Energy

Hybrid artificial photosynthesis technique produces hydrogen and methane

The enhanced hybrid artificial photosynthesis system produces hydrogen, which is used to them produce methane from carbon dioxide
The enhanced hybrid artificial photosynthesis system produces hydrogen, which is used to them produce methane from carbon dioxide
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The enhanced hybrid artificial photosynthesis system produces hydrogen, which is used to them produce methane from carbon dioxide
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The enhanced hybrid artificial photosynthesis system produces hydrogen, which is used to them produce methane from carbon dioxide
The Berkeley Lab team that led the development of the artificial photosynthesis system – L to R: Peidong Yang, Christopher Chang, and Michelle Chang
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The Berkeley Lab team that led the development of the artificial photosynthesis system – L to R: Peidong Yang, Christopher Chang, and Michelle Chang

Not content with using hybrid artificial photosynthesis to turn CO2 emissions into plastics and biofuel, researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) now claim to have produced an enhanced system that uses water and solar energy to generate hydrogen, which is in turn used to produce methane, the main element of natural gas, from carbon dioxide. Generating such gases from a renewable resource may one day help bolster, or even replace, fossil fuel resources extracted from dwindling sub-surface deposits.

Simply put, the process of photosynthesis turns light energyinto chemical energy. In plants and certain types of algae, energy fromincoming sunlight is used as the power source to synthesize simplecarbohydrates from carbon dioxide and water. In the original BerkeleyLab hybrid system, a membrane arrangement of nanowires created from silicon andtitanium oxide harvested solar energy and transported electrons to microbeswhere they used that energy to transform carbon dioxide into a range ofchemical compounds.

In the latest iteration of the artificial photosynthesis system, solar energy was captured via a similar membrane (but this timeconsisting of indium phosphide photocathodes and titanium dioxide photoanodes),which was employed to supply power for the splitting of water moleculesinto oxygen and hydrogen. The hydrogen was then conveyed to a collection ofmicrobes that used it to convert carbon dioxide into methane. Hence thehybrid system collected light energy and produced both hydrogen and methane.

"This study representsanother key breakthrough in solar-to-chemical energy conversion efficiency andartificial photosynthesis," said Professor Peidong Yang, a chemist withBerkeley Lab’s Materials Sciences Division. "By generating renewablehydrogen and feeding it to microbes for the production of methane, we can nowexpect an electrical-to-chemical efficiency of better than 50 percent and asolar-to-chemical energy conversion efficiency of 10-percent if our system iscoupled with state-of-art solar panel and electrolyzer."

The Berkeley Lab team that led the development of the artificial photosynthesis system – L to R: Peidong Yang, Christopher Chang, and Michelle Chang
The Berkeley Lab team that led the development of the artificial photosynthesis system – L to R: Peidong Yang, Christopher Chang, and Michelle Chang

Though the fundamentalconcept in the two artificial photosynthesis experiments is largely similar, inthe first tranche of work the researchers used an anaerobic bacterium, Sporomusa ovata, to transform carbondioxide when fed with electrons. In the latest iteration, the scientistspopulated the membrane with Methanosarcinabarkeri, which is an anaerobic archaeon (essentially a single-celledmicroorganism that has no cell nucleus or other membrane-bound organelles) thattransforms carbon dioxide using hydrogen itself.

In this way, water is turnedinto hydrogen by a hydrogen evolution reaction (HER), where the HER iscatalyzed by the addition of nickel sulfide nanoparticles thatoperate effectively under biologically compatible conditions.

"Using hydrogen as theenergy carrier rather than electrons makes for a much more efficient process asmolecular hydrogen, through its chemical bonds, has a much higher density forstoring and transporting energy," said Associate Professor of chemistry atBerkeley Lab, and member of the research team, Michelle Chang.

"While we were inspiredby the process of natural photosynthesis and continue to learn from it, byadding nanotechnology to help improve the efficiency of natural systems we areshowing that sometimes we can do even better than nature," added ProfessorYang.

Whilst this research is amulti-pronged approach to producing a range of gases and chemicals, it is alsoa method that brings living organisms into the mix. As such, even though purely electricalmethods of solar hydrogen production are increasing in efficiency, and it is possible to use solar energy combined with cheap and abundant mineral elements to create hydrogen, theidea of generating a range of useful, energy-rich gases using justsunlight, water, CO2 and naturally-occurring microbes in a process scaled-up tocommercial sizes holds a great deal of appeal in creating a trulyenvironmentally-friendly and self-sufficient energy production system.

