Controllable Synthesis of N[sub.2]-Intercalated WO[sub.3] Nanorod Photoanode Harvesting a Wide Range of Visible Light for Photoelectrochemical Water Oxidation

• Published in: Molecules (Basel, Switzerland) Switzerland), 2023-03, Vol.28 (7)
• Main Authors: Li, Dong, Lan, Boyang, Shen, Hongfang, Gao, Caiyun, Tian, Siyu, Han, Fei, Chen, Zhanlin
• Format: Article
• Language: English
• Subjects: Oxidation-reduction reaction
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28072987

A highly efficient visible-light-driven photoanode, N[sub.2]-intercalated tungsten trioxide (WO[sub.3]) nanorod, has been controllably synthesized by using the dual role of hydrazine (N[sub.2]H[sub.4]), which functioned simultaneously as a structure directing agent and as a nitrogen source for N[sub.2] intercalation. The SEM results indicated that the controllable formation of WO[sub.3] nanorod by changing the amount of N[sub.2]H[sub.4]. The β values of lattice parameters of the monoclinic phase and the lattice volume changed significantly with the n[sub.W]: n[sub.N2H4] ratio. This is consistent with the addition of N[sub.2]H[sub.4] dependence of the N content, clarifying the intercalation of N[sub.2] in the WO[sub.3] lattice. The UV-visible diffuse reflectance spectra (DRS) of N[sub.2]-intercalated exhibited a significant redshift in the absorption edge with new shoulders appearing at 470-600 nm, which became more intense as the n[sub.W]:n[sub.N2H4] ratio increased from 1:1.2 and then decreased up to 1:5 through the maximum at 1:2.5. This addition of N[sub.2]H[sub.4] dependence is consistent with the case of the N contents. This suggests that N[sub.2] intercalating into the WO[sub.3] lattice is responsible for the considerable red shift in the absorption edge, with a new shoulder appearing at 470−600 nm owing to formation of an intra-bandgap above the VB edges and a dopant energy level below the CB of WO[sub.3]. The N[sub.2] intercalated WO[sub.3] photoanode generated a photoanodic current under visible light irradiation below 530 nm due to the photoelectrochemical (PEC) water oxidation, compared with pure WO[sub.3] doing so below 470 nm. The high incident photon-to-current conversion efficiency (IPCE) of the WO[sub.3]-2.5 photoanode is due to efficient electron transport through the WO[sub.3] nanorod film.