Atomic force microscopy images of a Cu (100) electrode after different surface treatments and reaction settings. (a) Constant potential of −1.0  V versus RHE; Pulsed electrolysis: (b) E_a= 0.6  V, E_c= −1.0  V, t_a=t_c= 1  s. (c) The surface from panel (b) after a subsequent hour of potentiostatic electrolysis at −1.0  V versus RHE. (Reproduced from Ref. [62]. Copyright©2020, Springer Nature Limited). (d) Schematic depiction of the catalyst structure and composition during a cathodic pulse extracted from XAS and XRD data. (Reproduced from Ref. [25]. Copyright©2022, Springer Nature Limited). (e) Design and performance of ALPS-1, ALPS-2, and potentiostatic methods for Cu₃(DMPz)₃ Catalyst (Reproduced from Ref. [48]. Copyright©2023, American Chemical Society). (f) Faradaic efficiencies of the reaction products under static CO₂RR at  −1.35  V and under pulsed CO₂RR with E_c = − 1.35  V, E_a = 0.44 V, Δt_a = 30  s and different Δt_c values (30, 10, and 1  s). (g) Corresponding selectivity for H₂ and the main gaseous CO₂RR products as a function of Δt_c. Inset: calculated concentrations of Cu within cationic single site species (x_SAC), small Cu clusters (x_S), and large Cu nanoparticles (x_L). Shaded regions indicated as (i), (ii), and (iii) mark three distinct regimes with different selectivity trends, and dominated by different Cu species, as indicated in (h) (Reproduced from Ref. [114]. Copyright©2024, Springer Nature Limited).