Could Photocatalytic Water Splitters be the Future for Green Hydrogen?

While hydrogen may appear to be a green fuel, the truth is that most hydrogen is damaging to the climate due to how it is produced. But while researchers continue to find ways of generating green energy, photocatalytic converters may be the solution. What challenges does hydrogen face, what is a photocatalytic converter, and could a recent development make them a practical reality?

What challenges does hydrogen face?

If the Russo-Ukraine war has taught the energy sector anything, it’s that the age of fossil fuels will soon come to an end. Being reliant on another nation’s natural resources, which will eventually disappear, is bad for the environment, political stability, and national defence, which is why many are now turning to renewable sources of energy that do not rely on foreign nations with ulterior motives.  

However, the fact that solar and wind, the two most dominant renewable energy sources, are unreliable means that no nation on the planet has been able to rely solely on these. In addition to the problems presented by typical renewable energy sources, electric vehicles (EVs) also present challenges. While they may not consume fossil fuels during their operation, they require electricity to charge, which almost always comes from fossil fuels. Furthermore, the massive weight of batteries and the need for rare minerals can see vast amounts of environmental damage, which defeats the purpose of EVs.

Hydrogen is one solution to this energy problem as its combustion results in no CO2; it can be easily stored and can even be used to directly generate electricity in EVs via fuel cells that recombine hydrogen with oxygen. In fact, hydrogen is a far more ideal fuel source for larger vehicles such as trucks and lorries due to the energy density of hydrogen compared to batteries (this is why Tesla trucks are doomed to fail). 

But, as green as hydrogen may appear, hydrogen has a dark side that can make it more polluting than using fossil fuels alone. Two common methods for generating hydrogen exist, Steam Methane Reforming (SMR) and direct electrolysis of water. With SMR, methane is combined with steam and a catalyst to separate the hydrogen from methane while simultaneously creating CO2. Unless this CO2 is captured, the process of SMR results in CO2 emissions.

In electrolysis, electricity passed through water will result in the production of hydrogen and oxygen. If this electricity is derived from fossil fuels, the massive inefficiencies in this process will result in more CO2 being produced compared to just burning fossil fuels for direct energy use. If renewable energy sources are used, the unreliability of renewable energy can make hydrogen production extraordinarily challenging and, therefore, uneconomical.

What are photocatalytic converters?

One solution that may help with the production of green hydrogen is a device called a photocatalytic converter. Simply put, these devices can sustain a chemical reaction by using light as an energy source. While the term photocatalytic may sound man-made, a natural photocatalytic found in plants, called chloroplast, convert sunlight, water, and CO2 into oxygen and glucose, which drives all life on earth.

But other photocatalytic processes exist, and one that researchers have their eye on is the reaction of water with indium gallium nitride. With the combination of raised temperatures and sunlight, this material can be used to generate hydrogen. If natural light is used, the resulting hydrogen is green, as there is no need for energy derived from fossil fuels. 

However, one challenge such a production method faces is the low efficiency of indium gallium nitride. Given a unit area of land, installing solar panels with efficiencies exceeding 20% can be more economical instead of installing hydrogen generators that produce less than 6% in equivalent energy. 

Could a recent development in photocatalytic converters help hydrogen production?

Recently, researchers have published a paper whereby they have been able to increase the efficiency of an indium gallium nitride photocatalytic converter to over 9%. While this number may seem low, it is a major step forward in green hydrogen production that doesn’t rely on fossil fuels and other energy sources (besides light). 

While the process of increasing the efficiency is somewhat complex, the method used by the researchers primarily involves raising the water temperature to 70 degrees and concentrating sunlight. But instead of heating the water with traditional heaters, the researchers utilised the natural heating effect from sunlight to raise the temperature. Because this IR light isn’t used during the hydrogen production processes, thus making more use of sunlight. Furthermore, the researchers noted that the efficiency of the production process drops to 7% when using tap water and 6% when using seawater. This indicates that future systems could be placed offshore that gather sunlight, generate hydrogen, and do so entirely on their own, thanks to the abundant nature of the sun and water.

Whether this process will dominate the future hydrogen production market is still being determined as processes such as electrolysis can produce vast amounts of hydrogen in a short amount of time, but what is clear is that hydrogen will become a critical fuel source in the future.