An efficient, cost-effective, and earth-abundant catalyst that could drive the production of hydrogen from water without or with little external energy is the ultimate goal toward hydrogen economy. Herein, nanoplates of tungsten oxide and its hydrates (WO 3 ·H 2 O) as promising electrocatalysts for the hydrogen evolution reaction (HER) are reported. The square-shaped and stacked WO 3 ·H 2 O nanoplates are synthesized at room temperature under air in ethanol only, making it as a promising green synthesis strategy. The repeated electrochemical cyclic voltammetry cycles modified the surface of WO 3 ·H 2 O nanoplates to WO 3 as confirmed by X-ray photoelectron and Auger spectroscopy, which leads to an improved HER activity. Hydrogen evolution is further achieved from distilled water (pH 5.67) producing 1 mA cm –2 at an overpotential of 15 mV versus the reversible hydrogen electrode. Moreover, WO 3 ·H 2 O and WO 3 nanoplates demonstrate excellent durability in acidic and neutral media, which is highly desirable for practical application. Improved hydrogen evolution by WO 3 (200) when compared to that by Pt(111) is further substantiated by the density functional theory calculations.

Density functional theory (DFT) calculations were carried out on five transition metals (Co, Ni, Pd, Rh, Ru) to test their activities toward the biomimetic carbon dioxide hydration reaction. Periodic plane-wave calculations demonstrated the formation of surface species in accordance with the mechanism of the reaction known for α-carbonic anhydrase action. To determine different activation barriers for the different elementary steps involved in the reaction, DFT calculations using a cluster model of transition metals with Gaussian-type orbitals were carried out. The periodic and cluster calculations were found to correspond to a mechanism of the reaction constitituting seven steps, namely, surface adsorption of H2O, deprotonation and surface OH formation, adsorption of CO2, OH attack on adsorbed CO2, proton transfer, H2O attack on surface HCO3 – complex, and HCO3 – displacement by H2O. The behaviors of the metals were found to be different in a vacuum and in the solvated state, with Co being the best potential candidate for the biomimetic CO2 hydration reaction in a vacuum and Ru being the best candidate for the reaction in solution.

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Electronic structural analyses of hydrogen terminated metal doped carbon nanotube/graphene (M-CNT/Gr, MN-CNT/Gr, M = Ru/Rh) and ruthenium cluster decorated carbon nanotube/graphene (Ru-CNT/Gr) were carried out for examining the biomimetic catalytic activity towards CO hydration reaction. The carbonic anhydrase action was followed for the reaction of CO with HO resulting in a bicarbonate ion and a proton. All the catalysts were found to be active for CO hydration and the mechanism proved them to be biomimetic. Interconversion of CO to a HCO ion took place with five elementary steps viz. OH formation by HO dissociation, linear CO complexation, CO bending by nucleophilic attack of an OH ion over CO, HCO ion formation by intramolecular proton migration and HCO ion displacement by HO addition. Free energy landscapes over the catalysts were developed for CO hydration reaction. The activation energies of HO dissociation and CO bending were observed to be substantially smaller over Ru-CNT when compared to those over the other catalysts. Ru-CNT was found to be the best catalyst for CO hydration with the rate limiting step being HCO ion formation.