Fig. 4: Process of electron exchange between the CNTd series and free chlorine.
From: Intrinsic strain of defect sites steering chlorination reaction for water purification
a EPR test of CNTd and CNTd–S2 mixed with (the solid line) or without (the polygon dots) free chlorine. b Modified Koutecky–Levich plot of the free chlorine reduction measured by a rotating disk electrode apparatus for CNTd and CNTd–S2 to estimate the electron transfer number between the catalysts and free chlorine. The inset illustrates the reaction process of HOCl and catalyst onto the electrode. c Charge density difference and Bader charge analysis of CNTd without strain (0%) and with 6% strain reacting with HOCl, as calculated by DFT. The isosurfaces of green and yellow indicate the depletion and accumulation of electrons, respectively. d LSV curves of CNTd and CNTd–S2 with (the half–hollow dots) or without (the hollow dots) free chlorine. e Comparison of the adsorption energy and adsorption types between CNTd without strain (0) and with 6% strain toward free chlorine. The insets are schematic diagrams of HOCl adsorption onto the sites of the strained and unstrained. In‒situ Raman spectra to detect the intermediates in f CNTd–S2/free chlorine system and (g) CNTd/free chlorine system. h Free energy diagram of CNTd without strain (0%) and with 6% strain used for chlorination. IS: initial state; TS: transition state; FS: final state. The insets are schematic diagrams of HOCl decomposition processes onto the sites of the strained and unstrained.
