Cs2CuBr4 perovskite quantum dots confined in mesoporous CuO framework as a p-n type S-scheme heterojunction for efficient CO2 photoconversion

Cs₂CuBr₄ perovskite quantum dots confined in mesoporous CuO framework as a p-n type S-scheme heterojunction for efficient CO₂ photoconversion

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Zhijie Zhang^a, Xun Li^a, Huiling Tang^a^,^b, Junhao Wu^c, Chunxia Yao^*^,^b, Kui Li^*^,^c

Chinese Chemical Letters | 2024, 35(11) : 109700

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Chinese Chemical Letters | 2024, 35(11): 109700

• Communication •

Cs₂CuBr₄ perovskite quantum dots confined in mesoporous CuO framework as a p-n type S-scheme heterojunction for efficient CO₂ photoconversion

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Zhijie Zhang^a, Xun Li^a, Huiling Tang^a^,^b, Junhao Wu^c, Chunxia Yao^*^,^b, Kui Li^*^,^c

Affiliations

^a School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, China

^b Institute for Agro-food Standards and Testing Technology, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China

^c School of Chemistry and Chemical Engineering, Hainan University, Haikou 570228, China

Published: 2024-11-15 doi: 10.1016/j.cclet.2024.109700

Outline

Abstract

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Heterojunction engineering is recognized as a promising strategy to modulate the photocatalytic properties of semiconductors. Herein, lead-free Cs₂CuBr₄ perovskite quantum dots (PQDs) were confined in a mesoporous CuO framework and a p-n type S-scheme heterojunction of Cs₂CuBr₄/CuO (CCB/CuO) photocatalyst was fabricated. Experimental characterizations confirmed the effective confinement of the Cs₂CuBr₄ PQDs in the mesoporous CuO framework, which enabled intimate contact in the interface of CCB/CuO heterojunction, thus facilitating the interfacial charge migration and separation between p-type CuO and n-type Cs₂CuBr₄. Owing to the outstanding charge transport property and CO₂ adsorption capacity, the developed CCB/CuO heterojunction exhibited remarkably enhanced photocatalytic CO₂ conversion efficiency with an electron consumption rate (R_electron) of 281.1 µmol g⁻¹ h⁻¹, which was approximately 2.8 times higher than that of pristine Cs₂CuBr₄. These findings provide some insights into the rational engineering design of lead-free perovskite-based heterostructures for efficient photocatalytic CO₂ conversion.

Key words

Photocatalytic CO₂ conversion / Mesoporous CuO / Cs₂CuBr₄ / Perovskite quantum dots / S-scheme heterojunction

Cite this Article

Zhijie Zhang, Xun Li, Huiling Tang, Junhao Wu, Chunxia Yao, Kui Li. Cs₂CuBr₄ perovskite quantum dots confined in mesoporous CuO framework as a p-n type S-scheme heterojunction for efficient CO₂ photoconversion[J]. Chinese Chemical Letters, 2024 , 35 (11) : 109700 - . DOI: 10.1016/j.cclet.2024.109700

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With the massive consumption of fossil fuels and significant emissions of greenhouse gases, the world is faced with more and more serious energy shortage and climate issues. Especially, the emission of carbon dioxide has brought about great concern, as the CO₂ greenhouse effect has caused the notorious global warming. Therefore, the capture, storage, and conversion of CO₂, are of great significance to resolve the energy crisis and environmental issues [1–3]. By imitating the natural photosynthesis, photocatalytic CO₂ reduction to high-density hydrocarbon fuels using the inexhaustible solar energy is a green and sustainable approach [4,5]. Up to date, a variety of semiconductors have been explored as photocatalysts, including TiO₂ [6], metal-organic frameworks [7–10], single-atom catalysts [11,12], etc. The continuous exploration of low-cost, stable, and efficient photocatalysts for CO₂ reduction is one of the strategic alternatives for the practical application of such a promising technology.

