- Billions of human lives depend on a technology from 1910,
a single chemical reaction
that helps produce most of the food that you and I eat.
But there's a new technology,
a new invention that might help us
finally kill the old chemical reaction.
and revolutionize fertilizer.
Yeah, fertilizer.
Okay, let's do this.
First off, that century-old technology?
That's called the Haber-Bosch process.
So if you, like many chemists out there,
get wildly overexcited
about anything to do with Fritz Haber, relax, I got you.
We'll get into it in a little bit.
For now, though,
I wanna say something that might get me a little hate.
I personally find the Haber-Bosch process to be,
how do I put this?
Kind of boring.
Also, Fritz Haber is the father of chemical warfare.
So like, maybe not the best role model
for generations of young chemists to look up to?
What I wanna talk about today is the new technology,
a new discovery in chemistry
that might finally kill Haber-Bosch.
(upbeat music)
- That's because you don't understand it, though.
Because if you understood it,
you would think it's the coolest thing in the world.
- This is Leila,
she's a fact checker for "Reactions,"
and has a PhD in organometallic chemistry.
Leila is a Haber-Bosch super fan.
No, I don't understand why everyone likes it.
- Because it fundamentally changed
the course of human history.
- Yeah, 100 years ago.
- Imagine if the Wright brothers had invented a plane,
and we were still flying in that plane today.
- That'd be a problem!
- We were running out of fertilizer,
we were running out of fixed nitrogen,
but there was a genuine concern
that the world was gonna starve.
- [George] Plants need a ton of nitrogen to grow.
And in the early 1900s,
people were worried
that we didn't have enough nitrogen-containing fertilizer
to grow all the crops that we needed
to feed the very quickly growing global population.
- And the great thing about nitrogen
is we have an endless supply of it,
because it makes up about 80% of the air
that we breathe. - Right.
- Except when nitrogen is in the air,
it is two nitrogen atoms triply bonded together.
- Right.
- And these are stuck, and they're also really inert.
They won't react with anything.
- [George] Nitrogen in the air is N2,
and most plants cannot use N2 to grow.
So we need to put it into a form that they can use.
Converting nitrogen from N2
to a usable form for plants is called nitrogen fixation.
- Ammonia is one of your simplest forms of fixed nitrogen.
You've got a nitrogen in the middle,
you've got three hydrogens around it,
and you've got two electrons,
one lone pair at the top.
Dinitrogen, inert, not gonna do much.
- Right.
- Ammonia, suddenly you can put nitrogen in a lot of places.
- [George] Two chemists named Fritz Haber and Carl Bosch
came up with a way to do exactly that.
The Haber-Bosch process could take N2,
and can convert it to ammonia,
which could then be used for fertilizer.
And like I said before,
billions of people around the world
rely on food grown with fertilizer
produced by the Haber-Bosch process.
- Haber-Bosch process accomplishes
what is a tremendously difficult reaction
with wild efficiency.
And in the 100 years since,
there have only been tweaks around the edges,
'cause no one can beat this standard process.
- Like I said, boring.
But it's not just boring.
Look at this reaction again.
Nitrogen, that comes from dinitrogen gas
in the air all around us, no problem.
But where do you think the hydrogen comes from?
The roughly bazillions of tons of hydrogen gas
used in this reaction
come from hydrocarbons deep underground,
which you know as fossil fuels.
Not great.
Also, to get this reaction to go,
you have to jack up the temperature to 500 degrees, roughly,
and the pressure to almost 200 times atmospheric.
Most of this is also done using fossil fuels.
Now all of that means that this one reaction
uses about 1% of the world's total energy production,
and emits nearly 2% of the world's CO2.
That's about the same emissions
as the entire global airline industry.
And sure, look, you could do a lot of this
using renewable energy, but of course,
the Haber-Bosch process needs to be running constantly
to keep from damaging its catalyst,
and renewable energy these days tends to fluctuate.
So, not really a great option yet either.
Now scientists are working on tweaking the process
to work better with renewables,
producing hydrogen by splitting water
using solar energy, for example.
