Hierarchical PdNi alloy nanochains coupled with Ni(OH)2 nanosheets to enhance CO-poisoning resistance for the methanol oxidation reaction

Abstract

Hybridizing Pd-based electrocatalysts with Ni-based species has been recognized as an effective pathway to enhance the catalytic performance for the methanol oxidation reaction (MOR). However, doping Ni-based species with heterogeneous valences into Pd nanocrystals still remains challenging, although heterogeneous valence Ni species may result in improved properties of Pd from different aspects. Herein, a facile one-pot synthetic method is reported to simultaneously introduce alloyed Ni⁰ into Pd lattices and couple hydroxy Ni²⁺ species with a Pd surface, generating 1D porous PdNi alloy nanochains@Ni(OH)₂ nanosheet hybrids (PdNi NCs@Ni(OH)₂ NSs). Borane-tert-butylamine (C₄H₁₄BN) plays the key role in realizing the formation of Ni-based species with heterogeneous valence. On one hand, it works as a reducing agent to facilitate the doping of alloyed Ni⁰ into the lattice of Pd nanochains. On the other hand, it raises the solution pH value and converts the remaining [Ni(CN)₄]²⁻ into Ni(OH)₂ nanosheets. Each component of the PdNi NCs@Ni(OH)₂ NSs plays an important role: Pd serves as the active site, alloyed Ni⁰ modifies the electronic structure of Pd, and Ni(OH)₂ provides abundant OH_ads species to strengthen the anti-poisoning capability, thus greatly enhancing the activity, CO-tolerance, and durability for the MOR.