Selective incorporation of Pd nanoparticles into the pores of an alkyne-containing metal-organic framework VNU1 for enhanced electrocatalytic hydrogen evolution reaction at near neutral pH

A Pd@VNU1 composite catalyst was prepared by selective incorporation of Pd nanoparticles into the pores of an alkyne-containing metal-organic framework (MOF) VNU1. The host support VNU1 was synthesized from 1,4-bis (2[4-carboxyphenyil]ethynyl)benzene (H2CPEB) alkyne-containing linker and Zr(IV) salt using the solvent-thermal method. The structure of VNU1 was analyzed using Powder X-Ray Diffraction (PXRD). The morphology and chemical composition of Pd@VNU1 were studied by FE-SEM energy dispersive X-ray (EDX) and TEM methods. The Electro-catalytic performances of the VNU1 support and the Pd@VNU1 composite catalyst for the hydrogen evolution reaction were examined by Linear Sweep Voltammetry technique (LVS) in near neutral pH using an aqueous solution of 0.5 M Na2SO4 (pH 7.2) as an electrolyte. It was found that fine Pd nanoparticles with a diameter of 1-2 nm are selectively and homogeneously incorporated into the pores of VNU1 with an amount of ca. 4.5% by weight. The incorporation of Pd nanoparticles into the VNU1 lead to an improvement in the catalytic activity of the composite for the hydrogen evolution reaction (HER). The current density at 600 mV/RHE for HER of the Pd@VNU1 composite catalyst was 5.3 times higher than that of VNU1 support, and the overpotential requirement to reach a catalytic current density of 1.0 mA cm(-2) and 5 mA cm(-2) was 280 mV and 550 mV vs. RHE, respectively.