The path to artificial photosynthesis

Artificial catalysts imitate natural photo-synthesis.<br />Image

Artificial catalysts imitate natural photo-synthesis.
Image © HZB

HZB researchers describe efficient manganese catalyst capable of converting light to chemical energy

Scientists at the Helmholtz Center for Materials and Energy (HZB) in collaboration with the School of Chemistry and ARC Centre of Excellence for Electromaterials Science at Monash University, Australia, have precisely characterized a manganese catalyst’s electronic states. The catalyst is capable of converting light to chemical energy.

Through their work, Professor Emad Aziz, head of the HZB Institute “Methods for Material Development“, Professor Leone Spiccia from Monash University and their teams have taken an important leap forward in understanding photosynthesis – the method green plants use to obtain energy – in artificial systems. Today findings of the team have been published in the journal ChemSUSChem (DOI: DOI: 10.1002/cssc.201403219) and recently in the renowned Royal Society of Chemistry’s Journal of Materials Chemistry A. (DOI: 10.1039/c4ta04185b).

If sunlight could effortlessly be converted to chemical energy, our energy troubles would be a thing of the past. Green plants have evolved a special kind of mechanism to help them do just that: photosynthesis, the process by which plants take sunlight and, with its help, produce high-energy substances like sugar from water and carbon dioxide. But the molecules located in the so called “oxygen evolution centre” that facilitate this series of steps inside a plant cell are highly complex and sensitive. A current mission of scientists is simulating them in a laboratory setting and optimizing them for commercial energy production.

At his institute, Emad Aziz is doing research on artificial water splitting catalysts with the goal of getting them to perform at the level of the oxygen evolution center of photosynthesis. A while back, the scientists figured out what the chemical nature of these types of energy converters would need to be. Top candidates are manganese complexes embedded in a nafion matrix, a teflon-like polymer. Leone Spiccia´s lab developed and provided the samples. He says: “Under a bias, our manganese complexes produce nanoparticles of manganese oxides within nafion matrix. When exposed to light and biased simultaneously, these oxides promote water oxidation, a key and challenging reaction associated with the splitting water into oxygen and hydrogen. The hydrogen can be stored as an energy carrier.”

“The next step was to figure out which of the potential manganese complexes in nafion yields the best manganese oxides,“ says the scientist in charge of the experiments, Munirah Khan of the Freie Universität Berlin, holder of a DAAD and HEC(Pakistan) scholarship. She studied the formation of manganese oxides and their catalytic effect using X-ray light at BESSY II, the HZB’s synchrotron radiation source. In her doctorate research work, Khan used the RIXS method, which allowed her to select and further investigate the manganese species involved in catalytic processes with high precision.

Of the various manganese complexes, one in particular – designated Mn(III) by the scientists – turned out to be the one that most efficiently formed manganese oxides. “We are developing our methods to construct multi-dimension catalytic pathways for such novel materials in the energy and time scales. Our goal is to provide synthetic chemists with a full picture of the catalytic process under real test conditions in order to enhance their work on the function of these materials,“ says Emad Aziz, “and figure out if and under what conditions it might be used for technological application in converting light to chemical energy. If we succeed, it could mean we’re well on our way towards a continuous, environmentally-friendly, and cost-effective storage form of solar energy.“

hs

You might also be interested in

  • Scientists Develop New Technique to Image Fluctuations in Materials
    Science Highlight
    18.01.2023
    Scientists Develop New Technique to Image Fluctuations in Materials
    A team of scientists, led by researchers from the Max Born Institute in Berlin and Helmholtz-Zentrum Berlin in Germany and from Brookhaven National Laboratory and the Massachusetts Institute of Technology in the United States has developed a revolutionary new method for capturing high-resolution images of fluctuations in materials at the nanoscale using powerful X-ray sources. The technique, which they call Coherent Correlation Imaging (CCI), allows for the creation of sharp, detailed movies without damaging the sample by excessive radiation. By using an algorithm to detect patterns in underexposed images, CCI opens paths to previously inaccessible information. The team demonstrated CCI on samples made of thin magnetic layers, and their results have been published in Nature.
  • Recommended reading: Bunsen magazine with focus on molecular water research
    News
    13.01.2023
    Recommended reading: Bunsen magazine with focus on molecular water research
    Water not only has some well-known anomalies, but is still full of surprises. The first issue 2023 of the Bunsen Magazine is dedicated to molecular water research, from the ocean to processes in electrolysis. The issue presents contributions from researchers cooperating within the framework of a European research initiative in the "Centre for Molecular Water Science" (CMWS). A team at HZB presents results from the synchrotron spectroscopy of water. Modern X-ray sources can be used to study molecular and electronic processes in water in detail.
  • World record back at HZB: Tandem solar cell achieves 32.5 percent efficiency
    News
    19.12.2022
    World record back at HZB: Tandem solar cell achieves 32.5 percent efficiency
    The current world record of tandem solar cells consisting of a silicon bottom cell and a perovskite top cell is once again at HZB. The new tandem solar cell converts 32.5 % of the incident solar radiation into electrical energy. The certifying institute European Solar Test Installation (ESTI) in Italy measured the tandem cell and officially confirmed this value which is also included in the NREL chart of solar cell technologies, maintained by the National Renewable Energy Lab, USA.