Understanding and Optimizing Ultra-Thin Coordination Polymer Derivatives with High Oxygen Evolution Performance

Engineering low-crystalline and ultra-thin nanostructures into coordination polymer assemblies is a promising strategy to design efficient electrocatalysts for energy conversion and storage. However, the rational utilization of coordination polymers (CPs) or their derivatives as electrocatalysts has been hindered by a lack of insight into their underlying catalytic mechanisms. Herein, a convenient approach is presented where a series of Ni10-xFex-CPs (0 <= x <= 5) is first synthesized, followed by the introduction of abundant structural deficiencies using a facile reductive method (R-Ni10-xFex-CPs). The representative low-crystalline R-Ni8Fe2-CPs (R-NiFe-CPs) with a thickness of sub-2 nm display promising oxygen evolution reaction (OER) performance with a very low overpotential of 225 mV at 10 mA cm(-2)and high long-term durability over 120 h. Comprehensive investigations including X-ray absorption spectroscopy, density functional theory, and mass diffusion theory reveal strong synergistic effects of structural deficiencies on the OER activity. A super-Nernstian pH-dependence of 85.15 mV pH(-1)suggests that the catalytic OER mechanism of R-NiFe-CPs involved a decoupled proton-electron transfer (PT/ET) pathway, leading to notably higher OER activity compared to the concerted coupled proton-electron transfer pathway. New insights into the catalytic reaction mechanisms of CP-related materials open up new approaches to expedite the design of efficient electrocatalysts.