Stress-driven synthesis of multilayer borophene nanowalls on metal surfaces towards superior gas sensors

Among all two-dimensional (2D) materials, borophene exhibits excellent gas-sensing properties. Particularly, borophene nanowalls can offer exceptional gas-sensing ability due to their high surface-to-volume ratio and abundant adsorption sites, but experimental reports on the 2D nanowalls are currently lacking. Here, multilayer borophene nanowalls were successfully synthesized on aluminum foil substrates using chemical vapor deposition. The lattice mismatch between borophene and the Al substrate, reaching 22.56%, results in significant accumulated growth stress that drives the vertical growth of the nanowalls. By carefully tuning the growth conditions, we achieved controlled fabrication of nanowalls with tailored sizes, shapes, thicknesses, and densities. The multilayer borophene nanowalls were integrated into a resistive sensor device, which demonstrated outstanding performance, including an ultra-low detection limit of 200 ppb and an impressive sensitivity of 1050% at 100 ppm. The device also exhibited acceptable response and recovery times of 97 and 139 s, respectively, along with high selectivity. Furthermore, the multilayer borophene nanowalls showed excellent long-term stability, maintaining reliable performance even after 1000 stretching cycles, making them highly suitable for flexible and wearable applications. Our findings highlight the tremendous potential of multilayer borophene nanowalls as a cutting-edge material for high-performance gas sensing, paving the way for the development of advanced, flexible sensing technologies.