Strained Nickel Phosphide Nanosheet Array.

We develop strained nickel phosphide nanosheets with 5 nm thickness and several hundreds of nanometers lateral size aligned on the top of nickel foam/nickel sulfide support. The material is characteristic of substantial compressive strain of 5.6% along nickel-phosphorus bond length, originated from the in situ topotactic transformation. The architecture demonstrates excellent performances toward electrocatalytic hydrogen evolution with the turnover frequency exceeding its strain-free counterpart by a factor of 24. Further study reveals the strain effect leads to downshifts of the d-band center in Ni-P bonds, weakens the adsorption to hydrogen species, and in turn facilitates hydrogen formation and desorption for boosted catalysis.