Cyanogel‐Induced Facile Synthesis of Palladium Hydride for Electrocatalytic Oxygen Reduction

Abstract

Palladium hydride (PdHx) is one of the well‐known electrocatalytic materials, yet its synthesis is still a challenge through an energy‐efficient and straightforward method. Herein, we propose a new and facile cyanogel‐assisted synthesis strategy for the preparation of PdH0.649 at a mild environment with NaBH4 as the hydrogen source. Unlike traditional inorganic Pd precursors, the unique Pd‐CN‐Pd bridge in Pdx[Pd(CN)4]y·aH2O cyanogel offers more favourable spatial sites for insertion of H atoms. The characteristic three‐dimensional backbone of cyanogel also acts as a support scaffold resulting in the interconnected network structure of PdH0.649. Due to the incorporation of H atoms and interconnected network structure, the PdH0.649 achieves a high half‐wave potential of 0.932 V, a high onset potential of 1.062 V, and a low activation energy, as well as a long‐term lifetime for oxygen reduction reaction. Theoretical calculation demonstrates a downshift of the d‐band centre of Pd in PdH0.649 owing to the dominant Pd‐H incorporation that weakens the binding energies of the *OH intermediate species. Zn‐air batteries (ZAB) based on PdH0.649 exhibits high power density, competitive open circuit voltage, and good stability, exceeding that of commercial Pt black.