Highly Selective H₂ Production From Photoreforming of Formic Acid Triggered by Cu Single-Atom Sites in a Cocatalyst

Abstract

Photoreforming of formic acid (FA) represents a compelling technology for green hydrogen (H₂) production, but the application is limited by the relatively low activity and selectivity. Recent advancements have introduced transition-metal nitrides (TMNs) as a new class of co-catalysts for photocatalytic FA reforming, showing impressive performance but still having the disadvantage of suboptimal H₂ selectivity. Here, we present a novel Cu–W₂N₃ cocatalyst with abundant Cu single-atom sites. On combining with a CdS photocatalyst, the CdS/Cu–W₂N₃ system demonstrated an elevated H₂ generation rate of 172.69 μmol·h⁻¹ and superior H₂ selectivity in comparison to CdS/W₂N₃. Comprehensive experimental and theoretical investigations indicate that the introduction of Cu single-atom sites in Cu–W₂N₃ leads to a robust interaction with CdS, which optimizes the charge transfer. More significantly, the Cu single-atom sites modify the inert surface of the W₂N₃ cocatalyst, creating conducive electron transfer channels and leading to an abundance of active sites favorable for hydrogen evolution reaction (HER), consequently resulting in higher H₂ selectivity than pristine W₂N₃. This study provides a promising approach to achieving an efficient photoreforming reaction with specific selectivity via the design of novel cocatalysts with specialized active sites.

Keywords

formic acid / hydrogen evolution reaction / photocatalysis / selectivity / single-atom catalysts

References

[1] Y. You, S. Chen, J. Zhao, et al., “Rational Design of S-Scheme Heterojunction Towards Efficient Photocatalytic Cellulose Reforming for H₂ and Formic Acid in Pure Water,” Advanced Materials 36, no. 4 (2023): 2307962.

[2] K. Zhang, Z. Pei, and D. Wang, “Organic Solvent Pretreatment of Lignocellulosic Biomass for Biofuels and Biochemicals: A Review,” Bioresource Technology 199 (2016): 21-33.

[3] W.-M. Zhang, K.-W. Feng, R.-G. Hu, Y.-J. Guo, and Y. Li, “Visible-Light-Induced Iron Redox-Catalyzed Selective Transformation of Biomass Into Formic Acid,” Chem 9, no. 2 (2023): 430-442.

[4] K. Sordakis, C. Tang, L. K. Vogt, et al., “Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols,” Chemical Reviews 118, no. 2 (2018): 372-433.

[5] F. Valentini, V. Kozell, C. Petrucci, et al., “Formic Acid, a Biomass-Derived Source of Energy and Hydrogen for Biomass Upgrading,” Energy & Environmental Science 12, no. 9 (2019): 2646-2664.

[6] S. Zhai, S. Jiang, C. Liu, et al., “Liquid Sunshine: Formic Acid,” Journal of Physical Chemistry Letters 13, no. 36 (2022): 8586-8600.

[7] F. M. Schwarz, J. Moon, F. Oswald, and V. Müller, “Biological Hydrogen Storage and Release Through Multiple Cycles of Bi-Directional Hydrogenation of CO₂ to Formic Acid in a Single Process Unit,” Joule 6, no. 6 (2022): 1304-1319.

[8] Z.-H. Zhao, J.-R. Huang, D.-S. Huang, H. L. Zhu, P. Q. Liao, and X. M. Chen, “Efficient Capture and Electroreduction of Dilute CO₂ Into Highly Pure and Concentrated Formic Acid Aqueous Solution,” Journal of the American Chemical Society 146, no. 20 (2024): 14349-14356.

[9] R. M. Irfan, T. Wang, D. Jiang, et al., “Homogeneous Molecular Iron Catalysts for Direct Photocatalytic Conversion of Formic Acid to Syngas (CO+H₂),” Angewandte Chemie International Edition 59, no. 35 (2020): 14818-14824.

[10] S. Cao, Y. Chen, H. Wang, et al., “Ultrasmall CoP Nanoparticles as Efficient Cocatalysts for Photocatalytic Formic Acid Dehydrogenation,” Joule 2, no. 3 (2018): 549-557.

