First Authors: Mingli Qin, Mingqi He
Corresponding Authors: Hans Ågren, Lingfeng Gao, Youju Huang
DOI: 10.1007/s42114-025-01602-9
第一作者：秦明礼、何眀琦
Abstract Optoelectronic sensing technology plays a crucial role in modern information reception and transmission, and is currently widely applied in various fields such as bioengineering, medical and health care, and environmental protection. Advances in materials science and nanotechnology have further improved the performance and efficiency of photodetectors. In recent years, various nanomaterials such as graphene, MXene, transition metal disulfides, and perovskites have been used in the field of photodetection. Among these materials, bismuth oxychloride (BiOCl) shows great potential due to its unique layered structure, excellent optical properties, and stable chemical properties. However, BiOCl has a wide bandgap (3.2-3.4 eV) and can only respond to ultraviolet light, resulting in relatively low light utilization. Expanding the response spectral range of BiOCl-based photodetectors through simple modification methods (such as doping and vacancy engineering) is difficult, limiting its application in broadband photodetection. Furthermore, rapid carrier recombination also suppresses the photoelectric performance of BiOCl-based devices.
Combining BiOCl with other nanomaterials to construct heterojunctions is one effective strategy to overcome these obstacles. Associate Professor Gao Lingfeng and Professor Huang Youju of Hangzhou Normal University reported a hydrothermal method for preparing Ti3CN@BiOCl heterojunction materials, aiming to promote the transport of photogenerated carriers. The team systematically studied the effects of electrolyte type and concentration, light intensity, and external bias voltage on the photoelectric response behavior of the Ti3CN@BiOCl heterojunction material, and investigated the electron transport pathway in the heterojunction based on DFT theoretical calculations. Simultaneously, the addition of a small amount of hole-trapping agent Na2SO3 significantly improved the material's photoresponse performance. Through optimization of external conditions, the photodetector based on the Ti3CN@BiOCl heterojunction material exhibited a high photocurrent density (47.17 μA∙cm−2) and excellent photoresponsivity (12.50 mA∙W−1). Combined with its fast response (~0.04 s) and long-term stability (decay of ~0.005% per cycle), the Ti3CN@BiOCl heterojunction shows great potential in the field of photodetection and will also provide significant value for other high-performance optoelectronic devices.
Figure 1. Schematic diagram of the preparation of the working electrode, the measuring device, and the working mechanism.
Figure 2. (a) SEM image of Ti3AlCN MAX precursor. (b) SEM image of Ti3CN MXene. (c) Schematic diagram of BiOCl NSs modified Ti3CN MXene. (d) TEM image of Ti3CN@BiOCl NSs. (e) Lattice fringe image of Ti3CN@BiOCl NSs. (f) Selected electron diffraction image of Ti3CN@BiOCl NSs. (g) Elemental analysis image of Ti3CN@BiOCl NSs.
This paper characterizes the microstructure, geometry, and elemental composition of the prepared Ti3CN@BiOCl nanosheets using SEM, TEM, and EDS. As shown in Figure 2, the Ti3AlCN MAX precursor exhibits a dense structure. After HF etching of Al atoms, the Ti3CN MXene forms an accordion-like junction. BiOCl sheet-like structures can be found on the surface of the multilayer Ti3CN. The mapping images further analyzed the elemental composition of the heterojunction material. Furthermore, both the (101) crystal planes of Ti3CN and BiOCl can be detected by high-resolution transmission electron microscopy. All of these indicate that Ti3CN@BiOCl heterojunctions can be successfully prepared using a simple hydrothermal method.
Figure 3. (a) LSV curves of Ti3CN@BiOCl under different electrolytes. (b) Photoelectric response behavior of Ti3CN@BiOCl-PD in electrolytes of different concentrations. (c) Photoelectric response behavior of Ti3CN@BiOCl-PD under different bias voltages. (e) Fitting of Pph to Pλ under simulated light. (f) Distribution of Rph along electrolyte concentration and Pλ under simulated light.
As shown in Figure 3, the synthesized Ti3CN@BiOCl heterojunction material was directly used as the active electrode material of a photoelectrochemical (PEC) type photodetector (PD). The photoresponse performance of Ti3CN@BiOCl under different external conditions was systematically studied by changing the electrolyte concentration, optical power density (Pλ), and bias potential. As shown in Figure 3a, Ti3CN@BiOCl-PD did not show obvious redox peaks under alkaline electrolyte and 0-1 V conditions, indicating that the prepared Ti3CN@BiOCl-PD is stable under these conditions. As shown in Figures 3b, 3c, and 3d, the photocurrent increases with increasing electrolyte concentration and applied bias voltage. This can be attributed to the higher concentration of free conductive ions in the higher electrolyte concentration, which is also confirmed by the EIS spectrum (Figure 3c). Furthermore, the increase in bias voltage helps photogenerated carriers separate and transport more carriers in a short time, thus generating a larger photocurrent. Meanwhile, increasing the incident light power density can also effectively enhance the photoresponse of Ti3CN@BiOCl. This can be attributed to the increase in the number of photogenerated carriers as the photocurrent power density increases, thereby leading to the enhancement of the photocurrent.
Figure 4. (a) Response speed of Ti3CN@BiOCl-PD at different wavelengths. (b) Long-term stability test of Ti3CN@BiOCl-PD after 2000 cycles.
