Figure 4.

A) Structural scheme of phosphate, phosphite, and hypophosphite‐intercalated NiFe‐LDH a); b) the XRD patterns for standard NiFe‐LDH and as‐synthesized CO₃ ²⁻/NiFe‐LDH, H₂PO₂ ⁻+CO₃ ²⁻/NiFe‐LDH, H₂PO₂ ⁻/NiFe‐LDH, HPO₃ ²⁻/ NiFe‐LDH, and PO₄ ³⁻/NiFe‐LDH; c) FTIR spectra of the all as‐synthesized NiFe‐LDH nanosheets. B) TEM images of a) PO₄ ³⁻/NiFe‐LDH, b) HPO₃ ²⁻/ NiFe‐LDH, c) H₂PO₂ ⁻/NiFe‐LDH, and d) CO₃ ²⁻/NiFe‐LDH; insets show the representative thickness of the corresponding LDH. C) Electrocatalytic performance of as‐synthesized samples: a) polarization curves of H₂PO₂ ⁻/NiFe‐LDH, H₂PO₂ ⁻+CO₃ ²⁻/NiFe‐LDH, and CO₃ ²⁻/NiFe‐LDH; b) polarization curves of PO₄ ³⁻/NiFe‐LDH, HPO₃ ²⁻/NiFe‐ LDH, H₂PO2⁻/NiFe‐LDH, and CO₃ ²⁻/NiFe‐LDH; c) corresponding Tafel plots; d) C _dl calculations for the four catalysts. Reproduced with permission.69 Copyright 2017, Springer Link.