Accelerating Hydrogen Absorption and Desorption Rates in Palladium Nanocubes with an Ultrathin Surface Modification

Abstract

Exploiting the high surface-area-to-volume ratio of nanomaterials to store energy in the form of electrochemical alloys is an exceptionally promising route for achieving high-rate energy storage and delivery. Nanoscale palladium hydride is an excellent model system for understanding how nanoscale-specific properties affect the absorption and desorption of energy carrying equivalents. Hydrogen absorption and desorption in shape-controlled Pd nanostructures does not occur uniformly across the entire nanoparticle surface. Instead, hydrogen absorption and desorption proceed selectively through high-activity sites at the corners and edges. Such a mechanism hinders the hydrogen absorption rates and greatly reduces the benefit of nanoscaling the dimensions of the palladium. To solve this, we modify the surface of palladium with an ultrathin platinum shell. This modification nearly removes the barrier for hydrogen absorption (89 kJ/mol without a Pt shell and 1.8 kJ/mol with a Pt shell) and enables diffusion through the entire Pd/Pt surface.

Cyclic Voltammetry Study of Noble Metals and Their Alloys for Use in Implantable Electrodes

“…Palladium’s ability to absorb hydrogen and lower reversibility may also present barriers to application. Several reports have shown that engineering of the Pd material to vary grain size, lattice parameter, and alloying constituents may accelerate hydrogen sorption rates . Results shown here agree that these are worthwhile endeavors, and Pd-based materials should be considered as alternative implantable electrode materials.…”

“…Hydrogen diffusion into Pd occurs at a rate of 10 −11 m 2 /s, after first adsorbing onto the surface and then transferring through to the subsurface (the rate-determining step). 37 One possible interpretation is that faster scan rates limit the completion of the rate-determining transfer step needed for H absorption into Pd and its alloys. In that case, one would expect higher scan rates to decrease absolute values of CSC HA and CSC HD .…”

“…Hydrogen diffusion into Pd occurs at a rate of 10 –11 m 2 /s, after first adsorbing onto the surface and then transferring through to the subsurface (the rate-determining step). 37 …”

“…This points toward slower reaction kinetics at the Pd surface, possibly due to the aforementioned hydrogen absorption. Hydrogen diffusion into Pd occurs at a rate of 10 –11 m 2 /s, after first adsorbing onto the surface and then transferring through to the subsurface (the rate-determining step) …”

Phase Engineering of a Ruthenium Nanostructure toward High-Performance Bifunctional Hydrogen Catalysis

“…Phase engineering of nanomaterials has found a wide spectrum of applications in electrical, optical, (opto)­electronic, magnetic, and catalytic fields for functionality tuning. − As an additional knob to composition, size, and morphology tuning, phase control can achieve dramatically different electronic structures and thereby modulated physicochemical properties of nanomaterials. − In comparison to the substantial works on composition, size, and morphology tuning of metal nanomaterials, however, the study of phase modulation is relatively scarce and remains challenging, mainly arising from the difficulty in synthesizing unconventional crystal phases. − To achieve crystal phase-controlled synthesis of metal-based nanomaterials, diversified methods have been developed that can be classified into two categories, that is, direct synthesis and phase transformation. , In addition, the direct synthesis method is often combined with the phase transformation method such as high-temperature and high-pressure treatment to achieve precise phase modulation. , …”