fig3

Figure 3. (A) Graphic representation of the Cu/CeO_2-x-4 catalyst synthesis; (B) HRTEM images of the Cu/CeO_2-x-4 catalyst; (C) FEs of bare CeO₂; (D) Cu/CeO_2-x-1; and (E) Cu/CeO_2-x-4. This figure is quoted with permission from Xue et al. Copyright (2024) Elsevier^[58]; (F) Schematic representation of the synthetic process for Cu SAs/UIO-H₂; (G) The corresponding FEs for the reduction products of Cu SAs/UIO and (H) Cu SAs/UIO-H₂; (I) Long-term electrolysis of Cu SAs/UIO-H₂ at -0.66 V vs. RHE. This figure is quoted with permission from Bie et al. Copyright (2024) Elsevier^[62]. FE: Faradaic efficiency; HRTEM: high-resolution transmission electron microscopy; SAs: single atoms; RHE: reversible hydrogen electrode.