Enhanced water resistance of Pd/3DOM Ce0.7Zr0.3O2 catalysts in methane combustion

Three-dimensionally ordered macroporous (3DOM) Ce0.7Zr0.3O2-supported Pd (xPd/3DOM Ce0.7Zr0.3O2, x = 0.97, 1.49, and 2.10wt%) catalysts were fabricated using the polymethyl methacrylate (PMMA) microsphere-templating and polyvinyl alcohol (PVA)-protected reduction methods. It was found that the xPd/3DOM Ce0.7Zr0.3O2 samples with surface areas of 31.9−38.2 m2/g possessed a high-quality 3DOM architecture, with the Pd nanoparticles (NPs) being uniformly dispersed on the 3DOM Ce0.7Zr0.3O2 surface. Among all of the samples, 1.49Pd/3DOM Ce0.7Zr0.3O2 showed the best CH4 combustion activity: The T10%, T50%, and T90% (the temperatures at CH4 conversions = 10, 50, and 90%) were 270, 330, and 380oC, respectively; specific reaction rate at 260oC was 125.0 × 10−6 mol/(gPd s), and turnover frequency at 260oC (TOFPd) was 31.2 × 10−3 s−1. The good catalytic performance of 1.49Pd/3DOM Ce0.7Zr0.3O2 was associated with the well-defined 3DOM structure, high Pd NP dispersion, rich adsorbed oxygen species, and strong interaction between Pd NPs and 3DOM Ce0.7Zr0.3O2. Interestingly, the 1.49Pd/3DOM Ce0.7Zr0.3O2 sample also exhibited superior water-tolerant performance. The product analysis results after the in situ introduction of isotopic water demonstrated that the excellent water resistance of 1.49Pd/3DOM Ce0.7Zr0.3O2 was due to the interaction of oxygen and water to form the peroxy hydroxyl species on the sample surface after the water pretreatment, which was beneficial for the combustion of methane.