Molecular-level insights on the reactive facet of carbon nitride single crystals photocatalysing overall water splitting


Unraveling how reactive facets promote photocatalysis at the molecular level remains a grand challenge, while identification of the reactive facets can provide guidelines for designing highly efficient photocatalysts and unravelling the microscopic mechanisms behind them. Recently, a series of polytriazine imides (PTIs) was reported with highly crystalline structures; all had a relatively low photocatalytic activity for overall water splitting. Here, high-angle annular dark-field scanning transmission electron microscopy, energy dispersive spectroscopy mapping, and aberration-corrected integrated differential phase contrast imaging were used to study PTI/Li+Cl single crystals before and after in situ photodeposition of co-catalysts, showing that the prismatic {10\(\bar 1\)0} planes are more photocatalytically reactive than the basal {0001} planes. Theoretical calculations confirmed that the electrons are energetically favourable to transfer toward the {10\(\bar 1\)0} planes. Upon this discovery, PTI/Li+Cl crystals with different aspect ratios were prepared, and the overall water splitting performance followed a linear correlation with the relative surface areas of the {10\(\bar 1\)0} and {0001} planes. Our controlling of the reactive facets directly instructs the development of highly efficient polymer photocatalysts for overall water splitting.

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Fig. 1: The morphology and atomic structure of PTI/Li+Cl.
Fig. 2: The spatial distribution of the Pt co-catalysts after photodeposition.
Fig. 3: The electronic structure properties.
Fig. 4: Photocatalytic performances.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.


  1. 1.

    Fujishima, A. & Honda, K. Electrochemical photolysis of water at a semiconductor electrode. Nature 238, 37–38 (1972).

    CAS  PubMed  Google Scholar 

  2. 2.

    Lewis, N. S. Research opportunities to advance solar energy utilization. Science 351, aad1920 (2016).

    PubMed  Google Scholar 

  3. 3.

    Chen, S., Takata, T. & Domen, K. Particulate photocatalysts for overall water splitting. Nat. Rev. Mater. 2, 17050 (2017).

    CAS  Google Scholar 

  4. 4.

    Chen, X., Shen, S., Guo, L. & Mao, S. S. Semiconductor-based photocatalytic hydrogen generation. Chem. Rev. 110, 6503–6570 (2010).

    CAS  PubMed  Google Scholar 

  5. 5.

    Maeda, K. et al. Photocatalyst releasing hydrogen from water. Nature 440, 295–295 (2006).

    CAS  PubMed  Google Scholar 

  6. 6.

    Yu, J. & Kudo, A. Effects of structural variation on the photocatalytic performance of hydrothermally synthesized BiVO4. Adv. Funct. Mater. 16, 2163–2169 (2006).

    CAS  Google Scholar 

  7. 7.

    Zong, X. et al. Enhancement of photocatalytic H2 evolution on CdS by loading MoS2 as cocatalyst under visible light irradiation. J. Am. Chem. Soc. 130, 7176–7177 (2008).

    CAS  PubMed  Google Scholar 

  8. 8.

    Wang, Q. et al. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%. Nat. Mater. 15, 611–615 (2016).

    CAS  PubMed  Google Scholar 

  9. 9.

    Wang, Z. et al. Overall water splitting by Ta3N5 nanorod single crystals grown on the edges of KTaO3 particles. Nat. Catal. 1, 756–763 (2018).

    CAS  Google Scholar 

  10. 10.

    Liu, G., Yu, J. C., Lu, G. Q. & Cheng, H.-M. Crystal facet engineering of semiconductor photocatalysts: motivations, advances and unique properties. Chem. Commun. 47, 6763–6783 (2011).

    CAS  Google Scholar 

  11. 11.

    Yang, H. G. et al. Anatase TiO2 single crystals with a large percentage of reactive facets. Nature 453, 638–641 (2008).

    CAS  PubMed  Google Scholar 

  12. 12.