[11] T. Wang, L. Yang, D. Jiang, H. Cao, A. C. Minja, and P. Du, “CdS Nanorods Anchored With Crystalline Fep Nanoparticles for Efficient Photocatalytic Formic Acid Dehydrogenation,” ACS Applied Materials & Interfaces 13, no. 20 (2021): 23751-23759.

[12] T. Wang, M. Chen, J. Wu, and P. Du, “Highly Efficient Photocatalytic Formic Acid Decomposition to Syngas Under Visible Light Using CdS Nanorods Integrated With Crystalline W₂N₃ Nanosheets,” Journal of Materials Chemistry A 11, no. 5 (2023): 2246-2251.

[13] X. Ye, Y. Dong, Z. Zhang, et al., “Syngas Production by Photoreforming of Formic Acid With 2D V_XW_1−XN_1.5 Solid Solution as an Efficient Cocatalyst,” Frontiers in Energy 18, no. 5 (2024): 640-649.

[14] X. Ye, Y. Dong, Z. Zhang, et al., “Mechanism Insights for Efficient Photocatalytic Reforming of Formic Acid With Tunable Selectivity: Accelerated Charges Separation and Spatially Separated Active Sites,” Applied Catalysis, B: Environmental 338 (2023): 123073.

[15] H. Jin, Q. Gu, B. Chen, et al., “Molten Salt-Directed Catalytic Synthesis of 2D Layered Transition-Metal Nitrides for Efficient Hydrogen Evolution,” Chem 6, no. 9 (2020): 2382-2394.

[16] H. Jin, L. Li, X. Liu, et al., “Nitrogen Vacancies on 2D Layered W₂N₃: A Stable and Efficient Active Site for Nitrogen Reduction Reaction,” Advanced Materials 31, no. 32 (2019): 1902709.

[17] C. Gao, J. Low, R. Long, T. Kong, J. Zhu, and Y. Xiong, “Heterogeneous Single-Atom Photocatalysts: Fundamentals and Applications,” Chemical Reviews 120, no. 21 (2020): 12175-12216.

[18] T. Yang, X. Mao, Y. Zhang, et al., “Coordination Tailoring of Cu Single Sites on C₃N₄ Realizes Selective CO₂ Hydrogenation at Low Temperature,” Nature Communications 12, no. 1 (2021): 6022.

[19] Z.-H. Xue, D. Luan, H. Zhang, and X. W. (David) Lou, “Single-Atom Catalysts for Photocatalytic Energy Conversion,” Joule 6, no. 1 (2022): 92-133.

[20] L. Luo, L. Fu, H. Liu, et al., “Synergy of Pd Atoms and Oxygen Vacancies on In₂O₃ for Methane Conversion Under Visible Light,” Nature Communications 13, no. 1 (2022): 2930.

[21] H. Wang, H. Qi, X. Sun, et al., “High Quantum Efficiency of Hydrogen Production From Methanol Aqueous Solution With PtCu-TiO₂ Photocatalysts,” Nature Materials 22, no. 5 (2023): 619-626.

[22] H. Xiong, Y. Meng, S. Gu, et al., “Transition Metal Single-Atom Supported on W₂N₃ as Efficient Electrocatalysts for the Nitrogen Reduction Reaction: A DFT Study,” Colloids and Surfaces, A: Physicochemical and Engineering Aspects 698 (2024): 134583.

[23] S. Wang, X. Yu, Z. Lin, et al., “Synthesis, Crystal Structure, and Elastic Properties of Novel Tungsten Nitrides,” Chemistry of Materials 24, no. 15 (2012): 3023-3028.

[24] I.-K. Suh, H. Ohta, and Y. Waseda, “High-Temperature Thermal Expansion of Six Metallic Elements Measured by Dilatation Method and X-Ray Diffraction,” Journal of Materials Science 23, no. 2 (1988): 757-760.

