Polyoxometalate-derived molybdenum catalysts for the reverse water-gas shift reaction

Title : Polyoxometalate-derived molybdenum catalysts for the reverse water-gas shift reaction

Abstract:

The Reverse Water–Gas Shift (RWGS) reaction was investigated using catalysts derived from Keggin-type PolyOxoMetalates (POMs), including H₃PMo₁₂O₄₀ and H₃PW₄₀O₄₀, along with their Co(II) and Ni(II) salts. Under reaction conditions, molybdenum-based POMs decompose to form active Mo oxide species, which exhibit high catalytic activity, selectivity, and stability in the RWGS reaction.

Catalysts derived from H₃PMo₁₂O₄₀ supported on SiO₂, TiO₂, and γ-Al₂O₃ achieved 100% CO selectivity at CO₂ conversions of 31–33% at 600 °C and a CO₂:H₂ ratio of 1:1, approaching the thermodynamic equilibrium (39%). Among these, H₃PMo₁₂O₄₀/SiO₂ showed higher activity compared to MoO₃/SiO₂ with equivalent Mo loading, indicating a phosphorus-induced enhancement effect. This improvement is attributed to better dispersion of Mo oxide species, as confirmed by STEM analysis.

Mechanistic studies using chemical looping and H₂-TPR suggest that the RWGS reaction proceeds via a redox pathway, involving reduction of Mo(VI) to Mo(IV) by H2, followed by reoxidation with CO₂ to produce CO, consistent with a reverse Mars–van Krevelen mechanism. 

In contrast, tungsten-based POMs exhibited negligible activity due to their resistance to reduction under reaction conditions.

Biography:

Asma is currently a PhD student in the Department of Chemistry at the University of Liverpool. Her research focuses on heterogeneous catalysis, with particular emphasis on the preparation and development of catalysts for the Reverse Water Gas Shift (RWGS) reaction. She is working on designing efficient catalytic systems for CO₂ conversion and utilization. Asma has experience in catalyst synthesis and characterization techniques, including X-Ray Diffraction (XRD) and BET surface area analysis. Through her research, she aims to contribute to the development of sustainable catalytic processes and cleaner energy solutions.