But so far, they're producing on the order
of tens of kilograms of ammonia per day.
The global need for ammonia
is in the hundreds of millions of kilograms per day.
So the renewable powered Haber-Bosch process
is not really making a dent quite yet.
But we can't just stop doing it.
The Haber-Bosch process is critical
for about half the world's food production.
Half of the world's food production.
And as the global population increases,
so does our need for nitrogen fertilizer.
So chemists have been looking for a replacement
for the Haber-Bosch process for a long time.
Turns out, it's not easy.
N2 is one of the most stable unreactive molecules out there.
So, ripping these two nitrogens apart,
and sticking six hydrogens in here
takes a lot of careful wrangling.
Most promising way we've come up with to do it,
other than Haber-Bosch,
is called the nitrogen reduction reaction or NRR.
A nitrogen reduction reaction
is an electrochemical process
that directly reduces dinitrogen gas to ammonia.
There are a lot of different ways you could try to do that,
but the best tool we've found for the job so far
is lithium, because lithium is reactive enough
to break that very strong nitrogen-nitrogen triple bond.
So here's how we think the overall process works.
This?
This is just step one.
Six lithium ions come together with six electrons,
and a molecule of nitrogen
to form two molecules of lithium nitride.
And this (snaps fingers) is step two.
Two molecules of lithium nitride come together
with six hydrogen ions, also known as protons,
to form six lithium ions,
and two molecules of that sweet, sweet ammonia
that we've been looking for.
If you add these two reactions up,
you get the overall process.
Now, two important things to notice about this reaction.
The first is that here,
you have six lithium ions on the product side,
and here you have six lithium ions on the reaction side.
What that means is that lithium is catalytic.
This can wander back over here,
and participate in another cycle of the reaction.
That's great.
The second important thing to notice
is the form of hydrogen that this reaction uses.
Remember, the Haber-Bosch process
used molecular hydrogen, H2.
This reaction uses hydrogen ions H+, and electrons.
Now you can get this from H2, but what's the point?
You'd still be relying on fossil fuels
to power this reaction,
and that's not what we're trying to do here.
You could however, also get hydrogen ions
and electrons from water,
which is obviously way more sustainable
than getting it from fossil fuels.
You can electrolyze water in such a way
that you produce hydrogen ions and electrons,
and then in theory,
you could take those hydrogen ions and electrons
and cart them over to the lithium reduction reaction
where you reduce nitrogen to ammonia.
But no one's actually managed to do that second part yet.
It's still ongoing research, and we'll come back to it.
Anyway, the lithium nitrogen reduction reaction
was demonstrated almost 100 years ago
in this paper that I can't read, because it's in German.
But back in the 1990s,
researchers showed that it could be done
at room temperature, which is awesome,
and at about 50 times atmospheric pressure,
which is great compared
to the 200 times atmospheric pressure for Haber-Bosch.
But the yield was relatively low,
and its Faradaic efficiency was only 50 to 60%.
Faradaic efficiency is a measure of how many electrons
end up in the product,
versus how many electrons you pumped into the reaction.
For example, if you pump in 100 electrons
into this reaction, and 40 of them wander off
and engage in side reactions,
leaving only 60 in the ammonia, that's not that great.
Versus if you pump a 100 in,
and 98 of them end up in the ammonia,
and only two of them wander off, that's much better.
Now, in that nitrogen reduction reaction from the '90s,
the Faradaic efficiency was about 60%.
That means that roughly 40% of the energy
being put into the process was producing
other stuff that's not ammonia,
like lithium hydride and hydrogen gas,
which we don't want, and we certainly don't want
to be using energy to be making things we don't want
when what we're trying to make is ammonia.
Since the '90s, lots of people have tried
lots of different things to improve it.
One team used a different design
to get the yield quite a bit higher,
but their Faradaic efficiency went down to 35%.
For decades, there was a lot of wrangling,
but no Haber-Bosch killer,
until, and this is the part where things get exciting.
A single team recently made two big discoveries.
