Production of sulfur and hydrogen: splitting hydrogen sulfide with solar energy
No one who has cracked open a rotten egg will forget its infernal stench. Biofuel plants, sewage treatment plants, and petroleum refineries can generate substantial amounts of foul-smelling hydrogen sulfide gas, which is highly toxic at higher concentrations.
In the journal Angewandte Chemie, a team of Australian and Chinese researchers has now introduced an innovative photoelectrochemical process in which solar energy is used to split this undesirable by-product into sulfur and hydrogen, converting it to a source of raw materials.
A variety of techniques have been used to remove hydrogen sulfide (H2S) from polluted exhaust gases and occasionally put it to further use. While sulfur can be extracted in some processes, the hydrogen cannot. This is unfortunate because hydrogen is actually an important energy source for future fuel-cell technology.
Unfortunately, it isn’t possible to split H2S to gain hydrogen and sulfur simultaneously. Approaches using photochemical splitting seem particularly attractive because solar energy could be used to meet the high energy demand of this reaction.
However, no ecologically and economically feasible process has been found to date. This could now change thanks to a new approach developed by a team headed by Lianzhou Wang (University of Queensland, Australia) and Can Li (Chinese Academy of Sciences and Dalian Laboratory for Clean Energy, China).
Their success lies in a photochemical–chemical loop whose reactions are coupled through a redox pair. A redox pair is a combination of the reduced and oxidized form of the same element that can easily be interconverted. For their process, the researchers used either divalent and trivalent iron ions (Fe2+/Fe3+) or the iodide/triiodide (I−/I3−) system.
The hydrogen sulfide gas is introduced into the electrolyte of the anodic compartment of an electrochemical cell. Here, a chemical reaction causes it to be bound to the oxidized form of the redox pair (which is thus reduced) and converted to sulfur, which precipitates out as a yellow solid, and hydrogen cations (protons).
The protons can pass through the semipermeable membrane that separates the anodic and cathodic compartments. The second reaction is photoelectrochemical: as protons are reduced at the cathode by taking up electrons, the reduced form of the redox pair is returned to its oxidized state by giving up electrons at the anode. The driving force for this is sunlight, which generates “electron–hole pairs” at the photoanode. These holes can then be filled by the absorbed electrons.
The redox pairs continuously cycle between the oxidized and reduced forms so that the overall reaction is the splitting of hydrogen sulfide into sulfur and hydrogen by sunlight.
About the Author
Dr. Lianzhou Wang is a Professor at the School of Chemical Engineering and Research Director of Nanomaterials Centre, the University of Queensland (UQ), Australia. His main research interests include the design and development of semiconducting nanomaterials for applications in renewable energy conversion/storage systems, including photocatalysis, new-generation solar cells, and rechargeable batteries.
Author: Lianzhou Wang, University of Queensland (Australia), http://www.nanomac.uq.edu.au/lianzhou-wang
Title: An Integrated Photoelectrochemical–Chemical Loop for Solar-Driven Overall Splitting of Hydrogen Sulfide
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201400571
Lianzhou Wang | Angewandte Chemie International Edition
How Cells in the Developing Ear ‘Practice’ Hearing
30.11.2015 | Johns Hopkins Medicine
New Analysis Technique for Chiral Activity in Molecules
30.11.2015 | Korea Advanced Institute of Science and Technology
Before the fluid of the middle ear drains and sound waves penetrate for the first time, the inner ear cells of newborn rodents practice for their big debut. Researchers at Johns Hopkins report they have figured out the molecular chain of events that enables the cells to make “sounds” on their own, essentially “practicing” their ability to process sounds in the world around them.
The researchers, who describe their experiments in the Dec. 3 edition of the journal Cell, show how hair cells in the inner ear can be activated in the absence...
Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.
Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...
The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...
Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.
In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...
In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.
Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...
30.11.2015 | Event News
25.11.2015 | Event News
17.11.2015 | Event News
30.11.2015 | Earth Sciences
30.11.2015 | Life Sciences
30.11.2015 | Ecology, The Environment and Conservation