A stable and highly efficient visible-light-driven hydrogen evolution porous CdS/WO₃/TiO₂ photocatalysts

Qian, Yongteng,Yang, Mengke,Zhang, Fangfang,Du, Jimin,Li, Kaidi,Lin, Xialing,Zhu, Xinrui,Lu, Yayun,Wang, Weimin,Kang, Dae Joon Elsevier 2018 Materials characterization Vol.142 No.-

<P><B>Abstract</B></P> <P>It is well known that both catalytic efficiency and stability are the two important parameters of photocatalysts for visible-light-driven hydrogen production reactions. However, light-driven hydrogen evolution based applications still suffer from sluggish reaction kinetics due to the lack of high-performance photocatalysts. In this paper, we successfully synthesized a ternary porous CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> photocatalyst with high efficiency and stability via two-stage approach. The as-prepared samples are characterized by XRD, FESEM, EDS, TEM, XPS, and UV–Vis, respectively, which illustrated that the CdS and WO<SUB>3</SUB> moieties are in-situ formed inside the porous TiO<SUB>2</SUB>. Particularly, the photocatalytic hydrogen (H<SUB>2</SUB>) evolution rate of such ternary 8% CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> (molar ration of CdS:WO<SUB>3</SUB>:TiO<SUB>2</SUB> = 8:8:100) photocatalyst ranges up to 2106 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> under visible-light irradiation, which is higher than that of pure TiO<SUB>2</SUB> and other binary (CdS/TiO<SUB>2</SUB> and WO<SUB>3</SUB>/TiO<SUB>2</SUB>) porous photocatalysts. The superior H<SUB>2</SUB> evolution efficiency can be attributed to the coexistence of CdS and WO<SUB>3</SUB> in porous TiO<SUB>2</SUB> which can promote the interfacial charge transfer and separation as well as extend the light absorption up to the visible range.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly efficient and stable photocatalytic activity of CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> photocatalysts were synthesized by a two-step method. </LI> <LI> CdS and WO<SUB>3</SUB> inlaid on porous TiO<SUB>2</SUB> can extend the light absorption and enhance photogenerated electron-hole pairs separation. </LI> <LI> The porous structure can provide more reaction active sites and improve photoproduced-electrons and holes transport speed. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly efficient hydrogen evolution catalysis based on MoS₂/CdS/TiO₂ porous composites

Du, Jimin,Wang, Huiming,Yang, Mengke,Zhang, Fangfang,Wu, Haoran,Cheng, Xuechun,Yuan, Sijie,Zhang, Bing,Li, Kaidi,Wang, Yina,Lee, Hyoyoung Elsevier 2018 International journal of hydrogen energy Vol.43 No.19

<P><B>Abstract</B></P> <P>Efficient production of hydrogen through visible-light-driven water splitting mechanism using semiconductor-based composites has been identified as a promising strategy for converting light into clean H<SUB>2</SUB> fuel. However, researchers are facing lots of challenges such as light absorption and electron-hole pair recombination and so on. Here, new sheet-shaped MoS<SUB>2</SUB> and pyramid-shaped CdS <I>in-situ</I> co-grown on porous TiO<SUB>2</SUB> photocatalysts (MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB>) are successfully obtained <I>via</I> mild sulfuration of MoO<SUB>3</SUB> and CdO coexisted inside porous TiO<SUB>2</SUB> monolith by a hydrothermal route. The scanning electron microscopy and transmission electron microscopy results exhibit that the MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB> composites have average pore size about 500 nm. The 3%MoS<SUB>2</SUB> 10%CdSTiO<SUB>2</SUB> demonstrated excellent photocatalytic activity and high stability for a hydrogen production with a high H<SUB>2</SUB>-generation rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> under visible light irradiation even without noble-metal co-catalysts. The super photocatalytic performance of the visible-light-driven hydrogen evolution is predominantly attributed to the synergistic effect. The conduction band of MoS<SUB>2</SUB> facilitates in transporting excited electrons from visible-light on CdS to the porous TiO<SUB>2</SUB> for catalytic hydrogen production, and holes to MoS<SUB>2</SUB> for inhibiting the photocorrosion of CdS, respectively, leading to enhancing the efficient separation of electrons and holes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB>-CT photocatalysts have been successfully synthesized by two-step method. </LI> <LI> The porous structure can enhance photogenerated electron-hole pairs separation. </LI> <LI> The 3% MoS<SUB>2</SUB>-CT shows an excellent H<SUB>2</SUB> evolution rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly Efficient Photocatalysts Based on Lamellar-Shaped Bi2S3 Grown on TiO2 Monolith

Kaidi Li,Fangfang Zhang,Huiming Wang,Yalan Zhou,Lixin Zhao,Jimin Du,Yating Gao,Weimin Wang,강대준 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.09

