CO2 Cd(II) N–doped carbon Orange G adsorption adsorption studies amino group bio-phenol resin biochar bonding type carbo microsphere carbon capture and storage process (CCS) carbon dioxide carbon dioxide adsorption carbon gels carbon materials carbon nanotubes catalysis chemical functionalization co-activation method cross-link bond type doping electrocatalysis electrochemical analysis electrode material energy power density energy storage environmental remediation functionalized graphene oxide graphene