On the relevance of accurate input data for vibrational kinetics in air cold plasmas: the case of nitrogen fixation

The need for green chemistry processes is currently pressing the research world to find solutions suited for a direct use of inherently intermittent renewable energy sources. However, these solutions must be also energy efficient, due to the world-size magnitude of the production that has to be substituted in the near future. One of the top problems in this sense is the nitrogen fixation, responsible for at least 40% of world food production by the synthesis of fertilisers. Using air plasmas for this process is an old idea dating back to the first years of 1900, then rapidly substituted by other processes more economically but much less ecologically sustainable. Reaching a balance between these two aspects of a realistic sustainability using non-equilibrium plasmas is the present challenge. Chemical kinetics modelling including vibrational kinetics of heavy species is key in this sense, because it allows to experiment possible solutions in a much easier way than in the laboratory, provided the model is sufficiently complete and based on accurate input data, in order to smoothly reproduce the available experimental findings. The present paper is focussed on the state-of-the-art of some heavy-particle processes crucial in air plasmas in general and for nitrogen fixation in particular, including new specific rate coefficient data, on their comparisons with well-known data largely used in models and on their possible improvements in the near future.