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Atomic cobalt on nitrogen-doped graphene catalyst shows promise to replace platinum for hydrogen production

The Rice lab of chemist James Tour and colleagues at the Chinese Academy of Sciences, the University of Texas at San Antonio and the University of Houston have developed a robust, solid-state catalyst that shows promise to replace expensive platinum for hydrogen generation.

The new electrocatalyst, based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene (Co-NG), is robust and highly active in aqueous media with very low overpotentials (30 mV). In an open-access paper published in Nature Communications, the researchers suggested that the unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts.

Electrochemical reduction of water through the hydrogen evolution reaction (HER) is a clean and sustainable approach to generate molecular hydrogen (H2), which has been proposed as a future energy carrier. Catalysts are needed to improve HER efficiency by minimizing reaction kinetic barriers, which manifest themselves as overpotentials (η). Although platinum (Pt) is the most active HER catalyst, its scarcity and high cost limit its widespread use. Thus, the transition to a hydrogen economy calls for alternative electrocatalysts based on earth-abundant elements, such as non-precious metal oxides, sulfides, phosphides, carbides and borides. In spite of their low η for HER, the active sites of these inorganic-solid catalysts, like other heterogeneous catalysts, are sparsely distributed at selective sites (that is, surface sites or edges sites). To expose more active sites, these catalysts are generally downsized into nanoparticulate form and stabilized onto certain substrates. Graphene is such a substrate that has a large specific surface area (high catalyst loading), good stability (tolerance to harsh operational conditions) as well as a high electrical conductivity (facilitated electron transfer) and therefore has been widely used to disperse nanoparticles for advanced electrocatalysis.

The dispersing ability of graphene is, however, far from being fulfilled unless single-atom catalysis (SAC) is achieved. SAC represents the lowest size limit to obtain full atom utility in a catalyst and has recently emerged as a new research frontier. … Here, we report an inexpensive, concise and scalable method to disperse the earth-abundant metal, cobalt, onto nitrogen-doped graphene (denoted as Co-NG) by simply heat-treating graphene oxide (GO) and small amounts of cobalt salts in a gaseous NH3 atmosphere. These small amounts of cobalt atoms, coordinated to nitrogen atoms on the graphene, can work as extraordinary catalysts towards HER in both acidic and basic water.

—Fei et al.

In comparison tests, the new material nearly matched platinum’s efficiency to begin reacting at a low onset voltage—the amount of electricity it needs to begin separating water into hydrogen and oxygen.

This is an extremely high-performance material. No question, [platinum-carbon materials] are the best. But this is very close to it and much easier to produce and hundreds of times less expensive.

—James Tour

Ncomms9668-f4
Performance characterizations. (a) LSV of NG, Co-G, Co-NG and Pt/C. The inset shows the enlarged view of the LSV for the Co-NG near the onset region.

(b) Plot showing the molar number of H2 produced as a function of time. The straight line represents the theoretically calculated amounts of H2 assuming 100% Faradaic efficiency, and the scattered dots represent the produced H2 measured by gas chromatography. The overlapping of these two sets of data indicates that nearly all the current is due to H2 evolution. The error bars arise from instrument uncertainty.

(c) Tafel plots of the polarization curves in a.

(d) TOF values of the Co-NG catalyst (black line) along with TOF values for other recently reported catalysts. Fei et al. Click to enlarge.

The new catalyst is mixed as a solution and can be reduced to a paper-like material or used as a surface coating. Tour said single-atom catalysts have been realized in liquids, but rarely on a surface. This capability enables the building of electrodes, he noted. “It should be easy to integrate into devices.

The researchers discovered that heat-treating graphene oxide and small amounts of cobalt salts in a gaseous environment forced individual cobalt atoms to bind to the material. Electron microscope images showed cobalt atoms widely dispersed throughout the samples.

They tested nitrogen-doped graphene on its own and found it lacked the ability to kick the catalytic process into gear. But adding cobalt in very small amounts significantly increased its ability to split acidic or basic water.