As a newly emerging class of optoelectronic materials, halide perovskite quantum dots (PQDs) have attracted significant attention due to their unique advantages of high extinction coefficients, suitable energy band structure, and long carrier diffusion length [13,14]. Traditional lead-based PQDs, especially CsPbBr₃, have been extensively studied as photocatalysts for CO₂ conversion due to their excellent light harvesting ability and appropriate band positions [15–17]. However, the high Pb toxicity has impeded the practical applications of the lead-containing perovskites. In order to conquer this, researchers have diverted their attention to exploiting lead-free perovskites for photocatalysis. Among which, the Cu-based perovskite Cs₂CuBr₄ has been demonstrated as a promising candidate owing to its suitable bandgap and nontoxicity [18]. Nevertheless, the intrinsic large surface energy of PQDs makes them easy to agglomerate, which can affect their long-term stability. Moreover, the rapid recombination of photogenerated charge carriers in pristine PQDs is unfavourable for their photocatalytic activity. These problems can be overcome by confining the Cs₂CuBr₄ PQDs in a mesoporous semiconductor framework to construct a heterojunction.

Among various heterojunctions, the newly-emerging S-scheme heterojunction has received significant attention for its unique superiorities [19]. There are four types of S-scheme heterojunction: n-n junction, p-p junction, p-n junction, and n-p junction, where the left letter represents oxidation photocatalyst (OP) and the right one represents reduction photocatalyst (RP). Taken the p-n junction as an example, OP is a p-type semiconductor while RP is an n-type semiconductor. In any case, the precondition for the formation of an S-scheme heterojunction is that the conduction band (CB) position and Fermi level (E_F) of OP should be simultaneously lower than those of RP. Generally, the E_F gap between the n-type and p-type semiconductors is larger than that between n-type and n-type semiconductors. In other words, the p-n heterojunction has an intensified internal electric field (IEF) compared with the n-n heterojunction, which can provide a more powerful driving force for charge transfer. However, most of the reported S-scheme heterojunctions are n-n type, and the p-n type S-scheme heterojunction is rarely reported.

Copper oxide (CuO) is a p-type semiconductor with a monoclinic structure and narrow band gap (E_g = 1.2–2.0 eV) [20], which has been widely applied in catalysis, batteries, gas sensing, and photoelectrochemical cells [21,22]. Motivated by its good stability, availability, high absorption in visible light spectrum, and p-type semiconducting property, we intend to construct a p-n type S-scheme heterojunction by confining the Cs₂CuBr₄ PQDs in a mesoporous CuO framework, which is expected to bring about multiple advantages: Firstly, the confinement of Cs₂CuBr₄ in mesoporous CuO can effectively prevent the PQDs from aggregation; Secondly, the unique mesoporous structure of CuO can afford the photocatalyst with high specific surface area and numerous active sites, thus favoring the adsorption/activation of CO₂ molecules; Thirdly, the construction of S-scheme heterojunction between CuO and Cs₂CuBr₄ can simultaneously promote the charge separation and maximize the reduction/oxidation abilities of the CCB/CuO photocatalyst, which can lead to improved photocatalytic performance. Considering all the above merits, the CCB/CuO p-n heterojunction is expected to be a promising photocatalyst for CO₂ conversion.

The CCB/CuO p-n type S-scheme photocatalyst was fabricated by a facile impregnation approach (Fig. S1 in Supporting information). The crystal structures of the synthesized CuO, Cs₂CuBr₄, and CCB/CuO heterojunctions were investigated by XRD analysis. As shown in Fig. S2a (Supporting information), for pure CuO and Cs₂CuBr₄, all the diffractions peaks match well with the standard card of CuO (JCPDS card No. 9016105) and Cs₂CuBr₄ (JCPDS card No. 71–1462), implying that CuO and Cs₂CuBr₄ with high purity and crystallinity are obtained. For the XRD patterns of CCB/CuO heterojunctions, characteristic diffraction peaks of both CuO and Cs₂CuBr₄ could be observed, and the diffraction peaks of Cs₂CuBr₄ increase with its loading amount. Moreover, in the small-angle XRD patterns of CuO and the CCB/CuO heterojunctions (Fig. S2b in Supporting information), a distinct diffraction peak at ca. 0.7^° could be detected, which is characteristic of mesoporous materials [23]. The above results imply the successful synthesis of mesoporous CuO and the retainment of the mesoporous structure during the combined process.

