Pyrolyzed Cyanide-Bridged Ni-Fe MOF for Oxygen Evolution: Inactivation Pathways and Enhancement Mechanisms

Abstract

A cyanide-bridged Ni-Fe MOF@CNT composite (MOF = metal-organic framework; MWCNTs = Multi-Walled Carbon Nanotubes) was prepared using tricyanidoferrate, nickel salts, and conductive substrates of MWCNTs. The relationship between phase structure changes at different temperatures and oxygen evolution reaction (OER) performance was explored. The results show that the Ni-Fe MOF decomposes significantly above 600 °C, and there is an interaction between the decomposition products and MWCNTs. At a low loading (MOF mass fraction < 10%), MWCNTs penetrate Ni-Fe oxide nanocrystals, leading to good alkaline OER performance. However, at a high loading (MOF mass fraction > 10%), the Ni-Fe oxide crystal phase encapsulates MWCNTs, exhibiting poor catalytic performance due to the formation of dense crystals, reduced conductivity, and decreased surface area.Ni-Fe MOF's template role creates nitrogen defects in catalysts. Density functional theory shows nitrogen changes atom spacing near active sites, boosting catalytic function. This work offers valuable insights and an effective approach to addressing issues related to performance degradation encountered during the pyrolytic processing of non-noble-metal complex precursors for developing highly efficient and robust OER electrocatalysts.