First-Principles Prediction of New Complex Transition Metal Hydrides for High Temperature Applications

Abstract

Metal hydrides with high thermodynamic stability are desirable for high-temperature applications, such as those that require high hydrogen release temperatures or low hydrogen overpressures. First-principles calculations have been used previously to identify complex transition metal hydrides (CTMHs) for high temperature use by screening materials with experimentally known structures. Here, we extend our previous screening of CTMHs with a library of 149 proposed materials based on known prototype structures and charge balancing rules. These proposed materials are typically related to known materials by cation substitution. Our semiautomated, high-throughput screening uses density functional theory (DFT) and grand canonical linear programming (GCLP) methods to compute thermodynamic properties and phase diagrams: 81 of the 149 materials are found to be thermodynamically stable. We identified seven proposed materials that release hydrogen at higher temperatures than the associated binary hydrides and at high temperature, T > 1000 K, for 1 bar H2 overpressure. Our results indicate that there are many novel CTMH compounds that are thermodynamically stable, and the computed thermodynamic data and phase diagrams should be useful for selecting materials and operating parameters for high temperature metal hydride applications.

H2/D2 isotopic exchange: A tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts

“…5 and 6). MRu bimetallics (where M is an alkali metal) forming more stable hydrides [53], Ru hydride might be located at the periphery of Ru particles where the concentration of Na is the highest. In the promoted catalysts, more Ru atoms would be free of RuHx species, which may explain why they are less sensitive to residual H species.…”

Ruthenium Complex Hydride Catalysts as a Platform for Ammonia Synthesis

“…As the electric power generated from renewable energy sources becomes more technically and economically viable, nowadays much efforts have been placed on the electrolysis Haber-Bosch process (eHB), where renewable electricity is used to electrolyze H2O to produce H2, separate N2 from air and power the N2+H2 to NH3, etc [4][5] . To improve its compatibility with the renewable electricity as well as to reduce the energy cost, the eHB process generally requires an active catalyst that can operate at lower pressures (< 50 bar) and lower temperatures (< 673 K) 6 .…”

Structural, electronic, optical and elastic properties of the complex K2PtCl6-structure hydridesARuH6(A= Mg, Ca, Sr and Ba): first-principles study

“…All hydrides were synthesised by the direct reaction of a powdered mixture of the alkaline/alkaline-earth/rare-earth hydride and the transition metal in hydrogen at elevated temperatures (450-500 °C) and pressures (7-130 bar) [4]. Owing to their potential wide range of technological applications (at least for some of them) such as the hydrogen solid-state storage [16,17], rechargeable batteries [17], smart windows [18][19][20][21], switchable mirrors [12][13][14][15][16][17][18][19][20][21][22][23][24][25], etc. they have been the subject of intensive experimental and theoretical research efforts [23,[26][27][28].…”

“…Owing to their potential wide range of technological applications (at least for some of them) such as the hydrogen solid-state storage [16,17], rechargeable batteries [17], smart windows [18][19][20][21], switchable mirrors [12][13][14][15][16][17][18][19][20][21][22][23][24][25], etc. they have been the subject of intensive experimental and theoretical research efforts [23,[26][27][28]. For the aforementioned applications, especially for the hydrogen solid-state storage application, the requested hydrides should have some specific properties, such as fast kinetics of the hydrogenation/dehydrogenation processes without degradation of the material, low temperature at which the hydrogenation/dehydrogenation occurs, large hydrogen content, low total weight and powder form of hydrides [29,30].…”

“…Due to their high decomposition temperature T d , which is generally greater than 550 K, the CTMHs have been largely ignored for ambient temperature applications such as hydrogen solid-state storage in fuel cell vehicles [31]. However, the high stabilities and high hydrogen density of these hydrides make them potentially attractive for high-temperature applications, such as the thermochemical storage of heat for solar thermal plants or excess industrial heat for which hydrogen discharge temperature exceeding 700 K are desired [23,31,32]. On other hand, the high temperature stabilities and semiconducting character of some of these materials led the researchers to the idea that these hydrides can be useful in semiconductor electronics [33,34], photovoltaics [35] and optoelectronic devices [36].…”