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RMIT researchers develop concept “proton flow battery”

RMIT University (Australia) researchers have developed a concept battery based on storing protons produced by splitting water—a reversible fuel cell with integrated solid proton storage electrode. As only an inflow of water is needed in the charge mode, and air in discharge mode, the system is called a “proton flow battery”.

This new concept has the potential to increase roundtrip efficiency compared to the conventional hydrogen-based electrical energy storage system by eliminating the intermediate steps of hydrogen gas production, storage, and recovery.

The concept integrates a composite metal hydride–nafion electrode into a reversible proton exchange membrane (PEM) fuel cell. During charging, protons produced from splitting water are directly combined with electrons and metal particles in one electrode of a fuel cell, forming a solid-state metal hydride as the energy storage. To resupply electricity, this process is reversed.

The research, published in the International Journal of Hydrogen Energy, found that, in principle, the energy efficiency of the proton flow battery could be as high as that of a lithium-ion battery, while storing more energy per unit mass and volume.

Its hydrogen storage capacity was measured to be 0.6 wt% of hydrogen, although the amount of hydrogen recovered to run the device in fuel cell mode was much lower. These results provide initial confirmatory evidence that the proton flow battery concept is technically feasible, though additional research is still required to enhance both storage capacity and reversibility.

—Andrews and Mohammadi

Lead researcher Associate Professor John Andrews said the novel concept combined the best aspects of hydrogen fuel cells and battery-based electrical power.

Powering batteries with protons has the potential to be a much more economical device than using lithium ions, which have to be produced from relatively scarce mineral, brine or clay resources. Hydrogen has great potential as a clean power source and this research advances the possibilities for its widespread use in a range of applications—from consumer electronic devices to large electricity grid storage and electric vehicles.

—John Andrews

The published paper is the first to articulate and name the proton flow battery concept, and the first to include an experimental preliminary proof of concept.


  • John Andrews, Saeed Seif Mohammadi (2014) “Towards a ‘proton flow battery’: Investigation of a reversible PEM fuel cell with integrated metal-hydride hydrogen storage,” International Journal of Hydrogen Energy, Volume 39, Issue 4, Pages 1740-1751 doi: 10.1016/j.ijhydene.2013.11.010



This is only studies, there are no results. Till then the earth temperature is rising fast. Food prices are rising as profits for the richs. This website is working for the richs and is creating inflation. These researchers are finding nothing but are paid at high price.


Gorr, Why so grumpy?

I'm not clear on whether this concept consumes water in the process, but it sounds like users would have to add distilled water from time to time.

The professor's contention that this could be cheaper than lithium because it doesn't require scarce elements depends on some pretty big assumptions about how much costs can be reduced for what is essentially an inefficient fuel cell at this stage in the research.

Still, if 10 years hence it goes as hoped, maybe it would help defer "peak-lithium," or some such. I like that it appears no less efficient at storing and discharging than lithium. That's something most H2 energy storage schemes can not say.


This seems to combine a reversible PEM with MOF H2 storage, basically. I don't think any extra water is needed, it splits water, it makes water.

They have not addressed the platinum catalyst issue and costs. If you are going to mention lithium, you also need to talk about platinum.

Roger Pham

H2 energy storage scheme can be even more efficient than lithium battery if the waste heat can be used effectively. For example, if the electrolyzers are placed in vicinity of apartments, hotel and offices, the 80-degree-C waste heat from electrolysis can be used for absorptive coolers and water heater in the summer from solar and wind energy. The H2 output will be released into a city-wide piping system with underground H2 reservoir. At sundown, local FC will provide power and waste heat for space cooling and water heating in the evening. In the winter, FC will use the H2 from the local piping system and reservoir to provide power and waste heat for space heating.

There is no way that lithium battery can provide seasonal-scale energy storage that will be needed in order to completely avoid usage of fossil-fuel energy.

