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Chinese Journal of Catalysis
2024, Vol. 64
Online: 18 September 2024

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Cover: Prof. Bingjun Xu and coworkers conducted a systematic study on the reaction mechanism of propane dehydrogenation over the Ga/H-ZSM-5 system, proposing that the active species Ga₂O₂²⁺ catalyzes the C–H bond activation in propane molecules. This mechanism involves a two-step catalytic cycle consisting of activation and β-elimination, which propane undergoes on Ga₂O₂²⁺. The study identifies two distinct types of Ga₂O₂²⁺ species in different chemical environments, with the catalytic cycle being completed only on the Ga₂O₂²⁺ species that corresponds to the high wavenumber peak in the infrared spectrum. This finding provides new insights and references for exploring the reaction mechanisms of other catalysts in propane dehydrogenation. Read more about the article behind the cover on page 32–43.

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S-scheme heterojunction with ultrafast interfacial electron transfer for artificial photosynthesis Sihang Mao, Rongan He, Shaoqing Song 2024, 64:  1-3.  DOI: 10.1016/S1872-2067(24)60102-6 Abstract ( 216 )   HTML ( 25 )   PDF (1665KB) ( 96 )

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Perfecting HER catalysts via defects: Recent advances and perspectives Chengguang Lang, Yantong Xu, Xiangdong Yao 2024, 64:  4-31.  DOI: 10.1016/S1872-2067(24)60105-1 Abstract ( 255 )   HTML ( 20 )   PDF (15185KB) ( 101 )   Defect engineering has become a promising approach to improve the performance of hydrogen evolution reaction (HER) catalysts. Non-noble transition metal-based catalysts (TMCs) have shown significant promise as effective alternatives to traditional platinum-group catalysts, attracting considerable attention. However, the industrial application of TMCs in electrocatalytic hydrogen production necessitates further optimization to boost both catalytic activity and stability. This review comprehensively examines the types, fabrication methods, and characterization techniques of various defects that enhance catalytic HER activity. Key advancements include optimizing defect concentration and distribution, coupling heteroatoms with vacancies, and leveraging the synergy between bond lengths and defects. In-depth discussions highlight the electronic structure and catalytic mechanisms elucidated through in-situ characterization and density functional theory calculations. Additionally, future directions are identified, exploring novel defect types, emphasizing precision synthesis methods, industrial-scale preparation techniques, and strategies to enhance structural stability and understanding the in-depth catalytic mechanism. This review aims to inspire further research and development in defect-engineered HER catalysts, providing pathways for high efficiency and cost-effectiveness in hydrogen production.

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C-H bond activation of propane on Ga2O22+ in Ga/H-ZSM-5 and its mechanistic implications Zhaoqi Zhao, Yunzhu Zhong, Xiaoxia Chang, Bingjun Xu 2024, 64:  32-43.  DOI: 10.1016/S1872-2067(24)60065-3 Abstract ( 195 )   HTML ( 8 )   PDF (3392KB) ( 69 )   Supporting Information Propane dehydrogenation (PDH) on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production, while the detail mechanism remains debatable. Ga2O22+ stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work. Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga2O22+ species corresponding to the infrared GaH band of higher wavenumber (GaHHW) in reduced Ga/H-ZSM-5, instead of the overall Ga2O22+ species, by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio. This disparity in Ga2O22+ species stems from their differing capacity in completing the catalytic cycle. Spectroscopic results suggest that PDH proceeds via a two-step mechanism: (1) C-H bond activation of propane on H-Ga2O22+ species (rate determining step); (2) β-hydride elimination of adsorbed propyl group, which only occurs on active Ga2O22+ species corresponding to GaHHW.

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Why the abnormal phenomena of D-band center theory exist? A new BASED theory for surface catalysis and chemistry Zelong Qiao, Run Jiang, Jimmy Yun, Dapeng Cao 2024, 64:  44-53.  DOI: 10.1016/S1872-2067(24)60100-2 Abstract ( 324 )   HTML ( 17 )   PDF (3041KB) ( 97 )   Supporting Information Since the D-band center theory was proposed, it has been widely used in the fields of surface chemistry by almost all researchers, due to its easy understanding, convenient operation and relative accuracy. However, with the continuous development of material systems and modification strategies, researchers have gradually found that D-band center theory is usually effective for large metal particle systems, but for small metal particle systems or semiconductors, such as single atom systems, the opposite conclusion to the D-band center theory is often obtained. To solve the issue above, here we propose a bonding and anti-bonding orbitals stable electron intensity difference (BASED) theory for surface chemistry. The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory, but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites. Importantly, a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory, where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5 Å. In short, the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.

