Developing efficient propane dehydrogenation (PDH) processes without uses of expensive Pt- and toxic CrOx-based catalysts are of broad interest and great importance. Co-feeding of hydrogen is a widely-adopted strategy to improve catalytic performance of various catalysts in the PDH reaction. Herein, we systematically study the promotion effect of co-fed H2 on different oxide catalysts in the PDH reaction. It comes mainly from the alleviated poisoning effect on ZnO and additionally from H2 reduction-enhanced coordination-unsaturated Zr3+ active sites on ZrO2, while mainly from the formation of dynamically-cycles metastable gallium hydride species on Ga2O3 capable of activating the C–H bond activation of propane at significantly reduced barriers \(\left( {{{\rm{C}}_{{3}}}{{\rm{H}}_{{8}}} + 2{\rm{Ga(III}}{{\rm{)}}_{{\rm{G}}{{\rm{a}}_{\rm{2}}}{{\rm{O}}_{{3}}}}}{\rm{ - }}{{\rm{H}}^{\rm{*}}} = {{\rm{C}}_{\rm{3}}}{{\rm{H}}_{{6}}} + 2{{\rm{H}}_{{2}}} + 2{\rm{Ga(III}}{{\rm{)}}_{{\rm{G}}{{\rm{a}}_{{2}}}{{\rm{O}}_{{3}}}}}} \right)\) . During the Ga2O3-catalyzed PDH reaction with co-fed H2, the \({\rm{Ga(III}}{{\rm{)}}_{{\rm{G}}{{\rm{a}}_{{2}}}{{\rm{O}}_{{3}}}}}{\rm{ - }}{{\rm{H}}^{\rm{*}}}\) species initially forms by H2 dissociation, then reacts with C3H8 to produce C3H6 and H2, and finally gets recovered by H2 dissociation, leading to the dynamically-cycled hydride active site on Ga2O3 with greatly enhanced catalytic performance. Such a hydride catalysis is highly sensitive to the structure of Ga2O3, being more efficiently on Ga2O3{111} facets than on Ga2O3{100} facets. A fine Ga2O3 nanocatalyst with a high ratio of exposed {111} facets and a large specific surface area is fabricated to give a C3H6 space-time yield (STY) as high as \({{4}}{{.9}}\,{\rm{k}}{{\rm{g}}_{{{\rm{C}}_3}{{\rm{H}}_6}}}/\left( {{\rm{k}}{{\rm{g}}_{{\rm{catalyst}}}}\,{\rm{h}}} \right)\) with a C3H6 selectivity of 96.5% and a good recyclability in the PDH reaction with co-fed H2 at 550 °C. These results provide an alternative strategy for developing none-Pt- and none-toxic CrOx-based PDH catalysts.
