Large-Scale Synthesis of Electrochemically Active Titanium Diboride-Based Nanosheets by High-Energy Ball Milling

AlB<inf>2</inf>-type layered metal diborides have sought renewed research attention in recent years on account of their ability to yield XBenes─their quasi-two-dimensional (2D) counterparts. These quasi-2D nanostructures present exciting avenues to utilize the rich science offered by metal diborides. While a range of approaches have been developed to exfoliate layered metal diborides, the ability to obtain XBenes in a scalable manner is in its incipient stages─this is a critical bottleneck in translating their rich nanoscience into tangible technology. In this work, we present a scalable approach that employs high-energy ball milling to exfoliate titanium diboride (TiB<inf>2</inf>) into its quasi-2D counterparts at the gram scale. We first show that milling TiB<inf>2</inf> crystals for an optimal duration (6 h) and at a specific balls-to-powder ratio (20:1) yields multi-layer-thick nanosheets (∼5-10 nm thick). Second, by using Rietveld refinement and Raman spectroscopy, we show that the chemical integrity of TiB<inf>2</inf> is retained to a large extent upon exfoliation─there is an associated formation of defects within the crystal structure of TiB<inf>2</inf> that evolve with milling. Finally, we show that upon milling, the native electrochemical activity of TiB<inf>2</inf> is enhanced by several folds. This ability to obtain nanosheets of TiB<inf>2</inf> in a scalable manner using a high-energy ball mill bridges a critical missing link in the fast-growing science on nanoscaling AlB<inf>2</inf>-type metal borides.