abstract

Nowadays, the assembling of hybrid water electrolysis using hydrazine oxidation reaction (HzOR) instead of the slow anodic oxygen evolution reaction (OER) has been established as a favorable technology for efficient hydrogen (H2) production. Nevertheless, it is still critical to develop highly effective bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and HzOR. In this work, we propose a facile approach for the design and synthesis of single Pd nanoparticles decorated bimetallic NiCo2O4 nanoplates as a bifunctional electrocatalyst for both HER and HzOR. First, the NiCo2O4 nanoplates are synthesized by a combination of hydrothermal reaction and high-temperature calcination. Subsequently, single Pd nanoparticles with varying proportions are decorated on the NiCo2O4 nanoplates via facile pulsed laser irradiation (PLI), leading to the formation of Pd/NiCo2O4 composite. Synergistic interfaces between the NiCo2O4 nanoplates and the extremely active Pd nanoparticles are observed. The result is an optimized Pd/NiCo2O4 composite shows a remarkable electrocatalytic ability with a low overpotential of 294 mV(vs. RHE) for the HER and an ultra-small working potential of –6 mV (vs. RHE) for HzOR at 10 mA cm–2 in a 1 M KOH electrolyte. Thus, an overall hydrazine splitting (OHzS) electrolyzer with a longterm durability could be assembled with the Pd/NiCo2O4∥Pd/NiCo2O4 system, which presents the current densities of 10 and 100 mA cm−2 at respective low cell voltages of 0.35 and 0.94 V. Notably, the in-situ/operando Raman spectroscopy proves the formation of α-Co(OH)2 on the surface during the HER and that of γ-NiOOH during the HzOR. These species serve as active sites to enhance electrocatalytic activity. This work proposes a facile strategy for manufacturing bifunctional electrocatalyst that could be used in energy-savingH2 production.