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Stanford team reports new low-cost, non-precious metal catalyst for water splitting with performance close to platinum

Gong
Structure of the NiO/Ni-CNT hybrid. Blue = nickel, green = nickel oxide. Credit: Gong et al. Click to enlarge.

Researchers at Stanford University, with colleagues at Oak Ridge National Laboratory and other institutions, have developed a nickel-based electrocatalyst for low-cost water-splitting for hydrogen production with performance close to that of much more expensive commercial platinum electrocatalysts.

As described in their paper in Nature Communications, the catalyst comprises nanoscale ​nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls (NiO/Ni-CNT nano-hybrids). The researchers were able to make the electrocatalysts active enough to split water at room temperature with a single 1.5-volt battery, said Hongjie Dai, a professor of chemistry at Stanford. This marked the first time anyone has used non-precious metal catalysts to split water at a voltage that low, he added.

Nickel (Ni) and stainless steel are typically used in industry for water reduction and oxidation catalysis respectively in basic solutions. However, Ni metal is not an ideal water reduction or hydrogen evolution reaction (HER) catalyst due to its high overpotential (~200 mV) and large Tafel slope. The state-of-art HER catalyst is platinum (Pt) and its alloys, but the scarcity and cost of Pt limit its large-scale application for electrolysis. Active and stable non-precious metal-based HER catalysts in alkaline solutions have been pursued, including Raney Ni and Nickel molybdenum (NiMo) alloy. It remains difficult to achieve both high activity and stability matching those of Pt.

Here, we report a nickel oxide/nickel (NiO/Ni) hetero-junction-like structure attached to mildly oxidized carbon nanotube (NiO/Ni-CNT) exhibiting high HER catalytic activity close to commercial Pt/C catalysts in several types of basic solutions (pH = 9.5–14). The NiO/Ni nano-hybrids is fabricated serendipitously in a low-pressure thermal annealing experiment, affording partial reduction of nickel hydroxide (Ni(OH)2) coated on oxidized CNTs that acts as an interacting substrate to impede complete reduction and aggregation of Ni.

—Gong et al.

As reported in their paper, the team built an electrolyzer that achieves ~20 mA cm−2 at a voltage of 1.5 V at room temperature, and which may be operated by a single-cell AAA alkaline battery.

The mini electrolyzer used NiO/Ni-CNT as the water reduction catalyst and a high-performance NiFe-layered double hydroxide (NiFe LDH) water oxidation catalyst. The experiment was carried out in 1 M KOH at room temperature (~23 °C) and at ~60 °C.

The kinetics and thermodynamics were greatly improved at the higher temperature, showing lower voltage of ~1.42 V at 20 mA cm-2 and higher current increase, reaching 100 mA cm-2 at a voltage of ~1.45 V with good stability. The results suggest that the NiO/Ni-CNT catalyst could match the benchmark platinum catalyst for efficient electrolyzers with ultra-low overpotential, the team concluded.

The scientists do not fully understand the mechanics of the performance of the NiO/Ni-CNT catalyst; future work will tackle this and perform in situ spectroscopic techniques to elucidate the reaction mechanisms and pinpoint the HER active sites in the NiO/Ni material. However, they suggested that the high activity of NiO/Ni-CNT was due possibly to the nanoscopic NiO/Ni interfaces in the heterostructure.

The discovery was made by Stanford graduate student Ming Gong, co-lead author of the study. The nickel/nickel-oxide catalyst significantly lowers the voltage required to split water, which could eventually save hydrogen producers billions of dollars in electricity costs, according to Gong. His next goal is to improve the durability of the device.

The researchers also plan to develop a water splitter than runs on electricity produced by solar energy.

Other authors of the study are Wu Zhou, Oak Ridge National Laboratory (co-lead author); Mingyun Guan, Meng-Chang Lin, Bo Zhang, Di-Yan Wang and Jiang Yang, Stanford; Mon-Che Tsai and Bing-Joe Wang, National Taiwan University of Science and Technology; Jiang Zhou and Yongfeng Hu, Canadian Light Source Inc.; and Stephen J. Pennycook, University of Tennessee.

Principal funding was provided by the Global Climate and Energy Project (GCEP) and the Precourt Institute for Energy at Stanford and by the U.S. Department of Energy.

Resources

  • Ming Gong, Wu Zhou, Mon-Che Tsai, Jigang Zhou, Mingyun Guan, Meng-Chang Lin, Bo Zhang, Yongfeng Hu, Di-Yan Wang, Jiang Yang, Stephen J. Pennycook, Bing-Joe Hwang & Hongjie Dai (2014) “Nanoscale ​nickel oxide/​nickel heterostructures for active ​hydrogen evolution electrocatalysis” Nature Communications 5, Article number: 4695 doi: 10.1038/ncomms5695

Comments

Davemart

Potentially transformational as hydrogen can be readily transported mixed into the natural gas grid and stored in salt caverns.

