an oxygen vacancy (V_O)-rich amorphous layer, denoted as V_O-BTO/CN. This catalyst achieves a CH₄ yield of 26.8 μmol g⁻¹ h⁻¹ and nearly 100% exclusive selectivity for CH₄ over CO in photocatalytic CO₂ reduction, without the need for any sacrificial agents or cocatalysts. Both experimental and theoretical calculation results demonstrate that surface V_O and adjacent low-valence Ti³⁺ ions in BTO can efficiently adsorb and activate CO₂ molecules via the formation of a −C−O⋯⋮⋮−Ti−V_O− adsorption intermediate. This configuration plays a pivotal role in achieving high selectivity: it not only lowers the overall activation energy barrier but also steers the reaction pathway toward CH₄ formation rather than CO. As a result, V_O-BTO/CN achieves nearly 100% selectivity for visible-light-driven CO₂ reduction to CH₄. This work highlights the great potential of dual-active-site design through vacancy engineering for developing advanced photocatalysts toward efficient and selective CO₂ reduction.