Ir nanoclusters on ZIF-8-derived nitrogen-doped carbon frameworks to give a highly efficient hydrogen evolution reaction

The precise change of the electronic structure of active metals using low-active supports is an effective way of developing high-performance electrocatalysts. The electronic interaction of the metal and support provides a flexible way of optimizing the catalytic performance. We have fabricated an efficient hydrogen evolution reaction (HER) electrocatalyst, in which Ir nanoclusters are uniformly loaded on a nitrogen-doped carbon framework (Ir@NC). The synthesis process entails immersing an annealed zeolitic imidazolate framework-8 (ZIF-8), prepared at 900 °C as a carbon source, into an IrCl₃ solution, followed by a calcination-reduction treatment at 400 °C under a H₂/Ar atmosphere. The three-dimensional porous structure of the nitrogen-doped carbon framework exposes more active metal sites, and the combined effect of the Ir clusters and the N-doped carbon support efficiently changes the electronic structure of Ir, optimizing the HER process. In acidic media, Ir@NC has a remarkable HER electrocatalytic activity, with an overpotential of only 23 mV at 10 mA cm⁻², an ultra-low Tafel slope (25.8 mV dec⁻¹) and good stability for over 24 h at 10 mA cm⁻². The high activity of the electrocatalyst with a simple and scalable synthesis method makes it a highly promising candidate for the industrial production of hydrogen by splitting acidic water.