Differentiating structure of in situ and ex situ formation of laser-induced graphene hybrids

Laser-induced graphene (LIG) has been exploited in various fields, such as batteries, water treatment, and flexible actuators and sensors, with the advantages of ease in patternable fabrication and graphene/metal hybrid preparation. The in situ method which includes a single lase step and the ex situ method which uses two lase steps are both widely implemented to synthesize graphene/metal hybrids. However, the differences in the structures and properties of the resulting hybrids are not fully understood. Here, we investigate the advantages of ex situ and in situ methods for preparing LIG hybrids using NiFe/LIG as an example. The morphology, elemental composition, resistance to strong acid, and application in electrocatalysis and dye adsorption of ex situ and in situ NiFe/LIG hybrids were systematically studied and compared. Energy-dispersive X-ray spectrometry (EDS) and vibrating sample magnetometry (VSM) results confirmed the structural differences between the NiFe/LIG hybrids. Metal nanoparticles are mostly wrapped by carbon layers in the in situ NiFe/LIG hybrid, while the ex situ NiFe/LIG hybrid largely exposes the metal nanoparticles. These structural differences are significant for tailoring performance in applications, such as wastewater treatment and electrocatalysis. This work provides insights into the synthesis and properties of LIGs and has important implications for future applications.