Catalysts for FC and electrolyzer need not depend on Platinum. There are many promising non-Platinum catalysts that are in abundance and cheap to make.


Name a PEM in production without platinum.

Roger Pham

CellEra’s ground-breaking core technology enables the development and fabrication of Platinum-Free Membrane (PFM) fuel cells that retain many of the advantages of PEM fuel cells while eliminating the high price tag.


@ SJC,
Several approaches to metal (platinum)free FCs have been published. Here's one of them:


Those are announcements and web pages, I asked for production units, there is a major difference. There is no indication that these people are working without platinum, that IS the point.


I wrote a considerable analysis on the efficiency of a fuel cell system, which we are continually told is hopeless compared to batteries.
Unfortunately I can't now locate where I stored it, but basically as Roger says it is fine as long as the hydrogen is made using CHP.

One wrinkle he has not mentioned is that there is no need for high pressure storage in the home, as the natural gas network can handle an admixture of hydrogen just fine with minimal adaption, and that can be pulled out of the natural gas network with minimal losses either for distribution in hydrogen stations or storage in salt caverns and other locations.
The size of the storage is enough to actually iron out seasonal variation, a subject which solar advocates at present really try to avoid, with nonsensical and wholly inaccurate claims that they are running on sunshine when they are doing no such thing.

That gives a thermal plus hydrogen generation efficiency comfortably north of 80%.

At the other end of the use, the hydrogen in cars is around 60% efficient, but the losses there are occurring where they can be put to use too, for heating the car.

Fuel cells are certainly not at their ultimate possible efficiency either.

So fuel cells, and hydrogen from natural gas or perhaps even solar in the home can be done at 'good enough' efficiency, and has the considerable advantage of enabling a potential solution to storage issues, which currently is simply not talked about by solar advocates.


"a concept battery"

This is NOT a production battery, too often people on here mistake concepts for production. This is a reversible PEM with storage. If it is to compete with lithium ion batteries, it has to do it with cost and capacities in mind.

This announcement hints at being better than lithium ion for energy storage, but NO direct comparison is made, that is a bit misleading. To say there have been announcement about platinum free PEMs without showing this is what is used here is a further speculation.

Building assumptions upon assumptions does not lead to the truth, it compounds more speculation, it diverges from the truth. Suffice it to say that there is insufficient information here to provide an accurate evaluation and conclusion.


Spot on that this is still not proven technology.

That was why I had not previously bothered posting to this thread, and did so only when Roger talked about CHP.

SOFC works fine in this application though, and does not use platinum.
I have suggested alternate means of hydrogen storage, so even if this does not pan out, it seems to me that a hydrogen fuel cycle is perfectly possible.


the proton are combine to metallic small particles to form metal-hydride but how about the OH- ? they need to be combined in a stable but reversible form...?


Basically, this is a unitized regenerative fuel cell (URFC) that integrates a metal hydride storage electrode into a reversible proton exchange membrane (PEM) fuel cell - this is described in the article. NASA tested a URFC in 2003. However, this was not very efficient and used a lot of platinum.

A similar concept to the RMIT “proton flow” battery is being developed by GE and Lawrence Berkeley National Laboratory that they call a water based high energy density flow battery (see

The GE/LBNL battery probably will not use any platinum. there are many examples, CellEra as Roger pointed out is platinum free, however it is an alkaline membrane fuel cell. The ACAL Energy PEM fuel cell is also platinum free at the cathode using a vanadium/molybdenum flow cathode. The GE/LBNL battery could be using a cathode similar to ACAL Energy except it may use an iron ion cathode as described in the above reference. On the anode side hydrogen would possibly come a metal borohydride (Dr. Grigorii L. Soloveichik of GE is an expert on these hydrides).
So technically the GE/LBNL concept is a redox flow battery, in reality it is a regenerative PEM fuel cell without any noble catalysts with very high energy density probably exceeding the energy density of Lithium Air batteries.