Here, the lamellar-shaped Bi2S3 grown on a porous TiO2 monolith was obtained by a two-step method including a sol–gel route and hydrothermal treatment. The photocatalytic activity of the as-synthesized Bi2S3/TiO2 composites was evaluated for photodegradation of methylene blue (MB) dye in aqueous solution under the visible-light irradiation. Based on our experimental results, 5% (molar ratio of Bi2S3 to TiO2) Bi2S3/TiO2 photocatalysts exhibited a maximum photodegradation rate of MB up to 96.9% under visible-light irradiation for 120 min. Our findings indicated that the lamellar-shaped Bi2S3 can extend the light absorption up to visible areas, and porous TiO2 can provide enhanced specific surface area and more mass transfer pathway to enhance the photodegradation efficiency. Furthermore, porous TiO2 can accept the electrons from the Bi2S3 conduction band due to the relatively positive electrode potential to impede the photoproduced electron and hole combination to result in advanced photocatalytic performance.

Real-time surgical tool detection in computer-aided surgery based on enhanced feature-fusion convolutional neural network

Liu Kaidi,Zhao Zijian,Shi Pan,Li Feng,Song He 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.3

Surgical tool detection is a key technology in computer-assisted surgery, and can help surgeons to obtain more comprehensive visual information. Currently, a data shortage problem still exists in surgical tool detection. In addition, some surgical tool detection methods may not strike a good balance between detection accuracy and speed. Given the above problems, in this study a new Cholec80-tool6 dataset was manually annotated, which provided a better validation platform for surgical tool detection methods. We propose an enhanced feature-fusion network (EFFNet) for real-time surgical tool detection. FENet20 is the backbone of the network and performs feature extraction more effectively. EFFNet is the feature-fusion part and performs two rounds of feature fusion to enhance the utilization of low-level and high-level feature information. The latter part of the network contains the weight fusion and predictor responsible for the output of the prediction results. The performance of the proposed method was tested using the ATLAS Dione and Cholec80-tool6 datasets, yielding mean average precision values of 97.0% and 95.0% with 21.6 frames per second, respectively. Its speed met the real-time standard and its accuracy outperformed that of other detection methods.

Porous NiCo2S4 Networks as Electrodes for Electrochemical Supercapacitors

Jimin Du,Kaidi Li,Yongteng Qian,Mengke Yang,Huiming Wang,Wen He,Viyada Harnchana 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12

Porous NiCo2S4 networks have been successfully synthesized by a facile one-pot solvothermal method without the use of any surfactant or template. Crystal structure, morphology, composition and surface area of the as-synthesized samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer– Emmet–Teller techniques. Owing to their porous nature and small crystalline size, the as-prepared NiCo2S4 networks based supercapacitor electrodes showed a high specific capacitance of 1250 F · g-1 at 1 A · g-1, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte.

Attention-based spatial–temporal neural network for accurate phase recognition in minimally invasive surgery: feasibility and efficiency verification

Shi Pan,Zhao Zijian,Liu Kaidi,Li Feng 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.2

Laparoscopic surgery, as a representative minimally invasive surgery (MIS), is an active research area of clinical practice. Automatic surgical phase recognition of laparoscopic videos is a vital task with the potential to improve surgeons’ efficiency and has gradually become an integral part of computer-assisted intervention systems in MIS. However, the performance of most methods currently employed for surgical phase recognition is deteriorated by optimization difficulties and inefficient computation, which hinders their large-scale practical implementation. This study proposes an efficient and novel surgical phase recognition method using an attention-based spatial–temporal neural network consisting of a spatial model and a temporal model for accurate recognition by end-to-end training. The former subtly incorporates the attention mechanism to enhance the model’s ability to focus on the key regions in video frames and efficiently capture more informative visual features. In the temporal model, we employ independently recurrent long short-term memory (IndyLSTM) and non-local block to extract long-term temporal information of video frames. We evaluated the performance of our method on the publicly available Cholec80 dataset. Our attention-based spatial–temporal neural network purely produces the phase predictions without any post-processing strategies, achieving excellent recognition performance and outperforming other state-of-the-art phase recognition methods.

