Interlayer confinement synthesis of Ir nanodots/dual carbon as an electrocatalyst for overall water splitting

Abstract

Rationally designing low-content and high-efficiency noble metal nanodots offers opportunities for enhancing their electrocatalytic performance for water splitting. However, the preparation of highly dispersed nanodot electrocatalysts remains a challenge. Herein, we report the interlayer confinement synthesis of sulfur-doped carbon-coated Ir nanodots on reduced graphene oxide (Ir@S–C/rGO) as an electrocatalyst for overall water splitting. The Ir@S–C/rGO composite is derived from a guest/host precursor of dodecyl sulfate (DS⁻)/hexachloroiridate (IrCl₆³⁻) co-intercalated MgAl-layered double hydroxide on a GO support. The composite has these advantages: Ir nanodots (1.7 ± 0.2 nm) with a low Ir amount of 6.2 wt%, S-doped carbonaceous encapsulation and a rGO support, as well as a large specific surface area of 194 m² g⁻¹ and meso-/macropore size distribution. The composite electrode requires overpotentials of 280 and 300 mV at 10 and 20 mA cm⁻², respectively, for the oxygen evolution reaction (OER) in alkaline conditions; and 20 and 35 mV at 10 and 20 mA cm⁻² for the hydrogen evolution reaction (HER) in alkaline conditions, respectively. Furthermore, a two-electrode electrolyzer yields a current density of 10 mA cm⁻² at 1.51 V for overall water splitting. Moreover, the density functional theory calculations show that the charge distribution of the Ir nanoclusters facilitates the enhancement of the electrocatalytic activity for the OER, and the sulfur-doped carbon lowers the work function of the Ir particles on graphene; both of which underpin the enhancement. Our guest/host-assisted interlayer nanoconfinement can promise an effective synthesis strategy for designing and preparing well-dispersed nanodots as promising electrocatalysts for water splitting.