Sunlight-driven hydrogen peroxide activation via copper hydroxyphosphate with broad spectrum response for imidacloprid degradation: Mechanism insight and DFT calculation
Haoran Zhang, Jiang Li, Yujiao Liu, Sihao Fu, T. Su, Lingyu Meng, Yunfei Wang, Nian Ma, Guocheng Liu, Qinghua Yan, Yanjun Xin, Shuaishuai Xin
Abstract
The copper hydroxyphosphate (Cu 2 (OH)PO 4 ) was prepared for imidacloprid degradation by activating hydrogen peroxide (H 2 O 2 ) under sunlight. The properties of narrow bandgap, rich oxygen vacancy and up-conversion for Cu 2 (OH)PO 4 endow it with fine optical responsiveness in broad solar spectrum. Based on density functional theory calculations, the fine responsiveness of Cu 2 (OH)PO 4 to near-infrared light was attributed to four unoccupied down-spin bands, and the photoinduced electrons were transferred from trigonal bipyramidal CuO 4 (OH) structure to octahedral CuO 4 (OH) 2 structure in Cu 2 (OH)PO 4 , which promoted photoinduced carrier separation. Compared to visible light and infrared light, the sunlight could promote H 2 O 2 activation through Cu 2 (OH)PO 4 for imidacloprid degradation, as more light energy was utilized by Cu 2 (OH)PO 4 in presence of ultraviolet light. The photoinduced electrons promote active species production by participating in H 2 O 2 activation and accelerating the redox of Cu(II)/Cu(I) on Cu 2 (OH)PO 4 surface, and • OH was the major active species for imidacloprid degradation in sunlight-driven Cu 2 (OH)PO 4 activating H 2 O 2 (Light+Cu 2 (OH)PO 4 + H 2 O 2 ) system. The degradation paths of imidacloprid were inferred by identifying degradation products and analyzing the sites in imidacloprid that are easily attacked by active species. The acute and potential toxicity of imidacloprid were effectively reduced by treatment in Light+Cu 2 (OH)PO 4 + H 2 O 2 system. The Light+Cu 2 (OH)PO 4 + H 2 O 2 system with good stability could be applied within a wider pH range (3.0–11.0), and the coexisting humic acid and anions (Cl − , SO 4 2− , NO 3 − and PO 4 3− ) slightly reduced the imidacloprid degradation. The HCO 3 − could accelerate imidacloprid degradation by promoting • OH production, and multiple pollutants were effectively degraded in Light+Cu 2 (OH)PO 4 + H 2 O 2 system.