Atom-thick graphene is the ideal substrate, Tour said, because of its high surface area, stability in harsh operating conditions and high conductivity. Samples of the new catalyst showed a negligible decrease in activity after 10 hours of accelerated degradation studies in the lab.

Co-authors of the paper are Rice graduate students Huilong Fei and Gonglan Ye, postdoctoral researcher Nam Dong Kim, alumni Errol Samuel and Zhiwei Peng, and Pulickel Ajayan, chair of the Department of Materials Science and NanoEngineering, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry at Rice; Juncai Dong and Dongliang Chen of the Beijing Synchrotron Radiation Facility at the Chinese Academy of Sciences, Beijing; research associate M. Josefina Arellano-Jiménez and José Yacamán, chairman of the Department of Physics, at the University of Texas at San Antonio; and graduate students Zhuan Zhu and Fan Qin and Jiming Bao, an associate professor of electrical and computer engineering, at the University of Houston.

The research was funded by the Air Force Office of Scientific Research Multidisciplinary University Research Initiative, the National Institute on Minority Health and Health Disparities from the National Institutes of Health, the Welch Foundation and the National Natural Science Foundation of China.

Resources

  • Huilong Fei, Juncai Dong, M. Josefina Arellano-Jiménez, Gonglan Ye, Nam Dong Kim, Errol L.G. Samuel, Zhiwei Peng, Zhuan Zhu, Fan Qin, Jiming Bao, Miguel Jose Yacaman, Pulickel M. Ajayan, Dongliang Chen & James M. Tour (2015) “Atomic cobalt on nitrogen-doped graphene for hydrogen generation” Nature Communications 6, Article number: 8668 doi: 10.1038/ncomms9668

Comments

HarveyD

This may open the door for eventual on-board lower cost H2 production for extended range (500+ Km) future FCEVs and/or much lower cost fixed production units?

Account Deleted

Harvey it is an electrolyser. This is the opposite of a fuel cell and it has no application in a car.

HarveyD

Henrik....eventually, with a mini (very efficient) low voltage electrolyser on board, fill your FCEV tank with plain water (if you live South) and drive away for 500+Km.

Your on-board battery would have to have enough capacity to supply the low voltage to the electrolyzer. Battery refills could be with braking regen, roof top solar cells, road side recharging etc.

Of course, the first applications would be for fixed H2 production units.

Account Deleted

Harvey an electrolyser cannot produce hydrogen without electricity. What are you thinking? You want to put a battery and an electrolyser in a fuel cell car so that they can make hydrogen for the fuel cell that then makes electricity to the motor. May I suggest using the battery directly and drop the inefficient electrolyser and fuel cell. Do you even know how stupid you sound?

SJC

Harvey has slipped into perpetual motion mode.
There are been advances in electrolyzets recently, they lead to smaller and less expensive devices.

Lad

Hydrogen has no place in road vehicles; BEVs are the ticket there; however, it would work in hybrid airliners for long distance travel.

In the future I see Fuel Cells used to create electricity to drive ducted fan aircraft and hyperloops to displace air travel in the medium distance intercity routes. The less fossil fuels we burn in the upper atmosphere, the better.

HarveyD

Plain water would become your FC (partial) fuel supply. Panasonic roof-hood top H2 solar panels would split water to produce H2 to complement the H2 tank and extend (double?) FCEV range on sunny days.

The same or similar Panasonic H2 roof top solar panels would refill your home + FCEV H2 supply. Panasonic claims that by 2020 or so, their H2 solar panels could supply enough low cost H2 for the house FC + FCEV without much help from the grid. Surplus electricity could be returned to the grid on very sunny days to make the house + FCEV energy neutral.

DaveD

Distilled, clean water...the only thing on the planet that cost more than gasoline and is harder to come by. Hey, we got so much lying around...we should use that in our cars instead! The answer to all California's problems! Let's use up more of the water supply to drive cars around!!!! Woohoo!!!

