Mechanochemical Alkali-Metal-Salt-mediated synthesis of ZnO nanocrystals with abundant oxygen Vacancies: An efficient support for Pd-based catalyst

• High surface area ZnO was synthesized by a mechanochemical alkali-metal-salt-mediated method. • A high Pd dispersion was easily achieved on this porous ZnO. • As-made Pd-ZnO catalyst displayed good performance in methanol steam reforming process. • Abundant Oxygen vacancies in ZnO did play an important role in methanol steam reforming performance. Zinc oxide is a key material in catalysis. Designing of ZnO crystal aggregates with the surface defect has received significant attention. Herein, we synthesized ZnO aggregates with tiny primary nanoparticles through a mechanochemistry-assisted salt-templating (potassium chloride) method. Interestingly, this KCl-templating strategy could lead to significant increase in specific surface area (SSA) of ZnO (up to 91 m 2 /g), whereas commercial ZnO-COM has a SSA of 5 m 2 /g. Meanwhile, this strategy via ZnCl 2 -KCl solid solution has also created a number of oxygen vacancies into ZnO aggregates. With these attractive features, as-made Pd-ZnO catalyst showed outstanding performance in methanol steam reforming, especially at low temperature (20 % Conversion and 95 % CO 2 Selectivity at 150 °C). Current strategy provides a gateway for the rational design of ZnO-based catalytic materials.