Photo: Schematic
diagram of the step-by-step synthesis process for the preparation of Ti.MoP.
Courtesy: Korea Institue of Science and Technology(KIST).
The key to
promoting the hydrogen economy represented by hydrogen vehicles is to produce
hydrogen for electricity generation at an affordable price. Hydrogen production
methods include capturing by-product hydrogen, reforming fossil fuel, and
electrolyzing water. Water electrolysis in particular is an eco-friendly method
of producing hydrogen, in which the use of a catalyst is the most important
factor in determining the efficiency and price competitiveness. However, water
electrolysis devices require a platinum (Pt) catalyst, which exhibits
unparalleled performance when it comes to speeding up the hydrogen generation
reaction and enhancing long-term durability but is high in cost, making it less
competitive compared to other methods price-wise.
There are
water electrolysis devices that vary in terms of the electrolyte that dissolves
in water and allows current to flow. A device that uses a proton exchange
membrane (PEM), for instance, exhibits a high rate of hydrogen generation
reaction even with the use of a catalyst made of a transition metal instead of
an expensive Pt-based catalyst. For this reason, there has been a great deal of
research on the technology for commercialization purposes. While research has
been focused on achieving high reaction activity, research on increasing the
durability of transition metals that easily corrode in an electrochemical
environment has been relatively neglected.
The Korea
Institute of Science and Technology (KIST) announced that a team headed by Dr.
Sung-Jong Yoo from the Center for Hydrogen-Fuel Cell Research developed a
catalyst made of a transition metal with long-term stability that could improve
hydrogen production efficiency without the use of platinum by overcoming the
durability issue of non-platinum catalysts.
The
research team injected a small amount of titanium (Ti) into molybdenum
phosphide (MoP), a low-cost transition metal, through a spray pyrolysis
process. Because it is inexpensive and relatively easy to handle, molybdenum is
used as a catalyst for energy conversion and storage devices, but its weakness
includes the fact that it corrodes easily as it is vulnerable to oxidation.
In the
case of the catalyst developed by the research team at KIST, it was found that
the electronic structure of each material became completely restructured during
the synthesis process, and it resulted in the same level of hydrogen evolution
reaction (HER) activity as the platinum catalyst. The changes in the electronic
structure addressed the issue of high corrosiveness, thereby improving
durability by 26 times compared to existing transition metal-based catalysts.
This is expected to greatly accelerate the commercialization of non-platinum
catalysts.
Dr. Yoo of
KIST said, "This study is significant in that it improved the stability of
a transition metal catalyst-based water electrolysis system, which had been its
biggest limitation. I hope that this study, which boosted the hydrogen
evolution reaction efficiency of the transition metal catalyst to the level of
platinum catalysts and at the same time improved the stability will contribute
to earlier commercialization of eco-friendly hydrogen energy production
technology."