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Aalto University team develops promising new electrocatalyst for hydrogen evolution reaction; one-hundredth the amount of Pt

26 March 2017

A group of Aalto University (Finland) researchers led by professors Tanja Kallio and Kari Laasonen has developed a manufacturing method for hydrogen evolution reaction (HER) electrocatalysts that use only one-hundredth of the amount of platinum generally used in commercial products.

They achieved pseudo atomic-scale dispersion of Pt—i.e. individual atoms or sub-nanometer clusters—on the sidewalls of single-walled carbon nanotubes (SWNTs) with a simple and readily up-scalable electroplating deposition method. These SWNTs activated with an ultra-low amount of Pt exhibit a similar activity to that of a commercial Pt/C with a notable higher (~66-333 fold) Pt loading for catalyzing hydrogen evolution reaction (HER) under the acidic conditions required in proton exchange membrane technology. A paper on their work is published in the journal ACS Catalysis.

Graphical_abstractweb_en
DFT (density functional theory) suggests that carbon nanotubes stabilize single platinum atoms and that hydrogen evolution reaction takes place more efficiently on their surfaces, compared to conventional platinum nanoparticles. Source: Aalto University. Click to enlarge.

Platinum-based catalysts currently have shown the most efficient electrocatalytic activity for the hydrogen evolution reaction (HER, 2H+ + 2e- → H2). However, the high price and scarcity of Pt oblige us to reduce the amount of Pt used in electrocatalytic materials. A promising strategy to reduce the use of Pt is the synthesis of single-atom or pseudo atomic-scale Pt. In this strategy, the size of Pt particles further decreases from nano- to sub- nanometer or atomic scale. Consequently, the catalytic properties of the atomic-scale metal can be also drastically changed, providing the possibility of selective tuning of the catalyst activity. Nevertheless, the atomic-scale catalysts are not stable because of their high surface energy and therefore, they should be decorated on the supports providing strong metal–support interactions to prevent the agglomeration of atoms.

… we have shown in this work that pseudo atomic-scale metallic Pt can be easily stabilized on the intact carbon network of the pristine single-walled carbon nanotubes (SWNTs). Furthermore, here, relatively large amount of Pt atoms is mainly located within the outermost surface layer of the electrode, resulting in the maximum noble-metal efficiency while the minimum number of platinum atoms are utilized.

—Tavakkoli et al.

The Aalto catalysts resemble pseudo atomic-scale Pt systems which mainly consist of a few to tens of Pt atoms dispersed on the sidewalls of the SWNTs. The Pt loading is only 0.19-0.75 at% (atomic percentage) at the electrode surface and characteristic peaks for Pt cyclic voltammograms are undetectable.

The atomic dispersion increases the portion of the surface active-atom sites and therefore, notably lower Pt loading is needed for attaining a high catalytic activity.

Kalliolaasonenkauppinen1web_fi
TEM (tunneling electron microscope) image of a carbon nanotube decorated with platinum clusters (bright color). Click to enlarge.

The SWNT/at-Pt electrodes showed extraordinary electrocatalytic activities for HER, close or even higher than that of Pt/C. DFT calculations revealed that the SWNT sidewall can efficiently immobilize Pt atoms, indicating the potential of SWNTs as a support catalyst for the atomic dispersion of Pt. The calculations also demonstrated that single Pt atom sites on the SWNT can electrocatalyze HER as efficiently as bulk Pt. Thi work opens up a new avenue to produce active electrochemical catalyst materials with ulta-low Pt loading but with ultra-high electrochemical activity.

—Tavakkoli et al.

Kallio emphasizes that so far the functionality of the electrocatalyst developed at Aalto University has only been proven in laboratory conditions.

In small-scale conditions and at room temperature, the electrocatalyst is stable and usable for a long time. The next step is to increase the scale of production and test the functionality of the electrocatalyst in practical applications, which are often carried out at a higher temperature.

—Tanja Kallio

Resources

  • Mohammad Tavakkoli, Nico Holmberg, Rasmus Kronberg, Hua Jiang, Jani Sainio, Esko I Kauppinen, Tanja Kallio, and Kari Laasonen (2017) “Electrochemical activation of single-walled carbon nanotubes with pseudo atomic-scale platinum for hydrogen evolution reaction” ACS Catalysis doi: 10.1021/acscatal.7b00199

March 26, 2017 in Catalysts, Fuel Cells, Hydrogen, Nanotech | Permalink | Comments (5)

Comments

Another set of multi million dollar lab experiments and subsequant costly article that is almost not publish anywhere and bring zero comments. Did you ever try to think how costly are these experiments and how useless they are. Science is mainly financial fraud. That's what happen when we do not work in a free market anymore...

@Gorr: Don;t be so negative. if one of these comes good, we could be up to our eyes in H2 from waste electricity.
H2 is not the best fuel from a storage point of view, but if you could find a way of storing it (by cracking longer chain hydrocarbons) (or whatever), it would be a great boon.

So I say continue with the research.
+ they have 2 comments on this one.

Hydrogen can be created where you dispense it. With renewable energy contracts trucks and buses can get fuel while selling the oxygen to lower costs.

Could this eventually improve the efficiency and lower the cost of electrolizers and FCs?

If so, our huge clean Hydro-Wind electricity surpluses, specially during periods outside peak demands hours(about 19 hours/day during work days and 24 hours/day on weekends and Holydays) could be used to produce/compress and store clean H2 and produce clean electricity during peak demand hours.

There has been a lot of progress, adding heat uses less electricity, using renewable electricity stops waste. There are several terrawatt hours wasted with wind and solar because fossil base load can't or won't reduce output.

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