    Yu, J., Qi, L. & Jaroniec, M. Hydrogen production by photocatalytic water splitting over Pt/TiO2 nanosheets with exposed (001) facets. J. Phys. Chem. C 114, 13118–13125 (2010).

    CAS  Google Scholar 

  13. 13.

    Han, X. et al. Synthesis of titania nanosheets with a high percentage of exposed (001) facets and related photocatalytic properties. J. Am. Chem. Soc. 131, 3152–3153 (2009).

    CAS  PubMed  Google Scholar 

  14. 14.

    Bi, Y. et al. Facet effect of single-crystalline Ag3PO4 sub-microcrystals on photocatalytic properties. J. Am. Chem. Soc. 133, 6490–6492 (2011).

    CAS  PubMed  Google Scholar 

  15. 15.

    Zhang, J., Zhang, P., Wang, T. & Gong, J. Monoclinic WO3 nanomultilayers with preferentially exposed (002) facets for photoelectrochemical water splitting. Nano Energy 11, 189–195 (2015).

    CAS  Google Scholar 

  16. 16.

    Mu, L. et al. Enhancing charge separation on high symmetry SrTiO3 exposed with anisotropic facets for photocatalytic water splitting. Energy Environ. Sci. 9, 2463–2469 (2016).

    CAS  Google Scholar 

  17. 17.

    Li, R. et al. Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4. Nat. Commun. 4, 1432 (2013).

    PubMed  Google Scholar 

  18. 18.

    Wang, X. et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat. Mater. 8, 76–80 (2009).

    CAS  PubMed  Google Scholar 

  19. 19.

    Zheng, Y., Lin, L., Wang, B. & Wang, X. Graphitic carbon nitride polymers toward sustainable photoredox catalysis. Angew. Chem. Int. Ed. 54, 12868–12884 (2015).

    CAS  Google Scholar 

  20. 20.

    Ong, W.-J. et al. Graphitic carbon nitride (g-C3N4)-based photocatalysts for artificial photosynthesis and environmental remediation: are we a step closer to achieving sustainability? Chem. Rev. 116, 7159–7329 (2016).

    CAS  PubMed  Google Scholar 

  21. 21.

    Cao, S., Low, J., Yu, J. & Jaroniec, M. Polymeric photocatalysts based on graphitic carbon nitride. Adv. Mater. 27, 2150–2176 (2015).

    CAS  PubMed  Google Scholar 

  22. 22.

    Kessler, F. K. et al. Functional carbon nitride materials—design strategies for electrochemical devices. Nat. Rev. Mater. 2, 17030 (2017).

    CAS  Google Scholar 

  23. 23.

    Wang, X. et al. Metal-containing carbon nitride compounds: a new functional organic–metal hybrid material. Adv. Mater. 21, 1609–1612 (2009).

    CAS  Google Scholar 

  24. 24.

    Li, Y. et al. Implementing metal-to-ligand charge transfer in organic semiconductor for improved visible-near-infrared photocatalysis. Adv. Mater. 28, 6959–6965 (2016).

    CAS  PubMed  Google Scholar 

  25. 25.

    Gao, G., Jiao, Y., Waclawik, E. R. & Du, A. Single atom (Pd/Pt) supported on graphitic carbon nitride as an efficient photocatalyst for visible-light reduction of carbon dioxide. J. Am. Chem. Soc. 138, 6292–6297 (2016).

    CAS  PubMed  Google Scholar 

  26. 26.

    Huang, P. et al. Selective CO2 reduction catalyzed by single cobalt sites on carbon nitride under visible-light irradiation. J. Am. Chem. Soc. 140, 16042–16047 (2018).

    CAS  PubMed  Google Scholar 

  27. 27.

    Thomas, A. et al. Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts. J. Mater. Chem. 18, 4893–4908 (2008).

    CAS  Google Scholar 

  28. 28.