"Weselected methane as an initial target owing to the ease of product separation,the potential for integration into existing infrastructures for the deliveryand use of natural gas, and the fact that direct conversion of carbon dioxideto methane with synthetic catalysts has proven to be a formidable challenge,"said Chris Chang, another professor of chemistry at Berkeley Lab and a member of the research team. "Since we still get the majority of our methane from naturalgas, a fossil fuel, often from fracking, the ability to generate methane from arenewable hydrogen source is another important advance."

The results of this latest research were recently published in the journal Proceedings of the National Academy of Sciences (PNAS).

Source: Berkeley Lab

10 comments
Chandran
if this can be done cheaply and popularised without a Patent Protection, this can be solution for Atmospheric Carbon dioxide ?
MikeW
This looks like a game changer and cannot be allowed to be placed in the 10-20 year out bin nor locked up in patents without production. I have no problem with patents as long as the product/process is being implemented.
bobbo_says
" this can be solution for Atmospheric Carbon dioxide " /// I don't think so as all it does is recycle atmospheric carbon? The C needs to be sequested, eg by making nanotubes or concrete. But..... it could be "part of" some other solution. I've always thought "Science" has the answer to AGW correction.............it will just come too late.
Fretting Freddy the Ferret pressing the Fret
"... solar-to-chemical energy conversion efficiency of 10-percent... " Certainly, this is good news, but at the moment the 10 percent is still too low to be practical. If we're using commercial solar panels and scale it up, what is left of that 10 percent? If you're using it to burn in a NG fired power plant, the end solar-to-electrical energy efficiency becomes even lower, maybe 1-3%. That number wouldn't justify the costs of using the solar panels to produce natural gas.
JohnnyJohnson
Maybe I've got this all wrong but I see 2 problems if this is a global process. 1. We already have water shortages in several places world wide - just picture thousands of liters of water per day for global production. 2. Just picture thousands of pressure tanks of Carbon dioxide that has been pulled from the atmosphere daily for global production. When will the atmosphere be over saturated with oxygen, released from the process, that man can no longer survive. When will carbon dioxide be so depleted that plants start to die. Any of these can cause the end of mankind.
Douglas Bennett Rogers
This can easily use sea water, even if it has to be distilled. Path length water due to desert water use is a much bigger problem than CO2. Can't be used to leverage down the wealth of populations, though.
Cuckoo
JohnnyJohnson, The hydrogen creates a by-product of (dum dum dum) H2O! Solved. ;)
JenniferRoyal
So stupid... I'll tell you why: You are relying on a living organism for the entire system to work. I see this being nothing but a huge waste of money. These are chemists, not geneticists. THAT'S who you really need. If you want some biologically based method of creating a fuel source. You create it from scratch, to do exactly what you want, and withstand the environmental conditions that are required. All that aside, This is nothing new. It's also not ARTIFICIAL PHOTOSYNTHESIS. They are using electrolysis (very standard process that's been around for well over two centuries) and, then using the Oxyhygrogen (HHO) that is created (electrolysis results in ATOMIC hydrogen, NOT MOLECULAR hydrogen) to do what exactly? We seem to be missing some huge step in the process because atomic hydrogen (H) nor molecular hydrogen (H2) are the same thing as carbon dioxide (CO2). So how are these "microbes" processing the hydrogen and converting it exactly? I don't know, something here just sounds... WRONG. BTW, things like oil and methane actually ARE renewable resources. Maybe people are too stupid to realize this, but all that stuff is the result of dead, decaying, organic matter. That means plants, animals, etc. The swamps, wetlands, forests, and grave yards of today will be the oil fields of the future.
warren52nz
@JenniferRoyal "electrolysis results in ATOMIC hydrogen, NOT MOLECULAR hydrogen" I'm pretty sure that's wrong. If you put an atomic hydrogen atom near another they will form H2 almost instantly. I found many articles about electrolysis that say the products are H2 and O2.
Riaanh
@JenniferRoyal, yes you are right, coal, oil and mind methane are indeed renewable. The only problem is that it takes a little bit of time...... - The coal formation process takes millions of years. The coal in use today started to form over 300 million years ago as living trees, ferns and other types of plant material. Coal is a nonrenewable resource because the time it requires for formation far exceeds the rate at which man uses it