Synergistic photo-enhanced electrocatalysis of Pt–ZnO–Bi2O3 heterojunction for methanol oxidation under visible light illumination. (20th October 2022)

• Record Type: Journal Article
• Authors: Bera, Kamal Kanti; Chakraborty, Malay; Bera, Shyamal Kanti; Chowdhury, Anupam; Ranjan Das, Mahima; Mondal, Mousumi; Bhattacharya, Swapan Kumar
• Is Part Of: Energy advances. Volume 1:Number 11(2022)
• Page Start: 908
• Page End: 925
• Publication Date: 2022-10-20
• Subjects: Periodicals; Fuel cells; Electrochemistry; Chemical engineering; Thermoelectricity; 621.31242
• DOI: 10.1039/d2ya00166g
• Languages: English
• ISSNs: 2753-1457

Abstract

Abstract : The synergistic effect of Pt–ZnO–Bi2 O3 ternary heterojunction is observed and mechanistic paths are proposed for the photo-electrooxidation of methanol in alkali under visible light irradiation. Abstract : Pt-based bismuth oxide (Bi2 O3 ), zinc oxide (ZnO), and Bi2 O3 –ZnO heterojunctions were synthesized and tested in the photo-electrocatalytic oxidation of methanol in alkali under visible light irradiation. The decreased band gaps in Bi2 O3 (2.05–2.36 eV) and ZnO (2.61–2.94 eV) in the ternary junctions compared to those in Pt–ZnO (2.95 eV), Pt–Bi2 O3 (2.25 eV), bare Bi2 O3 (2.71 eV) and bare ZnO (3.38 eV) are seemingly responsible for the enhancement of light-absorption causing synergistic catalytic effects. The cyclic voltammetric peak current density of the ternary heterojunction, PZ5B1 (ZnO : Bi2 O3 = 5 : 1) is improved 5.2, 4.1, and 3.6 times that of Pt–Bi2 O3, Pt–ZnO and commercial Pt/C, respectively, under visible light. The composite PZ25B1 (ZnO : Bi2 O3 = 25 : 1) exhibited 1.62 times greater activity under light than the corresponding dark value. The light response gradually increases with the increasing mass percentage of ZnO having a maximum value in PZ25B1 and decreases again. Due to the smallest Pt size (2.51 nm) and high electrochemical surface area (30.9 m 2 g −1 ) in PZ25B1, methanol adsorption increases and the small bandgap helps absorb more visible light and creates large number of holes, which makes methanol oxidation faster. The negative shift of the peak potential under illumination in the CO stripping experiment indicates easy removal of adsorbed CO species on the Pt surface of the catalysts. The charge-transfer conductance of the best light-responsive and highly stable catalyst, PZ25B1 is 1.86 times greater in light than that in the dark. The stability of the PZ25B1 catalyst is judged from multiple cycling in cyclic voltammetry and chronoamperometric study. Chromatography experiments help in the identification of MOR product selectivity and mechanistic pathways.