Layered double hydroxide nanosheets as efficient photocatalysts for NO removal: Band structure engineering and surface hydroxyl ions activation

We demonstrated the partial Ni2+ substitution for Mg2+ in Mg2Al-layered double hydroxide nanosheet (Ni/LDH) significantly improved its photocatalytic performance in removing the ppb-level NO pollutant from air. With 25 % of Mg2+ substituted, the Ni/LDH delivered the highest NO removal efficiency of 42.10 % (87.2 % of them were mineralized to nitrate) under UV-light irradiation. Such a robust performance with the low energy input (8 W) made Ni/LDH among the top photocatalysts for NO removal. We evidenced the OH− carried by Ni/LDH transformed to ·OH radicals by trapping the photoexcited holes. This unique feature was intriguing as the OH− at layer surfaces of LDH were abundant, fully exposed and dynamically supplemented by atmospheric water, which endowed Ni/LDH with superior ·OH production capability even under low atmospheric moistures. The positive contribution of Ni2+ arose from its function in optimizing band structure and activating the OH− of LDH, leading to enhanced reactive oxidative species production.