Tailoring Cu–CeO₂ catalysts to elucidate the morphology–activity relationship in low-temperature water–gas shift reaction

The low-temperature water-gas shift (WGS) reaction confronts critical challenges of sluggish kinetics, inadequate H₂ yield and CO conversion, necessitating the development of high-activity catalysts to effective clean energy production with reduced energy consumption. In this study, we systematically investigate the relationship between the physicochemical properties of Cu-based catalysts supported on CeO₂ with tailored morphologies (nanorods, nanospheres, and nanocubes) and catalytic performance. Cu-CeO₂(R) achieves 52.3 % CO conversion and 79.88 mL/gH₂O H₂ production at 370 °C-nearly twice those of Cu-CeO₂(P) under identical conditions-with an apparent activation energy of 55.25 kJ·mol^-1. This outstanding performance stems from proper oxygen vacancy concentration (OVC, 2.23 × 10²¹ cm^-3) and ordered Cu⁺-[O_v]Ce³⁺ interfacial sites induced by strong metal-support interaction (SMSI) within Ce_1-xCu_xO₂ solid solutions. In contrast, Cu-CeO₂(S) and Cu-CeO₂(C) display relatively lower maximum CO conversions (45.97 % at 410 °C and 43.7 % at 370 °C, respectively), due to excessive defect oxygen (34.41 % and 44.89 %) that strongly adsorbs reaction intermediates, postponing the WGS rate by 15-20 %. In-situ spectroscopy reveals that CeO₂ morphology modulates oxygen vacancy (O_v) distribution and CuCe interfacial structures, giving rise to distinct adsorption states and binding strengths of CO/CO₂ on Cu/CuO_x nanoclusters with varied valence states and dispersions. Cu-CeO₂(S) and Cu-CeO₂(C) exhibit complex carbonation pathways, featuring dynamic evolution of intermediates from monodentate to bidentate to polymeric carbonates, attributed to surface site diversity and cross-interactions of Cu sites. This work elucidates the morphology-activity relationship of Cu-CeO₂ catalysts, providing insights for the rational design of highly active low-temperature WGS catalysts.