Scientists develop a cheap and efficient photocatalyst for hydrogen production

Due to a specific preparation method that leads to the formation of vacancies in the material structure, the material can significantly increase photocatalytic hydrogen production compared to commercially used titanium dioxide. The material is also inexpensive, environmentally friendly, and can easily be prepared and activated using solar radiation. The results of the research have been published in the journal Scientific Reports.

“Our intention was to develop a graphitic carbon nitride suitable for hydrogen generation. The literature shows that its properties can be easily improved by vacancies. In such a process, no additional elements are added to the material, but instead some atoms are removed to create voids in the structure, i.e. vacancies. We found that their formation increased the efficiency of the material by about four times more than if it had been prepared in the conventional way.  In addition, it turned out that compared to titanium dioxide, a classical photocatalyst, our material is 60 percent more efficient,” said the first and corresponding author of the study, Petr Praus from the Institute of Environmental Technology, which is part of CEET, and the Department of Chemistry and Physico-Chemical Processes at the Faculty of Materials Science and Technology at VSB-TUO.

This method is very simple, cheap and environmentally friendly. While titanium dioxide needs to deliver ultraviolet radiation to function, which increases the cost of the process, graphitic carbon nitride is able to absorb visible radiation. In addition, the researchers chose melamine, a commonly available and inexpensive chemical, as a feedstock. Therefore, the developed nanomaterial also has great potential for practical applications.

“The material is cutting edge and is being researched by hundreds of teams around the world. However, no one has yet observed significant hydrogen yields due to vacancy complexes, and we are the first to do so. In fact, using positron annihilation spectroscopy, we have found that vacancies do not form individually, but always in complexes. The mechanism is not yet completely clear, and we are working on it through mathematical modelling. However, it can be assumed that the vacancy complexes are related to the increase in material efficiency,” added Professor Praus.

Graphitic carbon nitride is a metal-free semiconductor with a narrow band gap of around 2.7 eV (459 nm), which implies that it is capable of absorbing visible radiation. These properties make the material interesting for various applications, not only in photocatalysis but also in solar cell manufacturing, imaging, biotherapy and detection of certain compounds.

Text: Martina Šaradínová, PR specialist for R&D
Photo: Reactor for photocatalytic hydrogen production
ImageSME: SME (BSE + SE) micrographs of CN (left) and CN-Ar0 (right). Source: PP archive