Synergistic catalytic effect of fluorine coordination in defects engineered nitrogen-doped 3D-Hierarchical Zn polymer-derived carbon as efficient bifunctional electrocatalysts.

Metal-free electrocatalysts for Hydrogen evolution reaction (HER) and Oxygen evolution reaction (OER) are highly desirable alternatives to expensive metal electrocatalysts. Herein, two metal-free heteroatom doped electro catalysts PCF-800 (carbon doped with fluorine) and PCFN-800 (carbon co-doped with nitrogen and fluorine) have been derived from the pyrolysis of ZnTFBDC and ZnTFBDC(1,10phen) accordingly. Both showed stunning performance for HER and OER in comparison with commercially available multiwall Nano carbon tubes. The graphitic and pyridinic carbon sites are generated in PCF-800 and PCFN-800 during the thermal polymerization process. These catalytic sites are responsible for excellent activity in terms of overpotential and Tafel slopes for HER process. Synthesized catalysts showed HER activities that are comparable to commercially available 20%Pt/C. PCFN-800 showed stability for about 30 h with a little decrease in current. Moreover, the mechanistic approach for HER and OER theoretical work was done and it has been found that the ΔG *H value for PCFN-800 is 0.51 eV that is less than 0.71 eV for N-doped carbon material for HER process. [Display omitted] • Fluorine and Nitrogen doped nanostructured hierarchical carbon is derived from Zn polymer. • High surface area with a wide range of porosity and catalytic active sites are found in derived carbon. • N and F co-doping of carbon produced excellent HER/OER catalytic activity. • Good Stability of electrode is found in alkaline media. • Mechanistic studies by DFT validate the contribution of F-coordination toward improved bifunctional catalysis. [ABSTRACT FROM AUTHOR]