Direct observation of active catalyst surface phases and the effect of dynamic self-optimization in NiFe-layered double hydroxides for alkaline water splitting

Abstract

Identification of active catalyst surface phases and the influence of dynamic self-optimization in NiFe-layered double hydroxides for alkaline water splitting.

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

“…The Ni 2p 1/2 and Ni 2p 3/2 spectra were further deconvoluted into four peaks in which two peaks at binding energies of 855.2 and 872.6 eV are assigned to Ni 2+ , and another two peaks at 856.1 and 873.7 eV could be ascribed to high valence of Ni 3+ . [39] In line with the CV characterization in Figure 4a, the O-NiFe(II,III)-LDH exhibits a noticeable increase in high valence of Ni with respect to pristine NiFe(II,III)-LDH. For the H-NiFe(II,III)-LDH sample, it indicates that Ni 2+ is easily transformed into Ni 3+ by appling a OER or HER polarization potential on working electrode.…”

“…As shown in Figure a, in the Ni 2p XPS spectrum, there are two major spin‐orbit peaks (Ni 2p 1/2 and Ni 2p 3/2 ) besides two shakeup satellite peaks located at 861.7 and 879.7 eV. The Ni 2p 1/2 and Ni 2p 3/2 spectra were further deconvoluted into four peaks in which two peaks at binding energies of 855.2 and 872.6 eV are assigned to Ni 2+ , and another two peaks at 856.1 and 873.7 eV could be ascribed to high valence of Ni 3+ . In line with the CV characterization in Figure a, the O‐NiFe(II,III)‐LDH exhibits a noticeable increase in high valence of Ni with respect to pristine NiFe(II,III)‐LDH.…”

“…In brief, for HER process, the Ni and Fe sites can participate in the water dissociation and they synergically optimize the reaction route, leading to the improvement of HER activity. [39] But especially for OER process, the valence state of Ni species in LDH would increase dramatically, and the Fe species at Ni 2+ site formed Fe-O-Fe motifs which are beneficial to stabilize high-valence Fe during OER. [32] The high-valence metal species are responsible for the OER activity, whereas it is still difficult to determine which one is the exact OER active site.…”

Asymmetric Air Cathode Design for Enhanced Interfacial Electrocatalytic Reactions in High‐Performance Zinc–Air Batteries

“…[15] Meanwhile the peak at 1075 cm −1 indicates the presence of intercalated carbonate ions. [16] In contrast, the spectrum of GDF exhibits no obvious peaks at the above bands, verifying that the chemical components on the two faces are completely different.…”

“…The spectrum of OCF clearly shows the characteristic peaks of brucite‐like Ni(OH) 2 as well as a peak corresponding to incorporated FeOOH (Fe 3+ ), which indicates low crystallinity 15. Meanwhile the peak at 1075 cm −1 indicates the presence of intercalated carbonate ions 16. In contrast, the spectrum of GDF exhibits no obvious peaks at the above bands, verifying that the chemical components on the two faces are completely different.…”