Researchers from the University of Houston have reported a significant breakthrough with a new oxygen evolution reaction catalyst that, combined with a hydrogen evolution reaction catalyst, achieved current densities capable of supporting industrial demands while requiring relatively low voltage to start seawater electrolysis.
Nature Communications – Non-noble metal-nitride based electrocatalysts for high-performance alkaline seawater electrolysis
Researchers say the device, composed of inexpensive non-noble metal nitrides, manages to avoid many of the obstacles that have limited earlier attempts to inexpensively produce hydrogen or safe drinking water from seawater.
a major obstacle has been the lack of a catalyst that can effectively split seawater to produce hydrogen without also setting free ions of sodium, chlorine, calcium and other components of seawater, which once freed can settle on the catalyst and render it inactive. Chlorine ions are especially problematic, in part because chlorine requires just slightly higher voltage to free than is needed to free hydrogen.
The catalysts were integrated into a two-electrode alkaline electrolyzer, which can be powered by waste heat via a thermoelectric device or by an AA battery.
Cell voltages required to produce a current density of 100 milliamperes per square centimeter (a measure of current density, or mA cm-2) ranged from 1.564 V to 1.581 V.
The voltage is significant, Yu said, because while a voltage of at least 1.23 V is required to produce hydrogen, chlorine is produced at a voltage of 1.73 V, meaning the device had to be able to produce meaningful levels of current density with a voltage between the two levels.
Seawater is one of the most abundant natural resources on our planet. Electrolysis of seawater is not only a promising approach to produce clean hydrogen energy, but also of great significance to seawater desalination. The implementation of seawater electrolysis requires robust and efficient electrocatalysts that can sustain seawater splitting without chloride corrosion, especially for the anode. Here we report a three-dimensional core-shell metal-nitride catalyst consisting of NiFeN nanoparticles uniformly decorated on NiMoN nanorods supported on Ni foam, which serves as an eminently active and durable oxygen evolution reaction catalyst for alkaline seawater electrolysis. Combined with an efficient hydrogen evolution reaction catalyst of NiMoN nanorods, we have achieved the industrially required current densities of 500 and 1000 mA cm−2 at record low voltages of 1.608 and 1.709 V, respectively, for overall alkaline seawater splitting at 60 °C. This discovery significantly advances the development of seawater electrolysis for large-scale hydrogen production.
SOURCES- Nature Communications
Written By Brian Wang, Nextbigfuture.com
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20 thoughts on “Progress to a Hydrogen Economy With Better Production from Seawater”
Yeah, 99% of the users would never bother recondensing the resulting water vapour. Though there might be some applications, such a remote desert locations, where it would be worth while running the exhaust through a coiled metal tube.
You would get all the energy storage you need for the world but not get enough fresh water out to do much towards global fresh water requirements.
Ha ha yeah. The proportion of water (even just global fresh water) required for the hydrogen economy would be tiny. The H2 is just an energy store. To use the energy it reacts with O2 from air and converts back to fresh water. Why even bother using sea water when even a tiny proportion of fresh water would be used for H2 energy store before converting it back to fresh water.
The energy of hydrogen is ~121 MJ/kg.
So if you are running say a hydrogen fuel cell at 100% efficiency to give the energy of a hydrogen car, say 80 kW.h = 288 MJ = 2.4 kg H2.
Now that sounds like a very small amount of hydrogen especially compared to the hundreds of kg of batteries to provide the same energy.
But that much H2 reacts to form 21kg of water. Which isn’t much water, but this is for one car running though one charge cycle. So to an individual driving for one day, 21 kg of water is more than enough for drinking over that time. Probably 25kg with realistic efficiencies.
That we don’t need amounts of energy storage that if we recombine Oxygen and Hydrogen for electricity storage generation they will create substantial amount of water.
On a second thought however, we may reach a point that sea water splitting and recombination may reach such efficiencies and low price that the energy cycle can be closed for the purpose of desalination only, with the energy generated going toward sea water splitting, and that may be a desalination breakthrough.
Could you explain what you mean?
Your instincts about the relative size of the energy budget and the oceans are not correct.
Any energy storage that stores enough energy to be useful could go boom (ie. release the energy in a sudden, damaging way) if it goes wrong.
Even springs can kill someone if they are big and loaded with lots of strain. Just have something go wrong when working on a car suspension. Or the string snap on a high draw weight crossbow.
H plus Space Solar Power is the future, on Earth and in Space.
So do lots of other things that we use routinely.
Just pointing out that normal desalination costs about 1-1.5 USD per m3  of water. With a 100% efficiency, the above scheme would require about 4400 kWh , or about (at 3c per kWh) 130 USD per m3. A pretty expensive way to make clean water, if you ask me….
So I am pretty sure that they would not condense the water after producing it locally in a vehicle (such as an airplane)….
1000 kg *(2/18)*1000g/kg*1mol/1g/*6*10^23atoms/mol*1,5V*1,6*10^-19C =16 GJ = 4.44 MHh ~ 4400 kWh
Considering for example, how much gasoline we are using today compared to how much water, these can be done only in small quantities.
As Andrew says, there’s a lot of hydrogen, but one complication could be if there was a largely hydrogen powered economy, and a probable high leakage rate ( hydrogen is very good at getting through seals, and even metals.) Any leaked hydrogen would float to the top of the atmosphere, and be oxidised to water faster than leaking to space. Water molecules above the tropopause are powerful global warming gases, and could also affect the ozone layer.
Doesn’t hydrogen go boom? Oh, the humanity!
There is an awful lot of hydrogen in earth’s oceans. I’d be a lot more worried about Helium.
I always get worried a hydrogen economy…. like unforeseen complications about depleting water from the oceans and hydrogen gas slow leaking out of the upper atmosphere into space…
Great! They found a cheap catalyst. So how much is the process to produce hydrogen, energy and water going to cost.
Using an AA battery to split seawater into hydrogen and oxygen so you can recombine them to get cheap desalination?
Let’s just try to rewrite this in a non-ridiculous way.
An electrolyser, (amusingly the lab prototype could run on an AA battery though obviously only at a tiny, proof-of-concept scale) can be used to split seawater into hydrogen and oxygen without generating other gases such as chlorine. This hydrogen and oxygen can then be stored and/or transported and later recombined to produce energy, at which point the waste product will be clean, fresh, water.
Once again, I will mention H2Pro, who claim over 98% energy efficiency for producing hydrogen from water. They have a paper on their press page.
The missing link in moving to a hydrogen economy is energy inexpensive and safe storage. More progress needs to be done with Metal hydrides Hydrogen storage. https://www.sciencedirect.com/science/article/pii/S0360319919302368
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