Conventional catalysts for producing hydrogen through water electrolysis typically consist of valuable metals, making them quite costly. Nonetheless, more affordable options have emerged, such as cobalt-manganese catalysts, which exhibit excellent activity and long-term stability. The crucial element that contributes to these qualities is manganese. For a significant duration, the reason behind manganese’s important role remained a mystery. Recent research has finally unraveled the underlying mechanism.
Hydrogen, an important energy carrier, can be derived from water via electrolysis, particularly effective with cobalt spinel electrocatalysts that incorporate manganese. Despite this efficiency, the reasons were previously unclear.
Traditional catalysts for hydrogen generation through water electrolysis often involve precious metals, resulting in high costs. Fortunately, more economical alternatives, like cobalt-manganese catalysts, have come into play. These catalysts not only exhibit high activity but are also stable over extended periods. The presence of manganese is vital for these characteristics, yet its critical role was not understood for quite some time. Researchers from various German institutions, including Ruhr University Bochum, the Max Planck Institutes for Sustainable Materials and Chemical Energy Conversion, Forschungszentrum Jülich, and the University of Duisburg-Essen, have now uncovered this mechanism. Their findings were published in the journal Advanced Energy Materials on October 7, 2024.
The synergy of multiple methods led to significant breakthroughs
Through the application of electrical voltage, water is divided into hydrogen and oxygen, with the oxygen evolution reaction being the limiting factor. Consequently, scientists are in pursuit of the most effective catalysts for this phase. Typically, cobalt electrocatalysts, when featuring a specific geometric configuration known as the spinel structure, are not only inefficient but also lack long-term stability. Fortunately, this scenario changes dramatically with the addition of manganese.
The research team employed various techniques to meticulously examine the interactions occurring on the catalysts’ surface during water electrolysis. Their collaborative effort, within the framework of the Collaborative Research Center 247 “Heterogeneous Oxidation Catalysis in the Liquid Phase,” allowed them to observe the surface processes from different angles. “Pooling resources from several institutes enabled us to explore the electrode surface interactions using diverse methods, and this combination proved pivotal,” states Professor Tong Li, who oversees Atomic-Scale Characterization at Ruhr University Bochum. An expert in atomic probe tomography, she utilizes this technique to visualize material distribution at an atomic level, in conjunction with transmission electron microscopy, X-ray fine structure absorption, and X-ray photoemission spectroscopy.
Mangnesium’s behavior: akin to a bus passenger’s movements
The research team discovered that manganese dissolves from the cobalt spinel surface during the reaction and subsequently reattaches itself. “It’s similar to a passenger on a bus who keeps getting on and off,” Professor Tong Li explains.
