Efficient formic acid dehydrogenation on AuPd/N-TiO2: The role of N dopant and the effect of TiO2 crystalline phase

Abstract

Nitrogen-doped TiO2 (N-TiO2) was prepared by direct pyrolysis of the amino-functionalized titanium metal–organic framework NH2-MIL-125(Ti) in air, and highly dispersed AuPd nanoparticles were anchored on N-TiO2. The synthesized catalysts showed excellent activity for formic acid dehydrogenation. At 60 °C, the total turnover frequency value of Au2Pd8/N-TiO2-catalyzed dehydrogenation reaction was 7725 h−1, which was 2.9 times that of the N-free catalyst (Au2Pd8/TiO2) under the same conditions. The excellent performance of the Au2Pd8/N-TiO2 catalyst was attributed to the high content of anatase TiO2, the synergistic effect between the N-TiO2 support and the metal nanoparticles, the alloying effect between Au and Pd and the small size of the metal particles. The presence of N can enhance the interaction between AuPd and the support, effectively prevent the aggregation of AuPd on the surface of the support, and improve the catalytic activity and reusability of the catalyst. The effect of TiO2 crystalline phase (anatase and rutile) and N doping on the performance of Au2Pd8/N-TiO2-catalyzed formic acid decomposition was analyzed by means of theoretical calculations. The results showed that the anatase and N-TiO2-based catalysts could reduce the barrier for formic acid dehydrogenation. This work combined experiments with theoretical calculations to provide a new approach to the modification of formic acid dehydrogenation catalysts.