:)

Harvey, Henrik is right. Even if you do this...why would you haul it around in your car? you'd be spending electricity on board to split the water and make the hydrogen. It simply doesn't make sense.

SJC

100 kWH of energy to make 50 kWh of electricity to make 40 kWH hydrogen to make 20 kWh of electricity...you can see if you put the 50 kWH into batteries you would have 40 kWh for the controller/motor instead of 20 kWh.

Clint44281

SJC you are correct. To minimize the losses instead of using a fuel cell why isn't broad based acceptance of plasma delivered and Helmholtz received Direct Energy Conversion technologies being used?

SJC

There is a place for advanced electrolysis, but it may be stationary rather than mobile. Wind turbines that can produce off prime time to electrolyze then provide fuel to cars during the day.

Account Deleted

You are spot on SJC. We need lower cost and more efficient stationary electrolysers to make hydrogen for use in stationary power plants making electricity when solar and wind is not making enough for instance during winter time. So better electrolysers are an important piece of the puzzle that need to be solved before we can make a pollution free economy. During summer excess solar power and wind power can be used to make hydrogen that subsequently is compressed and pumped into depleted oil and gas fields for later use in conventional combined cycle plants. Cheaper solar, wind and electrolysers will make this economically viable at some point in time. You need giga watt scale facilities to make this economically possible. Otherwise hydrogen is an extremely expensive fuel. It cost 14 USD for 1 kg (one gallon of gas equivalent) at the hydrogen fuel stations for FCV. This is because these stations are ultra small scale and hydrogen is incredibly expensive and high tech to handle. It is either insanely high pressure or insanely cold as liquid hydrogen. Because it is invisible and non-smellable to humans it also requires a lot of expensive security technology to detect leaks and prevent explosions. It is the worst possible fuel for cars. It will never work with cars. But stationary power and perhaps aviation fuel and for sure rocket fuel make sense.

D

I think the all the hydrogen nay sayers are misiing the point. Hydrogen is a way to save and transport power. It can be far lighter than batteries and infrastructure to do so far easier to create. With a low cost electrlyzer would you need the high cost of batteries to have power at night? Batteries break down, even the best in 10 years time then what? I can easily see excess wind or solar making hydrogen and using hydrogen as power.

sd

I do not easily see excess wind or solar (power) in the near or medium future in most places in the world. Just add it to the grid.

DaveD

@D, on what planet do you think building a hydrogen infrastructure is easy to create? Do you understand all the issues to be overcome with hydrogen at all???

HarveyD

H2 lower cost massive production, storage and distribution ans usage has just started and will improve every other month/year in many countries.

Today's opposition will become tomorrow's supporters.

Roger Pham

@Henrik,
Unfortunately, Hydrogen from Solar and Wind is still far too expensive to replace Natural Gas.
However, Hydrogen from 5 cent electricity is already cost-competitive with petroleum, when the H2 will be made in sufficient quantity to permit economy of scale.

Most early-introduced items are expensive, for example, $14,000 for a 50-inch LCD TV at one time, now costing under $1,000. Hydrogen at $14 per kg now will soon cost under $6.6 per kg to be competitive with petroleum. At 5 cent per kWh electricity and 55 kWh per kg, the energy cost is only $2.75 per kg.

The technology for automotive H2-FCV is now at commercialization stage already. Toyota and Hyundai already offered FCEV's to customers, while Honda will soon release a FCEV to the market. H2 stations are being built in Europe, Japan, and CAliforia.

DaveD

@Harvey, and we'll all be riding unicorns and be big unicorn supporters!

SJC

You don't need a hydrogen "infrastructure" the advanced electrolysis at point of use has a power contract with the wind turbine people. Simple and effective.

Account Deleted

Roger you are very wrong. 1kg hydrogen is 33 kwh. You loose 50% of electrolysis and compression so you need 66 kwh. At 5 cents that is 3.3 USD per kg. Then we add 10 USD per kg for capital cost for the compressor, electrolyser, storage tanks, security equipment, and maintenance of all allt that super expensive hardware and labour cost to maintain it, insurance cost, etc, plus profit for anyone to invest in the first place. You get 14 USD per kg as it currently cost. It will not go down much for retail hydrogen I can assure you.

