With increasing global interest in renewable energy technology in the backdrop of climate change, energy storage at small and very large scales has become extremely relevant. Most sustainable technologies produce electricity (i.e. wind, solar PV). The challenge of our era is to change from fossil driven chemical processes to electrical ones while dealing with the intermittency of renewable sources. An economically feasible option for long term (seasonal) storage seems to be chemical feedstock, i.e. storing energy in form of binding energy of molecules. The main research question that has to be addressed urgently is the most effective way of converting electrical energy into molecules of high energy. In the transition from low energy molecules (e.g. N2, CO2) to high energy molecules (e.g. NH3, NO, CO) particularly the activation of chemical bonds (e.g. N≡N, O=C=O) should be tackled. Up to now solutions were mainly sought on material axis, however recent theoretical studies have revealed that there are intrinsic limitations of catalysis (i.e. scaling relationships) which keep the processes far from the optimum performance1. In this contribution, we will present a unique solution to the aforementioned limitations which is based on plasma aided electrocatalysis. We employ electrochemical cells with ionic conducting membranes2 that allow us to provide reacting species such as O-2, H+ on catalysts that can be used for the fixation of plasma activated N2. The current applied to these systems determines the flux of oxygen ions or protons while a radiofrequency plasma is used to increase the reactivity of nitrogen at low energy cost3. The presence of charges, in the plasma phase as well as on the surfaces exposed to the plasma, are key aspects to enhance catalysis. Surprisingly, up to now such synergistic effects were largely ignored. The spatial separation of N2 dissociation and catalytic formation of the target molecules provides true independent parameters to optimise the electrocatalytic reactions. The advantages of our approach compared to conventional plasma catalysis, catalysis or pure plasma processes will be discussed. Finally, the perspectives of the extension of our approach to water or carbon dioxide electrolysis will be addressed.

Plasma aided electrocatalysis for nitrogen fixation

2019 Spring National Meeting

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