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Alpha alumina (α‐Al2O3) are inert materials with outstanding thermal, chemical and mechanical stability. Herein, we fabricate porous single‐crystalline (PSC) α‐Al2O3 monoliths at centimeter scale to endow them with high catalytic activity while maintaining their stability. We reduce PSC α‐Al2O3 monoliths to create oxygen vacancies in lattice and stabilize them by the ordered lattice to construct unsaturated Al−O coordination structures for enhancing the catalytic activity. The generation of oxygen vacancy at 18e wyckoff position contributes to the unsaturated Al−O coordination. As a case study, we demonstrate the outstanding performance with conversion (≈34 %) and selectivity (≈95 %) toward non‐oxidative dehydrogenation of ethane to ethylene at 700 °C. We achieve the outstanding performance without obvious degradation even after a continuous operation over 1000 hours at 700 °C. [ABSTRACT FROM AUTHOR]

Preferential oxidation of CO in H2 (PROX) reaction is a promising solution to the on‐board purification of CO‐contaminated H2 fuel for use in next‐generation proton‐exchange membrane fuel cells (PEMFC). However, achieving high CO selectivity, activity and structural stability across the wide temperature window remains a great challenge. Herein, we fabricate centimeter scale interfacial PROX catalysts grown from nanoporous single‐crystalline Pr2O3 and Nd2O3 monoliths with lattice surface‐deposited Pt clusters at nanoscale. We demonstrate complete and selective removal of CO in H2 over an unprecedented wide temperature window (253–403 K). The monoliths are integrated with an operational PEMFC to purify the H2 fuel contaminated with CO (30 ppm) and enable stable power output for >400 h; over two thousand times longer than without. This work demonstrates that the nanoporous single‐crystalline oxide monoliths can simultaneously achieve the stability and overall performance required to realize practically useful PEMFCs. [ABSTRACT FROM AUTHOR]