Researchers have revealed that semiconductor electrodes can achieve green hydrogen production. They found that semiconductor materials enable the production of green hydrogen through (photo) electrochemistry.
The research team led by the University of Jyväskylä underlined that the novel atomic-level simulations and precise (spectro) electrochemical experiments reveal the basic mechanisms underlying the hydrogen evolution reaction on a prototypical titanium dioxide semiconductor and support the development of new materials for hydrogen production.
Less explored alternatives for hydrogen production
“Unlike traditional metal-based catalysts, semiconductor materials can utilize more common and less expensive elements,” said Professor Karoliina Honkala and Senior Lecturer, Academy Research Fellow.
“However, the development of semiconductor electrodes has been slowed down by the fact that their electrochemical and catalytic properties are not well understood.”
The team also revealed that the semiconductor materials are one possible but relatively little explored alternatives for hydrogen evolution.
Researchers developed a new approach, the constant inner potential density functional theory, which enables the inclusion of the electrode potential in the simulation of semiconductor electrochemistry.
Modeling semiconductor electrodes
“We developed this method two years ago, and it opens new possibilities for modeling semiconductor electrodes,” said Marko Melander from the University of Jyväskylä, who led the research.
“In the present study, we applied the method to the study of the hydrogen evolution reaction on a TiO2 semiconductor electrode. Our simulations showed how and why changing the electrode potential achieves hydrogen production on TiO2. Through the calculations made in collaboration with our partners, we predicted that local charge centers, polarons, form on the TiO2 surface and catalyze the hydrogen evolution.”
Experimental testing and validation of the computational results was a significant challenge that needed the application of highly advanced experimental methods. For example, state-of-the-art photoelectrochemical Raman measurements, in situ electron resonance spectroscopy, and operando photoelectron spectroscopy were used to verify the computational results, according to a press release.
“The experiments carried out by our collaborators were extremely demanding and time-consuming,” explained Honkala.
“Nevertheless, they directly demonstrated and confirmed that changing the electrode potential can be used to create polarons on the TiO2 surface. These charge centers then drive the hydrogen evolution reaction on TiO2 electrodes and probably also on other semiconductors.”
The research team also discovered electrode potential -controlled polaron formation is a previously unknown phenomenon in electrochemistry and does not occur on conventional metal electrodes. It’s believed that this phenomenon could be utilized in future catalyst design and materials development.
“We found that the formation of polarons enables semiconductor electrodes to avoid the so-called scaling relations,” said predict Honkala and Melander.
“On metallic electrodes, these laws limit and constrain the achievable catalytic activity. Our discovery of the potential-dependent polaron formation may lead to new approaches to avoid the scaling relations and thereby improvement in catalyst design.”
