Ultrastable Polymolybdate-Based Metal–Organic Frameworks as Highly Active Electrocatalysts for Hydrogen Generation from Water

Abstract

Two novel polyoxometalate (POM)-based metal-organic frameworks (MOFs), [TBA]3[ε-PMo(V)8Mo(VI)4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA(+) = tetrabutylammonium ion) and [TBA]3[ε-PMo(V)8Mo(VI)4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1'-biphenyl]-3,4',5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA(+) ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of ε(trim)(4/3), NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials. It shows an onset overpotential of 180 mV and a Tafel slope of 96 mV·dec(-1), and the catalytic current density can approach 10 mA·cm(-2) at an overpotential of 237 mV. Moreover, NENU-500 and NENU-501 maintain their electrocatalytic activities after 2000 cycles.

An Insight on the Electrocatalytic Mechanistic Study of Pristine Ni MOF (BTC) in Alkaline Medium for Enhanced OER and UOR

“…[41,42] Recently, Zhu et al studied Ni MOF (BDC) for UE in alkaline medium over glassy carbon (GC) and Ni foam substrate. [45] Notably, most of the catalysts show substrate dependent catalytic activity. [44] Qin et al investigated Polymolybdate based MOF for HER (1,3,5-Benzene tricarboxylate) on GC substrate.…”

Fe/Ni Metal–Organic Frameworks and Their Binder-Free Thin Films for Efficient Oxygen Evolution with Low Overpotential

“…37 Especially in the case of electrochemical catalysis, MOFs are consequently coated onto conductive substrates using binders, i.e., Nafion. 38 The application of these electrical insulating and inactive binders can deteriorate the conductivity of the electrode and may partially block the pores and active sites of MOF particles leading to diminished electrocatalytic performances. 13 To address this, a MOF membrane or thin film directly grown and tightly bonded on current collector without any binders is highly desirable.…”

Construction of Zeolite‐Like Cluster Organic Frameworks from 3 d–4 d/3 d–3 d Heterometallic Supertetrahedral Secondary Building Units: Syntheses, Structures, and Properties

“…Surprisingly,z eolitelike cluster organic frameworks based on heterometallic cluster SBUs are quite rare. [15] The possible reason is that integration of two kinds of metal ions with differenti nherent characteristic to one cluster may bring more difficulties to the syntheses.…”