The Truth About Hydrogen-Powered Vehicles: How Do They Actually Work?
- Yuvraj Singh
- Mar 6
- 9 min read
When we think about hydrogen powered vehicles, the image which comes to our mind is always of the “Hindenburg Hydrogen flying ship”. However today if we see Hydrogen vehicles are much safer and advanced then those days in the 1900s.
Today Hydrogen gas is the most prominent source of fuel in the sense of its efficiency. Hydrogen miraculously produces 143KJ/g of energy this can be compared with the other fuels in the figure 1.2.
Even the product of Hydrogen powered vehicles is just Water as the hydrogen combines with Oxygen to produce Water. So technically it has no disadvantage on the increasing global warming and Climate change issues.
Despite so many achievements of hydrogen as a fuel there are some massive issues due to which we are not able to achieve its full potential. So without wasting any more time let’s get started! and understand the whole chemistry behind hydrogen Fuel cells why Hydrogen cars are not just running on roads today
Table of Content -
What are Hydrogen Fuel Cells and Hydrogen Powered Vehicles?
Do you remember your 10th - 12th Class Chemistry books, talking about the Electrolysis chapter. The Graphite electrodes are placed into the electrolyte of Table salt (NaCl) dissolved in water and it produces the Oxygen and hydrogen as a product.
However the process happening in the Hydrogen powered vehicles are quite opposite & this is where the story becomes interesting. Instead of Hydrogen and Oxygen splitting into two products as they do in Electrolysis. They actually combine into one product. Guess what the product is? Offcourse water!
Chemistry behind Hydrogen-Powered vehicles. How do they work?
As I have already given you some ideas on basics of Hydrogen powered vehicles in the previous paragraph,So let's evaluate further upon them.
Step by Step process happening in the Hydrogen powered vehicles -
Step 1: The Input
The gases are supplied into the Fuel Cell: Hydrogen is pumped in from the hydrogen tank, and Oxygen is pulled in directly from the outside air.
Step 2: The Split (At the Anode)
The Hydrogen gas hits the Anode (the negative electrode) and splits into electrons and protons due to the platinum coating on the carbon electrode. The initial binding is known as Chemisorption, which triggers the Hydrogen Oxidation Reaction.
Chemical equation at the Anode: 2H₂ → 4H⁺ + 4e⁻
Step 3: The Journey
The protons (H⁺) of the Hydrogen pass straight through the Proton Exchange Membrane (PEM). The electrons (e⁻), however, are blocked. They must take the long path, traveling outside the fuel cell through a wire from the Anode to the Cathode, providing the electrical energy to spin the car's motor.
Step 4: The Reunion (At the Cathode)
On the other side, the Oxygen is waiting at the Cathode (the positive electrode). It combines with the electrons that are returning from the car's motor. I love to call this the "Reunion Reaction." Because all the hydrogen’s electrons and protons that separated at the Anode finally join back together with the Oxygen at the Cathode, forming pure water!
Fig 1.4 :Infographic of a 4-step hydrogen fuel cell: gas input, hydrogen splitting, electron journey, and cathode reunion forming water
Understanding Hydrogen-Powered vehicles fuel cell in depth
But the thing some of you might be wondering now is that, How come the water vapor being produced on both sides of the in the Figure 1.3 Even when the reunion of particles happen only on the Cathode side, where oxygen is pumped into the fuel cell.
To answer that we need to understand the key idea about the Proton Exchange membrane (PEM). Actually the PEM is made up of polymers which is like a thin transparent sheet. For PEM to work efficiently, the most important thing it needs is its environment which should be humid.
Think about the Human lung which needs the moist surface for easier diffusion of oxygen through it. Same as the lungs, the PEM also needs the moist surface for smoother diffusion of protons of hydrogen through it
However the answer is still not clear right? That why? is the water vapor is produced on both sides. To answer that in simpler words - The water vapor produced on the Cathode side gets diffused down its water potential gradient. And this is how the PEM also stays humid without any extra effort or mechanism for keeping the PEM humid
Overcoming the misunderstanding which might be hindering you
Remember those 10th-grade chemistry books we talked about earlier? They often use highly simplified diagrams that make it difficult to understand the leap from basic electrolysis to an actual working fuel cell.
