Deciphering the alternating synergy between interlayer Pt single-atom and NiFe layered double hydroxide for overall water splitting

Single-atom catalysts (SACs) have enormous significance in heterogeneous catalysis. However, understanding how SACs function at the molecular level remains a huge challenge. Here, we report a general approach to anchor Pt single-atom intercalated in layered double hydroxide (LDH) and decipher the alternating synergy between Pt single-atom and Ni3Fe LDH support for overall water splitting. Aided with Tafel slope, interface species evolution and control experiments, operando electrochemical impedance spectroscopy (EIS) can distinguish interface charge transport and elementary reactions during hydrogen and oxygen evolution reactions (HER and OER). For HER, interlayer Pt single-atom vastly enhances electron transferability of LDH support, and Ni3Fe LDH support accelerates water dissociation, thus resulting in a mixture of mechanisms (Heyrovsky–Volmer and Tafel–Volmer) in 1 M KOH. For OER, interlayer Pt single-atom not only prompts active phase transition from NiFe LDH to Ni2+δFe3+ζOxHy, but also optimizes OER intrinsic activity of Ni2+δ–O–Fe3+ζ in Ni2+δFe3+ζOxHy. Overall, we provide a referential paradigm for SACs synthesis strategy and unscrambling its alternating synergy.