Crystal Facet Engineering in BiVO₄ for Photocatalytic Deep Oxidation of Nitric Oxide

BiVO₄ has garnered significant attention as a photocatalyst for water splitting and environmental remediation. The photocatalysis over BiVO₄ could be adjusted by the exposed facet but has not been explored over the NO abatement in ambient air. In this work, four distinct morphologies of monoclinic BiVO₄ crystals were hydrothermally synthesized by modulating the pH of the precursor solution. Among these, the sample with the preferentially exposed {040} facet exhibited a platelike fragmented morphology and demonstrated superior NO photocatalytic oxidation (79% removal rate) under visible light (>420 nm) over the one with the preferentially exposed {110} facet. Compared to the {110} facet, the {040} facet of BiVO₄ was more stable against oxygen vacancy formation and V⁵⁺ reduction to V⁴⁺ that could create a shallow midgap state. This higher stability, along with its higher flat-band energy, promotes the creation of superoxide radicals that are crucial for the thorough oxidation of NO. Singlet oxygen was found to be quite important in the oxidation of NO because NO₂ was produced even if water is absent in the air. This study highlights the considerable potential of BiVO₄-based catalysts for efficient atmospheric pollutant degradation.