The synergistic effect of non-compensated Cu/N co-doping and graphene enhances the dual-channel generation of H2O2 over TiO2 photocatalysts

doi:10.1016/S1872-2067(25)64799-1

Abstract

Abstract:

Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H₂O₂. In this study, a graphene-modified non-compensated Cu/N-co-doped titanium dioxide (Cu-N-TiO₂/rGO) photocatalyst was designed for the efficient synthesis of H₂O₂ via a dual-channel pathway. Precise modulation of the TiO₂ conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals. This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements. Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti³⁺ ions, the photogenerated charge recombination centers. The non-compensated doping of N effectively increased the solubility of Cu²⁺ ions in the titanium dioxide lattice, enhanced the adsorption of hydroxyl radical intermediates, and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H₂O₂. In addition, the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites, creating conditions for dual-channel reactions. The experimental results showed that the H₂O₂ yield of Cu-N-TiO₂/rGO under simulated sunlight reached 1266.7 µmol/L, which was 25.2 times higher than that of pristine TiO₂. This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization, which provided a new idea for the design of dual-channel H₂O₂ production photocatalysts.

Key words: Photocatalytic production of H₂O₂, Dual channel, Modulation of energy band structure, Cu/N co-doping

Qianqian Shen, Chenlong Dong, Shilong Feng, Xueli Zhang, Qiurong Li, Jinbo Xue. The synergistic effect of non-compensated Cu/N co-doping and graphene enhances the dual-channel generation of H₂O₂ over TiO₂ photocatalysts[J]. Chinese Journal of Catalysis, 2025, 78: 252-264.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(25)64799-1

https://www.cjcatal.com/EN/Y2025/V78/I11/252

Figures/Tables 7

Fig. 1. SEM images of TiO2 (a), Cu-N-TiO2 (b), and Cu-N-TiO2/rGO (c). TEM images of TiO2 (d) and Cu-N-TiO2/rGO (e). (f) HRTEM image of Cu-N-TiO2/rGO. (g-k) EDS maps of Cu-N-TiO2. (l) XRD patterns of TiO2, N-TiO2, Cu-TiO2, Cu-N-TiO2, and Cu-N-TiO2/rGO. (m) Magnified XRD peaks of the (101) surface.

Fig. 2. High-resolution XPS profiles of Ti 2p (a), O 1s (b), Cu 2p (c), and N 1s (d). (e) Schematic representation of the Cu2+ and N3? co-doped TiO2. (f) XRD patterns of the catalysts with different copper doping amounts. Enlarged XRD patterns (g) and copper doping concentrations (h) of Cu-TiO2 and Cu-N-TiO2.

Fig. 3. (a) UV-vis diffuse reflectance absorption spectra of TiO2, N-TiO2, Cu-TiO2, Cu-N-TiO2, and Cu-N-TiO2/rGO. The corresponding optical bandgaps (b), Mott-Schottky curves (c), and energy band structure diagrams (d).

Fig. 4. SPV spectra (a), PL spectra (b), transient photocurrent responses (c), EIS profiles (d), TRPL spectra (e), and photogenerated carrier lifetimes (f) of TiO2, N-TiO2, Cu-TiO2, Cu-N-TiO2, and Cu-N-TiO2/rGO.

Fig. 5. Contour plots showing the evolution of the femtosecond transient absorption spectra of TiO2 (a), Cu-N-TiO2 (b), and Cu-N-TiO2/rGO (c). Femtosecond transient absorption spectra of TiO2 (d), Cu-N-TiO2 (e), and Cu-N-TiO2/rGO (f). Kinetic decay curves of TiO2 obtained at 665 nm (g) and Cu-N-TiO2 (h) and Cu-N-TiO2/rGO (i) recorded at 625 nm.

Fig. 6. (a) H2O2 yields of TiO2, N-TiO2, Cu-TiO2, Cu-N-TiO2, and Cu-N-TiO2/rGO. (b) Comparative studies of the photocatalytic production of H2O2 under different reaction conditions. (c) Performances of Cu-N-TiO2/rGO and other photocatalysts. (d) Results of the Cu-N-TiO2/rGO cycling stability tests. (e) In-situ DRIFT spectra of Cu-N-TiO2/rGO obtained at different irradiation times during the photocatalytic production of H2O2. (f) Local magnification of the in-situ DRIFT spectra. (g,h) Free energy diagrams constructed for the H2O2 generation through the ORR and WOR pathways.

Fig. 7. Mechanistic diagram of the photocatalytic production of H2O2 over Cu-N-TiO2/rGO.

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The synergistic effect of non-compensated Cu/N co-doping and graphene enhances the dual-channel generation of H₂O₂ over TiO₂ photocatalysts

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