(Invited) Electroenzymatic Hydrogen Production: Mediated/Direct Electron Transfer Strategies and Continuous Product Analysis

Abstract

Metalloenzymes such as hydrogenases and nitrogenases are of interest to electrochemists for mechanistic study as well as applied biotechnological hydrogen and ammonia production. In order to interface these enzymes with electrodes mediated and direct electron transfer methods have been reported, each having their strengths and weaknesses. In addition to establishing efficient electron transfer with enzymes, dynamic product analysis is also desirable since rates of product formation (and the distribution of products) can be determined during an experiment with varying electrode potential (and thermodynamic driving force for heterogeneous electron transfer).Our recent efforts concerning the design of electrode:enzyme interfaces are presented here, including (i) mediated vs. direct electron transfer strategies, (ii) rotating ring disk electrochemistry, and (iii) continuous mass spectrometry and gas chromatography [1-2]. In this work, an [FeFe]-hydrogenase is employed as a model enzyme for molecular hydrogen formation, with a view to expand these approaches towards enzymatic electrocatalytic studies of nitrogenases. Limitations and difficulties of the presented approaches will be discussed.