Pyramid-like CdS nanoparticles grown on porous TiO₂ monolith: An advanced photocatalyst for H₂ production

Du, Jimin,Wang, Huiming,Yang, Mengke,Li, Kaidi,Zhao, Lixin,Zhao, Guoyan,Li, Sujuan,Gu, Xiaolei,Zhou, Yalan,Wang, Le,Gao, Yating,Wang, Weimin,Kang, Dae Joon Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Efficient production of H<SUB>2</SUB> via solar-light-driven water splitting by a semiconductor-based photocatalyst without noble metals is crucial owing to increasingly severe global energy and environmental issues. However, many challenges, including the low efficiency of H<SUB>2</SUB> evolution, low solar light absorption, excited electron–hole pair recombination, and slow transport of photoexcited carriers, must be resolved to enhance the H<SUB>2</SUB> photoproduction efficiency and photocatalyst stability. Here, a two-step method is used to synthesize advanced H<SUB>2</SUB>-generating photocatalysts consisting of pyramid-like CdS nanoparticles grown on a porous TiO<SUB>2</SUB> monolith, which show promising photocatalytic activity for the hydrogen evolution reaction. Furthermore, the stability of the photocatalysts is examined through long-term tests to verify their good durability. Without noble metals as cocatalysts, the photocatalyst can reach a high H<SUB>2</SUB> production rate of 1048.7μmolh<SUP>−1</SUP> g<SUP>−1</SUP> under UV–vis irradiation when the ratio of the CdS nanoparticles to TiO<SUB>2</SUB> is 5mol%. This unusual photocatalytic activity arises from the wide-region light adsorption due to the narrow band gap of CdS, effective separation of electrons and holes due to conduction band alignment at the CdS–TiO<SUB>2</SUB> interface, and favorable reaction sites resulting from the porous structure.</P>

Enhanced charge separation of CuS and CdS quantum-dot-cosensitized porous TiO₂-based photoanodes for photoelectrochemical water splitting

Du, Jimin,Yang, Mengke,Zhang, Fangfang,Cheng, Xuechun,Wu, Haoran,Qin, Huichuang,Jian, Qingsong,Lin, Xialing,Li, Kaidi,Kang, Dae Joon Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.3

<P><B>Abstract</B></P> <P>Photoelectrochemical (PEC) water splitting using high-performance catalysts shows considerable promise in generating environment-friendly hydrogen energy. Its practical applications, however, suffer from several shortcomings, such as low photocurrent density, large onset-voltage value, and poor durability. In this study, CuS and CdS quantum-dot-cosensitized porous TiO<SUB>2</SUB>-based PEC catalysts (CuS-CT) have been successfully synthesized via in situ sulfuration of CuO and CdO coexisting inside a porous TiO<SUB>2</SUB> monolith by a hydrothermal method. Compared to porous TiO<SUB>2</SUB>, CuS-sensitized porous TiO<SUB>2</SUB> (CuS-TiO<SUB>2</SUB>), and CdS-sensitized porous TiO<SUB>2</SUB> (CdS-TiO<SUB>2</SUB>) in terms of PEC performance, the CuS-CT photoanode exhibited a significantly high anodic photocurrent for water splitting under simulated sunlight radiation. The photocurrent produced by the optimized sample of 7% CuS-5% CdS-TiO<SUB>2</SUB> (7% CuS-CT) was nearly 2.7 times higher than that of pure porous TiO<SUB>2</SUB> at 1.0V versus a reversible hydrogen electrode (RHE). Porous TiO<SUB>2</SUB> possesses large surface areas that can drive fast electrolyte transport and afford more surface reaction active sites. On the other hand, CuS and CdS quantum dots not only broaden the visible light absorption range, but also improve photoinduced electron-hole separation efficiency. The co-sensitized multi-nanostructures photoanodes lead to a remarkable and promising application in PEC water splitting reactions.</P>

Controlled synthesis of nanoplate, nanoprism and nanopyramid-shaped CdSe decorated on porous TiO₂ photocatalysts for visible-light-driven hydrogen evolution

Yang, Mengke,Qian, Yongteng,Du, Jimin,Yuan, Sijie,Wang, Sijia,Zhu, Xinrui,Lin, Xialing,Li, Kaidi,Li, Sujuan,Kang, Dae Joon Elsevier 2018 Ceramics international Vol.44 No.11

<P><B>Abstract</B></P> <P>Herein, we report a successful synthesis of porous TiO<SUB>2</SUB> monoliths decorated with unique nanoplate, nanoprism, and nanopyramid-shaped CdSe particles through a mild selenylation of CdO embedded inside porous TiO<SUB>2</SUB> monoliths via a hydrothermal method in a very controlled manner. Compared with pure TiO<SUB>2</SUB>, as-synthesized CdSe/TiO<SUB>2</SUB> photocatalyst not only enhances light absorption but also leads to a highly efficient charge-carrier separation. Particularly, the nanoplate-shaped 7% CdSe/TiO<SUB>2</SUB> photocatalyst (molar percentages of CdSe to TiO<SUB>2</SUB> is 7:100) exhibits an exceptional hydrogen evolution rate up to 3650 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> without resorting to any noble-metal co-catalysts under visible-light irradiation owing to synergistic effects envisaged by a rational material design. Our results may provide a useful strategy to develop a highly-efficient visible-light-driven hydrogen production system via water splitting.</P>