Rapid electrocatalytic hydrogen cycling by enzymes: establishing the basis for future energy technology

Completed

Hydrogen and Fuel Cells(Fuel Cells)
Hydrogen and Fuel Cells(Hydrogen, Hydrogen production)

Basic and strategic applied research

PHYSICAL SCIENCES AND MATHEMATICS (Chemistry)

Not Cross-cutting

Professor FA Armstrong
Oxford Chemistry
University of Oxford

Standard

BBSRC

03 October 2005

02 October 2008

36 months

£358,442

Power; Transport

South East

BBSRC Energy Grants

Professor FA Armstrong, Oxford Chemistry, University of Oxford

Dr KA Vincent, Oxford Chemistry, University of Oxford

Objectives not supplied

The research involves novel electrochemical experiments on metalloenzymes known as hydrogenases that occur in microbial organisms to produce or oxidise hydrogen. Hydrogenases are important in the organisms because they are energy-producing catalysts. However, they can also be adsorbed on electrodes, in which form they show extremely high electrocatalytic activity, either in hydrogen production or hydrogen oxidation. They therefore offer an important solution to part of the future energy problem, which involves the production of hydrogen from electricity and conversion of hydrogen back to electricity. Indeed, we have been able to construct a fuel cell, with a hydrogenase adsorbed on the anode and a blue copper oxidase adsorbed on the cathode, that powers a light-emitting diode. Hydrogenases contain Fe or Fe and Ni at their active sites along with unusual carbon monoxide and cyanide ligands, and hydrogen is split heterolytically, which means the active site stabilises hydridic and protonic intermediates. Activity is attenuated, often permanently, by oxygen and carbon monoxide. These side reactions are poorly understood. The enzymes also contain Fe-S clusters to carry out long-range electron transfer, so that each enzyme molecule can exhibit several oxidation levels. These factors mean that hydrogenases are extremely complicated catalysts, and specific states that play important roles in catalysis or other transformations are difficult to generate for a spectroscopic or structural investigation. Their reactions will be studied by a suite of electrochemical techniques, known as protein film voltammetry, which has been developed in the Oxford laboratory and elsewhere. These techniques provide a highly detailed picture, both in terms of kinetics and energetics, of the different reactions that hydrogenases undergo, ranging from catalytic hydrogen cycling to inactivation by oxygen and carbon monoxide. We will investigate an important recent discovery of a hydrogenase that exhibits rapid catalytic hydrogen oxidation in the presence of carbon monoxide, and observation that is remarkable both in terms of the mechanistic insight and the technological implications that are highlighted. We will refine details of structurally characterised hydrogenases that are not resolved by conventional investigations. We will commence a program to detect and characterise hydrogenase activities in crude cell samples, identifying microbes that host hydrogenases having particular potential for interesting properties and technological development. This research will underpin the exploitation of hydrogenases as technological catalysts, either directly as stabilised enzyme-electrodes or by providing the knowledge required to design synthetic systems that will achieve high activity, specificity and stability.

14/12/07