Superior NOx photocatalytic removal over hybrid hierarchical Bi/BiOI with high non-NO2 selectivity: synergistic effect of oxygen vacancies and bismuth nanoparticles

Abstract

To achieve an efficient photocatalyst for NO pollution control, abundant oxygen vacancies and metallic bismuth (Bi) nanoparticles were simultaneously introduced into three-dimensional hierarchal BiOI via in situ self-reduction with aqueous NaBH₄. The obtained 20-Bi/BiOI exhibited superior NO_x (NO and NO₂) removal efficiency with high selectivity for non-NO₂, compared to pristine BiOI. After careful analysis of various characterization results, it was found that such an enhancement was attributed to the synergistic results of shallow donors formed by oxygen vacancies and the surface plasmonic resonance (SPR) effect of Bi nanoparticles, both of which contributed to the promotion of light harvesting and the suppression of the recombination of photoinduced charge carriers. What's more, oxygen vacancies can improve NO adsorption, strongly combine with NO₂, and facilitate the formation of ˙OH and ˙O₂⁻ radicals, promoting the deep oxidation of NO_x (NO and NO₂) to NO₂⁻ and NO₃⁻, robustly evidenced by the results of ion chromatography. Overall, this work highlights the synergistic effects of Bi and oxygen vacancies introduced by a self-reduction strategy and opens up an effective avenue for addressing NO pollution.