Low-defect Cu2O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting

doi:10.1016/S1872-2067(26)65202-3

Chinese Journal of Catalysis ›› 2026, Vol. 90: 243-252.DOI: 10.1016/S1872-2067(26)65202-3

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Low-defect Cu₂O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting

Linxiao Wu^a^,¹, Yumeng Han^a^,¹, Jinshui Cheng^a, Yushuai Sang^b, Xiang Chen^c, Yaqing Zhang^c, Xuewen Fu^c^,^e, Jingshan Luo^a^,^d^,^e^,^*()

^a Institute of Photoelectronic Thin Film Devices and Technology, State Key Laboratory of Photovoltaic Materials and Cells, Tianjin Key Laboratory of Efficient Utilization of Solar Energy, Ministry of Education Engineering Research Center of Thin Film Photoelectronic Technology, Nankai University, Tianjin 300350, China
^b Electron Microscope Center, Core Facility Platform, Tianjin University, Tianjin 300072, China
^c Ultrafast Electron Microscopy Laboratory MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin 300071, China
^d Frontiers Science Center for New Organic Matter, Nankai University, Tianjin 300071, China
^e Academy for Advanced Interdisciplinary Studies, Nankai University, Tianjin 300071, China

Received:2026-02-06 Accepted:2026-03-19 Online:2026-11-05 Published:2026-09-09
About author:First author contact:
¹Contributed equally to this work.

Author Contributions
L.W. and Y.H. contribute equally to this work. L.W. and J.L. conceived the idea and designed the experiment. L.W. conducted the device fabrication, characterization. Y.H. prepared the samples and tested the PEC performance. J.C. contributed to the discussion of the results. Y. S contributed to the polishing pretreatment. X.C., Y.Z. and X.F. collected PL and TRPL data. J.L. supervised the project. L.W. wrote the first draft, and J.L. finalized the manuscript. All authors contributed to the revision of the manuscript.
Supported by:
National Key Research and Development Program of China(2019YFE0123400);National Natural Science Foundation of China(52072187);National Natural Science Foundation of China(22122903);Tianjin Distinguished Young Scholar Fund(20JCJQJC00260)

Abstract

Abstract:

Cu₂O is among the most promising metal oxide semiconductors for solar water splitting, yet its performance is often limited by structural defects and poor charge transport. Here, we report a tartaric acid-assisted solution growth strategy to fabricate high-quality Cu₂O films (T-Cu₂O) with reduced defect density, prolonged carrier lifetimes, and enhanced electrical conductivity. Microstructural analysis reveals that T-Cu₂O films consist of vertically aligned columnar grains exceeding 1 μm in length, spanning the entire film thickness. This contrasts with the disordered grains formed in conventional lactic acid-assisted films (L-Cu₂O), which impede charge transport. Upon integration with overlayers and RuO_x cocatalysts, the T-Cu₂O photocathode delivers a photocurrent density of 8.0 mA cm^-2 at 0 V vs. RHE—23% higher than its L-Cu₂O counterpart. Surface photovoltage measurements further confirm significantly improved charge separation in T-Cu₂O. This work establishes a facile solution-based strategy for producing high-quality Cu₂O photoelectrodes with enhanced efficiency for photoelectrochemical water splitting.

Key words: Photoelectrochemical water splitting, Photoelectrode, Cu₂O, Electrodeposition, Tartaric acid

Linxiao Wu, Yumeng Han, Jinshui Cheng, Yushuai Sang, Xiang Chen, Yaqing Zhang, Xuewen Fu, Jingshan Luo. Low-defect Cu₂O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting[J]. Chinese Journal of Catalysis, 2026, 90: 243-252.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65202-3

https://www.cjcatal.com/EN/Y2026/V90/I11/243

Figures/Tables 5

Fig. 1. (a) XRD patterns of T-Cu2O electrodeposited from a tartrate stabilized copper sulfate solution and L-Cu2O film from a lactate-stabilized copper sulfate solution. Indexes were taken from the following patterns: Au PDF#99-0056, Cu2O PDF#05-0667, FTO PDF#41-1445. XPS spectra Cu 2p (b) and XPS O 1s spectra (c) of T-Cu2O film and L-Cu2O film. Top-view SEM images of T-Cu2O films with electrodeposition time of 1 min (d), 5 min (e), and 50 min (f). Top-view SEM images of L-Cu2O films with electrodeposition time of 1 min (g), 5 min (h), and 100 min (i).

Fig. 2. Cross-sectional SEM image (a), EBSD pattern-quality map (b), and EBSD orientation-distribution map (c) perpendicular to substrate highlighted by false colors within the related inverse pole figure of T-Cu2O film (electrodeposition time for 50 min). Cross-sectional SEM image (d), EBSD pattern-quality map (e), and EBSD orientation-distribution maps (f) perpendicular to substrate of L-Cu2O film (electrodeposition time for 200 min). (g,h) Schematic diagram of charge transport in Cu2O films.

Fig. 3. Mott-Schottky plots (a) and PL spectra (b) of T-Cu2O and L-Cu2O films. Streak camera images of TRPL of T-Cu2O (c) and L-Cu2O (d) films. (e,f) Corresponding decay traces of the near band emission extracted from (c) and (d) fitted using a biexponential function. C-AFM current mapping images of T-Cu2O (g) and L-Cu2O (h) films. CPD of T-Cu2O (i) and L-Cu2O (j) films.

Fig. 4. (a) J-V curve of T-Cu2O and L-Cu2O photocathodes (Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx) under continuous simulated one-sun AM 1.5 G (solid line) and dark condition (dashed line). (b) J-V curve of T-Cu2O and L-Cu2O photoelectrodes under chopped simulated AM 1.5G illumination. Statistical current density at 0 V vs. RHE (c) and onset potential (d) of Cu2O photoelectrodes under continuous simulated one-sun air mass 1.5 G condition. (e) IPCE spectra under monochromatic illumination of T-Cu2O and L-Cu2O photoelectrodes at 0 V vs. RHE. (f) Stability test of T-Cu2O photocathode at 0.5 V vs. RHE. All measurements were performed in a pH 5.0 electrolyte solution under constant stirring at 500 rpm.

Fig. 5. SPVM images of T-Cu2O (a) and L-Cu2O (b) photoelectrodes (Cu2O/Ga2O3/ZnGeOx/TiO2). SPVM images of T-Cu2O (d) and L-Cu2O (e) photoelectrodes with RuOx catalyst (Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx). The vertical height gradient denotes film surface topography, and the color gradient represents CPD. SPV spectra for T-Cu2O and L-Cu2O photoelectrodes without (c) and with (f) catalyst. Charge transfer efficiency (ηtransfer) (g) and charge separation efficiency (ηsep) (h) of Cu2O photocathodes. (i) The open-circuit potential of Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx photocathodes under chopped illumination condition in pH 5 electrolyte.

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Low-defect Cu₂O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting

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