Illuminating the Role of Formate in Photo-assisted Carbon Dioxide Methanation using SSITKA-DRIFTS

The use of solar energy to drive CO2 utilisation is a two birds one stone strategy, which helps to reduce greenhouse gasses while also embedding green energy into our modern economy. 1 Photocatalytic activation of surface adsorbate species may drive catalytic reaction under illuminated conditions. 2 However, the role of surface-adsorbate in photo-assisted catalytic reactions can be elusive and may be hard to detect with conventional diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Herein, we were able to isolate adsorbed formate, HCO2*, as the critical rate-determining species on NiOx/La2O3@TiO2 using DRIFTS in combination with steady-state isotopic transient kinetic analysis (SSITKA). Under a 532 nm LED illumination, we observed a fivefold increment in the vibrational contribution of HCO2*. This effect is echoed by an eight-fold improvement in CO2 conversion to methane under visible light illumination at 200 oC. The understanding is crucial to the design of low-temperature methanation catalysts which exploit the HCO2* photo-activation pathway.


1.        Kho, E. T. et al. A review on photo-thermal catalytic conversion of carbon dioxide. Green Energy Environ. 2, 204–217 (2017).

2.        Kale, M. J., Avanesian, T., Xin, H., Yan, J. & Christopher, P. Controlling Catalytic Selectivity on Metal Nanoparticles by Direct Photoexcitation of Adsorbate–Metal Bonds. Nano Lett. 14, 5405–5412 (2014).

Tze Hao Tan1, Bingqiao Xie1, Yun Hau Ng1, Siti Fatimah Binti Abdullah1, Hin Yin Marco Tang1, Nicholas Bedford1, Robert A. Taylor2, Kondo-Francois Aguey-Zinsou1, Rose Amal1, Jason Scott1

  1. School of Chemical Engineering, UNSW Sydney, NSW 2052, Australia
  2. School of Mechanical and Manufacturing Engineering, UNSW Sydney, NSW 2052, Australia

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