The mesoporous structure is supposed to provide the CuO framework with a high BET surface area. As shown in Fig. S3a (Supporting information), the N₂ adsorption-desorption isotherms of CuO and the CCB/CuO heterojunctions display a typical IV isotherm with a type H3 hysteresis loop, which is characteristic of mesoporous structured materials [24]. CuO has a high specific surface area of ca. 58.78 m²/g, and encapsulation of Cs₂CuBr₄ PQDs into the mesopores leads to decreased BET surface areas (Table S1 in Supporting information). This is because the presence of Cs₂CuBr₄ PQDs in the mesopores of CuO framework hinder N₂ adsorption during the BET measurement. This assumption is further confirmed by the pore size distribution curves. As shown in Fig. S3b and Table S1 (Supporting information), the pore sizes of CCB/CuO are smaller than that of CuO, and decrease gradually with the increased content of Cs₂CuBr₄ PQDs. This observation further indicates the successful loading of Cs₂CuBr₄ PQDs in the mesopores of the CuO framework.In order to examine the microstructure of the prepared Cs₂CuBr₄, CuO, and the loading state of Cs₂CuBr₄ PQDs on CuO, TEM and HRTEM images were performed. As shown in Fig. 1a, Cs₂CuBr₄ exhibits nanospherical structure with the sizes of 2–5 nm. The HRTEM image (Fig. 1b) displays a distinct interplanar spacing of 0.32 nm, which corresponds to the (203) plane of Cs₂CuBr₄. The TEM image of CuO is shown in Fig. 1c and Fig. S4 (Supporting information), which possesses abundant pores in the structure, indicating that mesoporous CuO has been successfully fabricated by duplicating the structure of the MCM-48 template. In the HRTEM image of CuO (Fig. 1d), the lattice spacing of 0.24 nm could be clearly observed, which is consistent with the (111) plane of CuO. The TEM image of the CCB/CuO heterojunction is shown in Fig. 1e, which indicates that the basic structure of the CuO framework is retained, with some small nanoparticles decorated in the pores. In the HRTEM image of the CCB/CuO heterojunction (Fig. 1f), the crystal lattices of Cs₂CuBr₄ and CuO could be observed, where the lattice spacing of 0.32 nm and 0.24 nm are in good agreement with the (203) and (111) planes of Cs₂CuBr₄ and CuO, respectively. The corresponding EDX spectra also certifies the presence of all the elements of Cs, Cu, Br, and O in the heterojunction catalyst (Fig. S5 in Supporting information). In addition, the elemental mapping of the CCB/CuO heterojunction (Fig. 1g) indicates that Cs₂CuBr₄ PQDs are evenly dispersed in the pores of CuO. All the above characterizations confirm the successful loading and homogeneous distribution of Cs₂CuBr₄ PQDs in the mesopores of the CuO framework.

The UV–vis DRS spectra (Fig. S6a in Supporting information) shows that both CuO and Cs₂CuBr₄ exhibit remarkable photoabsorption properties, with the absorption edge extended to the whole visible and partial infrared region. The CCB/CuO heterojunctions show intermediate photoabsorption properties between pristine CuO and Cs₂CuBr₄. The broad photoabsorption range illustrates small band gaps of CuO and Cs₂CuBr₄, which are determined to be 1.57 and 1.52 eV, respectively (Fig. S6b in Supporting information). The conducting type of Cs₂CuBr₄ and CuO is clarified by the Mott-Schottky (M-S) plots. As shown in Fig. S7a and b (Supporting information), the slope of the M-S plot of Cs₂CuBr₄ is positive, while that of CuO is negative, which indicates the n and p-type semiconductor characteristics of Cs₂CuBr₄ and CuO, respectively. Fig. S8 (Supporting information) presents the valence band XPS (VB-XPS) spectra of Cs₂CuBr₄ and CuO, which indicates valence band potentials (E_VB) of 0.86 and 1.83 eV for Cs₂CuBr₄ and CuO, respectively. Correspondingly, their conduction band potentials (E_CB) are calculated to be −0.66 and 0.26 eV by the formula of E_CB = E_VB - E_g. Based on the obtained values, the band energy positions of Cs₂CuBr₄ and CuO are drawn schematically. As shown in Fig. S9 (Supporting information), both the E_CB and E_VB of Cs₂CuBr₄ are higher than that of CuO. In other words, Cs₂CuBr₄ and CuO have staggered energy level alignments, which is an important prerequisite for the formation of S-scheme heterojunction.