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Chalcogen heteroatoms doped nickel-nitrogen-carbon single-atom catalysts with asymmetric coordination for efficient electrochemical CO2 reduction Jialin Wang, Kaini Zhang, Ta Thi Thuy Nga, Yiqing Wang, Yuchuan Shi, Daixing Wei, Chung-Li Dong, Shaohua Shen 2024, 64:  54-65.  DOI: 10.1016/S1872-2067(24)60103-8 Abstract ( 233 )   HTML ( 27 )   PDF (4046KB) ( 78 )   Supporting Information The electronic configuration of central metal atoms in single-atom catalysts (SACs) is pivotal in electrochemical CO2 reduction reaction (eCO2RR). Herein, chalcogen heteroatoms (e.g., S, Se, and Te) were incorporated into the symmetric nickel-nitrogen-carbon (Ni-N4-C) configuration to obtain Ni-X-N3-C (X: S, Se, and Te) SACs with asymmetric coordination presented for central Ni atoms. Among these obtained Ni-X-N3-C (X: S, Se, and Te) SACs, Ni-Se-N3-C exhibited superior eCO2RR activity, with CO selectivity reaching ~98% at -0.70 V versus reversible hydrogen electrode (RHE). The Zn-CO2 battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h. In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution, and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO2RR. Especially, for Ni-Se-N3-C, the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of *COOH formation, contributing to the promising eCO2RR performance for high selectivity CO production by competing with hydrogen evolution reaction.

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Poly(ethylenimine)-assisted synthesis of hollow carbon spheres comprising multi-sized Ni species for CO2 electroreduction Kaining Li, Yasutaka Kuwahara, Hiromi Yamashita 2024, 64:  66-76.  DOI: 10.1016/S1872-2067(24)60087-2 Abstract ( 98 )   HTML ( 4 )   PDF (14428KB) ( 39 )   Supporting Information Electrochemical CO2 reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion. The development of efficient catalysts with high conductivity and readily accessible active sites for CO2 electroreduction remains challenging yet indispensable. In this work, a reliable poly(ethyleneimine) (PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles (NPs) (denoted as Ni@NHCS), where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres, but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites. Benefiting from the unique structural properties of Ni@NHCS, the aggregation and exposure of Ni NPs can be effectively prevented, while the accessibility of abundant catalytically active Ni-Nx sites can be ensured. As a result, Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm-2 and a Faradaic efficiency of 93.0% at -1.0 V vs. RHE, outperforming those of its PEI-free analog. Apart from the excellent activity and selectivity, the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability. The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO2 reduction. Furthermore, the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.

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The role of titanium at the interface of hematite photoanode in multisite mechanism: Reactive site or cocatalyst site? Minfei Xie, Xing Ji, Huaying Meng, Nanbing Jiang, Zhenyu Luo, Qianqian Huang, Geng Sun, Yunhuai Zhang, Peng Xiao 2024, 64:  77-86.  DOI: 10.1016/S1872-2067(24)60093-8 Abstract ( 117 )   HTML ( 3 )   PDF (4076KB) ( 19 )   Supporting Information Hematite (α-Fe2O3) constitutes one of the most promising photoanode materials for oxygen evolution reaction (OER). Recent research on Fe2O3 have found a fast OER rate dependence on surface hole density, suggesting a multisite reaction pathway. However, the effect of heteroatom in Fe2O3 on the multisite mechanism is still poorly understood. Herein we synthesized Fe2O3 on Ti substrates (Fe2O3/Ti) to study the oxygen intermediates of OER by light-dark electrochemical scans. We identified the Fe-OH species disappeared and Ti-OH intermediates appeared on Fe2O3/Ti when pH = 11‒14, which significantly improved the OER performance of Fe2O3/Ti. Combined with the density functional theory calculations, we propose that Ti atom acts as cocatalyst site and captures proton from neighboring Fe-OH species under highly alkaline condition, thereby promoting the coupling of Fe=O and reducing the energy barrier of the non-electrochemical step. Our work provides a new insight into the role of heteroatom in OER multisite mechanism based on clarifying the reaction intermediates.