[25] J. Zhao, Y. Bai, Z. Li, et al., “Plasmonic Cu Nanoparticles for the Low-Temperature Photo-Driven Water-Gas Shift Reaction,” Angewandte Chemie International Edition 62, no. 13 (2023): e202219299.

[26] L. Xiong, Z. Yu, H. Cao, et al., “Converting Glycerol Into Valuable Trioses by Cu^δ+-Single-Atom-Decorated WO₃ Under Visible Light,” Angewandte Chemie International Edition 63, no. 12 (2024): e202318461.

[27] Y. Shen, C. Ren, L. Zheng, et al., “Room-Temperature Photosynthesis of Propane From CO₂ With Cu Single Atoms on Vacancy-Rich TiO₂,” Nature Communications 14, no. 1 (2023): 1117.

[28] T. Yano, M. Ebizuka, S. Shibata, and M. Yamane, “Anomalous Chemical Shifts of Cu 2p and Cu LMM Auger Spectra of Silicate Glasses,” Journal of Electron Spectroscopy and Related Phenomena 131-132 (2003): 133-144.

[29] Z. Meng, J. Zhang, C. Jiang, C. Trapalis, L. Zhang, and J. Yu, “Dynamics of Electron Transfer in CdS Photocatalysts Decorated With Various Noble Metals,” Small 20, no. 21 (2023): 2308952.

[30] Y. Xu, C. Cheng, S. Du, et al., “Contacts Between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p-n Heterojunctions,” ACS Nano 10, no. 5 (2016): 4895-4919.

[31] Z. Sun, H. Zheng, J. Li, and P. Du, “Extraordinarily Efficient Photocatalytic Hydrogen Evolution in Water Using Semiconductor Nanorods Integrated With Crystalline Ni₂P Cocatalysts,” Energy & Environmental Science 8, no. 9 (2015): 2668-2676.

[32] R. Li, T. Takata, B. Zhang, et al., “Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al-Doped SrTiO₃ Photocatalyst,” Angewandte Chemie International Edition 62, no. 49 (2023): e202313537.

[33] H. Cui, G. Zhu, Y. Xie, et al., “Black Nanostructured Nb₂O₅ With Improved Solar Absorption and Enhanced Photoelectrochemical Water Splitting,” Journal of Materials Chemistry A 3, no. 22 (2015): 11830-11837.

[34] L. Yuan, M. Y. Qi, Z. R. Tang, and Y. J. Xu, “Coupling Strategy for CO₂ Valorization Integrated With Organic Synthesis by Heterogeneous Photocatalysis,” Angewandte Chemie International Edition 60, no. 39 (2021): 21150-21172.

[35] W. Lin, F. Lin, J. Lin, Z. Xiao, D. Yuan, and Y. Wang, “Efficient Photocatalytic CO₂ Reduction in Ellagic Acid-Based Covalent Organic Frameworks,” Journal of the American Chemical Society 146, no. 23 (2024): 16229-16236.

[36] Y. Cao, L. Guo, M. Dan, et al., “Modulating Electron Density of Vacancy Site by Single Au Atom for Effective CO₂ Photoreduction,” Nature Communications 12, no. 1 (2021): 1675.

[37] C. W. Kellett, W. B. Swords, M. D. Turlington, G. J. Meyer, and C. P. Berlinguette, “Resolving Orbital Pathways for Intermolecular Electron Transfer,” Nature Communications 9, no. 1 (2018): 4916.

[38] F. Blobner, P. B. Coto, F. Allegretti, et al., “Orbital-Symmetry-Dependent Electron Transfer Through Molecules Assembled on Metal Substrates,” Journal of Physical Chemistry Letters 3, no. 3 (2012): 436-440.

[39] E.-X. Chen, L. He, M. Qiu, et al., “Regulating Electron Transfer and Orbital Interaction Within Metalloporphyrin-MOFs for Highly Sensitive NO₂ Sensing,” Chemical Science 15, no. 18 (2024): 6833-6841.

RIGHTS & PERMISSIONS

2025 The Author(s). Carbon Energy published by Wenzhou University and John Wiley & Sons Australia, Ltd.