Abstract
Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis. However, large-scale, cost-effective, and precursor-free methods to prepare ultrathin carbides are lacking. Here, we demonstrate a direct pattern method to manufacture ultrathin carbides (MoCx, WCx, and CoCx) on versatile substrates using a CO2 laser. The laser-sculptured polycrystalline carbides (macroporous, ~10–20 nm wall thickness, ~10 nm crystallinity) show high energy storage capability, hierarchical porous structure, and higher thermal resilience than MXenes and other laser-ablated carbon materials. A flexible supercapacitor made of MoCx demonstrates a wide temperature range (−50 to 300 °C). Furthermore, the sculptured microstructures endow the carbide network with enhanced visible light absorption, providing high solar energy harvesting efficiency (~72 %) for steam generation. The laser-based, scalable, resilient, and low-cost manufacturing process presents an approach for construction of carbides and their subsequent applications.
Highlights
Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis
The laser energy input produces this high energy α-MoCx (0 < x < 1) phase of MoCx (Supplementary Fig. 2), which has a threshold temperature of 1928 K in the phase diagram The product of α-MoCx/C has a much higher Gibbs free energy than the common α-Mo2C and βMo2C36–38 and the 2D-Mo2C achieved by CVD3,15,16
Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the broken-down sheets of the porous structure have a thickness of 10–20 nm and are comprised of randomly orientated nanocrystals (Fig. 1h–j, Supplementary Fig. 4d–e)
Summary
Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis. We demonstrate a direct pattern method to manufacture ultrathin carbides (MoCx, WCx, and CoCx) on versatile substrates using a CO2 laser. The state-of-the-art fabrication process for ultrathin 2D-TMCs (MXenes)[7,8,9,10] involves high temperatures (up to 1600 °C)[11] to generate the MAX phase (Mn+1AXn, where M is a transition metal, A is a group 12–16 element, and X is C or N) precursor and a hydrofluoric (HF) acid etching process to remove the A layer to form Mn+1XnTx (T: OH, OOH and other surface terminations)[9,12,13,14]. The laser-patterned carbide, using MoCx as an example, performs as an energy storage interdigit supercapacitor electrode having a wide operational temperature range (−50 °C to 300 °C in electrolyte). The exceptional thermal resilience of TMCs could enable a range of other applications such as carbide-based supercapacitors or solar-steam generation membranes operating in harsh environments
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