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Boosting photocatalytic hydrogen evolution enabled by SiO2-supporting chiral covalent organic frameworks with parallel stacking sequence Zheng Lin, Wanting Xie, Mengjing Zhu, Changchun Wang, Jia Guo 2024, 64:  87-97.  DOI: 10.1016/S1872-2067(24)60107-5 Abstract ( 100 )   HTML ( 4 )   PDF (7023KB) ( 35 )   Supporting Information Two-dimensional covalent organic frameworks (2D COFs) feature extended π-conjugation and ordered stacking sequence, showing great promise for high-performance photocatalysis. Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer, but the precise ordered alignment is limited due to the non-covalent π-stacking of COF layers, accordingly hindering out-of-plane transfer kinetics. Herein, we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO2 microsphere. Compared to the achiral COF analogues, the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration, thereby affording superior photocatalytic performance in hydrogen evolution from water splitting. Taking the simplest ketoenamine-linked chiral COF as a shell of SiO2 particle, the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g-1 h-1 along with the apparent quantum efficiency of 14.31% at 475 nm. Furthermore, the composite photocatalysts could be fabricated into a film device, displaying a remarkable photocatalytic performance of 178.0 mmol m-2 h-1 for hydrogen evolution. Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.

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Single atom doping induced charge-specific distribution of Cu1-TiO2 for selective aniline oxidation via a new mechanism Jiaheng Qin, Wantong Zhao, Jie Song, Nan Luo, Zheng-Lan Ma, Baojun Wang, Jiantai Ma, Riguang Zhang, Yu Long 2024, 64:  98-111.  DOI: 10.1016/S1872-2067(24)60104-X Abstract ( 87 )   HTML ( 2 )   PDF (4424KB) ( 29 )   Supporting Information Utilizing single atom sites doping into metal oxides to modulate their intrinsic active sites, achieving precise selectivity control in complex organic reactions, is a highly desirable yet challenging endeavor. Meanwhile, identifying the active site also represents a significant obstacle, primarily due to the intricate electronic environment of single atom site doped metal oxide. Herein, a single atom Cu doped TiO2 catalyst (Cu1-TiO2) is prepared via a simple “colloid-acid treatment” strategy, which switches aniline oxidation selectivity of TiO2 from azoxybenzene to nitrosobenzene, without using additives or changing solvent, while other metal or nonmetal doped TiO2 did not possess. Comprehensive mechanistic investigations and DFT calculations unveil that Ti-O active site is responsible for triggering the aniline to form a new PhNOH intermediate, two PhNOH condense to azoxybenzene over TiO2 catalyst. As for Cu1-TiO2, the charge-specific distribution between the isolated Cu and TiO2 generates unique Cu1-O-Ti hybridization structure with nine catalytic active sites, eight of them make PhNOH take place spontaneous dissociation to produce nitrosobenzene. This work not only unveils a new mechanistic pathway featuring the PhNOH intermediate in aniline oxidation for the first time but also presents a novel approach for constructing single-atom doped metal oxides and exploring their intricate active sites.

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Microenvironment and electronic state modulation of Pd nanoparticles within MOFs for enhancing low-temperature activity towards DCPD hydrogenation Zhiyuan Liu, Changan Wang, Ping Yang, Wei Wang, Hongyi Gao, Guoqing An, Siqi Liu, Juan Chen, Tingting Guo, Xinmeng Xu, Ge Wang 2024, 64:  112-122.  DOI: 10.1016/S1872-2067(24)60095-1 Abstract ( 74 )   HTML ( 3 )   PDF (7083KB) ( 32 )   Supporting Information Precise control of the local environment and electronic state of the guest is an important method of controlling catalytic activity and reaction pathways. In this paper, guest Pd NPs were introduced into a series of host UiO-67 MOFs with different functional ligands and metal nodes, the microenvironment and local electronic structure of Pd is modulated by introducing bipyridine groups and changing metal nodes (Ce6O6 or Zr6O6). The bipyridine groups not only promoted the dispersion Pd NPs, but also facilitated electron transfer between Pd and UiO-67 MOFs through the formation of Pd-N bridges. Compared with Zr6 clusters, the tunability and orbital hybridisation of the 4f electronic structure in the Ce6 clusters modulate the electronic structure of Pd through the construction of the Ce-O-Pd interfaces. The optimal catalyst Pd/UiO-67(Ce)-bpy presented excellent low-temperature activity towards dicyclopentadiene hydrogenation with a conversion of > 99% and a selectivity of > 99% (50 °C, 10 bar). The results show that the synergy of Ce-O-Pd and Pd-N promotes the formation of active Pdδ+, which not only enhances the adsorption of H2 and electron-rich C=C bonds, but also contributes to the reduction of proton migration distance and improves proton utilization efficiency. These results provide valuable insights for investigating the regulatory role of the host MOFs, the nature of host-guest interactions, and their correlation with catalytic performance.

