A Microdroplet-Confined Precipitation Route to Small-Sized Porous Catalysts and Thermal-Tolerant BaCO3-CuZnAlO for H2 Production.

Small sizes of active particles and porous microstructures are important features of advanced industrial catalysts. This work presents a microdroplet-confined precipitation (MDCPr) method to synthesize porous hydroxycarbonate precursors for deriving dual-porous and small-sized catalysts. In addition, their morphology can be further regulated through the addition of polymers. Moreover, MDCPr is demonstrated to be a general and scalable method for synthesizing versatile porous small-sized oxides, including low-/medium-entropy CuZnAlO, NiZnAlO, and NiCuZnAlO, to high-entropy NiCoCuZnAlO. Specifically, the model reaction of water-gas shift shows that the activity of a porous BaCO3-CuZnAlO catalyst is 2-2.5 times that of traditional solution precipitation and BaCO3-free Cu-ZnAlO catalysts. More valuable, BaCO3-CuZnAlO exhibits outstanding sintering resistance. Demonstrated by the practical H2 production from CH3OH steam reforming, the activity hardly deteriorates after working for 8 days at 320 °C and another 2 days at 330 °C. The in situ X-ray studies show that the thermally stable BaCO3 plays a key role in inhibiting the sintering of active Cu nanoparticles. These findings establish MDCPr as a versatile and scalable methodology for high-throughput screening and the development of highly efficient thermal catalysts.