    Zhang, Z. et al. High-pressure bulk synthesis of crystalline C6N9H3·HCl: a novel C3N4 graphitic derivative. J. Am. Chem. Soc. 123, 7788–7796 (2001).

    CAS  PubMed  Google Scholar 

  29. 29.

    Wirnhier, E. et al. Poly(triazine imide) with intercalation of lithium and chloride ions [(C3N3)2(NHxLi1−x)3LiCl]: a crystalline 2D carbon nitride network. Chem. Eur. J. 17, 3213–3221 (2011).

    CAS  PubMed  Google Scholar 

  30. 30.

    Algara-Siller, G. et al. Triazine-based graphitic carbon nitride: a two-dimensional semiconductor. Angew. Chem. Int. Ed. 53, 7450–7455 (2014).

    CAS  Google Scholar 

  31. 31.

    Lin, L., Yu, Z. & Wang, X. Crystalline carbon nitride semiconductors for photocatalytic water splitting. Angew. Chem. Int. Ed. 58, 6164–6175 (2019).

    CAS  Google Scholar 

  32. 32.

    Bojdys, M. J., Müller, J.-O., Antonietti, M. & Thomas, A. Ionothermal synthesis of crystalline, condensed, graphitic carbon nitride. Chem. Eur. J. 14, 8177–8182 (2008).

    CAS  PubMed  Google Scholar 

  33. 33.

    Lin, L. et al. Photocatalytic overall water splitting by conjugated semiconductors with crystalline poly(triazine imide) frameworks. Chem. Sci. 8, 5506–5511 (2017).

    CAS  PubMed  PubMed Central  Google Scholar 

  34. 34.

    Lin, L., Ou, H., Zhang, Y. & Wang, X. Tri-s-triazine-based crystalline graphitic carbon nitrides for highly efficient hydrogen evolution photocatalysis. ACS Catal. 6, 3921–3931 (2016).

    CAS  Google Scholar 

  35. 35.

    Waddell, E. M. & Chapman, J. N. Linear imaging of strong phase objects using asymmetrical detectors in STEM. OPTIK 54, 83–96 (1979).

    Google Scholar 

  36. 36.

    Lazić, I., Bosch, E. G. T. & Lazar, S. Phase contrast STEM for thin samples: integrated differential phase contrast. Ultramicroscopy 160, 265–280 (2016).

    PubMed  Google Scholar 

  37. 37.

    Chong, S. Y. et al. Tuning of gallery heights in a crystalline 2D carbon nitride network. J. Mater. Chem. A 1, 1102–1107 (2013).

    CAS  Google Scholar 

  38. 38.

    Ham, Y. et al. Synthesis and photocatalytic activity of poly(triazine imide). Chem. Asian J. 8, 218–224 (2013).

    CAS  PubMed  Google Scholar 

  39. 39.

    Kang, Y. et al. Selective breaking of hydrogen bonds of layered carbon nitride for visible light photocatalysis. Adv. Mater. 28, 6471–6477 (2016).

    CAS  PubMed  Google Scholar 

  40. 40.

    Li, X. et al. CsPbX3 quantum dots for lighting and displays: room-temperature synthesis, photoluminescence superiorities, underlying origins and white light-emitting diodes. Adv. Funct. Mater. 26, 2435–2445 (2016).

    CAS  Google Scholar 

  41. 41.

    Sun, S. et al. The origin of high efficiency in low-temperature solution-processable bilayer organometal halide hybrid solar cells. Energy Environ. Sci. 7, 399–407 (2014).

    CAS  Google Scholar 

  42. 42.

    Cao, Y. et al. Improved quantum efficiency for electroluminescence in semiconducting polymers. Nature 397, 414–417 (1999).

    PubMed  Google Scholar 

  43. 43.

    Kippelen, B. & Brédas, J.-L. Organic photovoltaics. Energy Environ. Sci. 2, 251–261 (2009).