That means that solar, for instance, can be sited in the south west and the power it produces used in the north east in winter, and overbuild of solar anywhere to help mitigate seasonal variation can be put to good use.

Hydrogen blending in NG pipelines:
http://www.nrel.gov/docs/fy13osti/51995.pdf

Salt Cavern Storage:
http://www.kbbnet.de/wp-content/uploads/2011/09/Present-trends-in-compressed-air-energy-and-hydrogen-storage-in-Germany1.pdf

Calgarygary

Can sea water be used? Are we talking large volumes of water? Is desalinized water a potential byproduct of power production from hydrogen?

electric-car-insider.com

An exciting development to be sure, but the inefficiencies of the energy conversion remain. I'd love to see sufficient developments to make long term storage, and long distance transport economically competitive, but it's really hard to imagine that moving atoms will ever be cheaper than moving electrons.

Davemart

evi:

You can't compare electricity which isn't there when you need it to electricity which is, even if it has incurred losses in the process.

Clearly when you can you use your electricity as directly as possible, but unless we can persuade the powers that be to build out nuclear that either means using fossil fuels to produce it or using renewables and storing it.

In any case electrolysis is of the order of 70% efficient, and in Germany the process heat is used so pushing the efficiency including heat up way over 80%.

Since charging the Leaf,for instance, loses 10-20% of the electricity from the wall, we are not doing too badly.

Both transport and storage of hydrogen is very efficient, and the efficiency of compression is coming down towards 95% efficient:
http://www.hydrogen.energy.gov/pdfs/review12/pd048_lipp_2012_o.pdf

Everything is lossy, that is thermodynamics for you, the question is are the losses low enough to cope with?

Since FCEVs work very well as a PHEV and so electricity when available for direct use could still be so used, this would seem to be all gain with no downside to me.

SJC

Gary,

I doubt sea water can be used, they probably use PEM electrolyzers which require distilled water with an alkaline additive. Water that comes out of a fuel cell could be used, but 60% of the sea water to fresh water is created by using multi stage condensers on power plant cooling sections.

Davemart

@CalgaryGary:

I did the sums once ages ago, and we are talking about substantial but not huge amounts of water, as the water is in no way used up, but simply processed and recycled.

I have no idea if salt water could be used.
Presumably you would not use that at first anyway, to avoid any problems from the salt.

The initial problem is increasing the durability of the catalyst, so lets solve that first!

I don't see the connection with desalination.

electric-car-insider.com

Davemart> You can't compare electricity which isn't there when you need it to electricity which is, even if it has incurred losses in the process.

You have a good point. So the question is, what is the best way to create zero carbon energy supply? Best as in most economic, because it's unlikely to win if it is substantially more expensive.

I'm not opposed to H2 per se, I just think it is unlikely to be a competitive transportation fuel. I also believe we are much more likely to have hi-efficiency transmission lines before we have high efficiency hydrogen pipelines.

Several kinds of technology breakthroughs would quickly change my mind. But until they happen, I'll place my bets on the "near targets" of solar, wind, hydrothermal, hydro (including pumped hydro, which currently provides 5% of California grid capacity) and cheaper battery grid storage.

Those do not provide a 100% solution, but they are here now and put us on a path of meeting viable targets.

Perhaps most importantly, several of them allow consumers to vote with their wallets - today.

Alain

Desalinating seawater only takes a small fraction of the energy it takes to split the same volume it into hydrogen, so if necessary, it will only decrease the efficience a little.
The amount of water needed for all your transportation needs is much smaller than what you use to flush your toilet.
5kg H2 ==> 40l H2O > 1000km driving.

Davemart

Well, evi,
We already have 'high efficiency hydrogen pipelines' as I detailed concisely in the 130 page Government study I linked to!
They are called: 'Natural gas pipelines' and they do the job just dandy.

For solar, wind, etc you either need to carry on using buckets of fossil fuels, as Germany does at the moment for instance with CO2 emissions 30% above the per capita European average, burning vast quantities of Russian gas and filthy lignite in the process, or you get involved with hydrogen for storage.

Every single scheme that I am aware of trying to put lots of renewables to use envisages or uses massive quantities of hydrogen.

It is only on blogs talking about electric cars that it is imagined that renewables can magically do the job without the use of hydrogen, and where fuel cells are seen as some kind of opposing force.