I’ll be honest with you—when I first tried to understand the difference between those textbook setups (figure 1.5) and these advanced fuel cells, I was completely tricked! It left me in a lot of confusion, and you might be struggling with the exact same thing. Let’s decode the difference together so you don't get stuck where I did.
Let's start with a basic question: What is the difference between an Anode and a Cathode? Write your answer down somewhere, whatever you remember from those books….., If your answer was, “A cathode is the negative electrode,” you are in for a surprise. You might be wondering how the idea totally flipped. But don’t worry, once you understand. You can call yourself the fuel cell expert, I guarantee you.
A Cathode is actually identified more by where the reduction (gain of electrons) is happening
Anode is identified by the electrode where the Oxidation (Loss of electrons) is happening
An easy way for you to remember this is -
An Ox = Anode - Oxidation
Red Cat = Reduction - Cathode
The above mnemonics are always true whether it is fuel cell or Electrolysis experiment in Chemistry lab
Advantages and Disadvantages of Hydrogen powered vehicles
In the very starting I mentioned hydrogen as a fuel having some massive achievements however on the other hand some disadvantages too, due to which the world is unable to take hydrogen’s full potential.
Advantages -
Hydrogen is the most efficient fuel
As I showed you the bar graph in the starting, it showed how efficient the Hydrogen is in comparison with other fuels. The main reason behind that is that Hydrogen doesn’t go through the process of combustion in fuel cells as a result most of the energy is converted into electrical energy. This allows the hydrogen to convert most of its energy from chemical energy → Electrical Energy → Movement of engine gyres and tyres.
Zero emission of CO2
This is the biggest advantage of using Hydrogen as fuel. Whereas all other fuel engines whether it is diesel or petrol engine all produce massive amounts of traces of CO2 gas into the environment which are massively contributing towards the increasing global warming. On the other hand Hydrogen powered vehicles only produce water as a product in form of water vapours leaving the tailpipe.
Non Toxic
Old cars are often thought of leaving a dark mocktail of toxic gases behind in the air as they move past you. But guess what, Hydrogen powered cars can be run as long as possible, they are in a good shape and are not rusted. This is because they don’t produce any harmful toxic gases except pure water.
Renewable (If produced by solar or wind energy)
The Hydrogen can be produced renewably using the process of electrolysis, however today most of the hydrogen is being produced non renewably using fossil fuels
Fun Fact - You can try separating Hydrogen and Oxygen from water at your home with very simple kitchen equipments -
This video has step by step details you can watch this hands on experiment
Lower flammability than petrol -
This might contradict with what I said before and gave an example of in the starting about the Hindenburg incident but this is true. That hydrogen is less flammable than petrol. Okay so let’s do some basic maths
Petrol catches fire at even 280°C. This means if petrol comes into contact with even hot engine or exhaust pipe the fuel tank can easily ignite especially in case of an acciddent where fuel tank gets ruptured
Hydrogen is much more robust in the sense of auto ignition. Hydrogen typically needs a temperature of 540°C to ignite which clearly means that hydrogen is less flammable.
Disadvantages -
Non - Renewable (If generated using nuclear fuel or fossil fuels)
This is where it starts to get a little controversial when talking about the hydrogen powered vehicle. This is because when we look at a greater picture today of the hydrogen powered vehicle industry. It doesn’t seem to be Renewable because today most of the Hydrogen comes under a category of grey hydrogen approximately 95%. This means the hydrogen is extracted by the natural gases like methane by heating it. This process of heating and extracting hydrogen is itself non - renewable as fossil fuels are still used for this. This extraction process of hydrogen currently make the whole hydrogen powered vehicles industry non - renewable.
Large fuel tank is required
This is another biggest issue with hydrogen powered vehicles. For instance if you need to drive 500 km (300 miles) with a petrol diesel car, you can easily drive with a fuel tank the size of a microwave.
