Swedish Consortium for Artificial Photosynthesis

 Leading the way to solar fuels

Solar fuel - the fuel of the future

We work along two tracks: artificial photosynthesis, and a photobiological approach. Both are aimed at production of hydrogen and other fuels from solar energy. Hydrogen is an environmentally friendly energy carrier that could replace fossil fuels. Only water is generated when hydrogen is either combusted or used in a fuel cell.

Our strategy is bridging many fields. Our work covers chemical design and synthesis, physical chemistry, advanced spectroscopy, biochemistry, biophysics, molecular biology and gene-technology to bio-reactor design and technology. This way the Consortium has carried out pioneering, unique work in the last 20 years.

Research areas

Natural photosynthesis

Project leaders: Stenbjörn Styring, Johannes Messinger

Basic research in natural photosynthesis has provided inspiration and guidelines for our development of artificial photosynthesis since the start. Our long-term integration of research in natural and man-made systems has become our signature and proven to be a fruitful apporach.

In photosynthesis, energy from sunlight is stored as chemical energy. This occurrs in green plants, algae and cyanobacteria. Electrons, which are needed to store the energy in the chemical form, are derived from water, the most abundant chemical in the biosphere. Water is oxidized to oxygen, electrons and protons by Photosystem II. Photosystem II generates a very high redox potential under unusually mild conditions (neutral pH and ambient temperature). This serves as inspiration for our artificial photosynthesis systems.

We investigate the function of Photosystem II and the mechanism for water oxidation usin biochemical methods and site-directed mutagenesis. The spectroscopic techniques we use to characterize Photosystem II are optical, fluorescence, X-ray and EPR spectroscopies.

Project Homepage 

The structure of Photosystem II, highlighting the water-oxidizing complex. From: Young et al. (2016) Nature 540, 453-457.
  

 Artificial photosynthesis

In artificial photosynthesis our long-term goal is to construct a synthetic, photochemical system that converts solar energy into a  fuel. The main principles of artificial photosynthesis are inspired by nature: (1) light absorption by molecular dyes; (2) photoinduced electron transfer from the dye in several steps leading to separation of reducing and oxidizing equivalents; (3) use of the reducing equivalents to produce a fuel, such as hydrogen or an alcohol; (4) use of the oxidizing equivalents to split water to oxygen, thereby extracting the electrons and protons needed for fuel generation.

Electron transfer reactions are critical to convert light energy into chemical energy. Our studies are focused on design and study of molecular systems for controlling photoinduced electron transfer and proton-coupled electron transfer, and for coupling photoinduced charge separation to multi-electron reactions.


1. Molecular catalysts for photo-driven water oxidation 

Project leaders: Stenbjörn StyringLeif Hammarström, Licheng Sun, Johannes Messinger, and Anders Thapper 

Our idea is to design molecular systems that can do light-driven catalysis. With molecular catalysts it is possible to control and fine tune the properties and activity of the catalyst. Our strategy is to synthesize metal-organic complexes  linked to photosensitizers, that can oxidize water using the energy in sunlight.

For about 20 years we have made a class of complexes containing Ruthenium (II), which can be excited by light. The Ru-complexes are  linked to other molecular complexes and catalysts, containing manganese or other metals. One of our results is the creation of a highly efficient molecular water oxidation catalyst based on ruthenium, which can be driven by light.

In another apporach we use nanoparticles or coordination compounds containing cobalt for light-driven water oxidation. We also continue to develop new materials, holding a steady eye on the developments in natural photosynthesis.

 

Above: A schematic representation of a complete cell for light driven water oxidation and hydrogen production. To the left is the oxidative half-cell that is the main focus of this research group. The water oxidation catalyst is made of amorphous cobalt oxide nanoparticles. To the right is the reductive, hydrogen producing, half-cell.


To the left: A highly active molecular catalyst for water oxidation with ruthenium, developed in Prof. Licheng Sun's group.


The catalyst can be incorporated together with a photosensitizer in a functional device (below).


Key papers: L. Duan et al. (2012) Nature Chem. 4, 418-423; Y. Gao et al. (2013) J. Am. Chem. Soc. 135, 4219-4222.

Project homepages:

Learn about dye-sensitized solar cells and ruthenium-based water-splitting catalysts here!

Learn about water-splitting catalysts based on cobalt and iron here!


2. Functional models of the FeFe-hydrogenase active site

Project leader: Sascha Ott

To create a system that produces hydrogen from solar energy, we created bioinorganic model complexes of the [FeFe] hydrogenase active site. In addition to advancing the development of hydrogen producing catalysts, we also contribute in the quest to understand the catalytic mechanism of the natural enzyme. At the same time, we utilize this knowledge to design and synthesize new catalysts that are structurally based on the [FeFe] hydrogenase motif. The catalytic performance of our complexes is tested by a variety of spectroscopic and electrochemical techniques. We are aiming to utilize our catalysts in conjunction with suitable photosensitizers to drive the reduction of protons by light.

A hydrogenase mimic coupled to a photosensitizer produces hydrogen under illumination.

Project homepage:

Learn more about hydrogenase mimics and photosensitizers here!

 

Electron transfer in molecular systems

Project leader: Leif Hammarström

We demonstrated the first example of accumulative electron transfer in a molecular system leading to a reversible, two-electron charge-separated state (no sacrifical agents used). This proof-of-principle experiment is a step towards bridging the gap between single-electron charge separation and multi-electron catalysts of fuel formation and water splitting.(Collaboration with Dr. Fabrice Odobel, Nantes University)

 

Proton-coupled electron transfer studies

An important theme in our biomimetic effort is that of coupled electron transfer reactions: (1) each absorbed photon leads to charge separation on a single-electron level only, while catalytic water splitting and hydrogen production are multi-electron processes. Therefore we need to control accumulative electron transfer on molecular components; (2) water splitting and proton reduction at the catalysts requires the management of proton release and/or uptake. This controls the electron transfer processes by proton-coupled electron transfer (PCET); (3) redox-active links between the photosensitizers and the catalysts are required to rectify the accumulative electron transfer reactions, and will often be the starting points of PCET.

Project homepage      

 

Photobiological fuel production

Project Leader: Peter Lindblad

Photobiology is fundamental science in the borderland between chemistry, cell- and molecular biology, and genetics. The vision is to use a combination of advanced gene technology and synthetic biology, to develop photosynthetic microorganisms to be used in future biotechnological applications. At present, this research project aims to develop cyanobacteria which convert solar energy into an energy carrier. The aim is direct conversion of solar energy into a fuel, not via biomass, focussing on hydrogen as well as  carbon-based fuels.

 Project homepage       


Right: Genetically engineered cyanobacteria growing in a photobioreactor. We develop synthetic biology tools and the possibilities to custom design and engineer microbial cells, to produce fuels via novel metabolic pathways.






Engineering of hydrogenase enzymes

Project leaders: Stenbjörn Styring, Ann Magnuson

To In this project we take a novel approach to improve the solar-driven hydrogen production from cyanobacteria, via targeted protein engineering. Our goal is to modify a native cyanobacterial uptake hydrogenase,  and turn it from being a hydrogen consumer, into being a net hydrogen producer. Our strategy is to introduce designed modifications in a cyanobacterial uptake hydrogenase, HupSL. By manipulating the redox poise of the iron-sulfur clusters in the small subunit of the hydrogenase, we can alter the electron transfer to and from the active site resulting in an altered catalytic activity. We have already shown our proof-of-concept in:

P. Raleiras et al. (2016) Energy. Environ. Sci., 2016, 9, 581-594.


 

 

Last update March 2017