Hydrogen 1kg need to be priced the same as gasoline 1gallon or perhaps 20% more in order to be competitive. The new Prius does 55mpg and is a larger more powerful car than the Mirai that does about 60mpg (h2 equivalents).

Onshore wind power on an average Midwest location is about 5 cents per kwh without any subsidies. This is cheaper than what is possible in a combined cycle natural gas plant if gas is 6 USD per MBTU. Problem is that gas is currently only 2.4 USD per mbtu. So windpower still need subsidies for ten more years unless natural gas goes up to 5 USD per mbtu. At current prices for natural gas nothing can compete. Coal power and nuclear are much more expensive and will be shot down fast in the next few years.

D

I can see Hydrogen coming back and easily passing batteries.
Sunlight from desserts can become hydrogen fuel producers. You do not need to tie the output to the electric grid just to a storage tank.
This reduces the complexity by quite a bit.
Short range trucks or rail can bring the hydrogen around as it does gasoline and many other fuels/chemicals. Hi pressure tanks exist. Wind or wave power can also be captured and utilized.
Also you always loose when creating power for storage. How much coal is burned to fuel that Volt or Prius?
In urban environments at night, generation of hydrogen to power your car, or generate more to power your home during the day when power is more expensive?
What if you can capture solar without batteries and all the complexity, instead you fire up your hydrogen fuel cell or generator using your own gas.
How would that lower the cost of solar ownership? Placing the storage tank under ground or near by in a shed would reduce the initial fear of using a storage tank.
And in the end I hope you can recapture the water to be reused. No special chemicals just a tank and a way to compress it. If I remember correctly burned chicken feathers make a great capture material for hydrogen.
http://cleantechnica.com/2009/06/24/hydrogen-fuel-tanks-made-from-chicken-feathers-could-save-55-million/

CheeseEater88

I have a serious question... so we know that H2 needs to be under $4/kg for today's sub $2/gal gasoline... but how much would companies pay for the high purity O2 produced by such electrolysis? $1-3/kg? So what would the net cost be? I'm just trying to figure out if we are only looking at half the equation...

Ultimately H2 and BEVs will have to compete with ICEs for a long while. Carbon neutral fuels/energy aren't just for the privileged BEV owner. There are several waste to fuel programs just getting started... we in the US probably could make enough fuel to cover the LD vehicles just from sewage and landfills. Lots of untapped resources to maintain the status quo at prices lower than when oil prices were the highest so far.

I'll probably drive my car until late 2017... If there is an effective BEV on the market with a cost of ownership close to what I would consider buying yeah I probably would buy it assuming it was largely comparable. I want to love BEVs, I'm just waiting for the day it makes sense for me.

Engineer-Poet

Oxygen is an extremely cheap industrial commodity.  A quick search finds a claim of 16 kWh per 1000 scf (roughly 50 kg), plus hardware amortization and O&M.  The energy cost is literally pennies per kg.

HarveyD

Very low cost clean Hydro-Wind electricity is available in our region for H2 electrolizers at:

1. $0.03/kWh (CAN) during peak hours (about 7 hours/day).

2. $0.01/kWh (CAN) outside peak hours (about 17 hours/day)

In other words, H2 electrolizers could operate in our region for 17 hours/days, Monday to Friday and 24 hours/day on Saturday and Sunday on clean energy @ 1 cent (CAN) (0.77 cent US) per kWh.

Coupled with future improved efficiency and reduced capital, H2 cost could drop to below $4/Kg by 2020/2022 or so.

The low cost clean electricity required is available wherever the H2 electrolizers would be installed and no H2 transportation would be required. Local H2 storage would be enough unless you want to pump some excess H2 into existing NG pipelines.

D

How do hospitals put oxygen into rooms? Oxygen on demand woth a side effect of generating hydrogen that could reduce power requirements might be interesting.

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