Non-conventional low-temperature reverse water–gas shift reaction over highly dispersed Ru catalysts in an electric field

Abstract

The reverse water–gas shift (RWGS) reaction, a promising carbon-recycling reaction, was investigated by applying an electric field to promote the reaction at a temperature of 473 K or lower. The highly dispersed Ru/ZrTiO₄ catalysts with an approximately 2 nm particle size of Ru showed high RWGS activity with a DC electric field below 473 K, whereas CO₂ methanation proceeded predominantly over catalysts with larger Ru particles. The RWGS reaction in the electric field maintained high CO selectivity, suppressing CO hydrogenation into CH₄ on the Ru surface by virtue of promoted hydrogen migration (surface protonics). The reaction mechanisms of the non-conventional low-temperature reverse water gas shift reaction were investigated and revealed using various characterization methods including in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements. With the DC electric field, the reaction proceeds via a redox reaction where the generated oxygen vacancies are involved in CO₂ activation at low temperatures. As a result, the electric field promotes both hydrogen migration and redox reactions using lattice oxygen/vacancies, resulting in high RWGS activity and selectivity even at low temperatures.