Hydrogen reduction of molybdenum oxide at room temperature
نویسندگان
چکیده
The color changes in chemo- and photochromic MoO3 used in sensors and in organic photovoltaic (OPV) cells can be traced back to intercalated hydrogen atoms stemming either from gaseous hydrogen dissociated at catalytic surfaces or from photocatalytically split water. In applications, the reversibility of the process is of utmost importance, and deterioration of the layer functionality due to side reactions is a critical challenge. Using the membrane approach for high-pressure XPS, we are able to follow the hydrogen reduction of MoO3 thin films using atomic hydrogen in a water free environment. Hydrogen intercalates into MoO3 forming HxMoO3, which slowly decomposes into MoO2 +1/2 H2O as evidenced by the fast reduction of Mo6+ into Mo5+ states and slow but simultaneous formation of Mo4+ states. We measure the decrease in oxygen/metal ratio in the thin film explaining the limited reversibility of hydrogen sensors based on transition metal oxides. The results also enlighten the recent debate on the mechanism of the high temperature hydrogen reduction of bulk molybdenum oxide. The specific mechanism is a result of the balance between the reduction by hydrogen and water formation, desorption of water as well as nucleation and growth of new phases.
منابع مشابه
Comparison of doped combination zirconium-tungsten, zirconium- molybdenum and molybdenum-tungsten on single-wall vanadium oxide nanotube in hydrogen gas adsorption
In this study, doped vanadium oxide nanotubes were evaluated using different software to study the absorption of hydrogen gas. Vanadium oxide nanotubes are one of the options for absorption and storage hydrogen gas. In this research study for the first time, the Monte Carlo simulation was used to investigate the hydrogen gas absorption behavior in molybdenum-tungsten, molybdenum-zirconium and z...
متن کاملThe role of carburization temperature on the molybdenum carbide surface and their catalytic activity
The surfaces of molybdenum carbide were varied by changing the carburization temperature between 823 and 1123 K. The surfaces of the catalytic material were investigated using in-situ temperature program carburization followed by temperature program reduction and oxidation. In-situ temperature program oxidation (TPO) showed the surfaces of the catalysts contain a similar amoun...
متن کاملElectrochemical Study of Hydrogen Adsorption/Reduction (HAR) Reaction on Graphene Oxide as Electrocatalyst for Proton Exchange Membrane Fuel Cells
In the current work, graphene oxide (GO) samples were prepared at room temperature from graphite flakes using a modified Hummer's method to produce metal-free electrocatalysts. The effect of the duration of the oxidation process on the structural, chemical and physical characteristics of the GO samples was evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ...
متن کاملHydrogen evolution activity of NiMo-MoO2 produced by mechanical milling
In this study, mechanical alloying was done by a high-energy planetary ball milling technique. A mixture of NiO and MoO3 and graphite powders were used as initial materials. After milling of powder mixture with 40 wt.% additional graphite, a temperature of 400, 550 and 1000 °C for 1 h was considered for the heat treatment of powder mixture. Also, powder mixtures containing 60, 80 and 100 wt.% a...
متن کاملOxygen reduction reaction on Pt/C at the presence of super paramagnetic of Fe3O4 nanoparticles for PEMFCs
In this paper the role of super paramagnetic iron oxide nanoparticles (SPI) on Platinum nanoclusters on activated carbon (Pt/C) for electrocatalytic oxygen reduction reaction was considered. Four composites of Pt/C and super paramagnetic iron oxide nanoparticles were prepared with the same total composites weight and different loading of Pt/C (1.2, 0.6, 0.4 and 0.3 mg ). The composite attached ...
متن کامل