Enhanced acidic hydrogen evolution reaction kinetics via nitrogen-doped iridium nanosheet with optimized hydrogen adsorption energy

[Display omitted] •A new two-dimensional metastable trigonal iridium oxide as precursor.•Nitrogen-doped iridium nanosheets for hydrogen evolution reaction.•Excellent hydrogen evolution reaction activity with overpotential of 19 mV@-10 mA cm−2.•Adjacent nitrogen modulates the strong hydrogen adsorption energy of iridium sites. The hydrogen evolution reaction (HER) is influenced by the adsorption/desorption of hydrogen intermediates on active sites. Nitrogen doping is a way to alter the electronic structure and boost the activity of metal electrocatalysts although the mechanism remains controversial. Here, nitrogen is incorporated into face-centered cubic iridium nanosheets (N-fcc-Ir-NSs) through the ammonia reduction of metastable two-dimensional pristine trigonal iridium oxide. With a nitrogen content of only 0.8 wt%, N-fcc-Ir-NSs exhibit a low overpotential of 19 mV at −10 mA cmgeo-2 and a Tafel slope of 18.6 mV dec-1 in sulfuric acid. The doped nitrogen reduces hydrogen adsorption energy by modulating the electronic structure of iridium atoms, and the combined effects of iridium sites with strong hydrogen adsorption energy and iridium sites near the nitrogen atoms with weak hydrogen adsorption energy improve the HER activity. Moreover, the presence of nitrogen causes iridium to donate more electrons to hydrogen and promotes hydrogen desorption.