Boron leaching: Creating vacancy-rich Ni for enhanced hydrogen evolution

Creating vacancy is often highly effective in enhancing the hydrogen evolution performance of transition metal-based catalysts. Vacancy-rich Ni nanosheets have been fabricated via topochemical formation of two-dimentional (2D) Ni₂B on graphene precursor followed by boron leaching. Anchored on graphene, a few atomic layered Ni₂B nanosheets are first obtained by reduction and annealing. Large number of atomic vacancies are then generated in the Ni₂B layer via leaching boron atoms. When used for hydrogen evolution reaction (HER), the vacancy-rich Ni/Ni(OH)₂ heterostructure nanosheets demonstrate remarkable performance with a low overpotential of 159 mV at a current density of 10 mA·cm⁻² in alkaline solution, a dramatic improvement over 262 mV of its precursor. This enhancement is associated with the formation of vacancies which introduce more active sites for HER along Ni/Ni(OH)₂ heterointerfaces. This work offers a facile and universal route to introduce vacancies and improve catalytic activity.