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Cu single-atom electrocatalyst on nitrogen-containing graphdiyne for CO2 electroreduction to CH4 Hao Dai, Tao Song, Xian Yue, Shuting Wei, Fuzhi Li, Yanchao Xu, Siyan Shu, Ziang Cui, Cheng Wang, Jun Gu, Lele Duan 2024, 64:  123-132.  DOI: 10.1016/S1872-2067(24)60106-3 Abstract ( 118 )   HTML ( 8 )   PDF (4054KB) ( 37 )   Supporting Information Developing Cu single-atom catalysts (SACs) with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO2 reduction reaction and understanding the structure-property relationship. Herein, a new graphdiyne analogue with uniformly distributed N2-bidentate (note that N2-bidentate site = N^N-bidentate site; N2 ≠ dinitrogen gas in this work) sites are synthesized. Due to the strong interaction between Cu and the N2-bidentate site, a Cu SAC with isolated undercoordinated Cu-N2 sites (Cu1.0/N2-GDY) is obtained, with the Cu loading of 1.0 wt%. Cu1.0/N2-GDY exhibits the highest Faradaic efficiency (FE) of 80.6% for CH4 in electrocatalytic reduction of CO2 at -0.96 V vs. RHE, and the partial current density of CH4 is 160 mA cm-2. The selectivity for CH4 is maintained above 70% when the total current density is 100 to 300 mA cm-2. More remarkably, the Cu1.0/N2-GDY achieves a mass activity of 53.2 A/mgCu toward CH4 under -1.18 V vs. RHE. In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N2 sites are more favorable in generating key *COOH and *CHO intermediate than Cu nanoparticle counterparts. This work provides an effective pathway to produce SACs with undercoordinated Metal-N2 sites toward efficient electrocatalysis.

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Deactivation mechanism of acetone to isobutene conversion over Y/Beta catalyst Chang Wang, Tingting Yan, Weili Dai 2024, 64:  133-142.  DOI: 10.1016/S1872-2067(24)60097-5 Abstract ( 80 )   HTML ( 1 )   PDF (4293KB) ( 23 )   Supporting Information The conversion of acetone derived from biomass to isobutene has attracted extensive attentions. In comparison with Brønsted acidic catalyst, Lewis acidic catalyst could exhibit a better catalytic performance with a higher isobutene selectivity. However, the catalyst stability remains a key problem for the long-running acetone conversion and the reasons for catalyst deactivation are poorly understood up to now. Herein, the deactivation mechanism of Lewis acidic Y/Beta catalyst during the acetone to isobutene conversion was investigated by various characterization techniques, including acetone-temperature-programmed surface reaction, gas chromatography-mass spectrometry, in situ ultraviolet-visible, and 13C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy. A successive aldol condensation and cyclization were observed as the main side-reactions during the acetone conversion at Lewis acidic Y sites. In comparison with the low reaction temperature, a rapid formation and accumulation of the larger cyclic unsaturated aldehydes/ketones and aromatics could be observed, and which could strongly adsorb on the Lewis acidic sites, and thus cause the catalyst deactivation eventually. After a simple calcination, the coke deposits could be easily removed and the catalytic activity could be well restored.

