A facile method for the selective decoration of graphene defects based on a galvanic displacement reaction

Inherent defects, such as grain boundaries (GBs), wrinkles and structural cracks, present on chemical vapor deposition (CVD)-grown graphene are inevitable because of the mechanism used for its synthesis. Because graphene defects are detrimental to electrical transport properties and degrade the performance of graphene-based devices, a defect-healing process is required. We report a simple and effective approach for enhancing the electrical properties of graphene by selective graphene-defect decoration with Pd nanoparticles (Pd NPs) using a wet-chemistry-based galvanic displacement reaction. According to the selective nucleation and growth behaviors of Pd NPs on graphene, several types of defects, such as GBs, wrinkles, graphene regions on Cu fatigue cracks and external edges of multiple graphene layers, were precisely confirmed via spherical aberration correction scanning transmission electron microscopy, field-emission scanning electron microscopy and atomic force microscopy imaging. The resultant Pd-NP-decorated graphene films showed improved sheet resistance. A transparent heater was fabricated using Pd-decorated graphene films and exhibited better heating performance than a heater fabricated using pristine graphene. This simple and novel approach promises the selective decoration of defects in CVD-grown graphene and further exploits the visualization of diverse defects on a graphene surface, which can be a versatile method for improving the properties of graphene. Decorating defects with palladium nanoparticles enhances the electrical properties of chemical vapour deposited graphene. Unlike other methods of synthesizing graphene, chemical vapour deposition can produce large areas of the two-dimensional material, but it also tends to create defects. Han-Bo-Ram Lee from Incheon National University and Taeyoon Lee from Yonsei University in South Korea, together with colleagues across the country, have shown that palladium nanoparticles automatically attach themselves to imperfections in chemical vapour deposited graphene, thereby improving its electrical properties. They chemical vapour deposited graphene on copper and dipped it in a palladium chloride solution. The greater chemical reactivity of defect sites in graphene causes palladium atoms to selectively attach to imperfections such as wrinkles, cracks and grain boundaries, creating nanoparticles at these sites. The researchers anticipate that the method could be used in the manufacture of smart mirrors and displays. Selective decoration of palladium nanoparticles on diverse graphene-defect sites. Graphene grown by chemical vapor deposition method has structural imperfections, such as grain boundaries, wrinkles and topological cracks, which cause reduced graphene-based device performance. Herein, we selectively decorated graphene defects with metal nanoparticles (Pd and Ag) by using a wet-chemistry-based galvanic displacement reaction within a few minutes without generating damage on graphene. The defect-decorated graphene showed a noticeable improvement in electrical characteristics, and defect-decorated graphene-based transparent heater showed better heating performance than a heater fabricated using pristine graphene.