Carbon-doped mesoporous TiO2-immobilized Ni nanoparticles: Oxygen defect engineering enhances hydrogen production

Constructing efficient, durable, and economical catalysts to promote hydrogen production from hydrous hydrazine (N2H4·H2O) is crucial, but still a great challenge. Herein, noble-metal-free Cr(OH)3-modified Ni nanoparticles (NPs) (2.7 nm) supported on defect-rich carbon-doped mesoporous TiO2 nanosheets (C-TiO2) were prepared for the first time via a simple and green wet-chemistry approach, in which the amount of oxygen defect in C-TiO2 can be easily regulated by adjusting the amount of carbon doping. Significantly, the defect rich Ni-Cr(OH)3/C-TiO2 catalyst presented 100% H2 selectivity, ultrahigh catalytic activity, and remarkable durability for N2H4·H2O dehydrogenation, with a turnover frequency (TOF) value of 266 h−1 at 323 K, more than 6-fold improvement than that of the Ni-Cr(OH)3/TiO2 (41 h−1), which is among the highest values reported so far for noble-metal-free catalysts. The superior catalytic efficiency and durability are mainly owing to the small-sized and electron-rich of Ni NPs induced by the oxygen defects in C-TiO2, where the more oxygen defects, the better the catalytic activity. Furthermore, the catalyst also showed outstanding catalytic efficiency (TOF = 577 h−1) and robust durability for complete dehydrogenation of hydrazine borane (N2H4BH3) at 323 K. This work provides inspiration for the construction of defect engineering and new insights for the development of low-cost and efficient heterogeneous hydrogen production catalysts.