Abstract
AbstractThe requirements for beneficial materials restructuring into a higher performance oxygen evolution reaction (OER) electrocatalyst are still a largely open question. Here erythrite (Co3(AsO4)2·8H2O) is used as a Co‐based OER electrocatalyst to evaluate its catalytic properties during in situ restructuring into an amorphous Co‐based catalyst in four different electrolytes at pH 7. Using diffraction, microscopy, and spectroscopy, a strong effect in the restructuring behavior is observed depending of the anions in the electrolyte. Only carbonate electrolyte can activate the catalyst material, which is related to its slow restructuring process. While the catalyst turnover frequency (TOF) undesirably reduces by a factor of 28, the number of redox active sites continuously increases to a factor of 56, which results in an overall twofold increase in current of the restructured catalyst after 800 cycles. The activation is attributed to an adequate local order, a high Co oxidation state close to 3+, and a high number of redox‐active Co ions. These three requirements for beneficial restructuring provide new insights into the rational design of high‐performance OER catalysts by electrochemical restructuring.
Highlights
The widespread transition use of renewable energy requires efficient energy storage solutions due to the fluctuating energy production from renewable sources such as sunlight or wind
The final activated material owns an adequate local order, a high Co oxidation state and a high number of redox-active Co ions, which we identify as the trinity for enhancing the oxygen evolution reaction (OER) activity
For the use of carbon-based fuels as energy storage, near-neutral pH operating conditions are desirable to couple the anodic OER to the cathodic CO2 reduction reaction since CO2-enrichment of the electrolyte leads to pH values close to 7.[4,5] Amorphous transition-metal oxides have shown outstanding catalytic properties at neutral pH. [6,7,8] Thanks to their unique atomic arrangement, these materials own structural flexibility and distinctive coordinated metal center.[9,10,11]
Summary
The widespread transition use of renewable energy requires efficient energy storage solutions due to the fluctuating energy production from renewable sources such as sunlight or wind. These tracking experiments were based on the methods and properties most commonly used to understand the electrochemical restructuring process.[10,12,15,40,46] How the changes of metal redox, loss of crystallinity, and anionic exchange relate to each other has been an important open question for understanding the mechanism of electrochemical restructuring In this regard, these three indicators were compared as a function of cycling in borate, carbonate, and phosphate electrolytes to identify trends and correlations (Figure 3). Supporting Information Supporting Information is available from the Wiley Online Library or from the author
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