Exfoliated CoNiAl-LDH@rGO 2D/2D Heterojunction for Sustainable Hydrogen Production via Ammonia Electrolysis

Ammonia offers promise as a hydrogen carrier and electrochemical fuel due to its high hydrogen content, ease of storage and transport, and well-established infrastructure. In this work, we report a sustainable and scalable strategy for synthesizing a bifunctional electrocatalyst by restacking exfoliated CoNiAl-layered double hydroxide (LDH) nanosheets with reduced graphene oxide (rGO), forming a 2D/2D heterojunction structure (CoNiAl-LDH@rGO). The eco-friendly water-based synthesis method avoids energy-intensive steps and ensures strong interfacial interactions between the active LDH nanosheets and conductive rGO layers. The resulting hybrid catalyst exhibits excellent performance for both the ammonia oxidation reaction (AOR) and the hydrogen evolution reaction (HER) in an alkaline ammonia electrolyte. It delivers a low overpotential of 245 mV for AOR with a Tafel slope of 65 mV dec–1 and a turnover frequency (TOF) of 0.0043 s–1 at 10 mA cm–2, indicating favorable reaction kinetics and intrinsic activity. For the HER, it achieves an overpotential of 114 mV and a TOF of 0.0157 s–1 at the same current density, demonstrating efficient hydrogen generation. In a two-electrode configuration using CoNiAl-LDH@rGO as both the anode and the cathode, the electrolyzer operates at a low cell voltage of only 1.517 V at 10 mA cm–2, maintaining exceptional operational durability over 48 h and achieving a high Faradaic efficiency of 92.58%. This work demonstrates the advantages of using earth-abundant LDH structure combined carbon supports, while also presenting an eco-friendly and scalable strategy for developing efficient electrocatalysts for low-energy hydrogen production via ammonia-assisted water electrolysis.