Molecularly Defined Interface Created by Porous Polymeric Networks on Gold Surface for Concerted and Selective CO2 Reduction

We report the design and synthesis of catalyst for electrochemical reduction of carbon dioxide, where the high geometric current of metal electrode and the excellent selectivity of molecular catalysts are combined. This was achieved by the construction of molecularly defined interface, here we term as MDI. Specifically, porous polymer networks (PPNs) based on tetrakis-5,10,15,20-(4-aminophenyl) porphyrin (H(2)TAPP) were directly synthesized by electrochemical oxidation deposition on electrode. The thickness of this polymer layer was precisely controlled from 20 to 120 nm by the number of voltammetry cycles. The formation of MDI, composed of the amine linked polymer and Au electrode, was evidenced by scanning electron microscopy (SEM), atomic force microscopy (AFM), and attenuated total reflectance infrared spectroscopy (ATR-IR). This interface was endowed with abundant amino groups and Au atoms, which provided excellent catalytic performance for electrochemical reduction of CO2 (CO2RR). Specifically, 95% of CO selectivity was achieved at the potential of -0.7 V (vs RHE), while the same gold surface only gave a 25% selectivity under the same condition. The thickness of PPN layer was found to be critical for the catalytic performance, and in this construct the ideal thickness was achieved at 60 nm.