Abundant Active Sites on the Basal Plane and Edges of Layered van der Waals Fe₃GeTe₂ for Highly Efficient Hydrogen Evolution

Abstract

van der Waals (vdW) metal chalcogenides have been extensively investigated as electrocatalysts for the hydrogen evolution reaction (HER); however, for the majority of these materials only the edges are active, thereby wasting most of the materials' surfaces. Recent research has focused on finding new materials with active basal planes. Herein, for the first time, we demonstrate that the hexagonal vdW Fe 3 GeTe 2 (FGT), also a spintronic candidate material, shows both basal plane and edge site HER activities. Partial exfoliation of bulk FGT through sonication increases both basal plane and edge sites leading to significantly improved overpotential. A subsequent compacting of the sample (using plasma sintering at room temperature) to produce a densified electrode leads to an impressive overpotential to drive a current density of 10 mA/cm 2 of −0.105 V. DFT free energy calculations not only showed that the high activity is due to the abundant active sites present on the hexagonal Te layer in FGT but also presented an even more HER active layer (106) containing both iron and tellurium active sites. Furthermore, the presence of a thin oxide layer on top of the active FGT layers, as found by XPS, suggests that the real active surface is likely a hybrid FGT/oxide layer. These results demonstrate the high basal plane and edge sites HER activity of FGT, thus opening a new avenue for the design and screening of related iron-based vdW materials, their composites, and their surface functionalization as high-performing electrocatalysts.

Bridging electrocatalyst and cocatalyst studies for solar hydrogen production via water splitting

“…27,28 Metal (Ni, Co, Fe, W, Mo, …) phosphides, nitrides, and carbides are also subjects of extensive studies owing to their advantageous electronic structures. 27,29–38 Tuning the metal composition has proven to be pivotal in realizing exceptional HER performance. 29 Such rationally designed EC compounds have realized comparable HER activities over a wide range of pH for practical applications.…”

“…62 Simple oxides and chalcogenides can be directly synthesized by liquid-phase methods under mild conditions, 62,63 whereas high-temperature annealing is often required to obtain phosphides, nitrides, and carbides from their corresponding preformed oxides. 34–36,51,52 Specifically, they are annealed with precursors (P = NaH 2 PO 2 ; N = NH 3 ; C = organic molecule) in a furnace at >300 °C for complete conversion. To assess the resulting material's electrocatalytic activity, powdered ECs are embedded on a conductive carbon substrate, and the composite is typically glued to an electrode surface using a Nafion binder.…”

Field-Dependent Magnetic Domain Behavior in van der Waals Fe$_3$GeTe$_2$

“…As an iron-rich layered compound, Fe 3 GeTe 2 has been reported to possess itinerant ferromagnetism with strong perpendicular anisotropy and a Curie temperature that varies between 100 -400 K depending on sample thickness or strain 9,10,14,16,[18][19][20][21] . Fe 3 GeTe 2 is being considered as a potential candidate for spintronic devices 14,15,[22][23][24] and also as an electrocatalyst 25 . Thus, it is necessary to understand the local magnetization behavior in Fe 3 GeTe 2 in response to external stimuli, such as strain, an external magnetic field, applied current and temperature, in order to gain insight into the energy landscape and the governing energy terms that control its magnetization behavior.…”

Novel Microporous Metal Phosphonates as Electrocatalyst for the Electrochemical Hydrogen Evolution Reaction

“…Notably, transition-metal-based materials have attracted immense attention due to their higher catalytic activities under alkaline conditions toward HER. Different classes of transition-metal-based (i.e., Ni, Co, Fe, Mo, and W) materials have been examined as HER electrocatalysts, which include alloys, 15 carbides and borides, 16 chalcogenides, 17 nitrides, 18 phosphates, 19 and phosphonates. 20 Among them, metal phosphonates have gained immense attention because they are hybrid materials consisting of metal ions bonded to the organophosphonic acid ligands.…”