NiAg_0.4 3D porous nanoclusters with epitaxial interfaces exhibiting Pt like activity towards hydrogen evolution in...

The necessity of Earth-abundant low-cost catalysts with activity similar to noble metals such as platinum is indispensable in order to realize the production of hydrogen through electrolysis of water. Herein, we report a relatively low-cost NiAg_0.4 3D porous nanocluster catalyst whose activity matches with that of the state-of-the-art Pt/C in 1 M KOH solution. The catalyst is designed on the principle of creating an interface between a metal having a positive Gibbs energy of hydrogen adsorption and a metal of negative Gibbs energy based on the volcano plot, to tune the Gibbs energy of hydrogen adsorption near zero for enhanced hydrogen evolution. The synthesized NiAg_0.4 3D porous nanoclusters are comprised of nanoparticles of lateral dimension ∼50 nm forming a 3D porous network with pores of 10 nm-80 nm. A high-resolution transmission electron microscopy image reveals the epitaxial growth of Ag (200) on the Ni (111) plane leading to the creation of abundant interfaces between the Ni and Ag lattices. The catalyst needs a low overpotential of 40 mV@10 mA cm^-2 with a Tafel slope of 39.1 mV dec^-1 in 1 M KOH solution. Furthermore, the catalyst exhibits a high specific activity of 0.1 mA cm^-2_(ECSA) at an overpotential (η) of 45 mV which matches with the specific activity of Pt/C 20% wt. catalyst (0.1 mA cm^-2@η = 26 mV). Density functional theory calculations reveal that the Ni-Ag interface furnishes a pathway with a reduced Gibbs energy of adsorption of -0.04 eV, thus promoting enhanced hydrogen evolution. In summary, this study reveals excellent HER activity at the Ni-Ag interface.