TY - JOUR

T1 - ZnO with Controllable Oxygen Vacancies for Photocatalytic Nitrogen Oxide Removal

AU - Hailili, Reshalaiti

AU - Ji, Hongwei

AU - Wang, Kaiwen

AU - Dong, Xing’an

AU - Chen, Chuncheng

AU - Sheng, Hua

AU - Bahnemann, Detlef W.

AU - Zhao, Jincai

N1 - Funding Information: Financial support by the National Natural Science Foundation of China (Nos. 21902161 and 22076193), the National Key R&D Program of China (No. 2020YFA0710303) and the Postdoctoral Science Foundation of China (Nos. 2019T120137 and 2018M641484) is gratefully appreciated. R.H. also gratefully acknowledges the support from the Alexander von Humboldt Foundation. We all thank National Supercomputer Center in LvLiang of China for DFT calculations on TianHe-2. Publisher Copyright: © 2022 American Chemical Society. All rights reserved.

PY - 2022/8/19

Y1 - 2022/8/19

N2 - Semiconductor-based photocatalysis is an ideal method for air purification by eliminating nitrogen oxide (NO). However, sluggish carrier separation, photocatalysts deactivation and incomplete oxidation are significant bottlenecks for photocatalytic treatment of indoor pollutant NO. Herein, ZnO with assorted structures is fabricated and undergoes further modification for deliberate surface defect constructions. Utilized flux agents during the synthesis provide a more feasible reducing atmosphere, under which spontaneous generations of the surface vacancies become easier, and gradient concentrations are precisely controlled. Photocatalyst characterizations affirm the successful creation of surface defects, which are further evaluated by solar-light-driven NO (ppb level) removal investigations. Results showed that ZnO rich in oxygen vacancies (VO-rich ZnO) exhibited 5.43 and 1.63 times enhanced NO removal with fewer toxic product NO2 formations than its counterparts pristine and VO-poor ZnO, respectively. Importantly, with higher VO on the unusual nonpolar facets, VO-rich ZnO does not only display enhanced NO conversion, but also shows the unselective NO removal process by producing NO3-. The plausible reaction mechanisms of promoted NO conversions are further investigated based on the surface VO, well-positioned band structures, and enhanced carrier separations. Results showed that the surface VO with gradient concentrations are not only promoted carrier separation, but also facilitate molecular oxygen activation, leading to the generations of strong oxidant superoxide radicals (·O2-), and contributing to the enhanced improved efficiency. Adsorption of small molecules (O2, H2O and NO) on the defective surface was further investigated by density functional theory (DFT) calculations, which validated the successful adsorption/activation of NO and O2, further contributed to the improved NO conversions.

AB - Semiconductor-based photocatalysis is an ideal method for air purification by eliminating nitrogen oxide (NO). However, sluggish carrier separation, photocatalysts deactivation and incomplete oxidation are significant bottlenecks for photocatalytic treatment of indoor pollutant NO. Herein, ZnO with assorted structures is fabricated and undergoes further modification for deliberate surface defect constructions. Utilized flux agents during the synthesis provide a more feasible reducing atmosphere, under which spontaneous generations of the surface vacancies become easier, and gradient concentrations are precisely controlled. Photocatalyst characterizations affirm the successful creation of surface defects, which are further evaluated by solar-light-driven NO (ppb level) removal investigations. Results showed that ZnO rich in oxygen vacancies (VO-rich ZnO) exhibited 5.43 and 1.63 times enhanced NO removal with fewer toxic product NO2 formations than its counterparts pristine and VO-poor ZnO, respectively. Importantly, with higher VO on the unusual nonpolar facets, VO-rich ZnO does not only display enhanced NO conversion, but also shows the unselective NO removal process by producing NO3-. The plausible reaction mechanisms of promoted NO conversions are further investigated based on the surface VO, well-positioned band structures, and enhanced carrier separations. Results showed that the surface VO with gradient concentrations are not only promoted carrier separation, but also facilitate molecular oxygen activation, leading to the generations of strong oxidant superoxide radicals (·O2-), and contributing to the enhanced improved efficiency. Adsorption of small molecules (O2, H2O and NO) on the defective surface was further investigated by density functional theory (DFT) calculations, which validated the successful adsorption/activation of NO and O2, further contributed to the improved NO conversions.

KW - carrier separation

KW - NO removal

KW - photocatalysis

KW - surface defects

KW - surface-interface

UR - http://www.scopus.com/inward/record.url?scp=85135977938&partnerID=8YFLogxK

U2 - 10.1021/acscatal.2c02326

DO - 10.1021/acscatal.2c02326

M3 - Article

VL - 12

SP - 10004

EP - 10017

JO - ACS catalysis

JF - ACS catalysis

SN - 2155-5435

IS - 16

ER -