Solar-driven water splitting at 13.8% solar-to-hydrogen efficiency

Lithium iron phosphate batteries have about 95% round trip efficiency. Some manufacturers say 98%. AC-DC-AC conversion is around 98%-99% efficiency now. So batteries are way ahead on efficiency.<p>Tesla is switching from lithium-ion to lithium iron phosphate for fixed battery installations.[1] The energy per unit weight is somewhat lower, but that doesn&#x27;t matter much for fixed installations. The safety is better, too - lithium iron phosphate batteries don&#x27;t have the thermal runaway problem. BYD, which is the biggest producer of batteries in the world, sells shipping container sized lithium iron phosphate sized battery packs for large scale solar backup.<p>[1] <a href="https:&#x2F;&#x2F;www.utilitydive.com&#x2F;news&#x2F;tesla-shifts-battery-chemistry-for-utility-scale-storage-megawall&#x2F;600315&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.utilitydive.com&#x2F;news&#x2F;tesla-shifts-battery-chemis...</a>

A lot of the discussion here is around hydrogen fuel cells for cars and aviation. Which would be cool. But the real reason we need “green” hydrogen now is for making steel and cement: <a href="https:&#x2F;&#x2F;www.vox.com&#x2F;energy-and-environment&#x2F;2019&#x2F;10&#x2F;10&#x2F;20904213&#x2F;climate-change-steel-cement-industrial-heat-hydrogen-ccs" rel="nofollow">https:&#x2F;&#x2F;www.vox.com&#x2F;energy-and-environment&#x2F;2019&#x2F;10&#x2F;10&#x2F;209042...</a>

I don&#x27;t get why people are acting like it&#x27;s an either or scenario. That said, one pro for hydrogen, is should be easily burnable in the current natural gas plants, which should easily cover off peak times without the need for batteries.<p>Another thing. I think we should question any plan that requires more mass mineral extraction than necessary. It&#x27;s not as if mining is an environmentally neutral thing, and there is more to restoring our planet that just getting surviving climate change.

I am speaking completely out of ignorance on this, so someone with a bit more familiarity with both physics and chemistry might be able to clarify.<p>------<p>From what I understand, one of the biggest issues with trying to replace commercial cross-country jets [1] with electric alternatives is due to the fact that there isn&#x27;t enough energy density in a battery to make that possible, and as a result, airplanes are a huge polluter towards climate change.<p>Would it make more sense to try and make hydrogen jets, at least if we can make the hydrogen relatively efficiently?<p>[1] I know jets really only make sense with fuel, replace &quot;jet&quot; with &quot;big airplane&quot;

The headline is &quot;solar-driven water splitting&quot;, but they do this by building an photovoltaic cell and connecting it to an electrolyser, just like everyone already does.<p>Moreover, the innovation here is that neither the solar cell nor the electrolyser require rare elements. As they say:<p>&gt; Sustainable water electrolysis requires that the anode and cathode catalysts are noble metal free and contain small amounts of other metals in order to lower system costs and facilitate recycling.<p>As for efficiency:<p>&gt; The measured [solar-to-hydrogen] efficiency is improved compared to all previous electrolyzers driven by low-cost [perovskite solar cells] that used solely Earth-abundant electrocatalysts but lower compared to the highest performing perovskite&#x2F;Si tandem devices that uses noble metal electrocatalysts, which reached an initial efficiency of 17% [solar-to-hydrogen].<p>So this setup is less efficient than what we already have. But it doesn&#x27;t require rare elements.

People often say how battery cars are more efficient than fuel cell cars, and we should focus our resources to the former. Some even called fuel cell cars dumb. This is short sighted in my opinion. If fuel cell cars are more popular, it encourages more green hydrogen production and investment. Once there are more green hydrogen, then we can truly decarbonize the chemical and industrial sectors. There are so many industrial processes requiring hydrogen as a reactant. Fuel cell cars can be a catalyst to decarbonize sectors well beyond the auto industry.

Two things are hardly ever spoken about when splitting water:<p>The pure oxygen is just as useful of a product and can be used to gasify woody biomass, plastics and other waste streams into more useful fuel sources such as syngas, or liquid fuels using the fischer-tropsch process. It is also useful for medical processes.<p>Second, natural gas lines can utilize something like 10% hydrogen...so we can store a large quantity in our existing infrastructure for use later that day, or in other locations.

One big electricity storage problem is seasonal - eg cold sunless winters. Eg batteries are great for daytime charging your car - but they aren&#x27;t great for storing up a whole summer&#x27;s worth of energy to burn in the winter. Hydrogen could do that.

We see the value in fuels like diesel being highly energy-dense. If we used the sun to create fuel like hydrogen or electricity, what is against simply creating (purified in some sense) man-made diesel and continue to use combustion engines?<p>We would not be contributing to the overall contribution of greehouse gases. Some arguments are diesel and friends are safer in storage and transportation than hydrogen.

I assume there are also costs to store and deliver hydrogen fuel? I&#x27;d like to see an EROEI comparison of electric vs. hydrogen.

This is not too bad. I&#x27;d prefer hydrogen fuel cells over massive toxic batteries that we&#x27;re going to have to dispose safely in a few years, from all those used Teslas! I don&#x27;t know about other countries, but most of the electricity generated here in Australia is from Coal and Natural gas. That&#x27;s an unfortunate fact. I don&#x27;t see any reason to buy an electric car until that changes. In the meantime if the solar driven hydrogen production efficiency increases then we can have an even cleaner future.

I did not investigate it properly but at first glance the efficiency is obtained via low current density of the electrolyser. That means high efficiency but low volume. That translates to more hardware needed to produce a unit of power.<p>State of the art electrolyzers are run at 1000x current densities. That roughly means 1000x installation cost.

The best way to understand hydrogen is Liebreich Hydrogen Ladder: <a href="https:&#x2F;&#x2F;www.rechargenews.com&#x2F;energy-transition&#x2F;liebreich-oil-sector-is-lobbying-for-inefficient-hydrogen-cars-because-it-wants-to-delay-electrification-&#x2F;2-1-1033226" rel="nofollow">https:&#x2F;&#x2F;www.rechargenews.com&#x2F;energy-transition&#x2F;liebreich-oil...</a><p>The best use cases for hydrogen are fertilser or in hydrocracking. We currently use primarily natural gas to produce hydrogen.<p>Urban or commuter cars are one of the worst use case for hydrogen. Electricity and batteries are way better.

Congratulations on the advancement, but wow, that&#x27;s still pretty bad. The only way this would become popular would be through being super cheap.

this will be used as an excuse to expand production of hydrogen made from carbon fuel on the basis that eventually the carbon will be made sustainably. Don’t fall for it.

A google search tells me there are far more efficient processes available, one almost at 25% efficiency. None of them commercially viable yet.

Solves the energy storage problem. Just add tanks.

Before people get too excited they might want consider the life time of the cell as indicated over a 10 hour test window.

&gt; high peak solar-to-fuel conversion<p>does it mean there&#x27;s a &quot;mean solar-to-fuel conversion&quot; to look for ?

Cool on the way to sustainable liquid fuels.

so how would a person go about making one of these for use at home?

Can someone please ELI5?