Ni-N synergy enhanced the synthesis of formic acid via CO2 hydrogenation under mild conditions

The direct CO(2 )hydrogenation to formic acid is appealing since it is a potential hydrogen storage material and can be a precursor of higher value-added products. Due to thermodynamic limitations, developing an efficient catalyst system for this process is quite a challenge. Herein, a Ni-based N-modified TiO2-supported catalyst that showed exemplary activity and selectivity toward formic acid synthesis (757 TON), which was reported to be the highest over noble metal-free catalyst system, is designed. The combined impact of Ni and N over TiO2 as a support was thoroughly investigated in this research for improved activity in the selective conversion of CO2 to formic acid. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy investigations showed direct coordination between Ni and N, which emphasizes the metal support interaction for significantly higher catalytic activity. In-depth characterization of Ni/ N-TiO2 reveals that CO2 undergoes insertion reaction with H-2 to yield formic acid on Ni0 as an active surface via the formate intermediate. Complementary DFT studies elucidate the pivotal effect of nitrogen doping on the TiO2 surface, which provides a more feasible pathway than pure TiO2 by lowering the activation barriers. More significantly, the catalyst demonstrated a steady performance in experiments involving continuous recycling and long-term study.

Automated summary

In this study, a Ni-based N-modified TiO2-supported catalyst was designed for the selective conversion of CO2 to formic acid. The direct coordination between Ni and N was found to enhance the catalytic activity significantly, and nitrogen doping on the TiO2 surface was shown to lower the activation energy barrier. The stable performance of this catalyst makes it potentially important for practical applications.