Electron‐Sponge Nature of Polyoxometalates for Next‐Generation Electrocatalytic Water Splitting and Nonvolatile Neuromorphic Devices

Abstract

Designing next‐generation molecular devices typically necessitates plentiful oxygen‐bearing sites to facilitate multiple‐electron transfers. However, the theoretical limits of existing materials for energy conversion and information storage devices make it inevitable to hunt for new competitors. Polyoxometalates (POMs), a unique class of metal‐oxide clusters, have been investigated exponentially due to their structural diversity and tunable redox properties. POMs behave as electron‐sponges owing to their intrinsic ability of reversible uptake‐release of multiple electrons. In this review, numerous POM‐frameworks together with desired features of a contender material and inherited properties of POMs are systematically discussed to demonstrate how and why the electron‐sponge‐like nature of POMs is beneficial to design next‐generation water oxidation/reduction electrocatalysts, and neuromorphic nonvolatile resistance‐switching random‐access memory devices. The aim is to converge the attention of scientists who are working separately on electrocatalysts and memory devices, on a point that, although the application types are different, they all hunt for a material that could exhibit electron‐sponge‐like feature to realize boosted performances and thus, encouraging the scientists of two completely different fields to explore POMs as imperious contenders to design next‐generation nanodevices. Finally, challenges and promising prospects in this research field are also highlighted.

Capacitor or Memristor: Janus Behavior of Polyoxometalates

“…POMs exhibit a well-defined and thermally stable metal–oxo cluster core with high structural and chemical diversity. By adjusting the ligand periphery and the types of metals used, POMs can be modified for many different applications, for example, as switching elements in data memory devices , or as electrocatalysts for water splitting reactions . Typically, POMs are anionic species, which entail stabilization by additional countercations.…”

“…This additional charge must be stabilized either by the POM framework, surrounding countercations, or in the case of functionalized POMs, also by ligands. In other words, POMs can act as an electron sponge . However, the uptake of additional electronic charge results in a situation aside from the thermodynamic minimum, which means that the molecule is anxious to release electrons and thus to act as a molecular capacitor.…”