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Single-atom modified graphene cocatalyst for enhanced photocatalytic CO2 reduction on halide perovskite Hui Fu, Jin Tian, Qianqian Zhang, Zhaoke Zheng, Hefeng Cheng, Yuanyuan Liu, Baibiao Huang, Peng Wang 2024, 64:  143-151.  DOI: 10.1016/S1872-2067(24)60081-1 Abstract ( 136 )   HTML ( 7 )   PDF (5689KB) ( 60 )   Supporting Information Metal halide perovskite (MHP) has become one of the most promising materials for photocatalytic CO2 reduction owing to the wide light absorption range, negative conduction band position and high reduction ability. However, photoreduction of CO2 by MHP remains a challenge because of the slow charge separation and transfer. Herein, a cobalt single-atom modified nitrogen-doped graphene (Co-NG) cocatalyst is prepared for enhanced photocatalytic CO2 reduction of bismuth-based MHP Cs3Bi2Br9. The optimal Cs3Bi2Br9/Co-NG composite exhibits the CO production rate of 123.16 μmol g-1 h-1, which is 17.3 times higher than that of Cs3Bi2Br9. Moreover, the Cs3Bi2Br9/Co-NG composite photocatalyst exhibits nearly 100% CO selectivity as well as impressive long-term stability. Charge carrier dynamic characterizations such as Kelvin probe force microscopy (KPFM), single-particle PL microscope and transient absorption (TA) spectroscopy demonstrate the vital role of Co-NG cocatalyst in accelerating the transfer and separation of photogenerated charges and improving photocatalytic performance. The reaction mechanism has been demonstrated by in situ diffuse reflectance infrared Fourier-transform spectroscopy measurement. In addition, in situ X-ray photoelectron spectroscopy test and theoretical calculation reveal the reaction reactive sites and reaction energy barriers, demonstrating that the introduction of Co-NG promotes the formation of *COOH intermediate, providing sufficient evidence for the highly selective generation of CO. This work provides an effective single-atom-based cocatalyst modification strategy for photocatalytic CO2 reduction and is expected to shed light on other photocatalytic applications.

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Vacancy engineering mediated hollow structured ZnO/ZnS S-scheme heterojunction for highly efficient photocatalytic H2 production Fangxuan Liu, Bin Sun, Ziyan Liu, Yingqin Wei, Tingting Gao, Guowei Zhou 2024, 64:  152-165.  DOI: 10.1016/S1872-2067(24)60099-9 Abstract ( 154 )   HTML ( 6 )   PDF (11462KB) ( 65 )   Supporting Information Designing a step-scheme (S-scheme) heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H2 production activity. Herein, a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies (VO, Zn-ZnO/ZnS) is rationally constructed via ion-exchange and calcination treatments. In such a photocatalytic system, the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption. Moreover, the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes, respectively, which are beneficial for promoting the photo-induced carrier separation. Meanwhile, the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity. As expected, the optimized VO, Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H2 production rate of 160.91 mmol g-1 h-1, approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS, respectively. Simultaneously, the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S‐scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier. This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar‐to‐fuel energy conversion.

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Interface engineering via temperature-dependent self-transformation on SnS2/SnS for enhanced piezocatalysis Wenrou Tian, Jun Han, Najun Li, Dongyun Chen, Qingfeng Xu, Hua Li, Jianmei Lu 2024, 64:  166-179.  DOI: 10.1016/S1872-2067(24)60101-4 Abstract ( 123 )   HTML ( 2 )   PDF (4426KB) ( 20 )   Supporting Information Heterojunction has been widely used in vibration-driven piezocatalysis for enhanced charges separation, while the weak interfaces seriously affect the efficiency during mechanical deformations due to prepared by traditional step-by-step methods. Herein, the intimate contact interfaces with shared S atoms are ingeniously constructed in SnS2/SnS anchored on porous carbon by effective interface engineering, which is in-situ derived from temperature-dependent self-transformation of SnS2. Benefiting from intimate contact interfaces, the piezoelectricity is remarkably improved due to the larger interfacial dipole moment caused by uneven distribution of charges. Importantly, vibration-induced piezoelectric polarization field strengthens the interfacial electric field to further promote the separation and migration of charges. The dynamic charges then transfer in porous carbon with high conductivity and adsorption for significantly improved piezocatalytic activity. The degradation efficiency of bisphenol A (BPA) is 6.3 times higher than SnS2 and H2 evolution rate is increased by 3.8 times. Compared with SnS2/SnS prepared by two-step solvothermal method, the degradation efficiency of BPA and H2 evolution activity are increased by 3 and 2 times, respectively. It provides a theoretical guidance for developing various multiphase structural piezocatalyst with strong interface interactions to improve the piezocatalytic efficiency.