Pollution and environmental deterioration have raised concerns amongst shareholders and policymakers. As such, stringent measures have been put in place to curb the use of fossil fuels to reduce greenhouse gas emissions into the atmosphere. Hydrogen is a promising alternative green renewable energy source to reduce fossil fuels and natural gas consumption. However, safe storage and rapid release remain the main challenge in the utilization of hydrogen energy. Moreover, promising hydrogen storage materials such as HCOOH requires highly selective and efficient catalysts to achieve an efficient hydrogenation process. Recently, the use of N-doped carbon materials as a support to synthesize catalysts for the decomposition of HCOOH has attracted significant research attention owing to their remarkably good electrical conductivity, large pore structures, and large specific surface area properties.
To date, several methods for preparing N-doped carbon materials, such as mixing the carbon materials with nitrogen sources and calcining at high temperature, have been developed. These conventional methods, however, have several drawbacks that limit their applications. Additionally, they do not conform to the requirements of green and sustainable production. The use of plasma technology, an environmentally friendly and efficient method for preparing N-doped carbon materials, overcomes most of these drawbacks and is more appropriate for HCOOH decomposition. Based on the existing literature, plasma technology can achieve effective treatment of the support, thereby improving the catalyst performance, even though its use is underexplored.
Motivated by these results, the group “Plasma Technology and Applications” led by Professor Lanbo Di and Professor Xiuling Zhang in Dalian University demonstrated the preparation of a Pd/C HCOOH dehydrogenation catalyst (Pd/C-P (NH3) with high activity and stability using simple NH3 cold plasma and activated carbon as support. The preparation mechanism was thoroughly investigated and analyzed. Their research work is currently published in the International Journal of Hydrogen Energy.
In their approach, Pd/C-C(NH3) and Pd/C-P(NH3) catalysts were prepared by heat treatment and cold plasma, respectively, using Ar and NH3 as working gas. The activity and stability of the synthesized catalysts were tested via formic acid dehydrogenation reaction. The authors reported that the HCOOH decomposition rate of the Pd/C-P(NH3) catalyst produced by NH3 cold plasma was about 89.2%, higher than that of commercial Pd/C and Pd/C-C(NH3) prepared by NH3 heat treatment. Additionally, results showed that NH3 cold plasma was milder than NH3 thermal treatment. The remarkable stability and high performance of Pd/C-P(NH3) catalysts were attributed to the effective N-doping of the carbon support generated by the low temperature and the small size and high dispersion of the Pd nanoparticles.
In summary, the research team successfully synthesized a Pd/C-P(NH3) HCOOH dehydrogenation catalyst using Ar and NH3 gases as working gas. The catalysts achieved remarkably high stability and catalytic activity. The hydrogen production of Pd/C-P(NH3) when used in first and third cycle are 1.24 and 13.24 times than that of commercial Pd/C. Therefore, atmospheric pressure NH3 cold plasma was proved to be a promising method for preparing high-performance Pd/catalysts for HCOOH dehydrogenation. In a statement to Advances in Engineering, Professor Lanbo Di explain their findings provides important guidance for the fabrication of high-performance carbon-supported metal catalysts.
Wang, H., Zhou, Y., Zhao, Q., Zhang, X., & Di, L. (2020). NH3 plasma synthesis of N-doped activated carbon supported Pd catalysts with high catalytic activity and stability for HCOOH dehydrogenation. International Journal of Hydrogen Energy, 45(41), 21380-21391.