Abstract
The inherent scalability, low production cost and mechanical flexibility of laser-induced graphene (LIG) combined with its high electrical conductivity, hierarchical porosity and large surface area are appealing characteristics for many applications. Still, other materials can be combined with LIG to provide added functionalities and enhanced performance. This work exploits the most adequate electrodeposition parameters to produce LIG/ZnO nanocomposites. Low-temperature pulsed electrodeposition allowed the conformal and controlled deposition of ZnO rods deep inside the LIG pores whilst maintaining its inherent porosity, which constitute fundamental advances regarding other methods for LIG/ZnO composite production. Compared to bare LIG, the composites more than doubled electrode capacitance up to 1.41 mF cm−2 in 1 M KCl, while maintaining long-term cycle stability, low ohmic losses and swift electron transfer. The composites also display a luminescence band peaked at the orange/red spectral region, with the main excitation maxima at ~ 3.33 eV matching the expected for the ZnO bandgap at room temperature. A pronounced sub-bandgap tail of states with an onset absorption near 3.07 eV indicates a high amount of defect states, namely surface-related defects. This work shows that these environmentally sustainable multifunctional nanocomposites are valid alternatives for supercapacitors, electrochemical/optical biosensors and photocatalytic/photoelectrochemical devices.
Highlights
Laser-induced graphene (LIG) and related composites have been studied in a wide range of applications, namely supercapacitors1–3, photodetectors[4], sensors, including gas, piezo and biosensors[5,6,7,8,9,10], and catalysis[11,12], among others
The direct laser writing (DLW) of laser-induced graphene (LIG) on PI sheets was accomplished using the parameters listed in Supplementary Table S1
Simple and scalable production of foam-like multilayer graphene and zinc oxide (ZnO) composites is attained via electrodeposition of ZnO rods on LIG
Summary
Laser-induced graphene (LIG) and related composites have been studied in a wide range of applications, namely supercapacitors1–3, photodetectors[4], sensors, including gas, piezo and biosensors[5,6,7,8,9,10], and catalysis[11,12], among others. Many efforts have been employed to combine graphene with environmentally sustainable transition metal oxides and wide bandgap semiconductors, among which zinc oxide (ZnO), with an energy bandgap of ~ 3.3 eV at room temperature (RT)[17]. Techniques such as h ydrothermal18, electrochemical[19,20,21,22,23], physical vapor d eposition[24,25] and laser-assisted synthesis[26,27,28,29] have been thoroughly explored to produce a wide variety of ZnO crystal morphologies and sizes. Pulsed electrodeposition, where the potential or current is alternated between deposition/ resting status, provides several advantages compared to the static potential (continuous) process, such as renewal of diffusing layer, promotion of ZnO nucleation and the possibility to control the growth via the employed duty cycle and pulse duration or frequency[22,29,40]
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