Green H2 Generation from Seawater Deploying a Bifunctional Hetero‐Interfaced CoS2‐CoFe‐Layered Double Hydroxide in an Electrolyzer

This work illustrates the practicality and economic benefits of employing a hetero-interfaced electrocatalyst (CoS₂@CoFe-LDH), containing cobalt sulphide and iron-cobalt double-layer hydroxide for large-scale hydrogen generation. Here, the rational synthesis and detailed characterization of the CoS₂@CoFe-LDH material to unravel its unique heterostructure are essayed. The CoS₂@CoFe-LDH operates as a bifunctional electrocatalyst to trigger both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline seawater (pH 14.0) while showcasing low overpotential requirement for HER (311 mV) and OER (450 mV) at 100 mA cm^{- 2} current density. The identical CoS₂@CoFe-LDH on either electrode in an H-cell setup results in simultaneous H₂ and O₂ production from seawater with a ≈98% Faradaic efficiency with an applied potential of 1.96V@100 mA cm^{- 2}. Next, this CoS₂@CoFe-LDH catalyst is deployed on both sides of a membrane electrode assembly in a one-stack electrolyzer, which retains the intrinsic bifunctional reactivity of the catalyst to generate H₂ and O₂ in tandem from alkaline seawater with an impeccable energy efficiency (50 kWh kg^-1-of-H₂). This electrolyzer assembly can be directly linked with a Si-solar cell to produce truly green hydrogen with a solar-to-hydrogen generation efficiency of 15.88%, highlighting the potential of this converting seawater to hydrogen under solar irradiation.