Revealing the Impact of Pulsed Laser-Produced Single-Pd Nanoparticles on a Bimetallic NiCo<sub>2</sub>O<sub>4</sub> Electrocatalyst for Energy-Saving Hydrogen Production via Hybrid Water Electrolysis
Raja Arumugam Senthil, Sieon Jung, Ahreum Min, Anuj Kumar, Cheol Joo Moon, Monika Singh, Myong Yong Choi
Abstract
Nowadays, the assembling of hybrid water electrolysis using a hydrazine oxidation reaction (HzOR) instead of a slow anodic oxygen evolution reaction (OER) has been established as a favorable technology for efficient hydrogen (H 2 ) 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 NiCo 2 O 4 nanoplates as a bifunctional electrocatalyst for both HER and HzOR. Initially, the NiCo 2 O 4 nanoplates are synthesized by a combination of hydrothermal reaction and high-temperature calcination. Subsequently, single-Pd nanoparticles with varying proportions are decorated on NiCo 2 O 4 nanoplates via facile pulsed laser irradiation (PLI), leading to the formation of Pd/NiCo 2 O 4 composites. The optimized Pd/NiCo 2 O 4 composite shows a remarkable electrocatalytic ability with a low overpotential of 294 mV for the HER and an ultrasmall working potential of −6 mV (vs RHE) for the HzOR at 10 mA cm –2 in a 1 M KOH electrolyte. Thus, an overall hydrazine splitting (OHzS) electrolyzer with the Pd/NiCo 2 O 4 ∥Pd/NiCo 2 O 4 system presents the current densities of 10 and 100 mA cm –2 at respective low cell voltages of 0.35 and 0.94 V. Notably, in situ/operando Raman spectroscopy confirms the surface formation of α-Co(OH) 2 during the HER and γ-NiOOH during the HzOR. Furthermore, the density function theory (DFT) calculations demonstrate that the decoration of Pd onto NiCo 2 O 4 facilitates the optimization of both the hydrogen adsorption free energy (Δ G H* ) and enhancement of hydrazine dehydrogenation kinetics. This work introduces a facile strategy for fabricating bifunctional electrocatalysts, potentially useful in energy-saving H 2 production.