Monolayer Iron and Iron-Rich Hydroxide Nanosheets Exfoliated from High-Quality Green Rust for Enhanced Electrocatalytic Oxygen Evolution Reaction

摘要

Ultrathin nanosheets of Ni-, Co-, and Pe-based (oxy)hydroxides exhibit promising catalytic activity for the oxygen evolution reaction (OER) in water electrolysis under alkaline conditions. It has been revealed that Fe may play a crucial role in the catalytic process of Ni- or Co-based catalysts. However, it lacks effective methods to prepare and study pure Fe hydroxide nanosheets. In the present work, we report a topochemical synthesis of mixed-valent Fe2+—Fe3+ layered double hydroxides (LDHs), i.e., Green Rust (GR), featured with much higher quality and crystallinity compared to the traditionally synthesized ones. Monolayer Fe2+—Fe3+ LDH nanosheets with a thickness of ~0.8 nm were derived from the GR product. In addition, a series of Ni-bearing Fe-rich LDH nanosheets were successfully prepared by the same method. The OER catalytic performance of the obtained Fe-rich LDH nanosheets achieved a small overpotential with // = 290 mV(3>10 mA cm-2 in 1 M KOH, which either outperforms or is comparable to the most active Ni—Fe LDH catalysts. The monolayer Fe +—Fe3+ LDH nanosheets may be ideal for exploring the fundamental physicochemical properties of iron hydroxides from a molecular-scale perspective as well as serving as a building block for the assembly with other functional materials to obtain hybrid nanocatalysts.