Holmium-engineered Graphitic Carbon Nitride via Molten Salt Synthesis for CO₂ Photoreduction

Abstract

Under the impetus of the “dual carbon” strategy, photocatalytic CO₂ reduction technology has attracted significant attention due to its sustainable characteristics. In this study holmium-doping graphitic carbon nitride (Ho/g-C₃N₄) photocatalysts were synthesized via a molten salt method and investigated for enhanced CO₂ photoreduction. The incorporation of Ho into the g-C₃N₄ can induce an increase in specific surface area and a red-shift in absorption edge from 474 nm to 488 nm with a reduced bandgap from 2.72 eV to 2.33 eV. The optimal 3% Ho/g-C₃N₄ exhibits an exceptional CO production rate of 74.1 µmol·g⁻¹·h⁻¹ with 92.6% selectivity under visible light irradiation (λ>420 nm). Mott-Schottky measurement indicates a 120 mV negative shift in conduction band potential (−0.59 V vs. RHE). This enhancement in photocatalytic performance can be attributed to the created localized states within the bandgap for promoting electron transitions, the improved charge separation, the enhanced light absorption and the intensified reducing capacity, which facilitate the overall reaction process. This work provides the reference for developing efficient CO₂ reduction photocatalysts.

Keywords

Photocatalysis / CO₂ reduction / Ho/g-C₃N₄ / Molten salt

References

[1] FuC H, LiD, ZhangJ W, GuoW, YangH, ZhaoB, ChenZ M, FuX, LiangZ Q, JiangLChem. Res. Chinese Universities, 2023, 39891.

[2] RenC Y, BaiR, ChenW, LiJ P, ZhouX D, TianX C, ZhaoFChem. Res. Chinese Universities, 2023, 39389.

[3] LiuA Y, CohenM LScience, 1989, 245841.

[4] JinR R, YouJ G, ZhangQ, LiuD, HuS Z, GuiJ ZChem. Res. Chinese Universities, 2014, 301706

[5] ZhangY J, ThomasA, AntoniettiM, WangX CJ. Am. Chem. Soc., 2009, 13150.

[6] YanS R, ZhangL, ShiS H, RenY Y, LiuW H, LiY J, DuanF, LuS L, DuM L, ChenM QChem. Res. Chinese Universities, 2025, 41121.

[7] IkramM, KhanM I, RazaA, ImranM, Ul-HamidA, AliSPhysica E, 2020, 124114246.

[8] ZhaoB B, ZhongW, ChenF, WangP, BieC B, YuH GChinese J. Catal., 2023, 52127.

[9] TengY, ChenJ H, HuangY H, ZhouZ C, WangX D, KuangD B, ChenH YAppl. Catal. B-Environ., 2023, 335122889.

[10] TengY, NingL L, TanC W, ZhaoJ, XiongY W, ZouH L, YeZ M, ZhangX M, KuangD B, LiY JAdv. Funct. Mater., 2025, 352414892.

[11] ZhouC S, ZhouM, LuK Q, HuangW Y, YuC L, YangKJ. Mater. Sci. Technol., 2025, 233166.

[12] JianL, ZhouN, SangS K, MengS G, LowJX, LiYChinese J. Catal., 2024, 65163.

[13] MengL H, ZhaoC, ChuH Y, LiY H, FuH F, WangP, WangC C, HuangH WChinese J. Catal., 2024, 59346.

[14] WangF L, LiX W, LuK Q, ZhouM, YuC L, YangKChinese J. Catal., 2024, 63190.

[15] WangZ H, ZouG J, ParkJ H, ZhangKSci. China Mater., 2024, 67397.

[16] WangK N, YangT T, DawsonG, ZhangJ F, ShaoC F, DaiKChem. Res. Chinese Universities, 2025, 41123

[17] LuY, WangH J, YuP F, YuanY F, Shahbazian-YassarR, ShengY, WuS Y, TuW G, LiuG Y, KraftM, XuRNano Energy, 2020, 76105158.

[18] YaoQ F, LiuP, YangF, ZhuY L, PanY G, XueH T, MaoW W, ChuLSci. China Mater., 2024, 673160.

[19] WangX Y, ZhaoZ W, ZahraK, LiJ J, ZhangZ CChem. Res. Chinese Universities, 2023, 39580.

[20] YuZ P, LiY F, Torres-PintoA, LaGrowA P, DiaconescuV M, SimonelliL, SampaioM J, BondarchukO, AmorimI, AraujoA, SilvaA M T, SilvaC G, FariaJ L, LiuL FAppl. Catal. B-Environ., 2022, 310121318.

[21] LiuX F, LuoY N, LingC C, ShiY B, ZhanG M, LiH, GuH Y, WeiK, GuoF R, AiZ H, ZhangL ZAppl. Catal. B-Environ., 2022, 301120766.

[22] ZhengX G, DuJ C, LiZ L, FuX J, YouY H, LiuYJ. Synth. Cryst., 2017, 46950

[23] LiuG M, DongG H, ZengY B, WangC YChinese J. Catal., 2020, 411564.

[24] ShanL S, LiuY, ChenY, ZhangX J, DaiH Z, XuD H, YuB Z, ZhangY, ChenS W, HeT, OuyangX PACS Sustainable Chem. Eng., 2025, 13311.

[25] HuangX, WangZ Y, ZhongY, JiangY, ChenS X, ChenJ W, DengS G, WangJChem. Eng. J., 2025, 507160812.

[26] PanY, LiuX J, ZhangW, ShaoB B, LiuZ F, LiangQ H, WuT, HeQ Y, HuangJ, PengZ, LiuY, ZhaoC HChem. Eng. J., 2022, 427132032.

[27] ZhengL F, ZhaoJ Q, DuZ X, ZongB N, LiuH CSci. China Chem., 2017, 60950.

[28] XiaoN, LiS S, LiuS, XuB R, LiY D, GaoY Q, GeL, LuG WChin. J. Catal., 2019, 40353

[29] YoneyamaH, YamashitaY, TamuraHNature, 1979, 282817.

[30] MuP, ZhouM, YangK, ZhouC S, MiY, YuZ Z, LuK Q, LiZ Q, OuyangS B, HuangW Y, YuC LSustainable Energy Fuels, 2021, 55814.

[31] ZhaoS, FangJ S, WangY Y, ZhangY W, ZhuoS PJ. Colloid Interface Sci., 2020, 561601.

[32] ZhaoZ Y, WangM Z, MaP J, ZhengY P, ChenJ Y, LiH Q, ZhangX B, ZhengK, KuangQ, XieZ XAppl. Catal. B-Environ., 2021, 291120101.

[33] ZengB Y, XiaT T, SunY L, ZhangP, WangW J, ZhaoKChem. Res. Chinese Universities, 2024, 40451.

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Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH

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