Pt(OH)x Coordination Engineering of Bifunctional Pt/NiFe LDH-O Catalyst for Robust Water Splitting.

Abstract

Modulating the coordination environment of metal active sites and adjacent atoms significantly enhances the catalytic activity of heterogeneous catalysts owing to the local synergistic effect between metal sites and supports. While layered double hydroxide (LDH)-supported Pt catalysts exhibit complementary advantages and exceptional performance in overall water splitting (OWS), the absence of a robust coordination structure between Pt and LDH constrains their activity and stability. Herein, we report a coordination engineering strategy to alter the coordination structure of Pt on the surface of NiFe LDH using atomic layer deposition (ALD) for OWS. The synthesized Pt/NiFe LDH-O catalyst, featuring the 2-coordinate Pt-OH and 6-coordinate Pt-Pt, exhibits a η₁₀ = 14 mV for hydrogen evolution reaction (HER), a η₁₀₀ = 287 mV for oxygen evolution reaction (OER), and an effective OWS activity (η₁₀ = 1.496 V) for over 200 h. Combining structural and electrochemical characterizations, we confirmed that the coordination engineering affected the nucleation and growth of Pt on NiFe LDH, leading to a decrease of Pt-OH coordination and an increase of Pt-Pt coordination, thereby enhancing the hydrolysis capability of Pt and shifting the rate-determining step (RDS) from the Volmer step to the Heyrovsky step, which contributed to the excellent OWS performance. The density functional theory (DFT) results demonstrated that the electronic structure of NiFe LDH is considerably regulated by an increase in Pt-Pt coordination, facilitating charge redistribution. Our investigation provides deep insights into the coordination regulating the electrocatalytic activity of LDH-supported metal catalysts.