Enhanced methane yield by photoreduction of CO2 at moderate temperature and pressure using Pt coated, graphene oxide wrapped TiO2 nanotubes

Abstract

Photocatalytic conversion of CO2 into hydrocarbons is one of the most sought-after approaches as it not only helps for its mitigation and utilization but does so through the renewable solar energy. Development of suitable materials and protocols to achieve better efficiency in photoconversion has been projected as one of the grand challenges in the 21st century. However, the stability of CO2 leads to a high thermodynamic barrier for its conversion into value added chemicals. In this work, we report the design and fabrication of novel three-component nanostructured photocatalyst material comprising TiO2 nanotube arrays, reduced graphene oxide and Pt nanoparticles. TiO2 nanotubes fabricated by electrochemical anodization are functionalized by chemically deposited graphene oxide layers and Pt particles deposited by sputtering technique. The photocatalysts are characterized for the crystallinity, morphology, and composition through XRD, FE-SEM and EDAX studies. Such a combination ensures easier separation of photogenerated charges as well as better catalytic activity. Further, the photoreduction experiments are carried out at moderately higher temperature of about 80 °C and at about 1.8 atm pressure in an indigenously designed batch reactor to partly overcome the thermodynamic barrier. We have achieved a high methane generation rate of about 3.42 mmol/g/hr. The possible reaction mechanisms are discussed.