EDL Supercapacitor Electrode Performance Analysis of Group-VIB and Group‑X Transition Metal Adsorbed and Doped Graphene: A Density Functional Theory Based Comparative Investigation

For the first time, the work presents a comprehensive comparative study of different Group-VIB (Cr, Mo, W) and Group-X (Ni, Pd, Pt) transition metal (TM) adsorbed and doped two-dimensional (2D) graphene (Gr) electrodes for electric double layer (EDL) supercapacitor applications using a density functional theory (DFT) based theoretical approach. The work systematically analyzes the stability of adsorption/formation, structural–electronic property correlation, excess charge density (Q_exc), and quantum capacitance (C_Q) variations with local electrode potential. Next, over a standard range of EDL capacitance (C_EDL), the total interfacial capacitance (C_T) variation with respect to C_EDL is analyzed, and the performance of TM adsorbed/doped Gr is extensively benchmarked against pristine Gr. The results indicate that the TM adsorption and doping on Gr are potential material engineering techniques for improving the C_Q and thereby C_T. Specifically, the present work demonstrates that Cr and Mo adsorption and doping are relatively most stable in nature, which further ensures symmetric anode/cathode operation with a large C_Q owing to the introduction of large density of states (DOS) near the Fermi level (E_F). In essence, the work offers detailed theoretical insight on TM adsorption and doping in Gr for systematic electrode performance optimization for high-performance EDL supercapacitor design.