    CAS  Google Scholar 

  44. 44.

    Brédas, J.-L., Norton, J. E., Cornil, J. & Coropceanu, V. Molecular understanding of organic solar cells: the challenges. Acc. Chem. Res. 42, 1691–1699 (2009).

    PubMed  Google Scholar 

  45. 45.

    Li, G., Chang, W.-H. & Yang, Y. Low-bandgap conjugated polymers enabling solution-processable tandem solar cells. Nat. Rev. Mater. 2, 17043 (2017).

    CAS  Google Scholar 

  46. 46.

    Kattel, S., Liu, P. & Chen, J. G. Tuning selectivity of CO2 hydrogenation reactions at the metal/oxide interface. J. Am. Chem. Soc. 139, 9739–9754 (2017).

    CAS  PubMed  Google Scholar 

  47. 47.

    Wang, D., Liu, Z.-P. & Yang, W.-M. Revealing the size effect of platinum cocatalyst for photocatalytic hydrogen evolution on TiO2 support: a DFT study. ACS Catal. 8, 7270–7278 (2018).

    CAS  Google Scholar 

  48. 48.

    Chen, J. S. et al. Constructing hierarchical spheres from large ultrathin anatase TiO2 nanosheets with nearly 100% exposed (001) facets for fast reversible lithium storage. J. Am. Chem. Soc. 132, 6124–6130 (2010).

    CAS  PubMed  Google Scholar 

  49. 49.

    Maeda, K. et al. Noble-metal/Cr2O3 core/shell nanoparticles as a cocatalyst for photocatalytic overall water splitting. Angew. Chem. 118, 7970–7973 (2006).

    Google Scholar 

  50. 50.

    Shen, B. et al. Atomic spatial and temporal imaging of local structures and light elements inside zeolite frameworks. Adv. Mater. 32, 1906103 (2020).

    CAS  Google Scholar 

  51. 51.

    Kirkland, E. J. Advanced Computing in Electron Microscopy (Springer Science and Business Media, 2010).

  52. 52.

    Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    CAS  Google Scholar 

  53. 53.

    Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    CAS  Google Scholar 

  54. 54.

    Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Google Scholar 

  55. 55.

    Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    CAS  Google Scholar 

  56. 56.

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  PubMed  Google Scholar 

  57. 57.

    Grimme, S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27, 1787–1799 (2006).

    CAS  PubMed  Google Scholar 

  58. 58.

    Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13, 5188–5192 (1976).

    Google Scholar 

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This work was financially supported by the National Key R&D Program of China (2018YFA0209301), the National Natural Science Foundation of China (U1905214, 21961142019, 21425309, 21761132002, 21861130353, 21802021, 21973014, 51701170 and 51871058), the Chang Jiang Scholars Program of China (T2016147), the project of science and technology plan of Fujian Province (2018J01520) and the 111 Project (D16008). This work made use of the TEM resources at Fuzhou University and the Nanoport Europe of Thermo Fisher Scientific in the Netherlands. Z. Yu thanks A. Carlsson for professional assistance in iDPC imaging.

Author information




X.W. conceived and designed the experiment. L.L., Z.L. and J.Z. synthesized the experimental samples and carried out most of the characterization, as well as the photocatalytic reactions. Z.L. and Z.Y. performed the SEM and TEM characterizations. Z.Y. analysed the TEM data. X.C. and W.L. carried out the DFT calculations. X.W. supervised the experiments. All the authors discussed the results and wrote the manuscript.

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Correspondence to Xinchen Wang.

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Supplementary Information

Supplementary Figs. 1–21 and Tables 1–2.

Supplementary Data Atomic coordinates 1

Optimized computational model.

Supplementary Data Atomic coordinates 2

Optimized computational model.

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Lin, L., Lin, Z., Zhang, J. et al. Molecular-level insights on the reactive facet of carbon nitride single crystals photocatalysing overall water splitting. Nat Catal (2020).

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