Application of In Situ Techniques for the Characterization of NiFe‐Based Oxygen Evolution Reaction (OER) Electrocatalysts

Abstract

Developing high-efficiency and affordable electrocatalysts for the sluggish oxygen evolution reaction (OER) remains a crucial bottleneck on the way to the practical applications of rechargeable energy storage technologies and water splitting for producing clean fuel (H ). In recent years, NiFe-based materials have proven to be excellent electrocatalysts for OER. Understanding the characteristics that affect OER activity and determining the OER mechanism are of vital importance for the development of OER electrocatalysts. Therefore, in situ characterization techniques performed under OER conditions are urgently needed to monitor the key intermediates together with identifying the OER active centers and phases. In this Minireview, recent advances regarding in situ techniques for the characterization of NiFe-based electrocatalysts are thoroughly summarized, including Raman spectroscopy, X-ray absorption spectroscopy, ambient pressure X-ray photoelectron spectroscopy, Mössbauer spectroscopy, Ultraviolet-visible spectroscopy, differential electrochemical mass spectrometry, and surface interrogation scanning electrochemical microscopy. The results from these in situ measurements not only reveal the structural transformation and the progressive oxidation of the catalytic species under OER conditions, but also disclose the crucial role of Ni and Fe during the OER. Finally, the need for developing new in situ techniques and theoretical investigations is discussed to better understand the OER mechanism and design promising OER electrocatalysts.

Fe2+‐Doped Layered Double (Ni, Fe) Hydroxides as Efficient Electrocatalysts for Water Splitting and Self‐Powered Electrochemical Systems

“…Among extensive research in non‐noble electrocatalysts utilized in alkaline condition, Fe‐doped nickel‐based (oxy)‐hydroxides (NiFe‐O x H y ) show impressive oxygen evolution reaction (OER) reactivity with complex catalytic mechanisms . However, for NiFe‐O x H y , it still exhibits large overpotential (η) for practical large‐scale application.…”

Metal–Organic Frameworks Based Electrocatalysts for the Oxygen Reduction Reaction

“…Operando in situ monitoring the growth of MOFs and the transformation process to derivatives is essential for developing new electrocatalysts. Advanced testing techniques combining electrochemical measurements with in situ spectroscopy (Fourier‐transform infrared spectroscopy (FT‐IR), Raman, X‐ray photoelectron spectroscopy (XPS), and EXAFS) or in situ scanning probe microscopy can be helpful in the real‐time analysis of the dynamic reaction mechanism of ORR …”

“…Operando in situ monitoring the growth of MOFs and the transformation process to derivatives is essential for developing new electrocatalysts. Advanced testing techniques combining electrochemical measurements with in situ spectroscopy (Fourier‐transform infrared spectroscopy (FT‐IR), Raman, X‐ray photoelectron spectroscopy (XPS), and EXAFS) or in situ scanning probe microscopy can be helpful in the real‐time analysis of the dynamic reaction mechanism of ORR With the advances of computer science and quantum chemistry, the combination of experimental and theoretical studies will give new insights into the synergetic effects and create many new opportunities for the discovery and breakthrough in advanced electrocatalysts …”

Bimetallic Metal‐Organic Framework‐Derived Nanosheet‐Assembled Nanoflower Electrocatalysts for Efficient Oxygen Evolution Reaction

“…OER is a kernel process limited by the sluggish kinetics due to its four‐electron mechanism. Among all the potential and applied electrocatalysts, RuO 2 and IrO 2 are the most prominent electrocatalysts . Whereas, the scarcity, high cost and instability restrict their extensive application, which requires cost effective and abundant replacement for them…”