SiGNa Chemistry Inc. is launching a hydrogen-producing cartridge, the mobile-H2™, that will work with a portable, pocket-sized fuel cell charger to provide instant power for cell phones and other mobile devices. You simply add water to the cartridge, and the device will charge depleted batteries on the go. For further convenience, any water will do (even waste water). Unlike solar battery chargers, you don’t need to worry about getting enough sunlight. According to its press materials, these cartridges provide a steady level of power from beginning to end.

This sounds a bit like magic, but it actually involves some well-known chemistry. SiGNa’s hydrogen cartridge technology is based on the combination of sodium and silicon in the form of sodium silicide (NaSi). Normally, sodium metal reacts violently with water to produce hydrogen gas. SiGNa has found a technique to take full advantage of the reducing power of sodium without the safety concerns.

SiGNa hasn’t released details on the synthesis of their sodium silicide. However, based on publications from SiGNa’s CEO and collaborators, we know that, in the past, they have absorbed sodium into silica by coating commercially available silica gel with a liquid sodium-potassium alloy (Na 2 K) to create a black powder. They then give the powder various heat treatments to create a material with enhanced stability.

SiGNa’s sodium silicide might have a similar production process. NaSi is stable for long periods in open air (over two years) and reacts controllably with water.

When SiGNa’s sodium silicide meets water, it immediately produces low-pressure hydrogen gas (H 2 ). Then, a low-cost fuel cell device, such as myFC’s Powertrekk, converts the H 2 gas into electricity to recharge batteries. The other products of this reaction are simply heat and sodium silicate (Na 2 Si 2 O 5 ), which is a common compound that is used in cements, textiles, automobiles, and other materials. The heat released can be recaptured and used within the electricity-making process, so we assume that this won’t amount to a super hot device that’ll be uncomfortable to carry around.

While devices like the Powertrekk are portable for extended trips away from a power grid, they might not be more convenient than just carrying around more charged batteries. First, you would need to buy a fuel cell charger like the Powertrekk, which has yet to be priced. Second, you would need to bring a supply of cartridges with you.

The fuel cell devices are reusable, but the hydrogen-producing cartridges are not. Cartridges have to be replaced once the active sodium silicide is used up. Lithium batteries, on the other hand, are reusable. In some ways, you’re trading the inconvenience of carrying multiple batteries for carrying a bunch of mobile-H2™ cartridges. To figure out if this tradeoff is worthwhile economically and environmentally, we spoke with Michael Lefenfeld, SiGNa’s CEO.

Ars Technica: Can you tell us a bit about the mobile-H2? When will it be available?

Michael Lefenfeld: Our most recent release is a small 5 watt hour canister that we’re now launching in conjunction with the Powertrekk device by myFC. It should be available at the end of summer and the beginning of fall.

Ars: How much will the cartridges and the myFC device cost?

Lefenfeld: The price of the cartridges hasn’t been released yet because we’re still going into the large ramp up of large scale manufacturing. Obviously 5 watt hours is about the same energy as 4 AA batteries, so we’re going to need to come in cheaper than that, but we don’t have the price for it, yet. The myFC price is also not determined, yet.

Ars: Are the cartridges recyclable? What happens to them when they’re done?

Lefenfeld: They are recyclable. The byproduct of the reaction is the material known as sodium silicate, the main ingredient in toothpaste and also used in glass manufacturing and cement. The stuff is found in the ground pretty regularly. There are no toxic metals, and there are no heavy metals used in our process. Everything is based on aluminum and pretty much our chemicals. It’s not toxic and can be thrown away in municipal waste. There’s also a program that we’re trying to get into place, but probably won’t be ready right away—it’s for the exchange of these canisters, because all the parts are reusable.

Ars: What’s the advantage over just buying a lot of batteries and having them charged and ready? I can reuse lithium batteries. What’s the advantage of these cartridges, which you have to replace? You also have to buy a myFC Powertrekk, and how long will that device last?

Lefenfeld: The Powertrekk device will last a very long time. It’s literally an electric engine. There’s no reason for it to degrade unless you run over it or something. So that’s not a worry.

The price point of the cartridges is, in a way, so much more competitive than buying a lot of batteries. Recharging batteries even in the developed world is difficult. Think of it when you’re in the airport, and everybody is searching for that one outlet to charge their cell phone or whatever. This allows you to be off that grid in a very competitive fashion. We estimate that at the largest of scales, we can be probably 10 times cheaper per watt hour than AA batteries.

Ars: I’m reading that overall, the reaction yields 9.5 percent of H 2 gas by weight of water added. The DOE, for example, has a 9 percent goal, but that’s for the total weight. Do you have a percent yield for the total weight?

Lefenfeld: It’s 9.8 percent by weight of water. Plus, the DOE’s goal is for automotives, so we don’t deal with that. For our most advanced system with just pure sodium silicide and all the weight in water, we’re looking at somewhere on the order of five and change.

Ars: In your JACS papers, like the 2005 JACS communications, there are descriptions of producing material where you have sodium absorbed into silica. Is the reaction for the cartridge material something similar?

Lefenfeld: Not exactly. [In] that paper that you’re looking at there is more for our structural chemicals, where they’re absorbed in nanostructure systems and the electrons are delocalized, etc. This is more of a compound, so it’s a sodium silicide. Na and Si are equimolar. It’s a 5 electron shift. Silicon has more electron movements; sodium has 1, so that’s why you get such a high amount of hydrogen out.

But like the other materials in the JACS papers, sodium silicide production involves a similar platform process, like getting rid of the oxidation issues. It’s similar in features, but not the synthesis processes.

Ars: Does the efficiency decrease with different water?

Lefenfeld: No. We have programs with the military that are using urine. In some of the markets that we’re looking into, like in some of the emerging markets, potable water is a very scarce resource. We pride ourselves in not taking away one resource to provide another. We want to minimally take away drinking water. Electricity is great, but you need water to survive.

Ars: What do you see in the future for these cartridges? Can you expand this to vehicles, or will that require a complete redesign?

Lefenfeld: Small vehicles, not cars. Bikes, scooter, golf carts, those types of things. We’re not looking at this as an energy replacement for gasoline.

Overall, SiGNa's mobile-H2™ have potential, especially in developing nations, where there are limited access to electric outlets. The ability to use impure water, even urine, with the cartridges is an advantage as well. However, without knowing the price of the fuel-cell chargers and the cartridges, we cannot comment on their economic viability. If the recycling program that Lefenfeld mentioned can be set up, the cartridges would be even a better option for people who need portable battery chargers.

Listing image by SiGNa Chemistry Inc.