And you can't see this,
but this is a nature paper, and this is a science paper.
And for one team to have a nature paper and a science paper,
I mean, color me impressed, okay?
Anyway, their first big discovery came
when they were looking for a good proton shuttle.
Remember how I said that the electrolysis of water
could theoretically generate our hydrogen ions?
Well, for this to work,
you need a molecule that can take the hydrogen ions
from where they're generated,
and deliver them to where they react.
What that means is you need a proton shuttle,
a molecule that has a hydrogen
that it can easily lose, being deprotonated,
or easily gained back, being protonated.
Ideally, you'd want a proton shuttle
that you could deprotonate and reprotonate all day long,
without the shuttle itself changing.
Ethanol is a commonly used proton shuttle.
It can be deprotonated, and it can be reprotonated.
But, ethanol can also react with stuff.
For example, it can be oxidized
in your classic exploding moonshine still reaction.
(flame whooshes)
Now, you don't want that happening
to your proton shuttle
any more than you want it happening in your moonshine still.
Not that you have a moonshine still, 'cause it's illegal.
So to get around that, they tried using phosphonium salts,
which are far more stable than ethanol,
as the proton shuttle.
Specifically, since I know you don't wanna hear this,
they used salts like trihexyltetradecylphosphonium.
Andrew wrote this script, and in the script,
there's a stage direction that says, you know,
George struggles to say the name properly,
and Andrew will cut multiple versions of it together
for it to be funny.
But you gotta hit me with a harder chemical name than that.
Trihexyltetradecylphosphonium.
It's so easy.
And when they tried out
their nitrogen reduction reaction
using trihexyltetradecylphosphonium salts,
they found that the yield was about 10 times higher
than the original one from 30 years ago,
and the Faradaic efficiency was 69%.
Not bad.
All this happened at room temperature,
which is awesome,
and only about 20 times atmospheric pressure.
That's better than the 50 times atmospheric pressure
from the '90s, and way better
than Haber-Bosch's 200 times atmospheric pressure.
But these researchers were not done yet.
Next, they wanted to look at the electrolyte,
the stuff that allows all the ions
in these reactions to move around.
As you can guess, that's pretty important,
because lithium is constantly moving,
splitting nitrogen before being kicked out by hydrogen.
But research on batteries,
of which, (battery clatters) oops.
But, research on batteries
has shown that the electrolyte typically used
in these nitrogen reduction reaction experiments
is actually not that great for cycling lithium ions.
So instead, they tried something
that's known to work better for that,
a bisflitrip (stammering).
This one is harder.
A bis(trifluoromethylsulfonyl)imide electrolyte.
And by using this new electrolyte,
their yield went up even higher,
three times their earlier yield,
and 100 times the yield of the original
lithium mediated nitrogen reduction reactions
from the '90s.
And, the Faradaic efficiency is up to 98 or 99%.
That's pretty great.
As someone who is tired of hearing about Haber-Bosch, me,
that is exciting.
But there's more.
If you call now, we will double your contribution.
But wait, there's more.
Here is what this device looks like.
It's tiny.
You don't need to do this on massive scales.
You could synthesize your ammonia right where you need it.
So farmers could make it themselves, on demand.
It could also theoretically be scaled up
to giant industrial plants, like what we have now,
for Haber-Bosch ammonia production, theoretically.
So, have we killed Haber-Bosch?
Hm, no, we have not.
This is still an experimental demonstration,
but it's got high yield,
it's got almost 100% efficiency,
and it happens at ambient temperature,
and only about 15 times atmospheric pressure.
And all of that makes it, in my opinion,
the most promising Haber-Bosch alternative
in over 100 years of trying.
And maybe the most exciting thing of all
is that we are on the verge of never
having to talk about Fritz Haber, ever again.
I mean, there were plenty of great chemists 100 years ago
who did not encourage their governments
to try and poison people.
Who did not try and harvest gold out of seawater
for 10 years based on a basic math error.
Who did not encourage their spouses to, you know what,
actually that's kind of dark.
You should just google that one.