Davemart

Hi Alain:
I don't know about the rest of your figures, but 5kg of hydrogen aren't going to move you 1000km.
You get around 60-70miles/kg, so around 500km is more like it.
I think that you are probably looking at the 33kwh or so in 1kg of hydrogen and thinking about how far that would move a BEV, but the fuel cell still needs to convert it back to electricity at around 50% efficiency or so.

HarveyD

Water is plentiful and cheap and soon will be H2.

With cheap and plentiful fuel (H2), FCEVs could become an interesting alternative for Extended range and cold weather EVs.

electric-car-insider.com

> Every single scheme that I am aware of trying to put lots of renewables to use envisages or uses massive quantities of hydrogen.

Interesting, that is not the data I am seeing, and it seems to be a rather sweeping statement.

In southern latitudes, we don't need to massively overbuild for seasonal variation. We just need to solve for day/night and wind variation. That is possible with grid storage, which appears to be fairly near term. Not just batteries like Ambri, but pumped hydro, which is in widespread use in California and solar thermal storage. Energy giant NRG is betting big on renewables, presumably David Crane has a good grasp of the viable grid mix.

I don't know what the long term renewable solution is for winter in northern latitudes where solar is not sufficient, but I'm not seeing a lot of investment in large-scale electricity to hydrogen projects. Some small scale demonstrators, yes, but nothing on scale that will make a dent in coal and gas.

Here in the states, wind (and gas) are displacing coal.


Calgarygary

Thanks for input.
I now calculate that 1 kwh electricity generated by a fuel cell would produce about 0.4 liters of water which might be of some value if one were to bottle it for high end restaurants but on doing some research I find that even in Saudi Arabia the cost of producing desalinized water on a large scale is only about 1/3 cent per litre so the volume produced from a fuel cell would be insignificant in terms of value even in water short areas.

electric-car-insider.com

Davemart, I really appreciate your posting links to interesting and worthwhile reports. But I do sometimes wonder if you read those reports or just hope that others won't, and that posting them somehow give your assertion more credibility, even when the cited work pretty much refutes your assertion. The pipeline report is a pretty good example.

We do not "already have" NG pipelines capable of transporting hydrogen, this is a proposal under consideration. The report itself says that the membranes to extract the hydrogen at the delivery end are still under development.

Cost is a huge consideration. Did you read the part about the extraction cost being $0.30 to $1.30 per kg. ouch!

Relatively low concentrations of hydrogen, 5%–15% by volume, appear to be feasible with very few modifications to existing pipeline systems or end-use appliances. However, this assessment of feasibility will vary from location to location. Higher concentrations introduce additional challenges and required modifications. Preliminary cost estimates suggest that hydrogen could be extracted economically at pressure regulation stations. For a station with a pressure drop from 300 to 30 psi, we estimate an extraction cost ranging from $0.3–$1.3 per kg hydrogen for a 10% hydrogen blend, depending upon the capacity and recovery rate.

Note also that they are talking about 5%-%15 concentrations of H2, meaning that you would, at best, still be on an 85% fossil fuel economy.

The report clearly says that extraction is a long term solution, not a near term one.

This report pretty much totally refutes your argument that H2 distribution by pipeline is viable, except in the long term, and at high cost.

Davemart

evi:
I don't see what is sweeping at all in stating that 'every single scheme THAT I AM AWARE of uses hydrogen for storage'
That simply invites anyone who is familiar with schemes which don't to give me the reference, as I certainly don't know about every scheme.
I am talking about, for instance, the German Energiewende scheme, down to the scale of this for the Isle of Wight in the UK:
http://fuelcellsworks.com/news/2013/02/21/acta-and-ecoisland-sign-letter-of-intent-for-isle-of-wight-domestic-hydrogen-partnership/

Your idea of 'Southerly latitudes' is rather different to mine.
Anywhere much north of San Diego there is pronounced seasonal variation, which you either overbuild for, in which case why not use the surplus to generate hydrogen which will keep until the winter, or you throw it away, or you don't overbuild and you use fossil fuels.

It is impossible to cover the whole of a large subject in single posts in blogs, but essentially there is a hierarchy of storage for energy, and if you want to store lots of it you need CAES which I don't fancy as it is very dubious environmentally, or you need hydrogen.

Pumped storage is well and good (geddit?) but there ain't much energy in a lot of water lifted to a fair old height.
The classic example is Norway, where they store a lot of energy, for Scandinavia not just themselves, but can only store so much, and in droughts run into trouble.

Without a handy mountain, you have problems.

On top of that at ~80% round trip efficiency it is pretty lossy also.

Norway in its own plans puts a lot of emphasis on hydrogen.

The best overview I am aware of of the potentials and limits of storage systems is on this blog:
http://physics.ucsd.edu/do-the-math/

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