Novel Fe-doped TiO2 metal-organic framework for electrocatalytic hydrogen evolution reaction

Abstract

A novel approach has been adopted to synthesize titanium oxide-based metal organic framework (MOF), which was doped with iron to increase its efficiency in hydrogen evolution reaction. Scanning electron microscopic images reveal the structure of bare titanium dioxide-based MOF as smooth and aggregated, while doping with iron renders a rough and irregular structure. Mineral phases of ferro-pseudobrookite, anatase, rutile and brookite were prevalent in the doped powder. The presence of iron and titanium in its structure is further confirmed by the deconvoluted spectra from x-ray photoelectron spectroscopy. 0.1 (M) iron doped powder showed an excellent current density of 10 mA/cm2 at an onset potential of 0.345 V, in a three-electrode system. Additionally, its Tafel slope value is 129.6 mV/dec, when compared to the undoped form (168.8 mV/dec), indicating the faster kinetics. Hydrogen evolution reaction is guided by Volmer-Heyrovsky pathway. Electrochemical active surface area of bare MOF powder is 0.62 cm2 while that for 0.1 (M) doped MOF powder is 0.965 cm2. This powder shows extremely good stability and retains its structural integrity even after 1000 linear sweep voltammetry cycles. Density functional theory calculations revealed an increase in the adsorption energy of water molecules attachment in the presence of iron, suggesting an enhanced HER activity.