Researchers at the University of Oxford’s Department of Engineering Science have made major advances towards realising green hydrogen – the production of hydrogen by splitting water, powered by renewable energy. Their approach, which focuses on bio-engineering bacteria to become ‘hydrogen nanoreactors’, could open the way towards a cost-effective, zero carbon method of generating hydrogen fuels.
Hydrogen could play a key role in helping us achieve net-zero emissions, since this burns cleanly without releasing CO2. However, current industrial hydrogen production depends heavily on fossil fuels, generating approximately 11.5–13.6 kilograms of CO2 emissions per kilogram of hydrogen produced.
In the new study, the researchers used a synthetic biology approach to convert a species of bacteria into a cellular ‘bionanoreactor’ to split water and produce hydrogen using sunlight. By generating a highly-efficient, stable and cost-effective catalyst, this overcomes one of the critical challenges that has been holding back green hydrogen to date.
Lead author Professor Wei Huang (Department of Engineering Science, University of Oxford) said: ‘Currently, most commercially used catalysts for green hydrogen production rely on expensive metals. Our new study has provided a compelling alternative in the form of a robust and efficient biocatalyst. This has the advantages of greater safety, renewability, and lower production costs all of which can improve long-term economic viability.’
In nature, specific microorganisms can reduce protons (H+) to hydrogen (H2) using hydrogenase enzymes, however this is limited to low yields due to constraints, such as low electron transfer rate. Up to now, this has prevented microorganisms from being used as effective hydrogen catalysts.
To overcome this, the Oxford researchers engineered the bacterium Shewanella oneidensis to concentrate electrons, protons, and hydrogenase in the space between the inner and outer membrane (known as the periplasmic space, 20-30 nm wide). This species is ‘electroactive’, meaning that it can transfer electrons to or from solid surfaces outside their cells.