Modelling & verification of the effect of the surface activation on the hydrogen adsorption of 3D printed PEEK component through nitrogen and graphene oxide nanoparticles

The utilization of polymer-based materials in energy-saving fields is limited due to their insulative features, which causes low electrochemical hydrogen adsorption capability. Therefore, in this research, the attempts have been made to induce the conductive feature for activation of the electrochemical storage capability of PEEK. For this aim, at the first stage, simulation was carried out using python to evaluate the effect of addition of the nitrogen heteroatom and Graphene oxide nanoparticles for activation of electron and proton transfer paths. Then, verification was carried out using experiment procedure. Firstly. PEEK specimens were fabricated through 3D printing (Filament Direct Melting (FDM)) method under the obtained optimized condition, at 375 °C of nozzle temperature and 30 mm.s-1 travelling speed. Surface functionalization was carried out by doping of N-heteroatom and GO NPs through the hydrothermal method at 180 °C for 10 h. Fourier-Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy and X-ray photonic spectroscopy (XPS) analysis were carried out to ensure successful nitrogen and GO doping. The comprehensive electrochemical hydrogen adsorption capacity tests were carried out through cyclic voltammetry (CV), galvanostat charge/discharge, and electrochemical impedance spectroscopy (EIS) in 1.5 M KOH solution at room temperature. Results demonstrated a fine consistency with the simulated results and illustrated that by applying surface modification on the 3D printed PEEK, the specific capacitance was improved successfully from 2.66 (for pure porous as-3D printed PEEK) to 13.18 and 47.93 mAh.g-1 for nitrogen-doped and GO-doped PEEK, respectively. This significant enhancement is attributed to the formation of the conductive electron transfer path through nitrogen heteroatoms or GO NPs on the surface of as-printed PEEK specimens, which is shown through thermodynamics modelling of adsorption process. Additionally, the GO nanolayer was formed on the surface of the as-3D-printed porous PEEK substrate as a consequence of GO nanoparticles doping and flower-like morphology was obtained.