A New Si/TiO2/Pt p-n Junction Semiconductor to Demonstrate Photoelectrochemical CO2 Conversion

Author(s)

Guaraldo, Thais Tasso ^{[1, 2]} ; de Brito, Juliana Ferreira ^[2] ; Wood, David ^[1] ; Boldrin Zanoni, Maria Valnice ^[2]

Affiliation

^[1] Univ Durham, Sch Engn & Comp Sci, Durham DH1 3LE - England

^[2] UNESP, Chem Inst Araraquara, BR-14800060 Araraquara, SP - Brazil

• Document type: Journal article
• Source: Electrochimica Acta; v. 185, p. 117-124, DEC 10 2015.
• Web of Science Citations: 13

Abstract

This work presents a new Si/TiO2/Pt p-n junction semiconductor prepared by sputtering, chemical vapor deposition (CVD), photolithography and lift-off techniques. XRD, EDS, FE-SEM, diffuse reflectance (DRS) and photocurrent vs potential curves had been used for semiconductor characterization. The material was designed for high porosity and uniformity of both TiO2 and Pt deposits; both TiO2 anatase phase formation and Pt presence were confirmed. This semiconductor has a characteristic of high light absorption in the ultraviolet and visible regions. A good photocurrent response for the cathodic region was obtained in a CO2 saturated solution (-1.0 mA under -0.8 V and UV-vis light), confirming electron-hole pair formation and CO2 electron scavenging. A small Si/TiO2/Pt electrode (1 x 1 cm) was employed in photoelectrocatalytic CO2 reduction, forming methanol (0.88 mmol L-1), ethanol (2.60 mmol L-1) and acetone (0.049 mmol L-1) as products reaching a Faradaic efficiency of 96.5%. These results had been obtained under the following optimal experimental conditions: 0.1 mol L-1 NaHCO3, pH 8 saturated with CO2, 125 W UV-vis irradiation (from 250 to 600 nm) and -0.8 V applied potential. Suitable charge transfer mechanisms in the electrode surface, and products formation after CO2 reduction, are proposed. (C) 2015 Published by Elsevier Ltd. (AU)

• FAPESP's process: 12/11141-1 - Novel composite anodes using a silicon, titanium dioxide and platinum grid structure
• Grantee: Thais Tasso Guaraldo
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 13/25343-8 - Simultaneous Oxidation of Organic Compounds in Wastewater Petroleum and Reduction of Dissolved CO2 by Photoelectrocatalysis
• Grantee: Juliana Ferreira de Brito
• Support Opportunities: Scholarships in Brazil - Doctorate