Conjugated Coordination Polymer Aerogels with Increased Accessibility of Well-Defined Single-Atom Metal Sites as a New Paradigm of Electrocatalysts

Abstract

Developing high-performance single-atom catalysts (SACs) with maximum metal utilization efficiency is of significance, which presents enormous potentials to be extensively applied. It is desired yet challenging to elaborately tailor the coordination structures of active sites in SACs and simultaneously enable sufficient accessibility of these active sites to reactants. Here, a facile and general strategy to prepare conjugated coordination polymer aerogels (CCPA) with porous architectures that can markedly increase the accessibility of their elaborately-tailored active sites, which as a new electrocatalyst paradigm can fully present both the structural advantages of SACs and aerogel materials, is reported. Taking nickel (Ni) as an example, Ni-based CCPA (Ni-CCPA) and its counterpart Ni-CCP with non-aerogel feature are studied as a proof-of-concept case. Electrochemical measurements show that, relative to Ni-CCP, Ni-CCPA exhibits appreciably higher performance toward alkaline oxygen evolution reaction (OER). Both the experimental results and theoretical simulations unravel that the improved OER performance of Ni-CCPA arises from the accelerated OH⁻ diffusion within its porous architecture and enhanced OH⁻ concentration near its highly exposed active sites at its high-curvature surfaces with localized electric fields. Importantly, as evidenced by the Cu-CCPA and Zn-CCPA examples, such strategy can be promisingly applied to prepare high-performance CCPA targeted toward various catalytic reactions and beyond.