The chemical state of elements in CCB/CuO heterojunction and the interaction between Cs₂CuBr₄ and CuO were studied by XPS. The full scan XPS spectra (Fig. 2a) shows that the CCB/CuO sample exhibits all the expected elements of Cs, Cu, Br, and O. The high resolution XPS spectra of Cs 3d in pristine Cs₂CuBr₄ and CCB/CuO heterojunction are compared in Fig. 2b. The Cs 3d spectra for pristine Cs₂CuBr₄ exhibits two binding energy peaks at 738.3 and 724.5 eV, corresponding to Cs 3d_3/2 and Cs 3d_5/2, respectively. After formation of heterojunction with CuO, these two peaks display a positive shift by 0.5 eV to 738.8 and 725.0 eV, respectively. Similarly, the Br 3d and Cu 2p spectra also exhibit positive shift (Figs. 2c and d). Conversely, the peaks of Cu 2p spectra for the CCB/CuO heterojunction exhibits a negative shift compared with that of pristine CuO (Fig. 2e). Similar to that of Cu 2p spectra, the peak of the lattice oxygen in CCB/CuO also shifts negatively to lower values in relative to that of CuO (Fig. 2f). The above phenomena indicate that the electrons cloud density of Cs₂CuBr₄ decreases upon the formation of heterojunction, while the electrons cloud density of CuO increases [25]. In other words, the electrons transfer from the CB of Cs₂CuBr₄ to the CB of CuO in the CCB/CuO heterojunction. Such a directional electron transfer could create an internal electric field (IEF) at the interface pointing from Cs₂CuBr₄ to CuO, facilitating the formation of S-scheme heterojunction between CuO and Cs₂CuBr₄.

ESR spectra is further performed to gain more convincing evidence of the charge transfer direction in the CCB/CuO heterojunction. As shown in Fig. 2g, characteristic DMPO-·O₂⁻ signals are detected for the pristine Cs₂CuBr₄ and CCB/CuO heterojunction, while hardly perceptible DMPO-·O₂⁻ signal is detected for pristine CuO, since its conduction band potential is more positive than that of O₂/·O₂⁻ (−0.33 V vs. NHE) [26]. In addition, the DMPO-·O₂⁻ signal for the CCB/CuO heterojunction is much stronger than that of Cs₂CuBr₄, implying effective electron accumulation in the CCB/CuO heterojunction. This phenomenon provides additional evidence to verify that the photoexcited electrons in the CB of CuO transfer to the VB of Cs₂CuBr₄ via the S-scheme electron transfer route in the CCB/CuO heterojunction, rather than the type II mode [27]. Work function (null) is a critical parameter to investigate the electron delivery direction within semiconductor heterojunctions. As shown in Figs. 2h and i, the work function of CuO (111) and Cs₂CuBr₄ (203) are 5.381 and 4.927 eV, respectively, indicating that CuO has a lower Fermi level than Cs₂CuBr₄ PQDs, which meet the requirement for establishing S-scheme heterojunction.

Photo-irradiated KPFM was performed to confirm the enhanced charge transfer driven by the IEF. Figs. 3a-c present the KPFM images and the corresponding surface potential profiles of CuO under dark and light conditions, which indicate a trivial change of the surface potential (5.4 mV) before and after light irradiation. Such a slight variation implies the rapid charge carrier recombination of pristine CuO. In contrast, the surface potential of CCB/CuO undergoes a remarkable increasement of 24.5 mV under light irradiation, as a result of the photogenerated electrons depletion on the surface (Figs. 3d-f) [28]. Such a significant difference in the surface photovoltage between CuO and CCB/CuO verifies that the photogenerated electrons of CuO transfer to Cs₂CuBr₄ PQDs confined in pores under light illumination.

Based on the above analysis, the S-scheme charge transfer mode of CCB/CuO is illustrated in Fig. 3g. When the p-type CuO and n-type Cs₂CuBr₄ are delicately contacted, a p-n heterojunction of CCB/CuO would be formed, in which electrons spontaneously slide across the interface from n-type Cs₂CuBr₄ to p-type CuO until their Fermi levels are aligned. Consequently, an electron depletion layer will be formed at the Cs₂CuBr₄ side, where Cs₂CuBr₄ is positively charged. On the contrary, an electron accumulation layer will be formed at CuO side, where CuO is negatively charged. The establishment of the space charge region leads to the formation of a strong IEF directing from Cs₂CuBr₄ to CuO. When the CCB/CuO heterojunction is irradiated, the IEF would lead the photo-excited electrons on the CB of CuO to recombine with the photo-excited holes on the VB of Cs₂CuBr₄. As such, the interfacial charge separation and transfer are facilitated, and simultaneously retaining the strongly reducing electrons at the Cs₂CuBr₄ side for CO₂ reduction.

