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New efficient electrolysis process for direct hydrogen production from biomass; 16.7% of energy required for water electrolysis

Researchers at Georgia Tech, with colleagues at Hunan University and the Institute of Metal Research, Chinese Academy of Sciences, have devised a novel, efficient electrolysis approach for hydrogen evolution directly from native biomasses—cellulose, lignin and even wood and grass powders—to hydrogen at low temperature. A paper on their work is published in the RSC journal Energy and Environmental Science.

Using an aqueous polyoxometalate (POM)—phosphomolybdic acid (H3[PMo12O40] and silicotungstic acid (H4SiW12O40)—as a catalyst at the anode, the raw biomass is oxidized and electrons are transferred to POM molecules by heating or light-irradiation.

Polyoxometalates (POMs) are a subset of metal oxides that represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form dynamic structures that can range in size from the nano- to the micrometer scale. Heavy interest in POMs began in the 1990s.

In the current work, protons from biomass diffuse to the cathode and are reduced to hydrogen. The electric energy consumption can be as low as 0.69 kWh per normal cubic meter of H2 (Nm−3 H2) at 0.2 A cm−2—only 16.7% of the energy consumed for the reported water electrolysis. Unlike the traditional electrolysis of alcohols, a noble-metal catalyst is not required at the anode.

GA

Resources

  • Wei Liu, Yong Cui, Xu Du, Zhe Zhang, Zisheng Chaob and Yulin Deng (2015) “High efficiency hydrogen evolution from native biomass electrolysis” Energy Environ. Sci. doi: 10.1039/C5EE03019F

  • De-Liang Long, Ryo Tsunashima, and Leroy Cronin (2010) “Polyoxometalates: Building Blocks for Functional Nanoscale Systems” Angew. Chem. Int. Ed. 49, 1736 – 1758 doi: 10.1002/anie.200902483

Comments

Davemart

I don't understand this.

I normalised cubic metre of hydrogen weighs around 0.09kg:
http://www.keengas.com/technical-tips/conversion-data.htm

1kg of hydrogen contains around 33kwh of energy (LHV)

So 0.09 contains around 3kwh of energy.
the 0.69 kwh they use to produce this is around 23% of the that energy.

If they reckon that that is only 16.7% of the energy used in water electrolysis, which is around 70% efficient, that does not make any sense

So 3kwh of energy would take over 4kwh of energy to produce 3kwh, or well over 100%

The real figures are nothing like that.

Anyone help me out?

laszlo

..'only 16.7% of the energy consumed for the reported water electrolysis..'

This statement obviously needs clarification!

Calgarygary

If it takes 4 kwh of electrical energy to produce 3 kwh equiv of hydrogen, whereas it takes 0.69 kwh of electrical input using the method described to produce the same kwh equivalent of hydrogen. 0.69/4 * 100 = 17.25%.

Doesn't include the energy to collect and prepare the biomass or the catalyst one would presume.

HarveyD

Net energy required to extract H2 from NG, bio-mass, water and/or other feed stocks is dependent of technology and feed stock used.

Gross (total) energy used, including all the energy used to provide, transport, process the feed stocks, is another ball game but should be fully considered?

Eventually, extracting H2 from water on an as required basis, with higher efficiency, should be one of the winning technology.

Davemart

Calgary Guy:

It does take just over 4kwh of electricity to produce 3kwh of hydrogen, for a loss of around 1kwh at around 70% efficiency.

The 0.69kwh this method is supposed to use would produce 3kwh, not 4kwh of hydrogen.

So efficiency is around 80%

Your figures only seem to work if it took around 7kwh of electricity in normal electrolysis to produce 3kwh of hydrogen.

Calgarygary

Dave
I read the 16.7 as a comparison rather than an efficiency so 0.69 kwh to produce 1 m3 H as opposed to 4 kwh to produce 1 m3 H still makes sense to me, however, I may be totally confused.

If I were to calculate efficiency of the process I'd use output/input which would be 1m3H2 or 3 kwh / 0.69 kwh = 434% but that ignores the energy in the biomass which is not given.

In any event if it ever makes it to commercialization the critical factor will be cost which is easier for me to understand.

Engineer-Poet

Clever, but nothing about yield.

If this could be used to remove and consume lignocellulose from mixed waste, it would be a big advance.  Pre-digest all the biodegradable stuff, perhaps recover plastics, and only landfill the stable leftovers.  If the system is cheap enough it might even make a good dump load for unreliable electric generators.

kalendjay

Apparently the key is to induce an organic chemical reaction over different sites of one or two saccharides to produce free or charged protons which have enough difference of charge to readily produce diatomic hydrogen. Any waste heat in the process may go a long way to split down the carbon-carbon bonds of the cellulose, which could be low temperature overall but very hot on the nano level.

An organic chemist would easily understand this but I ain't climbing over the paywall today.

The second citation mentions a "periodic table of metal oxides" which is what is being proposed for all compounds to help predict their rules of reactivity and what else. So we will see cheaper catalysts brought to do the same thing as the catalysts in this article, but with more specific compounds as starters.

yaa

To 1 st floor:
Reference said that Hydrogen is believed to be an effective substitute for gasoline as 9.5 kg of hydrogen is sufficient enough to replace 25 kg of gasoline. So 1 kg H2 =2.63Kg gasoline

yaa

I think the author use 0.7 KWh/4.3 KWh=16.3; 4.3 KWh is for water electrolysis at 1.8 V

SJC

Gasify the lignin to make bio synthetic fuels.

Engineer-Poet

Lignin?  Lignin is listed as one of the feedstocks.

What we don't know is how much of the feedstock is actually consumed, or what sort of stuff remains.

SJC

They are not going to get biomass near the point of use, storing and transporting hydrogen is a problem. Make cellulose ethanol then gasify the lignin.

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