Dendritic Ferroselite (FeSe2) with 2D Carbon-Based Nanosheets of rGO and g-C3N4 as Efficient Catalysts for Electrochemical Hydrogen Evolution

Nanostructured transition metal dichalcogenides are demonstrated to be potential catalysts to produce molecular hydrogen through electroreduction of water. Finding an efficient and cost-effective catalyst as a substitute for a platinum-based catalyst for sustainable hydrogen production is still a major issue, more so for large-scale production. Herein, we have designed dendritic ferroselite (FeSe2) hybrid nanocomposites with 2D g-C3N4 and reduced graphene oxide (rGO) nanosheets, that is, FeSe2/g-C3N4 and FeSe2/rGO as electrocatalysts for hydrogen evolution reaction (HER). Interestingly, FeSe2/rGO exhibited higher performance compared to FeSe2/g-C3N4. The highly conductive 2D FeSe2/rGO hybrid with an aligned curvy rippling surface and dendritic morphology demonstrates an onset potential of 218 mV at a current density of 10 mV/cm2 versus reversible hydrogen electrode in comparison to that of FeSe2/g-C3N4 showing an onset potential of 437 mV. The detailed density functional theory (DFT) calculations were performed to investigate the intrinsic catalytic sites and Gibbs free energy (ΔGH*) of hydrogen adsorption for the HER process. The DFT calculations displayed 0.33 V less overpotential for carbon atoms of g-C3N4 (0.97 V) compared to rGO (1.3 V). In contrast, hybrids of FeSe2/rGO (0.86 V) display lower overpotential when compared to FeSe2/g-C3N4 (1.63 V), which is in agreement with experimental results. Electrochemical impedance spectroscopy reveals lower charge transfer resistance (Rct) for FeSe2/rGO. The high hydrogen evolution activity of FeSe2/rGO is due to the electrocatalytic synergistic effect of iron diselenide and rGO, contributing to the optimum free energy for HER and improved electron mobility.