Kinetically controlled shock-wave route to turbostratic boron-carbon-nitride nanosheets

Turbostratic boron carbon nitride (tBCN) is highly attractive for energy storage and catalysis owing to its rotationally disordered stacking and expanded interlayer spacing, yet direct synthesis of tBCN with high in-plane crystallinity remains challenging. Here, we demonstrate that a shock tube, as a non-equilibrium reactor, converts melamine and boric acid into tBCN nanosheets within 2-3 ms at reflected-shock temperatures > 6,000 K, with ultrafast quenching at ∼10⁶ K/s that kinetically traps a metastable turbostratic phase. The resulting nanosheets exhibit a few-layer morphology, expanded interlayer spacing, clear Moiré patterns, and high in-plane crystallinity, as confirmed by high-resolution transmission electron microscopy (HRTEM). Electrochemical analysis reveals a high double-layer capacitance (C_dl) of 878 mF cm^-2, substantially exceeding that of conventional BCN-based electrodes, which is attributed to the enlarged interlayer spacing and abundant defect sites in the turbostratic framework. This solvent-free, catalyst-free, single-step process offers a scalable and sustainable route to turbostratic nanomaterials for energy storage and optoelectronic applications.