The Basics of Hydrogen Generation

July 22, 2013

For most of us chemistry lessons are a dim and distant memory, so an article about the workings of a hydrogen gerator might seem like a horrifying reminder of school days past. In fact, the basic principles behind H2 generation are surprisingly easy to grasp – one of the things that makes hydrogen such a fascinating source of renewable energy. We'll use the refueling station of the i-H2GO as an example of a simple system.

 

Let's start with a quick recap about water. Water's chemical name is, of course, H2O, which just means two parts hydrogen to one part oxygen. Due to the way these two elements are bonded, the hydrogen atoms have a very slight positive charge while the oxygen carries a slight negative charge. However, as long as the molecules remain bonded the overall charge of water is neutral. Therefore, one of the easiest and cleanest ways to generate hydrogen is just to split water into its component atoms – separate out the hydrogen from the oxygen. This is where the refueling station comes in.

 

The i-H2GO refueling station us a simplified version of a process that happens on a much larger scale in certain kinds of industrial generators. The key component of the station is the ‘electrolyzer’ – this is the device that separates the hydrogen from the oxygen. A basic electrolyzer consists of: a negative electrode called a cathode, a positive electrode called an anode, a battery to power the electrodes and water with soluble salt.

 

The principle is straightforward. Once the water is poured in and the battery is switched on, the positively charged hydrogen particles (ions) are attracted to the cathode while the negatively charged oxygen heads for the anode. The reason for the salt is that pure water is a poor conductor of electricity – about one millionth as conductive as salt water. The i-H2GO refueling station uses the exact same principle but has an electrolyzer that’s a little fancier. There are three layers – top and bottom are the anode and the cathode, and in the middle is a polymer electrolyte membrane (PEM) which replaces the salt solution. The membrane is a fantastic medium for the hydrogen ions to travel through and means we can avoid contaminating the water. However, it also requires a layer of platinum either side of the membrane to act as a catalyst.

 

The hydrogen builds up around the cathode and quickly its forced through a tube leading from the cathode to the gas chamber under the plunger. As the chamber fills the plunger is pushed upwards. The oxygen leaves the system via the bubble valve, hence the tiny bubbles that emerge when therefueling station is up and running.

 

So there you have the essential principles behind generating hydrogen from water. Ideally the battery that charges the electrolyzer will itself be charged by renewable energy – the iH2GO comes with a solar panel for just this reason. Then, every stage of the process is eco-friendly and, more importantly, self-sustaining.

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