A thermo-photo hybrid process for steam reforming of methane: highly efficient visible light photocatalysis

Abstract

Steam reforming of methane (SRM) is one of the most important industrial processes, which produces 95% of hydrogen used in the USA. However, SRM is an endothermic reaction, which requires a high energy input and a high reaction temperature (>800 °C) for the current process. Furthermore, its products must be subjected to a water–gas shift (WGS) process. A photocatalytic process is expected to solve the energy issue and to eliminate the necessity of WGS for SRM. However, the hydrogen yield from the current photocatalytic steam reforming of methane (PSRM) is very low (μmol h⁻¹ g⁻¹ level), which is far below industrial interest. This work demonstrates that a Pt/blackTiO₂ catalyst dispersed on a light-diffuse-reflection-surface is excellent for efficient visible-light PSRM. Under visible light illumination on the catalyst by filtering UV light from AM 1.5G sunlight, CH₄ and H₂O were directly converted into H₂ and CO₂ without WGS, leading to a high H₂ yield of 185 mmol h⁻¹ g⁻¹ with a quantum efficiency of 60% at 500 °C. The yield is 3 orders of magnitude larger than the reported values, which can be attributed to the synergistic effect between potential and kinetic energies. This opens up a new opportunity for hydrogen production from water and natural gas using solar energy.