Photocatalytic reduction of CO₂ was conducted under visible light irradiation to assess the photocatalytic performances of the synthesized samples. The yields of reduction products after reaction for 4 h over different catalysts are illustrated in Fig. 4a. For Cs₂CuBr₄ and the CCB/CuO heterojunctions, CO and CH₄ are detected as the main reduction products. No gaseous product is generated by pristine CuO, which could be due to its insufficient reduction potential considering its positive E_CB. However, when the CuO framework is loaded with Cs₂CuBr₄ PQDs, the developed CCB/CuO heterojunctions exhibit significantly enhanced photocatalytic performances for CO₂ reduction. Especially, the products yield for the 0.5CCB/CuO sample is found to be the highest, with the production rates of 60.88 µmol g⁻¹ h⁻¹ for CO and 19.91 µmol g⁻¹ h⁻¹ for CH₄. These values correspond to an electron consumption rate (R_electron = 2R(CO) + 8R(CH₄)) high up to 281.1 µmol g⁻¹ h⁻¹, which is 2.8 times higher than that of pristine Cs₂CuBr₄ PQDs (Fig. 4b). Additionally, the CO₂ photoreduction performance of CCB/CuO is higher than other similar PQDs-based photocatalytic systems (Table S2 in Supporting information), which highlights the merits of the current system.

In addition, blank tests were performed to examine the origin of the gaseous products, as shown in Fig. 4c. The blank experiments without light irradiation or the photocatalyst show negligible production of gases, implying that the reaction is carried out by photocatalysis. Blank experiments were also conducted in Ar system. The insignificant production of gaseous products may be originated from the photoreduction of adsorbed CO₂ on the catalyst surface, indicating that the carbonaceous products in the photocatalytic reaction come from CO₂. The carbon source of produced CO and CH₄ was further traced by using a ¹³C isotopic label. As shown in Fig. 4d, the peaks with the m/z values of 17 and 29 are assigned to the photogenerated ¹⁷CH₄ and ¹³CO, respectively, indicating that the gaseous products are indeed originated from the reduction of CO₂.

In order to assess the stability and reusability of the 0.5CCB/CuO sample, cyclic experiments were performed under the same conditions. The photocatalyst exhibits no significant reduction of photocatalytic efficiency after five cycles (Fig. 4e), indicating its excellent reusability. Moreover, long-term test shows that the 0.5CCB/CuO heterojunction displays good long-time stability, with almost linear production of CH₄ and CO for over 28 h (Fig. 4f). Especially, no significant change of phase structure or morphology is found in the XRD pattern (Fig. S10 in Supporting information) and TEM image (Fig. S11 in Supporting information) of 0.5CCB/CuO before and after reaction, demonstrating excellent stability of the photocatalyst.

The visible-light-induced transient photocurrent density provides a useful indication of the charge separation efficiency of a semiconductor photocatalyst. Fig. S12a (Supporting information) displays the transient photocurrent densities of Cs₂CuBr₄, CuO, and CCB/CuO catalysts over several light on-off cycle modes. Obviously, the photocurrent densities of CCB/CuO heterojunctions are significantly enhanced compared with pristine Cs₂CuBr₄ and CuO, indicating that the construction of CCB/CuO heterojunction could effectively promote the separation of photogenerated electrons and holes. Moreover, electrochemical impedance spectroscopy (EIS, Fig. S12b in Supporting information) results show that the CCB/CuO heterojunctions possess smaller semicircle in contrast with the pristine counterparts, which manifests accelerated interface charge transfer of the heterojunction photocatalyst. The superiority could be attributable to the creation of IEF by the formation of S-scheme heterojunction between Cs₂CuBr₄ and CuO, which is beneficial for the charge separation.

