(Keynote) Electrochemical Routes to Nitrogen Fixation: Comparisons, Pitfalls and Breaking in through the Cat Flap

Abstract

The electrosynthesis of ammonia from nitrogen and water is a topic of considerable interest in the quest for sustainable and decentralized NH3 production (Catal. Today, 2017, 286, 57-68). It is, however, a remarkably difficult process to perform and the literature abounds with false-positives for electrochemical ammonia generation. In this talk, we shall survey some of the approaches for electrochemical nitrogen fixation that have been proposed, before then examining in detail one example from the author’s laboratory of a false-positive for nitrogen reduction electrocatalysis. In this example, tin(II) phthalocyanine complexes (previously reported as active electrocatalysts for nitrogen reduction to ammonia in aqueous solution), were shown not to be electrocatalysts for this transformation at all, with the amount of ammonia detected being essentially the same under N2 and under Ar. Instead, apparent ammonia generation was shown to be a consequence of contaminants in the as-prepared tin(II) phthalocyanine complexes (Electrochim. Acta, 2017, 258, 618-622). Finally, we shall discuss alternative mechanisms for nitrogen fixation that do not rely on the direct reduction of dinitrogen to ammonia in aqueous solution.