Carbon-free energy from solar water splitting

January 24, 2017, Lawrence Livermore National Laboratory
This is a schematic illustration of a photoelectrochemical cell for water splitting. The absorption of photons on the photoanode (left) generates electron and hole carriers. The electrons will flow through the circuit to the photocathode and evolve hydrogen (right), while the holes will evolve oxygen (left). Credit: Peter Allen/The Institute for Molecular Engineering, University of Chicago

A Lawrence Livermore National Laboratory (LLNL) scientist and collaborators are fine tuning the mechanisms to generate hydrogen from water and sunlight.

Hydrogen production offers a promising approach for producing scalable and sustainable carbon-free energy. The key to a successful solar-to-fuel technology is the design of efficient, long-lasting and low-cost photoelectrochemical cells (PECs), which are responsible for absorbing sunlight and driving reactions.

LLNL's Lawrence Fellow Anh Pham, Assistant Professor Yuan Ping from the University of California at Santa Cruz and Professor Giulia Galli from the University of Chicago and Argonne National Laboratory (formerly an LLNL scientist) reviewed the use of first-principles methods to understand the interfaces between photoabsorbers, electrolytes and catalysts in PECs.

The key to building an efficient PEC relies on the availability of abundant semiconducting photoelectrode materials that are responsible for absorbing sunlight and driving water-splitting reactions.

"Despite steady efforts and some breakthroughs, no single material has yet been found that simultaneously satisfies the efficiency and stability required for the commercialization of PEC hydrogen production technology," Pham said.

The research appears in the Jan. 9 edition of the journal Nature Materials .

The team shows that with growing complexity of PEC architectures, understanding the properties of the interfaces between its components is key to predict novel, better performing materials and eventually to optimize the device performance.

In this study, the team discussed open challenges in describing PEC interfaces using first-principles techniques, focusing on the interplay between their structural and electronic properties. The scientists also reviewed first-principles techniques relevant for the study of solid-liquid interfaces, the structural and electronic properties of photoelectrode-water and photoelectrode-catalyst water interfaces and open theoretical challenges in the simulation of PEC interfaces.

Explore further: New approach to water splitting could improve hydrogen production

More information: Tuan Anh Pham et al. Modelling heterogeneous interfaces for solar water splitting, Nature Materials (2017). DOI: 10.1038/nmat4803

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humy
not rated yet Jan 24, 2017
"Hydrogen production offers a promising approach for producing scalable and sustainable carbon-free energy."

No, it doesn't!
Hydrogen can only merely be used to store energy because, ignoring energy wastage due to the energy convection to make it, it TAKES the same amount of energy to make hydrogen as what is released when it is used.
We need to go all renewable but the whole idea of the hydrogen economy is a terribly deeply flawed strategy that will just get in the way of what needs to happen.
humy
not rated yet Jan 24, 2017
"The key to building an efficient PEC relies on the availability of abundant semiconducting photoelectrode materials that are responsible for absorbing sunlight and driving water-splitting reactions."

Why not use those electrons for electricity and have a supergriid? -a far more practical idea. No need for impractical difficult-to-store and dangerous hydrogen.
antialias_physorg
5 / 5 (4) Jan 24, 2017
it TAKES the same amount of energy to make hydrogen as what is released when it is used.

Which would be a lot better than any other kind of storage (e.g. syngas, since Carnot cycles are very inefficient). And since building large tanks is vastly cheaper than building large batteries - what exactly is better than hydrogen storage?

The only thing that is comparable would be hydro power storage. But that is already being used to close to maximum potential and cannot store enough for longer periods of sub-par energy production.
humy
not rated yet Jan 24, 2017
it TAKES the same amount of energy to make hydrogen as what is released when it is used.

Which would be a lot better than any other kind of storage (e.g. syngas, since Carnot cycles are very inefficient). And since building large tanks is vastly cheaper than building large batteries - what exactly is better than hydrogen storage?
.

