Tunable Metal–Support Interactions between Copper and Cobalt Oxides for Enhanced Methanol Steam Reforming

Exploring metal–support interactions (MSIs) between Cu and metal oxides is crucial for the design of efficient copper-based catalysts. Here, we demonstrate that interactions between metallic Cu and cobalt oxides can be continuously tuned under reductive conditions. A series of (quasi) in situ characterizations was conducted on Cu/Al2O3 catalysts doped with different Co loadings. The results show that both the chemical state and spatial distribution of Co species evolve markedly with Co content. At low Co loadings, Co addition slightly enhances Cu dispersion and induces limited electronic modulation. With increasing Co loading, reducible CoOx species migrate and partially encapsulate Cu nanoparticles, forming a strong metal–support interaction (SMSI) structure and generating abundant Cu–CoOx interfacial sites. These interfacial sites exhibit enhanced intrinsic activity for methanol steam reforming (MSR). However, excessive Co doping leads to deep reduction of CoOx to metallic Co, which promotes methanol cracking and decreases MSR activity and CO2 selectivity. Cu20CoAl exhibits the optimal intrinsic MSR performance among the investigated catalysts, delivering an H2 yield 1.5 times that of CuAl at identical Cu loading. These findings uncover tunable Cu–CoOx interactions and provide mechanistic guidance for the rational design of Cu-based MSR catalysts.