Powered by DFT: Screening Methods That Accelerate Materials Development for Hydrogen in Metals Applications

Abstract

CONSPECTUS: Not only is hydrogen critical for current chemical and refining processes, it is also projected to be an important energy carrier for future green energy systems such as fuel cell vehicles. Scientists have examined light metal hydrides for this purpose, which need to have both good thermodynamic properties and fast charging/discharging kinetics. The properties of hydrogen in metals are also important in the development of membranes for hydrogen purification. In this Account, we highlight our recent work aimed at the large scale screening of metal-based systems with either favorable hydrogen capacities and thermodynamics for hydrogen storage in metal hydrides for use in onboard fuel cell vehicles or promising hydrogen permeabilities relative to pure Pd for hydrogen separation from high temperature mixed gas streams using dense metal membranes. Previously, chemists have found that the metal hydrides need to hit a stability sweet spot: if the compound is too stable, it will not release enough hydrogen under low temperatures; if the compound is too unstable, the reaction may not be reversible under practical conditions. Fortunately, we can use DFT-based methods to assess this stability via prediction of thermodynamic properties, equilibrium reaction pathways, and phase diagrams for candidate metal hydride systems with reasonable accuracy using only proposed crystal structures and compositions as inputs. We have efficiently screened millions of mixtures of pure metals, metal hydrides, and alloys to identify promising reaction schemes via the grand canonical linear programming method. Pure Pd and Pd-based membranes have ideal hydrogen selectivities over other gases but suffer shortcomings such as sensitivity to sulfur poisoning and hydrogen embrittlement. Using a combination of detailed DFT, Monte Carlo techniques, and simplified models, we are able to accurately predict hydrogen permeabilities of metal membranes and screen large libraries of candidate alloys, selections of which are described in this Account. To further increase the number of membrane materials that can be studied with DFT, computational costs need to be reduced either through methods development to break bottlenecks in the performance prediction algorithm, particularly related to transition state identification, or through screening techniques that take advantage of correlations to bypass constraints.

Nano-Intermetallic InNi3C0.5 Compound Discovered as a Superior Catalyst for CO2 Reutilization

“…In the last decade, significant advances have been achieved in the atomistic-theoretical calculations, enabling us to computationally construct molecular and crystalline structures and to reveal the reaction pathways on the catalyst surface at atomic-molecular level (Nicholson et al., 2014, Qin et al., 2018, Studt et al., 2014, Mao et al., 2017). Therefore, the RWGS reaction mechanism on InNi 3 C 0.5 is first investigated by the density functional theory (DFT) calculations.…”

“…Against all odds, the tantalizing progresses in nano-intermetallic catalysis (Stamenkovic et al., 2007, Studt et al., 2014) open an opportunity for designing and tailoring qualified RWGS catalysts because nano-intermetallic has fascinating prospects in catalysis field, with their tunable components and ratios, variable constructions, and reconfigurable electronic structures, distinctly different from their single metals (Stamenkovic et al., 2007, Armbrüster et al., 2012, Ji et al., 2010). Particularly, their precise atomic ordering structure can provide rational predictions of the effects of geometry and electronic structure on their catalytic properties for required reactions (Wang et al., 2013, Nicholson et al., 2014, Qin et al., 2018). One of the recent pertinent examples is the discovery of a Ni 5 Ga 3 nano-intermetallic, which strikingly shows that the Ni, originally active for CO 2 methanation, turns itself suddenly into a qualified CO 2 -to-CH 3 OH catalyst after Ga alloying (Studt et al., 2014), because this intermetallic offers the unique Ga-rich sites for CH 3 OH formation.…”

Recent developments in membranes for efficient hydrogen purification

“…Influences of alloy content, membrane thickness, test conditions and potential contaminants (CO and H 2 O) on performances of Pd-alloy membranes have been widely and intensively investigated via experimental study. Moreover, detailed density functional theory (DFT) and Monte Carlo techniques have been used to predict the hydrogen permeability and the resistance to poisoning of the membranes based on diverse alloys, giving the guideline for the design of Pd-alloy membranes [26,27].…”

Grain Boundary Segregation in Pd-Cu-Ag Alloys for High Permeability Hydrogen Separation Membranes

“…First-principles modelling has been demonstrated to be a powerful tool in the development of membrane materials [ 24 ]; as an example, density functional theory (DFT) has been used to systematically screen for novel binary intermetallic systems for hydrogen separation membranes [ 25 ]. A few studies have also investigated ternary alloys for membranes.…”