Yes, "building large tanks is vastly cheaper than building large batteries" of the same size, BUT what about the massive energy cost of producing and then liquefying/pressurizing all that hydrogen to fill that tank?
Batteries are vastly cheaper form of energy storage per joule than any hydrogen tank storage.
There are good reasons we still use batteries rather than tanks of hydrogen; the latter is just too expensive and problematic.
antigoracle
1 / 5 (3) Jan 24, 2017
"Hydrogen production offers a promising approach for producing scalable and sustainable carbon-free energy."

No, it doesn't!
Hydrogen can only merely be used to store energy because, ignoring energy wastage due to the energy convection to make it, it TAKES the same amount of energy to make hydrogen as what is released when it is used.
We need to go all renewable but the whole idea of the hydrogen economy is a terribly deeply flawed strategy that will just get in the way of what needs to happen.

Your astronomical stupidity is now amusing.
It would actually take more energy to get the hydrogen.
It would be a waste of energy to try and explain why to an ignoramus like you.
gkam
2 / 5 (4) Jan 24, 2017
In a hydrogen economy, hydrogen is also a working fluid, not strictly a fuel, as we have understood it. We change it back and forth with electrolyzers and fuel cells.

Anti-smart only thinks in terms of the Old Ways.
antialias_physorg
5 / 5 (1) Jan 24, 2017
There are good reasons we still use batteries rather than tanks of hydrogen;

The reason is just a measure of scale. For small scales batteries are better. But for larger scale hydrogen is better. And it's not even sure whether 'large' doesn't already start on the order of car/truck. But for real grid storage? There's no way that amount of massive batteries are cheaper.

Since you're producing the stuff from excess energy, anyways 8which costs nothing to the point where you get paid that you store the stuff) the compression costs don't matter at all. only the initial investment and the upkeep is relevant. And batteries need vastly larger upkeep than tanks.
humy
not rated yet Jan 24, 2017
"Hydrogen production offers a promising approach for producing scalable and sustainable carbon-free energy."

No, it doesn't!
Hydrogen can only merely be used to store energy because, ignoring energy wastage due to the energy convection to make it, it TAKES the same amount of energy to make hydrogen as what is released when it is used.
We need to go all renewable but the whole idea of the hydrogen economy is a terribly deeply flawed strategy that will just get in the way of what needs to happen.

Your astronomical stupidity is now amusing.
It would actually take more energy to get the hydrogen.
.

That is what I clearly implied.
humy
not rated yet Jan 24, 2017
There are good reasons we still use batteries rather than tanks of hydrogen;

The reason is just a measure of scale. For small scales batteries are better. But for larger scale hydrogen is better. And it's not even sure whether 'large' doesn't already start on the order of car/truck. But for real grid storage? There's no way that amount of massive batteries are cheaper.

Since you're producing the stuff from excess energy, anyways 8which costs nothing to the point where you get paid that you store the stuff) the compression costs don't matter at all. only the initial investment and the upkeep is relevant. And batteries need vastly larger upkeep than tanks.

If all that is true, why are we still using batteries rather than hydrogen?
Why haven't some investors not yet made a huge profit from making that happen? -what's the big hold up?
antialias_physorg
not rated yet Jan 25, 2017
If all that is true, why are we still using batteries rather than hydrogen?Why haven't some investors not yet made a huge profit from making that happen? -what's the big hold up?

Because we haven't had renewables for long. Up to now they provided so little energy that storage wasn't needed. That is changing rapidly. Storage solutions become something worth investing as in some countries renewables start frequently producing more than can be used.

And note that we aren't using batteries for (grid level) storage at all.

Another issue is that the technology of fuel cells is advancing so rapidly that it's very easy to bet on the wrong horse. Investors like tried-and-true technologies that cannot be easily overtaken (i.e. cash cows).
antialias_physorg
not rated yet Jan 25, 2017
I just checked around a bit and there are actually the first hydrogen storage units being built (one already in operation). Germany has currently about 60 projects (mostly prototype/research) in the making for various storage methods. Batteries for short term levelling and grid stability (seconds to hours) and hydrogen for longer periods.

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