The mesoporous CuO framework can not only facilitate the charge separation in Cs₂CuBr₄, but also promote the CO₂ absorption. As is well known, the abundant pores in a mesoporous material could afford a large surface area and strong adsorption of reactant molecules, which is significant for the subsequent catalytic reaction [29,30]. Hence, the CO₂ uptake capacity of the samples was investigated by CO₂ adsorption/desorption curves. As shown in Fig. S13 (Supporting information), pristine Cs₂CuBr₄ exhibits poor CO₂ adsorption capacity at 273 K, while the CCB/CuO heterojunction shows an CO₂ adsorption capacity 2.35 times higher than that of Cs₂CuBr₄. Moreover, the temperature-programmed desorption of CO₂ (CO₂-TPD) was performed, which is regarded as an effective technique to probe the interaction between the catalyst and adsorbed CO₂ molecules [31,32]. As shown in Fig. S14 (Supporting information), the CCB/CuO heterojunction displays higher CO₂ desorption temperature than pristine Cs₂CuBr₄, accompanied with a larger peak area under the desorption curve, indicating improved CO₂ adsorption capacity and stronger interaction with CO₂ molecules of the CCB/CuO catalyst.

To further track the evolution of reaction intermediates over the CCB/CuO catalyst during CO₂ photoreduction, in-situ DRIFTS is monitored. As shown in Fig. 4g, no signals can be detected in the dark condition (0 min), however, several distinct signal peaks begin to appear under light condition with increasing irradiation time. The appearance of these signals imply the formation of reaction intermediates, mainly including ^•CO₂⁻ radical at 1213 and 1260 cm⁻¹, hydrocarboxylate (HCO₃⁻) at 1391 and 1447 cm⁻¹, bidentate carbonate species (b-CO₃²⁻) at 1318 and 1600 cm⁻¹, and monodentate carbonates (m-CO₃²⁻) at 1516 cm⁻¹ [33,34]. Especially, a crucial intermediate for CO generation, COOH*, is detected at 1558 and 1650 cm⁻¹. Based on the in situ DRIFTS analysis, the CO₂ photoreduction pathway is proposed as the following steps (Fig. 4h): First, CO₂ molecules are adsorbed on the surface of CCB/CuO and activated to form CO₂*, which is the main reaction intermediate. On the other hand, some of CO₂ molecules react with H₂O to form H₂CO₃, which can be easily further decomposed into protons (H⁺) and HCO₃⁻/CO₃²⁻. Then, the produced H⁺ and electrons react with CO₂* to form the key intermediate of COOH*, which is further converted to CO* or CH₃O* by H⁺ and e⁻. Finally, CO* is desorbed from the catalyst surface to generate CO, while CH₃O* is hydrogenated to CH₄ with the photogenerated electrons.

Based on the above analysis, the mechanism for the enhanced CO₂ photoreduction performance of CCB/CuO is extrapolated and depicted in Fig. 4i. When the CCB/CuO photocatalyst is irradiated by visible light, both Cs₂CuBr₄ PQDs and CuO could absorb light and produce photo-generated electrons at their CB and photo-generated holes at their VB. Due to the lower E_F position of CuO than that of Cs₂CuBr₄, the photoexcited electrons of Cs₂CuBr₄ move directly to the CB of CuO. Such electron transfer results in an IEF at the interface of the p-n heterojunction directing from Cs₂CuBr₄ to CuO. Driven by the IEF, the photoexcited electrons on the CB of CuO would recombine with the photo-excited holes on the VB of Cs₂CuBr₄. As such, the photo-excited electrons are accumulated at the CB of Cs₂CuBr₄ while the photo-excited holes are accumulated at the VB of CuO. Therefore, spatial charge separation of CCB/CuO heterojunction is achieved, while maintaining the high reduction potential at the Cs₂CuBr₄ side for efficient CO₂ photoreduction. Besides, as evidenced by the CO₂ adsorption/desorption curves and CO₂-TPD, the use of mesoporous CuO as the framework to confine Cs₂CuBr₄ PQDs can promote the adsorption of CO₂ molecules, which is beneficial to the subsequent photoreduction reaction. Benefiting from all the above advantages, the developed CCB/CuO heterojunction exhibits significantly enhanced photocatalytic performance for CO₂ reduction.

In summary, lead-free Cs₂CuBr₄ PQDs were encapsulated in a mesoporous CuO framework, obtaining an efficient p-n type S-scheme heterojunction of CCB/CuO for photocatalytic CO₂ reduction. The S-scheme charge transfer mechanism of the CCB/CuO heterojunction was confirmed collectively by various characterization techniques and theoretical calculations. The potential of the developed CCB/CuO heterojunction in photocatalytic CO₂ reduction was evaluated under visible light. Interestingly, a remarkable electron consumption rate (R_electron) of 281.1 µmol g⁻¹ h⁻¹ was achieved by the CCB/CuO heterojunction, which was 2.8 times higher than that of pristine Cs₂CuBr₄. The improved photocatalytic activity of the CCB/CuO heterojunction could be attributed to the enhanced charge separation efficiency and promoted CO₂ adsorption capability. Our present research may open new avenues for the development of more effective PQDs-based photocatalytic systems for solar-to-fuel conversions.

