Electrochemical Flocculation Integrated Hydrogen Evolution Reaction of Fe@N‐Doped Carbon Nanotubes on Iron Foam for Ultralow Voltage Electrolysis in Neutral Media

Hydrogen (H₂) production is a key step in solving the energy crisis in the future. Electrocatalytic water splitting suffers from sluggish anodic oxygen evolution reaction (OER) kinetics leading to low energy conversion efficiency. Herein, a strategy is presented that integrates anodic electrochemical flocculation with cathodic hydrogen production from water splitting in 0.5 m Na₂SO₄. Iron encapsulated in a nitrogen-doped carbon nanotubes array on iron foam (Fe@N-CNT/IF) is employed as an electrode for the hydrogen evolution reaction (HER), and the Fe@N-CNT/IF possesses superior HER activity requiring an overpotential of 525 mV to achieve 10 mA cm⁻², which is close to that of 20 wt% Pt/C. Benefiting from the lower oxidation potential of iron (E°Fe/Fe2+, 0.44 V) than that of OER (E ⁰ OH-/O2, 1.23 V), the cell voltage for integrated electrochemical flocculation and H₂ production is significantly reduced by 1.31 V relative to overall water splitting to achieve 20 mA cm⁻². More important, the production of electrochemical flocculation can be applied to water purification, because of the excellent adsorption capacity. Finally, metal-carbon electrocatalysts are prepared again by pyrolysis of flocculation adsorbents containing toxic heavy metals and organics. This result provides a new direction for designing a heterogeneous electrolysis system for energy conversion and environmental treatment applications.