Self-doping of Nb2O5NC by cathodic polarization for enhanced conductivity properties and photoelectrocatalytic performance

Author(s)

Khan, Saad Ullah ^{[1, 2, 3]} ; Hussain, Sajjad ^[2] ; Lima Perini, Joao Angelo ^{[1, 3]} ; Khan, Hammad ^[2] ; Khan, Sabir ^{[1, 3]} ; Boldrin Zanoni, Maria Valnice ^{[1, 3]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Inst Chem, Rua Prof Francisco Degni 55, BR-14800060 Araraquara, SP - Brazil

^[2] GIK Inst Engn Sci & Technol, Fac Mat & Chem Engn, Topi, KP - Pakistan

^[3] Sao Paulo State Univ UNESP, Inst Chem, Natl Inst Alternat Technol Detect Toxicol Evaluat, BR-14800060 Araraquara, SP - Brazil

• Document type: Journal article
• Source: Chemosphere; v. 272, JUN 2021.
• Web of Science Citations: 1

Abstract

A simple novel electrochemical reduction approach was developed for the self-doping of Nb4+ in niobium oxide nanochannels (Nb2O5NC), changing the conductivity, optical properties, and photocatalytic properties of the material. Nb2O5NC was synthesized using different electrolytes: 0.4 wt% HF in 1 M H2SO4 (EI), 0.4 M NH4F in glycerol (EII), and 0.25 g NH4F with 4 vol% water in glycol at 50 degrees C (EIII). Field emission scanning electron microscopy (FEG-SEM) analysis showed well-organized arrays of Nb2O5 nanochannels produced on Nb foil, with varying tube diameters in the order EII < EI < EIII and film thickness in the order EI < EII < EIII, which drastically affected the photocurrent vs. potential curves. In order to self-dope the Nb2O5, the samples were electrochemically reduced in 0.1 M KH2PO4 buffer solution (pH 10) for 5 min, at -2.5 V vs. Ag/AgCl, resulting in the doped samples denoted P-EI, P-EII, and PEIII. The results showed that reduction of Nb(5+)to Nb4+ occurred for all the Nb2O5NC samples, leading to decreased surface charge transfer resistance between the Nb2O5NC and the electrolyte, as well as increases of the charge carrier density and photocurrent for all the self-doped samples, compared to undoped samples. Sample P-EI was also tested for the degradation of reactive red 120 (RR120) dye, achieving efficient photoelectrocatalytic degradation of a 10 mg L-1 dye solution. These results reveal that the self-doping approach can enhance the photoelectrocatalytic properties of Nb2O5 photoanode, offering an alternative way for the removal of reactive dyes. (C) 2021 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 14/50945-4 - INCT 2014: National Institute for Alternative Technologies of Detection, Toxicological Evaluation and Removal of Micropollutants and Radioactivies
• Grantee: Maria Valnice Boldrin
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/18057-7 - CO2 reduction aiming to generate value-added compounds by photocatalysis/photoelectrocatalysis using ionic liquid in a pressurized reactor
• Grantee: João Angelo de Lima Perini
• Support Opportunities: Scholarships in Brazil - Post-Doctoral