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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

Engineer-Poet

Of the two references of yours I checked out, one was about pumping hydrogen, and the NREL piece scarcely discusses pumping at all.  The limiting fraction of hydrogen isn't mentioned, but the ranges mentioned were on the order of 10-20%, with one cited British study going as high as 25%.  That's still less than 10% hydrogen by energy.

Pipelines don't use positive-displacement (piston) pumps.  The problem with adding hydrogen is that the density falls, and the dynamic pressure in centrifugal or axial pumps is proportional to density (½ρv²).  So, your pump outlet pressure goes down at the same time that the energy density of the gas in the pipeline is falling.  To make up for this you have to either add pumps or increase their speed, which the design may not allow easily or cheaply.  To handle pure H2 the pump speed needs to nearly triple.

DME is more of a diesel fuel.  MeOH has more energy per mole of carbon and is more easily transported and stored, and the power density of an engine designed for MeOH can be much higher than a diesel.  The problem with both of them is where you get the carbon.

HarveyD

Once the high cost of making H2 has been solved; storing, transporting, distributing and using it efficiently will certainly be improved to make it one of the best future all around flexible and clean energy source.

Roger Pham

Let's not make an H2 infrastructure harder than it needs to be. We know well how to handle NG, which is a gas, we will be able to handle H2 without problem.

Why move on to H2?
1). NG is a finite resource while H2 is renewable
2). Methane is a potent GHG 20x stronger than CO2. Methane in NG or synthetic methane leakage is a potent contribution to GW.
3). Synthetic methane or ammonia as H2 carriers are much less efficient than using H2 itself.
4). Battery is great as short term storage but cannot provide seasonal scale capacity. Battery cannot be charged as quickly as H2 can be filled up.

With excess of solar and wind capacity and with depletion on NG, a local H2 piping system will be used to connect H2 generators to end users and to H2 storage depots. Old NG piping due for replacement should be replaced with new H2-compatible pipes, so that in the next few decades, most of the piping will be H2 compatible and upgrade cost for remaining will be minimal.

H2 is 1/3 as energy dense as NG but is 2-3 x more efficient so the volume required is comparable to NG.

SMR method of H2 production may be cheaper than electrolytic H2 from solar or wind in the USA, but in countries that must import NG at 2-3 x the price of NG in the USA, solar or wind H2 may be competitive.

HarveyD

Yes RP, clean renewable energies have a bright future even if their direct cost is a bit higher. However, fossil and bio-energy sources total cost is already higher than REs in many cases.

Davemart

@EP:
Its always good when you have time to run your eye over stuff, as it keeps me on my toes!

Perhaps though I should re-iterate that there is no way on God's earth that I can perform an engineering evaluation.

The best I can manage is to find the 'best' ie the most authoritative sources I can manage, usually governmental, and to check for when they have obviously gone batty, which is surprisingly frequently by using basic math and noting things like that you would in no way need an equally extensive hydrogen network to that of natural gas, which one study ludicrously assumed as noted above.

Other than that though, all I can really do is not that the people in a position to know think that they can make it work.
That is not the same as it actually being up and running of course, but we are not going to sit around discussing done deals, anymore than we ask if it is possible for average people to have electricity in their homes, although no doubt in 1900 or so the internet was abuzz with that discussion!;-)

As a passing example of my inability to do anything remotely resembling a technical evaluation, I only just found out today whilst googling that they are considering using fibre for dedicated hydrogen pipelines to mitigate embrittlement.

I can add up reasonably well, and have a fair level of reading comprehension at times.
Other than that all I can really do is check out what the big studies think we can do.

Engineer-Poet

I didn't train as a nuclear engineer or physicist, but I've learned to read the stuff on isotope abundances and fission probabilities well enough to get useful info out of it (not everything an expert might get, but something).  Dig in those reports and even as a non-expert you'll see what they say, and what they don't say.

SJC

low-cost water-splitting for hydrogen production

This reduces the cost for the electolyzer, which is good. If you input heat, the production rate goes up, if you have the waste heat. It is still the idea of putting electrical power on the grid or making hydrogen at the point of use, since you don't have a use for the O2 at point of use, that is wasted. Reforming natural gas will still be the cost effective method.

Davemart

@EP:
Oh, I have a good look at them.
It is more on the lines of checking to see for anything daft, then doing a precis in my head to see what the bottom line is though.
I try to distinguish between the bits I can reasonable have a view on, and the bits I can't.

That is not to say I always manage to extract the essence correctly, of course I don't, but that is what I am trying for.

Common sense judgements do not always work though as I am reminded every morning when I get in the shower.

If you were looking for a dangerous activity, you would imagine that putting high voltage electricity into a water filled environment then standing in the water would be lethal.

There are not a lot of casualties from that though, it is slipping in the shower which kills, not the electricity usually.

So I try to suspend too many 'common sense' snap judgements.

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