Surface structure–activity relationships of Cu/ZnGaOX catalysts in low temperature water–gas shift (WGS) reaction for production of hydrogen fuel

Abstract

A new species’ class of Cu-, Ga- and Zn-based rate catalysts was prepared by a systematic co-precipitation technique at the different related pH values (6.5–8.0) along with calcination functional conditions, influencing components’ physical properties, these were characterized, and their application performance for water–gas shift (WGS) reaction was researched. Substances were analysed by various experimental methods, namely chemisorption, temperature-programmed reduction (TPR) characterisation, diffraction, physisorption and microscopy. A homogenous size dispersion of the compounds with smaller granular particles was obtained for catalysis, implemented with high pH-resulting outputs. H2 TPR profiles revealed a tailored stronger effect of Cu–Zn on Ga for process, operated with low pH-conditioned forms. Over Cu/ZnGaOX, WGS was sensitive to Cu, which was primarily active. Catalytic chemical reactivity, activity and selectivity were also found to be critically dependent on material lattice structure, copper surface area and metal–support interaction phenomena. The temperature-programmed surface reaction with mass spectrometry (TPSR–MS) measurements showed that formulations, synthesised at the pH of 8.0, enabled reaching >99% of the equilibrium yield CO conversion at 260 °C. An increase in the converted CO, oxidation and H2 productivity with the integral steam content in gaseous feed flow was achieved. The heterogeneous phase processing at the correlated pH of 7.6 demonstrated the highest formed CO product at the temperature of 200 °C, compared with literature. This is particularly promising for reagent purity hydrogen-fed fuel cells. The kinetics for each co-precipitated solid was evaluated regarding the efficiency for the WGS in a fixed bed reactor. Keywords: Syngas, Hydrogen, Cu/ZnGaOX catalyst, Water–gas shift (WGS), Steam reforming reactions, Fuel cell systems