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

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. This work not only opens up a new avenue for the development of high‐efficiency Pt‐free catalysts but also provides an original approach and insight into the synthesis of PdHx. [ABSTRACT FROM AUTHOR]