Fig. 7: QXAFS technique exploring real-time kinetic processes.

Cu K-edge XANES (a) and FT-EXAFS spectra (b) for Cu–N–C during the first 400 s of CO₂RR under static −1.35 V potential. The inset in a shows a structure model of the Cu single sites. Evolution of FT-EXAFS (c, e) and XANES (d) spectra during pulsed CO₂RR with E_c = −1.35 V, Ea = 0.44 V and Δt_a = Δt_c = 30 s. c, d Changes in the catalyst during the first 200 s under pulsed CO₂RR. e Changes in the catalyst during the first 1400 s under pulsed CO₂RR. Black dashed lines in (b, c, e)-EXAFS data fitting results. Vertical dotted lines in (b, c, e) mark the positions of the main FT-EXAFS features corresponding to the bonds between singly dispersed Cu sites and their nearest neighbors (blue line), and the Cu–Cu bonds in metallic Cu clusters (red line). Depicted spectra are averages over 20 s (a, b), 6 s (c, d) or 60 s (e). f Schematic representation of the main processes taking place under pulsed CO₂RR: conversion of singly dispersed sites into metallic species (i), particle growth (ii), fragmentation of particles (iii), and conversion of small clusters into singly dispersed sites (iv)⁶⁸ (reproduced with permission from ref. ⁶⁸. Copyright 2024, Spring Nature).