No abstract

A highly transparent, flexible, patternable, and wearable heater by a single-step supersonic kinetic spraying.

Ultrathin black phosphorus (BP) is one of the promising two-dimensional (2D) materials for future optoelectronic devices. Its chemical instability in ambient conditions and lack of a bottom-up approach for its synthesis necessitate efficient etching methods that generate BP films of designed thickness with stable and high-quality surfaces. Herein, reporting a photochemical etching method, we demonstrate a controlled layer-by-layer thinning of thick BP films down to a few layers or a single layer and confirm their Raman and photoluminescence characteristics. Ozone molecules generated by O2 photolysis oxidize BP, forming P2O5-like oxides. When the resulting phosphorus oxides are removed by water, the surface of BP with preset thickness is highly flat and self-protective by surface oxygen functional groups. This method provides a fabrication strategy of BP and possibly other 2D semiconductors with band gaps tuned by their thickness.

In this study, we demonstrate rapid and facile supersonic cold spray deposition of Zn2SnO4 /SnO2/CNT nanocomposite supercapacitor electrodes with promising combinations of power and energy density. Cyclic voltammetry confirmed the capacitive behavior of the optimized electrode, with specific capacitance reaching 260 F·g–1 at a current density of 10 A·g–1. We attribute this high performance to the optimal combination of CNT (carbon nanotube; double-layer capacitance) and Zn2SnO4 /SnO2 (pseudocapacitance) properties. The mesoporous and accessible surface of the CNT significantly contributed to the excellent retention (approximately 93%) of the specific capacitance after 15000 galvanostatic charge/discharge cycles. In addition, the supercapacitor exhibited a remarkable energy density, electrochemical properties, and mechanical stability. The materials and approach presented here can enable cost-effective, efficient, and scalable production of high-performance supercapacitor electrodes.