Boron Clusters for Metal-Free Water Splitting

TL;DR

This paper introduces transition-metal-free boron cluster catalysts for water splitting, demonstrating superior activity and durability by leveraging unique water interactions and electronic properties, representing a paradigm shift in OER catalysis.

Contribution

It presents a novel class of boron cluster catalysts with enhanced OER activity and stability, driven by unique water interactions and electronic structures, challenging traditional metal-based catalysts.

Findings

Boron clusters outperform Co3O4 in OER activity.

Water adsorbs on B12 clusters, indicating a new OER pathway.

Density functional theory explains the electronic factors promoting water activation.

Abstract

Electron-deficient boron clusters are identified as a fundamentally new class of oxygen evolution reaction (OER) catalysts, entirely free of transition metals. Selective sodium extraction from NaAlB14 and Na2B29 via high-pressure diffusion control introduces hole doping into B12 icosahedral frameworks, resulting in OER activity exceeding that of Co3O4 by more than an order of magnitude, and exceptional durability under alkaline conditions. B12 clusters are known for their superchaotropic character, which destabilizes hydrogen bonding in water. In this system, H2O, instead of OH-, preferentially adsorbs on the catalyst surface, suggesting a distinct OER pathway mediated by molecular water. This adsorption behavior contrasts with conventional transition-metal oxides and reflects the unique interfacial properties of the boron clusters. Density functional theory reveals unoccupied p orbitals and unique local electric fields at the cluster surface, both of which could promote the water activation. These findings suggest a paradigm shift in OER catalysis, in which the unique interaction between B12 clusters and water drives the reaction, replacing the conventional role of redox-active metals. Hole-doped boron clusters thus offer a promising platform for designing high-performance and durable water-splitting catalysts, opening new avenues for OER design beyond conventional transition-metal chemistry.