Exploring the role of promoters (Au, Cu and Re) in the performance of Ni–Al layered double hydroxides for water-gas shift reaction

Abstract

Water-gas shift (WGS) reaction is well-known industrial process targeting hydrogen production. Designing well-performing and economically profitable WGS catalysts is the key toward production of pure hydrogen for application in fuel cell processing systems. Promotional role of Au, Cu, or Re in the WGS performance of Ni–Al formulations derived from hydrotalcite precursor was analysed on the basis of deep characterization by BET, XRD, UV–Vis, XPS, and TPR measurements of as-prepared and WGS-tested samples. Additionally, modification by ceria was examined. WGS results revealed that catalyst behaviour was strongly dependent on promoter type. The best performance exhibited gold-promoted Ni–Al layer double hydroxide modified with ceria. This system showed a superior catalytic activity as 99.7% CO conversion at 220 °C that correlated well with significantly enhanced reducibility of support. Although Au-containing CeO2-modified Ni–Al catalyst outperformed WGS activity of Cu- and Re-promoted analogues, stability of Re-containing sample and enhanced activity of Cu-based sample after tests at different reaction conditions manifested promising results. They leave open space for future investigations addressing improved catalyst performance by tuning Re4+/Re7+ redox structures or optimizing catalyst composition.