Dynamic Adsorption of Molybdate Promoted Self‐Optimization and Self‐Healing of NiFe/NiMo in Alkaline Water Electrolysis

Why It Matters

The catalyst’s self‑optimizing and self‑healing traits dramatically extend electrode lifespan while slashing energy consumption, accelerating commercial alkaline electrolyzer deployment.

Key Takeaways

• NiFe/NiMo reaches 100 mA cm⁻² at 99 mV HER overpotential
• OER overpotential 233 mV for same current density
• Free MoO₄²⁻ enables HER self‑optimization and OER self‑healing
• MoO₄²⁻ suppresses Fe leaching, maintaining catalyst stability
• Two‑electrode cell operates at 1.707 V for 100 mA cm⁻²

Pulse Analysis

Alkaline water electrolysis is gaining traction as a cost‑effective pathway to green hydrogen, yet its widespread adoption hinges on catalysts that can efficiently drive both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) over long periods. Conventional bifunctional materials often suffer from rapid degradation, especially on the OER side where iron leaching erodes activity. Introducing a heterojunction of nickel‑iron layered double hydroxide (NiFe‑LDH) and nickel‑molybdenum (NiMo) nanostructures addresses this gap by combining HER‑active nanopillars with OER‑active nanosheets, delivering low overpotentials at industrially relevant current densities.

The breakthrough lies in the strategic use of free molybdate ions (MoO₄²⁻) dissolved in the alkaline electrolyte. During HER, MoO₄²⁻ adsorbs onto NiFe‑LDH surfaces, dynamically tuning electronic states and exposing more active sites, which translates into a 99 mV overpotential at 100 mA cm⁻². For OER, the same ions act as a protective agent, either inhibiting iron dissolution or re‑adsorbing leached Fe back onto the catalyst, effectively “self‑healing” the electrode and preserving performance. This dual functionality reduces the need for frequent catalyst replacement and minimizes operational downtime.

From a market perspective, the NiFe/NiMo system’s ability to run a two‑electrode electrolyzer at just 1.707 V for 100 mA cm⁻² represents a significant energy saving, directly lowering the levelized cost of hydrogen. The approach is compatible with existing alkaline cell designs, facilitating scale‑up without major redesigns. As the industry seeks to meet aggressive decarbonization targets, such self‑optimizing, durable catalysts could become a cornerstone of next‑generation hydrogen production infrastructure, prompting further investment in molybdate‑mediated electrolyte engineering.