But if you want to drive the same distance of 500 Km (300 miles) you need a fuel tank of the size of the full-size 40-foot city bus behind your vehicle just to make it to the next town.
That is significantly inefficient and a waste of space.
There might be a new confusion rising up maybe - that if I said” hydrogen is the most efficient fuel in today's date and the energy produced by burning hydrogen is 140KJ/g which is double of any other fuel when burned”. Then why do we need such a large fuel tank?
The answer lies in chemistry. If you see the periodic table you will find that Hydrogen is the first atom and this is the root cause of the issue. Hydrogen is the least dense diatomic gas meaning it takes a vast volume to fit in.
The scientist needs to compress the hydrogen to fit the hydrogen in the tank. This increases pressure in the tank up to 10,000 PSI and currently this is the biggest challenge and too expensive
Very Few Filling stations for Hydrogen powered vehicles
Last but not the least. There are very few hydrogen filling stations in the world currently in 2026 (when I’m writing this). However this is an issue which can be solved over time. This problem also existed with the Electrical car charging stations, but now they are commonly found especially in developed countries if you see!
Conclusion
I feel that hydrogen powered cars are the future of tomorrow’s car industry which will end the era of cars powered by petrol and diesel. Despite so many achievements of the hydrogen powered vehicles there is still a significant amount of pollution still produced by the hydrogen powered vehicles which is by their wheels. Yes you heard it correctly when any car runs on the road the dust is blown off into the air. According to an estimation about 70% of the pollution is caused by the tyres. Here is a table for
reference
Source | Percentage of pollution contributed |
Tyre Wear & Road Dust | ~60% to 70% |
Brake Wear | ~20% to 30% |
Engine Exhaust (Tailpipe) | < 10% |
As you can see only 10% of the pollution is produced by engine exhaust and there is a massive amount of pollution coming from the friction between tyre and road. There is still a need for heavy research on how we can reduce tyre wear & road dust pollution. Until then. I would suggest you to travel shorter distances by bicycle or just take a walk till there. If you want me to create a video on that topic on YouTube or write a blog,you can tell me in the comments below.
Frequently Asked Questions (FAQ)
Q1: Do hydrogen cars actually produce water?
Answer: Yes! When hydrogen and oxygen react inside a fuel cell, the only byproduct is pure water vapour. In fact, if you look closely at the engineering, water vapour exits from both the negative electrode (anode) and positive electrode (cathode) to keep the internal polymer membrane perfectly humid.
Q2: Are hydrogen cars 100% zero-emission?
Answer: The vehicle itself produces zero emissions of CO2 and is completely non-toxic. However, the fuel is only truly renewable if the hydrogen is produced using solar or wind energy. If the hydrogen is generated using fossil fuels (called Grey Hydrogen), the manufacturing process is non-renewable and still creates carbon pollution.
Q3: Is hydrogen gas highly flammable and dangerous in a car crash?
Answer: Surprisingly, hydrogen actually has a lower practical flammability than petrol. Because it is Element #1 and incredibly light, a punctured hydrogen tank will shoot the gas straight up into the atmosphere. Unlike heavy petrol that pools under the car and traps passengers in flames, hydrogen physically escapes the danger zone in seconds.
Q4: Why do hydrogen cars need such a large fuel tank?
Answer: A large fuel tank is required because hydrogen gas has incredibly low volumetric density. Because hydrogen atoms lack heavy neutrons, the gas is extremely "fluffy" and takes up massive amounts of space. To fit enough fuel into the car, engineers must violently compress the gas to 10,000 PSI inside thick, armored carbon-fiber tanks.
Q5: Why aren't hydrogen cars everywhere yet?
Answer: While the technology is incredible, there are three major roadblocks: the technology is currently expensive, the cars require a completely redesigned engine or fuel cell system, and as yet, there are very few 'filling stations' where a car can actually be topped up with hydrogen.
Sources
Published on : 6 March, 2026
Last Edited on : 6 March,2026
Written by: Yuvraj Singh
AS Level Student & Science Enthusiast
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