Ultra-fine size-controlled Pt (111) nanoparticles supported on mesoporous titania as an efficient photoelectrocatalyst for hydrogen evolution

Abstract

Synthetic methods that allow tuning of well-defined Pt nanoparticles on metal-oxide support are much desirable in catalysis research. In this work, we report a synthetic strategy for tuning Pt nanoparticles (NPs) on titania support, which is widely used in the catalytic field. The Pt NPs size was varied from 1 to 5 nm with the variation of template concentration. The catalyst showed high metal dispersion (68–32%) as compared to 2% metal dispersion for the catalyst synthesized with the conventional method. The catalytic activity of the catalyst was demonstrated using photoelectrochemical hydrogen production in CO2 atmosphere in alkaline medium at potential ca. -0.9 V vs. Ag/AgCl. The photoelectrode gave photocurrents of −28.76 mA-cm−2 and -7.87 mA-cm−2 under UV and visible light irradiations, respectively. The catalyst showed the highest activity (−7.87 mA-cm−2) for hydrogen production amongst metal oxide based photoelectrodes under visible light. The variation of Pt metal loading on the mesoporous titania was studied. First principles based DFT calculations favored the bicarbonate dissociation route into formic acid with the conversion of bicarbonate into formate as the rate determining step. The adsorption energy of bicarbonate over the catalyst was calculated as −2.17 eV, whereas carbon dioxide showed adsorption energy of −1.34 eV.