“Inverse Strain Effect in Atomic Scale”—Enhanced Hydrogen Evolution Activity and Durability in Cu-Substituted Palladseite

Since the preceding decade, strain engineering has been playing a vital role in modifying the activity of electrocatalysts. Incorporation of tensile strain into a Pd-based system usually requires substitution with larger atoms (usually a third row expensive transition metals). This work provides a unique strategy of introducing tensile strain by the substitution of small and low cost copper atoms (inverse strain effect) at the palladium sites of Pd17Se15. The Pd atom being in the +2 oxidation state adsorbs hydrogen very weakly, and Se, in its elemental state, binds weakly to H* adsorbate. However, the presence of Pd modulates the electronic structure of Se to have ΔGH* close to 0 and favors the progress of the reaction. Cu substitution further lowers ΔGH*, thus favoring the reaction. This unique synergistic effect between the two processes is accountable for better activity, high stability of 30 000 cycles and significantly high turnover frequency of 126.3 s–1 for (CuPd)17Se15.