Unveiling the Mechanism of Plasma-Catalytic Low-Temperature Water–Gas Shift Reaction over Cu/γ-Al₂O₃ Catalysts

Abstract

The water-gas shift (WGS) reaction is a crucial process for hydrogen production. Unfortunately, achieving high reaction rates and yields for the WGS reaction at low temperatures remains a challenge due to kinetic limitations. Here, nonthermal plasma coupled to Cu/γ-Al₂O₃ catalysts was employed to enable the WGS reaction at considerably lower temperatures (up to 140 °C). For comparison, thermal-catalytic WGS reactions using the same catalysts were conducted at 140-300 °C. The best performance (72.1% CO conversion and 67.4% H₂ yield) was achieved using an 8 wt % Cu/γ-Al₂O₃ catalyst in plasma catalysis at ∼140 °C, with 8.74 MJ mol^-1 energy consumption and 8.5% H₂ fuel production efficiency. Notably, conventional thermal catalysis proved to be ineffective at such low temperatures. Density functional theory calculations, coupled with <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy, revealed that the plasma-generated OH radicals significantly enhanced the WGS reaction by influencing both the redox and carboxyl reaction pathways.