Scrutinizing Synergy and Active Site of Nitrogen and Selenium Dual-Doped Porous Carbon for Efficient Triiodide Reduction

Abstract

Electrocatalytic interconversion of iodide/triiodide is the key for state-of-the-art iodine-involved energy technologies, which is challenged by understanding the structure–activity relationship of the smart electrocatalysts with tuned active sites. Herein, active-site-enriched N,Se-co-doped porous carbon, denoted as NSeC, is crafted by a two-step approach of the template method and chemical doping. X-ray photoelectron spectroscopy and synchrotron X-ray absorption spectroscopy measurements substantiate the incorporation of extrinsic N and Se species into the carbon matrix. Raman spectroscopy reveals that the defect of densities within NSeC can be finely tuned by adjusting the doping temperature. The NSeC sample made at 900 °C shows a robust durability and a high electrocatalytic activity toward the triiodide reduction reaction with a relatively small charge-transfer resistance (0.75 Ω cm2) in parallel with a short electron lifetime (252.2 μs) participating in the triiodide reduction. Density functional theory calculations reveal that the high catalytic activity of the NSeC is due to the combined impacts, i.e., the synergy between N and Se species that helps to manipulate the adsorption process of iodine atoms and the active sites formed by the carbon atoms adjacent to quaternary N and Se atoms at the armchair edges. This work offers insights into both the design of efficient metal-free catalysts and the synergy of dual doping for efficient iodine-involved electrocatalysis for energy devices.