Direct Detection of Fe^VI Water Oxidation Intermediates in an Aqueous Solution

Abstract

In situ detection of highly‐oxidized metal intermediates is the key to identifying the active center of an oxygen evolution reaction (OER) catalyst, but it remains challenging for NiFe‐based catalysts in an aqueous solution under working conditions. Here, by utilizing the dynamic stability of the FeVIO42− intermediates in a self‐healing water oxidation cycle of NiFe‐based catalyst, the highly‐oxidized FeVI intermediates leached into the electrolyte are directly detected by simple spectroelectrochemistry. Our results provide direct evidence that Fe is the active center in NiFe‐based OER catalysts. Furthermore, it is revealed that the incorporation of Co into NiFe‐based catalyst facilitates the formation of FeVI active species, thus enhancing the OER activity of NiCoFe‐based catalyst. The insights into the mechanisms for the sustainable generation of FeVI active species in these NiFe‐based catalysts lay the foundation for the design of more efficient and stable OER catalysts.

Stable seawater oxidation with a self-healing oxygen-evolving catalyst

“…It has been proved that the self-healing of Fe active centers in the NiCoFe-B i catalyst is crucial to achieving stable freshwater oxidation under highly alkaline conditions. 29,37 Here, we believe that the activation of the selfhealing mechanism is also vital to the activity and stability of seawater oxidation under highly alkaline conditions. To prove this, we conducted a series of electrochemical tests concerning the effect of Fe(II) ions added to the alkaline artificial seawater.…”

“…S15, ESI†), the OER activity declined significantly compared with the NiCoFe-B i , because Co not only facilitates Fe redeposition but also promotes the formation of highly-oxidized Fe( vi ) intermediate species. 37 Furthermore, the self-healing effect was only found for Fe( ii ) ions added to the alkaline seawater, but not for the Ni( ii ) or Co( ii ) ions (Fig. S16, ESI†).…”

Bias-free photoelectrochemical H2O2 production with a solar-to-fuel conversion efficiency of 2.33%

“…The gradient Mg:Ta 3 N 5 photoanode was fabricated following our previously reported method. 19 Aer modifying the surface of the Mg:Ta 3 N 5 photoanode with a highly efficient borateintercalated nickel cobalt iron oxyhydroxide (NiCoFe-B i ) OER co-catalyst, 20,21 the PEC performance of the photoanode for the OER half reaction was tested in a standard three-electrode conguration. As shown in Fig.…”

Identifying Fe as OER Active Sites and Ultralow‐Cost Bifunctional Electrocatalysts for Overall Water Splitting

“…[ 23 ] Nevertheless, some studies found that the high activity of Ni of unary Ni‐based catalysts may be an illusion—it is the Fe impurities in the electrolyte that dramatically improve the performance. [ 24 ] Moreover, shorter FeO bonds [ 25–26 ] and Fe 4+[ 27–29 ] were observed during the OER in binary FeNi‐based OER catalysts, providing strong evidence for Fe being the active site.…”