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The Zhang Group

                     

 

"Life is nothing but an electron looking for a place to rest"

   - Albert Szent-Györgyi (Nobel Laureate in Physiology 1937)

 

Photosynthesis on an electrode

Photosynthesis is the primary light energy conversion process that underpins life, agriculture, and carbon/nitrogen/oxygen cycles on Earth. The complex chemistry and biophysics occuring within photosynthetic organisms are both inspirational and baffling to scientists of many disciplines, the unravelling of which could have far reaching impact on agricultural and bio-energy technologies in the future.

Electrochemistry is a sensitive and powerful technique for interrogating redox processes, and lies at the heart of many energy conversion technologies, sensor technologies, and synthetic processes. Here, we 'wire' photosynthetic proteins, components and even living organisms to electrodes for electrochemical analysis to better understand the fundamental redox chemistry, pathways, and bottlenecks that lie within biological photosynthesis. We work with with theoreticians to develop models for explaining, and eventually predicting and controlling electron transfer pathways at the bio-electrode interface. 

 

Semi-artificial photosynthesis and biophotovoltiacs

By wiring bio-hybride electrodes together in a two-electrode regime (what is known as 'semi-artificial photosynthesis') we can cherry pick and combine the strengths of biological catalysts, materials chemistry and engineering to generate solar chemicals and/or electricity. Already, prototype semi-artificial photosynthetic devices employing isolated proteins have demonstrated the ability for short-term bias-free water-splitting, and biophotovoltaic devices employing live photosynthetic cells have been shown to power sensors and low-tech devices. These emergent solar-energy conversion devices are attractive because they exploit earth abundant bio-components that have a wide catalytic repertoire, are self-regenerating and robust, and are amendable to bioengineering. Several challenges lie ahead for these devices, including the need to boost longevity and output. Here, we tackle these challenges and explore microoganisms and catalysts for different fuel forming pathways.

 

3D printing of (photo)electrochemical platforms
The choice of electrodes used in photoelectrochemical studies and applications matters enormously. In particular, the architecture of the electrode, the nano-roughness of the surfaces, and the properties at the surface and the bulk of the electrode all contribute to the overall performance of the bio-catalytic component. We explore 3D printing and other state-of-the-art fabrication methods to tailor electrodes and electrochemical cells to various bio-catalysts (from enzymes to cells). Coupled to this, we develop electrochemical methods to characterise the complex 3D electrode structures, complementing classical electron microscopy and imaging techniques.

 

Cyanobacteria

Cyanobacteria are one of the oldest and most abundant life forms on Earth (they thrive in the oceans, glaciers and even hot springs!), and are only going to become more abundant with global warming. They play important ecological roles, contributing to the regulation of the oxygen, carbon, nitrogen cycles in the ocean and atmosphere. One of the many intriguing properties they (and other photosynthetic micro-organisms) exhibit is that they are able to generate electricity under sunlight irradiation, much like a solar cell. Why and how do cyanobacteria do this? What can this tell us about their biological inputs and outputs? How do we best harness this energy to do useful chemistry? These are some of the questions that we are trying to answer about cyanobacteria and other photosynthetic biofilms using electrochemistry, synthetic biology (with our collaborators, the Howe group at Biochemistry) and a range of chemical biology approaches including fluorescence microscopy and ultra-fast spectroscopy.

 

Future research themes of interest...

Environmental and agricultural sensing

- Artificial extracellular polymeric matrices

- Quinone chemistry

- Biofilms

 

 

Related Publications 

Interfacing nature's catalytic machinery with synthetic materials for semi-artificial photosynthesis.
N Kornienko, JZ Zhang, KK Sakimoto, P Yang, E Reisner – Nature nanotechnology (2018) 13, 890
Photoelectrochemistry of Photosystem II in Vitro vs in Vivo
JZ Zhang, P Bombelli, KP Sokol, A Fantuzzi, AW Rutherford, CJ Howe, E Reisner – J Am Chem Soc (2018) 140, 6
Competing charge transfer pathways at the photosystem II-electrode interface
JZ Zhang, KP Sokol, N Paul, E Romero, R van Grondelle, E Reisner – Nat Chem Biol (2016) 12, 1046
Solar Water Splitting with a Hydrogenase Integrated in Photoelectrochemical Tandem Cells
DH Nam, JZ Zhang, V Andrei, N Kornienko, N Heidary, A Wagner, K Nakanishi, KP Sokol, B Slater, I Zebger, S Hofmann, JC Fontecilla-Camps, CB Park, E Reisner – Angewandte Chemie - International Edition (2018) 57, 10595
Wiring of Photosystem II to Hydrogenase for Photoelectrochemical Water Splitting.
D Mersch, C-Y Lee, JZ Zhang, K Brinkert, JC Fontecilla-Camps, AW Rutherford, E Reisner – J Am Chem Soc (2015) 137, 8541