Embedded CuO nanoparticles@TiO2-nanotube arrays for photoelectrocatalytic reduction of CO2 to methanol

Abstract

Herein, we report a simple approach to synthesize high-performance and structurally stable CuO nanoparticles catalyst embedded in TiO2 nanotube arrays for CO2 reduction. To summarize, anodic TiO2 nanotube arrays (TNTs) were electrochemical reductive doped in 1 mol/L (NH4)2SO4 solution to form an activated surface. Then CuO nanoparticles were successfully filled into the pores pace of TNTs by electrodeposition and heat treatment. The effects of Ti(Ⅲ) reduction doping were discussed by means of electrochemical impedance spectroscopy (EIS) and X ray photoelectron spectroscopy (XPS). Results show that partial Ti(Ⅳ) in TNTs can be reduced to Ti(Ⅲ) by electrochemical reduction, which leads to a significant improvement in TNTs surfactivity and then benefits the deposition of Cu nanoparticles to form a stable embedded structure. As a consequence, the composite electrodes showed higher photoelectrocatalytic performance for CO2 reduction. The maximum current of CuO-TNTs composite electrodes is up to −1.37 mA/cm2 at −0.5 V and high selectivity for methanol synthesis is also obtained in this case. At the same time, the amount of methanol produced by the CuO/self-doped TNTs composite electrode is about 15% higher than that by the CuO/TNTs electrode without reductive doping.