Bob Wallace

Lithium carbonate is currently selling for $12.50/kg. The price is a bit high because demand has increased recently and it will take a little time for new production to come on line. Before EVs/PHEVs started using a lot of lithium the price was around $8/kg.

The LEAF uses 4 kg of lithium. $50 at today's price, $32 when prices (probably) drop back down.

There's no shortage of lithium. We could extract all we need out of seawater if we ever used up the cheaper on land supply. Extracted it would likely cost about $40/kg.

BTW, platinum is currently selling for over $1,400/oz. About $5,000/kg.


I don't disagree with your basic argument that lithium carbonate is cheap and inexhaustible.

However, don't get confused between that and lithium.
Lithium carbonate is around 18% lithium by weight, and the Leaf uses around 4kg of lithium, not lithium carbonate.

So EVs use something under 1kg of lithium carbonate per kwh.

Refining the lithium carbonate to the required purity for car batteries is also pricey, and knocks the price up to something in the region of $50kg of lithium carbonate.

So the Leaf uses perhaps $1,100 worth of lithium carbonate, not too different from the present cost of platinum in fuel cells, in the new Toyota for instance, which uses 30 grams, around the same as a diesel car uses in its catalytic converter.

Both the use of platinum in fuel cells, and I would imagine, the refining costs of lithium carbonate can be reduced and do not represent an ultimate cost barrier.


Battery grade lithium carbonates price is currently around $6,000/tonne or $6/Kg and could drop as:

- less lithium carbonate is used per kWh for future nanotechnology batteries.
- more lithium mines start operation and production is multiplied.

Secondly, many future batteries may not use lithium?



You assume ACAL is regenerative, I see no mention of that.
You assume these people are using ACAL, I see no mention of that.
Assuming can lead you off the path.


The ACAL Energy fuel cell is an example of a fuel cell that does not have platinum in the cathode. It is not regenerative. The GE redox flow battery is an example of a regenerative fuel cell that may have a cathode similar to the ACAL Energy fuel cell.


Thanks for the information, the GE project is in the very early stages and may not really work or be practical at all. Not being critical, just trying to be accurate.

The original discussion had to do with costs. If you have one of these at 24 kWh and compare to an EV battery pack of 24 kWh, what is the cost? Also, what is the power density? They do not say that you can get 200 kW out of this.


I was in error on the price of battery grade lithium carbonate, which is in the region Harvey says:


However, my remarks on usage were correct.

The 15kwh Renault Kangoo uses 3kg of lithium, not lithium carbonate:

Multiply by 5.3 for lithium carbonate usage.

That works out to 1.06kg lithium carbonate/kwh.


So, if a 24 kWh battery pack uses $100 worth of lithium and a 24 kWh storage PEM uses $1000 of platinum, you see my point. Plus pouch batteries are designed to be mass produced, they are still working out the details of making each PEM plate cheap. Then there is that power density factor...


Batteries use a lot of other things as well as lithium, which incidentally costs out at about $150, not $100.

Is that important? with the rate precious metal use in fuel cells is declining, and it is already at similar levels to that in a diesel cat, the costs differential against just the lithium aside from the other materials in the battery may narrow substantially.

The power density may favour batteries, which is nicely taken care of by a relatively small 1-1.5kwh battery in fuel cell cars, but the energy density for a fuel cell system including all the components, the CF tanks etc, are way, way the other way about.

Excluding the common components such as electric motors, fuel cell systems run at around 1,500Wh/kg, many times anything we are anywhere near doing with batteries.

You see my point> ;-)

A.C. R.

Davemart, I do not see your point. The cost of noble metals in fuel cells isn't that high. There are fuel cells that use no expensive noble metals and are still ludicrously expensive. The cost are in manufacturing and assembly, fuel cells can't seem to get to the targets enthusiast groups (even entire government agencies) are talking about.

The average fuel cell cost is about $8000/kWe based on the total market divided by the total wattage.

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