To evaluate the practical applications of Ti3CN@BiOCl-PD, the authors investigated its response speed and long-term stability. As shown in Figure 4a, the tres/trec values of Ti3CN@BiOCl-PD at various wavelengths were all less than 0.08 s, indicating that the prepared Ti3CN@BiOCl-PD exhibits ultrafast photoresponse behavior. Figure 4b shows 2000 on/off signals collected from the freshly prepared Ti3CN@BiOCl-PD sample and the sample stored for one month. The photocurrent density of the fresh sample decreased from 46.26 μA∙cm−2 to 35.81 μA∙cm−2 (a decrease of approximately 0.011% per cycle), while the photocurrent density of the stored sample decreased from 31.96 μA∙cm−2 to 28.83 μA∙cm−2 (a decrease of approximately 0.005% per cycle). It is evident that the sample can still maintain a high photocurrent density, and the sample becomes more stable after one month, which can be attributed to the pre-permeation of the electrolyte. Combined with the material's excellent stability, this work not only highlights the broad prospects of BiOCl-based heterojunctions but also provides significant value for applications in other optoelectronic devices.
This related work was recently published in *Advanced Composites and Hybrid Materials*. The first authors are Mingli Qin, a master's student at Hangzhou Normal University, and Mingqi He, a postdoctoral researcher at Uppsala University. Associate Professor Lingfeng Gao and Professor Youju Huang from Hangzhou Normal University, and Professor Hans Ågren from Uppsala University are the co-corresponding authors.
Mingli Qin, Mingqi He, Jiahui Hou et al.A 2D-2D Ti3CN@BiOCl Heterojunction and Its Application in Photodetection, Advanced Composites and Hybrid Materials, 2026, 9, 69, https://doi.org/10.1007/s42114-025-01602-9
Gao Lingfeng: Associate Professor, School of Materials Science and Engineering, Hangzhou Normal University. His main research areas are the preparation of novel low-dimensional nanomaterials and their optoelectronic sensing properties. He has published over 40 SCI papers as first author/corresponding author in leading international journals (including 4 highly cited papers and 1 hot paper). He was selected for Shenzhen's Overseas High-Level Talent Program (Category C) in 2019 and Hangzhou's High-Level Talent Program (Category D) in 2021. He has led projects funded by the National Natural Science Foundation of China and the Zhejiang Provincial Natural Science Foundation.
Huang Youju: Professor, Doctoral Supervisor, National Excellent Young Scientist, Vice Dean, School of Materials Science and Engineering, Hangzhou Normal University. He received his Ph.D. from the University of Science and Technology of China in 2010, under the supervision of Professor Li Liangbin. From 2010 to 2014, he was a postdoctoral researcher at Nanyang Technological University, Singapore. From 2014 to 2019, he worked at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, as an associate researcher/project researcher. From 2017 to 2018, I was a visiting scholar at the Max Planck Institute for Polymer Research in Germany. In September 2019, I joined Hangzhou Normal University to establish a team focused on key materials for nanobiosensors. As the corresponding author, I have published over 100 SCI papers in journals such as *Science Advances*, *Journal of the American Chemical Society*, *Angewandte Chemie International Edition*, *Advanced Materials*, and *Chemical Society Reviews*. These papers have been cited over 12,000 times, with an H-index of 58. I hold 35 authorized Chinese and US invention patents. I have led over 20 research projects, including 7 National Natural Science Foundation of China (NSFC) projects. I received the inaugural Zhejiang Provincial Young Scientific and Technological Talent Award (2021), the Second Prize of Zhejiang Provincial Natural Science Award (2023, first author), and the First Prize in the National "Challenge Cup" Competition (2024, mentor). I was selected for the Zhejiang Provincial Overseas High-Level Talent Introduction Program (2016) and the NSFC Excellent Young Scientists Project (2022).
Beijing Perfectlight Technology Co., Ltd., established in 2006, is a national high-tech enterprise, a Zhongguancun high-tech enterprise, and one of the first batch of "Specialized, Refined, and Innovative" enterprises in Beijing. It has passed ISO 9001/14001/45001 management system certifications, and its after-sales service meets the GB/T 27922-2011 five-star standard. The company focuses on the R&D, production, sales, and service of intelligent, high-precision, and high-performance equipment and overall solutions. Its products cover more than ten series, including light sources, photoelectric/photothermal/thermocatalytic devices, characterization and testing systems, R&D equipment, and photosynthesis equipment, supporting research and development from basic research and pilot-scale testing to industrial scale-up. Perfectlight serves universities, research institutes, and enterprises, focusing on new energy, drug synthesis, fine chemicals, and new materials. Its products have entered over 3000 laboratories and are exported to nearly 50 countries, supporting the publication of over 9000 SCI papers. The company leads or participates in the formulation of national and industry standards, undertakes key national R&D programs, possesses multiple core intellectual property rights and "Beijing New Technology and New Product" certifications, and has assisted numerous enterprise users in building ton-level and hundred-ton-level photochemical production lines.
This article uses the PLS-FX300HU high-uniformity integrated xenon lamp light source for experiments. This light source is specifically designed for photoelectric material testing, and its main characteristics are as follows:
Flexible and adjustable light spot: It can output a rectangular uniform light spot from 10×10 mm² to 50×50 mm², with continuously adjustable size to meet the irradiation requirements of photoelectrodes of different sizes;
High uniformity: Extremely high light spot uniformity. When the spot size is no larger than 20×20 mm², its uniformity meets the Class A solar simulator standard, making it particularly suitable for precise measurement of photoelectric conversion efficiency (IPCE);
High light intensity: Output light power density limit ≥3000 mW/cm² (spot size 10×10 mm², direct output from focusing tube), meeting the experimental requirements for high-intensity uniform light;
Precise adjustment: Supports fine-grained control of output light intensity through either current adjustment or the use of an electric aperture.
