Surfactant-assisted exfoliation of tantalum diboride (TaB2) for electrochemical CO2 reduction

Abstract

Recent years have witnessed a renewed interest in utilizing AlB2-type metal borides for applications traditionally not envisaged for this family of ionic layered materials. This is due to a native synergy between the metal atoms and boron honeycomb planes that imparts them versatile physicochemical properties. This prospect is further augmented by their feasibility to be nanoscaled into quasi-two-dimensional (2D) forms–XBenes, as demonstrated by several recent studies. In this work, we show that such a nanoscale can also be extended to tantalum diboride (TaB2), a member of this family that has largely remained uncharted. We found that TaB2 can be exfoliated into few-layer-thick nanosheets (mean thickness of 4.5 nm) by using surfactant chemistry. The resultant nanosheets were found to retain their structural integrity to a large extent. We utilized the readily accessible Ta–B sites offered by these nanosheets to catalyze the electrochemical reduction of aqueous CO2. Moreover, we found that these TaB2 nanosheets facilitate the production of ethylene as the main carbon product, with faradaic efficiency reaching 75% at −0.85 V vs RHE. We obtain additional insights using DFT studies, which show how the interaction of CO2 with Ta and B atoms results in favorable CO2 adsorption for ethylene production.