Understanding the effect of mechanical strains on the catalytic activity of transition metals

Applicability of the d-Band Model to Predict the Influence of Elastic Strains on the Adsorption Energy of Different Adsorbates onto Pt and PtO2 Surfaces

The influence of elastic strains on the adsorption processes of seven adsorbates (H, C, N, O, CO, NO, and H) onto the surface of Pt(111) and PtO2 (110) has been investigated using density functional theory (DFT) simulations. The total adsorption energy was decomposed into mechanical and electronic contributions. Our results indicate that elastic strain in metals affects the adsorption energy by modifying the electronic structure of the surface rather than changing the physical space where the atoms reside after adsorption. In fact, the mechanical contribution to the adsorption energy in Pt was negligible compared to the electronic interaction and independent of the deformation. The mechanical contribution in the case of PtO2 was also independent of the applied strain, but its magnitude was slightly higher due to the ionic bonding between Pt and O atoms in the slab. The variation of the electronic contribution to the adsorption energy in Pt and PtO2 followed the predictions of the d-band model for all adsorbates, expanding its applicability to different adsorbates onto the same surface and to oxides.

Climbing the Hydrogen Evolution Volcano with a NiTi Shape Memory Alloy

Alkaline water electrolysis is a sustainable way to produce green hydrogen using renewable electricity. Even though the rates of the cathodic hydrogen evolution reaction (HER) are 2-3 orders of magnitude less under alkaline conditions than under acidic conditions, the possibility of using non-precious metal catalysts makes alkaline HER appealing. We identify a novel and facile route for substantially improving HER performance via the use of commercially available NiTi shape memory alloys, which upon heating undergo a phase transformation from the monoclinic martensite to the cubic austenite structure. While the room-temperature performance is modest, austenitic NiTi outperforms Pt (which is the state-of-the-art HER electrocatalyst) in terms of current density by ≤50% at 80 °C. Surface ensembles presented by the austenite phase are computed with density functional theory to bind hydrogen more weakly than either metallic Ni or Ti and to have binding energies ideally suited for HER.

Dual-plasmonic Au@Cu7S4 yolk@shell nanocrystals for photocatalytic hydrogen production across visible to near infrared spectral region

Near infrared energy remains untapped toward the maneuvering of entire solar spectrum harvesting for fulfilling the nuts and bolts of solar hydrogen production. We report the use of Au@Cu7S4 yolk@shell nanocrystals as dual-plasmonic photocatalysts to achieve remarkable hydrogen production under visible and near infrared illumination. Ultrafast spectroscopic data reveal the prevalence of long-lived charge separation states for Au@Cu7S4 under both visible and near infrared excitation. Combined with the advantageous features of yolk@shell nanostructures, Au@Cu7S4 achieves a peak quantum yield of 9.4% at 500 nm and a record-breaking quantum yield of 7.3% at 2200 nm for hydrogen production in the absence of additional co-catalysts. The design of a sustainable visible- and near infrared-responsive photocatalytic system is expected to inspire further widespread applications in solar fuel generation. In this work, the feasibility of exploiting the localized surface plasmon resonance property of self-doped, nonstoichiometric semiconductor nanocrystals for the realization of wide-spectrum-driven photocatalysis is highlighted.