Today's KNOWLEDGE Share:4,000% boost! Eco-friendly hydrogen on the horizon

Today's KNOWLEDGE Share

A team of researchers led by Ryuhei Nakamura at the RIKEN Center for Sustainable Resource Science (CSRS) in Japan has made significant strides in the field of sustainable hydrogen extraction. Their research, published in Nature Catalysis, details an innovative method of extracting hydrogen from water using a custom-made catalyst. By manipulating the catalyst’s 3D structure, they achieved a remarkable increase in stability and extended the catalyst’s lifetime by nearly 4,000%. This breakthrough has profound implications for the establishment of a sustainable hydrogen-based energy economy.

Water electrolysis using proton exchange membranes (PEMs) is a green electrochemical process that splits water into oxygen and hydrogen. The hydrogen produced can be stored and used later, for instance, to power an electric car when combined with a PEM fuel cell. However, PEM electrolysis has limitations that hinder its widespread industrial use, such as in power plants.

The chemical reactions necessary for this process occur in a highly acidic environment, and the most effective catalysts for these reactions are extremely rare earth metals like iridium. Nakamura explains, “Scaling up PEM electrolysis to the terawatt scale would require 40 years’ worth of iridium, which is certainly impractical and highly unsustainable.”

A breakthrough in acid-water electrolysis:

Nearly two years ago, Nakamura and his team developed a groundbreaking process that enabled acid water electrolysis without relying on rare earth metals. By inserting manganese into a cobalt oxide lattice, they created a process that depended solely on common and sustainable earth metals. Despite the success, the process was not as stable as required in a PEM electrolyzer. Building on their previous discovery, they have now developed a longer-lasting, earth-abundant catalyst.

The new catalyst is a form of manganese oxide (MnO2). The researchers found that the reaction stability could be increased over 40 times by altering the catalyst’s lattice structure. Oxygen in the 3D lattice structure of manganese oxide comes in two configurations: planar and pyramidal. The planar version forms stronger bonds with manganese, and the researchers discovered that increasing the amount of planar oxygen in the lattice significantly enhanced catalytic stability.

Testing and results:

The team tested four different manganese oxides, which varied in the percentage of planar oxygen. When using the version with the highest achievable percentage, 94%, the critical oxygen evolution reaction could be maintained in acid for one month at 1000 mA/cm2. The total amount of charge transferred in this case was 100 times more than anything seen in previous studies.

When tested in a PEM electrolyzer, water electrolysis could be sustained for about six weeks at 200 mA/cm2. The total amount of water electrolyzed in this time period, and therefore the amount of hydrogen produced, was ten times more than has been achieved in the past with other non-rare metal catalysts. Co-first author Shuang Kong notes, “Surprisingly, the improved stability did not come at a cost in activity, which is usually the case. A PEM water electrolyzer that generates hydrogen with an earth-abundant catalyst at a rate of 200 mA/cm2 is highly efficient.”

The road ahead:

While there is still work to be done, the researchers are optimistic about the potential for tangible, real-world applications that contribute to carbon neutrality. Industrial applications typically require a stable current density of 1000 mA/cm2 that lasts for several years, rather than a month. However, Nakamura is confident about the future, stating, “We will continue to modify catalyst structure to increase both current density and catalyst lifetime. In the long-term, our efforts should help achieve the ultimate objective for all stakeholders – to conduct PEM water electrolysis without the use of iridium.”

source:interestingenginnering