For as long as we can remember, hydrogen power has been an idealistic way out of the climate crisis for cars, and on the surface, it’s easy to see why. Harmful greenhouse gases such as carbon dioxide are completely removed and replaced with water, and they have a seemingly greater range than electric cars, allowing for a lot more flexibility in driving. What’s not to love?

As it turns out, a lot.

But before we jump to conclusions, let’s see how these cars actually work. Hydrogen-powered fuel cell vehicles (FCVs) rely on fuel cells within the car, which are essentially sites of electrolysing redox reactions that generate energy using the following reaction:
2H2 + O2 🡪 H2O
As anyone can expect, it is easy enough to source oxygen as we can find it in the air. Hydrogen, on the other hand, is a completely different story. Despite the fact that hydrogen is the most abundant element in the universe, it is nowhere to be seen in the atmosphere, so has to be synthesised by chemical means. The most common of the methods is steam methane reforming, whereby water reacts with methane:
CH2 + H2O 🡪 CO + 3H2
The glaring problem we find here is that the release of hydrogen also comes with the by-product of carbon monoxide. Alongside having an indirect effect on global warming by reacting to increase methane and ozone concentration in the air [1], carbon monoxide is also poisonous. This is because it binds to haemoglobin in red blood cells used to circulate oxygen 200-300 times better than oxygen itself [2] and so prevents oxygen from circulating in the body. The other most common process of extracting hydrogen is coal gasification, another harmful chemical process which uses coal:
3C + O2 + H2O 🡪 3CO + H2
CO + H2O 🡪 CO2 + H2
Coal gasification produces a whole 10-19 tons of CO2 per ton of H2 [3]: so much for clean energy considering these 2 processes constitute 95% of global hydrogen production.

So clearly hydrogen is unfit to be called ‘green’, but even then, what is preventing it from being used as an alternative in cars regardless? One thing is the price; hydrogen is too expensive to be used as a fuel, costing £10-15 per kilogram [4] in comparison to £1.36 per litre of petrol [5], whereby a litre of petrol is 0.737kg. This is made worse by poor energy efficiency; hydrogen cars have it at just 25-35% - [6]  similar enough to petrol cars yet it paling in comparison to the 70-90% efficiency of electric cars.

This would be a significant problem at least if there was enough infrastructure for the fuelling of hydrogen for cars in the first place. In the entire UK, there are just six hydrogen refuelling stations, [7] making extra range in comparison to EVs practically pointless. But there is more to the infrastructure problem than just fuelling stations: the storage of the high pressure hydrogen used in cars is incredibly dangerous, clear as in 2019, a massive blast at a Norwegian hydrogen fuel station injured several, with the cause of course being a simple loose tank plug [8]. The nail in the coffin has got to be though that this hydrogen has to be transported in trucks relying on fossil fuels, both endangering roads and increasing emissions.

However, amidst all the gloom and doom, there may be light at the end of the tunnel. The poor infrastructure and ridiculous price only align with a simple case of supply-and-demand: a low demand for hydrogen as a car fuel means that constructing vast infrastructure for it isn’t economically feasible. And hydrogen extraction is being pioneered in a range of environmentally friendly ways, including the electrolysis of water (funnily enough the exact reverse of the fuel cell reaction) and including the use of carbon capture and storage to reduce emissions. As a result, it isn’t like hydrogen is ruled out for the far future considering the innovation of chemical engineers and the like to make it sustainable. However, considering that EVs are becoming cheaper and longer, and considering the revelatory opportunity of charging them at home passively, it makes more sense to use them as our free ticket out of the climate crisis instead of the premature technology in hydrogen cars.

References

[1] - [Global Climate Change Linkages: Acid Rain, Air Quality, and Stratospheric Ozone (James C. White, Editor. Elsevier)]

[2] - [Physiology, Oxygen Transport and Carbon Dioxide Dissociation Curve (Sagar Pater, Alvin Jose, Shamim S. Mohiuddin)]

[3] - [The Colours of Hydrogen | The Belfer Centre for Science and International Affairs]

[4] - [Hydrogen cars: how fuel cell cars work, how much they cost and where you can refuel them]

[5] - [https://www.petrolprices.com/]

[6] - [Battery Electric Vs Hydrogen Fuel Cell: Efficiency Comparison]

[7] - [Where can I buy hydrogen and where is my nearest hydrogen filling station? | DrivingElectric]

[8] - [Norway fines Nel units $3 million over 2019 blast at hydrogen fuel station | Reuters]