fig18

Figure 18. (A) The k²x(k) oscillation curves and Fourier transform curves. Operando SR-FTIR measurements in the range of 600-4,000 cm^-1, reproduced with permission^[129]. Copyright 2021, Science Publishing Group; (B) The band position and peak intensity evolution of infrared signals assigned to NiO^* during OER, where the absorbance under the potential of 1.3 V is defined as “1” and absorbance under other potentials is plotted relative to that at 1.3 V, reproduced with permission^[92]. Copyright 2021, Wiley-VCH; (C) Operando Raman spectra of FeNi DHBQ/NF, reproduced with permission^[130]. Copyright 2023, Elsevier; (D) The in situ Raman spectra of Ni-MOFs NS along with CV test, reproduced with permission^[131]. Copyright 2023, Elsevier. SR: Synchrotron-radiation; FTIR: Fourier transform infrared spectroscopy; OER: oxygen evolution reaction; DHBQ: dihydroxy-1,4-benzoquinone; NF: nickel foam; MOF: metal-organic framework; NS: nanoarrays; CV: cyclic voltammetry.