New, highly stable catalyst can help turn water into fuel

Breaking the links between oxygen and hydrogen in water could be a sustainable solution for creating hydrogen, but it was difficult to find an economically viable technique for this. The researchers announced the discovery of a new hydrogen generating catalyst, which can remove many obstacles: abundance, stability under acidic conditions and efficiency.

In the newspaper Angewandte Chemie, researchers at the University of Illinois at Urbana-Champaign report an electrocatalytic material made from the mixture of metal compounds with a substance called perchloric acid.

Electrolysers use electricity to break water molecules into oxygen and hydrogen. The most effective of these devices use corrosive acids and electrode materials made of metal compounds of iridium oxide or ruthenium oxide. Iridium oxide is the most stable of the two, but iridium is one of the least abundant elements on Earth. The researchers are therefore looking for an alternative material.

"Much of the previous work was done with electrolysers made from two elements: a metal and oxygen," said Hong Yang, co-author and professor of chemical and biomolecular engineering at l & # 39; Illinois. "In a recent study, we discovered that if a compound contains two metallic elements – yttrium and ruthenium – and oxygen, the speed of division of water by velocity increases. "

Yao Qin, co-author and former member of Yang's group, first experimented with the process of making this new material using different acids and heating temperatures to increase the speed of the fractionation reaction of the material. ;water.

The researchers found that when they used perchloric acid as a catalyst and allowed the mixture to react under the effect of heat, the physical nature of the product containing yttrium ruthenate changed.

"The material has become more porous and also has a new crystalline structure, different from any solid catalysts we've made before," said Jaemin Kim, lead author and postdoctoral researcher. The new porous material developed by the team – a pyrochlore oxide of yttrium ruthenate – can fractionate water molecules at a higher rate than the current industry standard.

"Because of the increased activity that it promotes, a porous structure is highly desirable when it comes to electrocatalysts," Yang said. "These pores can be synthetically produced with nanoscale templates and ceramic materials, but they can not withstand the high temperatures required to make high quality solid catalysts."

Yang and his team examined the structure of their new material under the electron microscope and found that it was four times more porous than the original yttrium ruthenate developed in an earlier study and three times more than the iridium oxides. ruthenium used in commerce.

"It was surprising to find that the acid we chose as a catalyst for this reaction was found to improve the structure of the material used for the electrodes," Yang said. "This achievement was fortuitous and very precious to us."

The next steps for the group are to fabricate a lab-scale device for additional testing and to continue to improve porous electrode stability in acidic environments, Yang said.

"The stability of the electrodes in the acid will always be a problem, but we think we have found something new and different compared to other work in this area," Yang said. "This type of research will have a huge impact on the generation of hydrogen for sustainable energy in the future."

Pei-Chieh Shih graduate student Zaid Al-Bardanand and Argonne National Laboratory researcher Cheng-Jun Sun also contributed to this research.

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More information:
Jaemin Kim et al, A Porous Pyrochlore Y2 [Ru1.6 Y0.4 ]O7-δ electrocatalyst for increased performances with respect to the oxygen evolution reaction in acidic medium, Angewandte Chemie International Edition (2018). DOI: 10.1002 / anie.201808825