Understanding the role of elastic strain in modifying catalytic reaction rates is crucial for catalyst design, but experimentally, this effect is often coupled with a ligand effect. To isolate the strain effect, we have investigated the influence of externally applied elastic strain on the catalytic activity of metal films in the hydrogen evolution reaction (HER). We show that elastic strain tunes the catalytic activity in a controlled and predictable way. Both theory and experiment show strain controls reactivity in a controlled manner consistent with the qualitative predictions of the HER volcano plot and the d-band theory: Ni and Pt's activities were accelerated by compression, while Cu's activity was accelerated by tension. By isolating the elastic strain effect from the ligand effect, this study provides a greater insight into the role of elastic strain in controlling electrocatalytic activity.

On the basis of first principle density functional theory, we have studied the stability, electronic structure, and hydrogen storage capacity of a monolayer calcium doped graphane (CHCa). The stability of CHCa was further investigated using the ab initio molecular dynamics study. The binding energy of Ca on graphane sheet was found to be higher than its bulk cohesive energy, which indicates the stability of CHCa. It was observed that with a doping concentration of 11.11% of Ca on graphane sheet, a reasonably good H2 storage capacity of 6 wt. % could be attained. The adsorption energies of H2 were found to be 0.1 eV, within the range of practical H2 storage applications.

Highly organized crossed bilayer assemblies of nanowires (NWs) are made using directed hydrogen bonding between the protecting ligand shells of atomically precise cluster molecules anchored on NWs. Layers of quantum clusters remain sandwiched between two neighboring NWs at a defined distance, dictated by the core-size of the cluster, while the orientation of the ligands in space dictates the interlayer geometry.

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The influence of strain on catalytic activity has previously been examined directly by calculations and indirectly by experiments. The origin of the phenomenon has been attributed to strain-induced changes in the catalyst electronic structure. By employing a Pd-based metallic glass film capable of large elastic strains, we provide direct experimental evidence for catalytic activity being differently influenced by mechanically applied uniaxial tensile and compressive strains. We demonstrate the effect on the oxygen reduction reaction with cyclic voltammetry (CV) curves at different strain levels and compare X-ray photoelectron spectrometry (XPS) results for unstrained and strained (in uniaxial tension) specimens to confirm valence electron band shifts. The experimental findings are complemented by electronic structure calculations on single crystal Pd, as well as alloys with Cu and Si. The CV and XPS shifts observed in the experiments are consistent in both direction and magnitude to those predicted by theory for single crystal Pd.

Transition-metal-based systems show promising binding energy for hydrogen storage but suffer from clustering problem. The effect of light transition metal (M = Sc, Ti) decoration, boron substitution on the hydrogen storage properties of MOF-5, and clustering problem of metals has been investigated using ab initio density functional theory. Our results of solid-tate calculations reveal that whereas Ti clusters strongly Sc atoms do not suffer from this problem when decorating MOF-5. Boron substitution on metal-decorated MOF-5 enhances the interaction energy of both the metals with MOF-5. Sc-decorated MOF-5 shows a hydrogen storage capacity of 5.81 wt % with calculated binding energies of 20−40 kJ/mol, which ensures the room-temperature applicability of this hydrogen storage material.

Pseudomorphic catalytic systems can exhibit enhanced or inhibited activity relative to the pure surface parent metal, based on a combination of strain and ligand effects. In contrast, mechanically strained and dealloyed systems can exhibit pure strain effects. Density functional calculations for hydrogen adsorption at different coverages between 0.25 and 1 monolayer on biaxially strained Pd(111) are carried out to illustrate its differing catalytic behavior for the hydrogen evolution reaction (HER) in comparison to selected pseudomorphic Pd overlayers (Pd/M). The separation of the ligand and strain effects present in Pd/M pseudomorphs and the consequent modification of the binding strengths caused by them individually are estimated. The strain exhibits a systematic contribution to binding energy changes while the ligand effect can act to either intensify or weaken the strain effect. In certain systems (e.g., Pd/Ir) the ligand effect is more pronounced than the strain effect while in others (e.g., Pd/Au) the strain effect is larger. The individual contributions of strain and ligand effects to shifts in the d-band center are also calculated and found to correlate well with the observed binding energy changes. We suggest that in the absence of a ligand effectas would be expected in mechanically strained Pd (111)H binding is tunable, and a differential free energy of hydrogen adsorption of ∼0 eV (at 0 V vs RHE) is achieved at various combinations of strain and coverage. For pure Pd under compressive strain, this leads to a prediction of a broad region of enhanced activity for the HER which may compare favorably to Pd overlayers supported on more expensive metals such as Pt and PtRu.

Based on the first-principle density functional calculations we predict that Li-doped graphane (prehydrogenated graphene) can be a potential candidate for hydrogen storage. The calculated Li-binding energy on graphane is significantly higher than the Li bulk's cohesive energy ruling out any possibility of cluster formations in the Li-doped graphane. Our study shows that even with very low concentration (5.56%) of Li doping, the Li-graphane sheet can achieve a reasonable hydrogen storage capacity of 3.23 wt.%. The van der Waals corrected H2 binding energies fall within the range of 0.12-0.29 eV, suitable for practical H2 storage applications.