Surfactant-Assisted Exfoliation of Tantalum Diboride (TaB2) for Electrochemical CO2 Reduction

Recent years have witnessed a renewed interest in utilizing AlB<inf>2</inf>-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 (TaB<inf>2</inf>), a member of this family that has largely remained uncharted. We found that TaB<inf>2</inf> 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 CO<inf>2</inf>. Moreover, we found that these TaB<inf>2</inf> 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 CO<inf>2</inf> with Ta and B atoms results in favorable CO<inf>2</inf> adsorption for ethylene production.