Declaration of competing interest

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

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This work was financially supported by Natural Science Foundation of Shanghai (No. 22ZR1460700) and Shanghai Institute of Technology (No. XTCX2022–28).

Supplementary materials

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Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.109700.

References

Less

[1]

M. Lu, M. Zhang, J. Liu, et al., J. Am. Chem. Soc. 144 (2022) 1861–1871.

[2]

S. Li, J. Wang, L. Dong, et al., Chin. Chem. Lett. 34 (2023) 107633.

[3]

M. Zhang, P. Huang, J. Liao, et al., Angew. Chem. Int. Ed. 62 (2023) e202311999.

[4]

Z. Xin, X. Dong, Y. Wang, et al., Adv. Sci. 10 (2023) 2301261.

[5]

Q. Huang, Q. Niu, X. Li, et al., Sci. Adv. 8 (2022) 5598.

[6]

T. Di, J. Zhang, B. Cheng, et al., Sci. China Chem. 61 (2018) 344–350.

[7]

Y. Yang, H. Zhang, Y. Wang, et al., Adv. Mater. 35 (2023) 2304170.

[8]

H. Dong, X. Zhang, Y. Lu, et al., Appl. Catal. B: Environ. 276 (2020) 119173.

[9]

Y. Zhang, W. Han, Y. Yang, et al., Chem. Eng. J. 446 (2022) 137213.

[10]

L. Zhu, F. Hu, B. Sun, et al., Adv. Sustain. Syst. 7 (2023) 2200394.

[11]

C. Han, R. Qi, R. Sun, et al., Appl. Catal. B: Environ. 320 (2023) 121954.

[12]

H. Li, B. Zhu, B. Cheng, et al., J. Mater. Sci. Technol. 161 (2023) 192–200.

[13]

D. Yan, T. Shi, Z. Zang, et al., Small 15 (2019) 1901173.

[14]

P. Zhou, H. Chen, Y. Chao, et al., Nat. Commun. 12 (2021) 4412.

[15]

Y.F. Xu, M.Z. Yang, B.X. Chen, et al., J. Am. Chem. Soc. 139 (2017) 5660–5663.

[16]

Z. Chen, Y. Hu, J. Wang, et al., Chem. Mater. 32 (2020) 1517–1525.

[17]

Z. Dong, Z. Zhang, Y. Jiang, et al., Chem. Eng. J. 433 (2022) 133762.

[18]

Z. Zhang, D. Li, Y. Chu, et al., J. Phys. Chem. Lett. 14 (2023) 5249–5259.

[19]

J. Lu, Y. Wang, H. Li, et al., Chem. Eng. J. 470 (2023) 144294.

[20]

X. Jiang, X. Hu, M. Tarek, et al., J. CO2 Util. 40 (2020) 101222.

[21]

C. Wang, D. Higgins, F. Wang, et al., Nano Energy 9 (2014) 334–344.

[22]

A. Mahmood, F. Tezcan, G. Karda ¸ s, Int. J. Hydro. Energy 42 (2017) 23268–23275.

[23]

J. Sun, L. Sun, N. Han, et al., Sens. Actuat. B: Chem. 285 (2019) 68–75.

[24]

Z. Wen, W. Wu, Z. Liu, et al., Phys. Chem. Chem. Phys. 15 (2013) 6773–6778.

[25]

Y. Zhang, L. Shi, H. Yuan, et al., Chem. Eng. J. 430 (2022) 132820.

[26]

A. Idris, S. Zheng, L. Wu, et al., Chem. Eng. J. 446 (2022) 137197.

[27]

M. Xu, M. Lu, G. Qin, et al., Angew. Chem. Int. Ed. 61 (2022) 202210700.

[28]

Q. Sun, J. Xu, F. Tao, et al., Angew. Chem. Int. Ed. 61 (2022) 202200872.

[29]

J. Liu, Z. Gao, H. Han, et al., Chem. Eng. J. 185-186 (2012) 151–159.

[30]

Z. Zhang, D. Li, Z. Dong, et al., Sol. RRL 7 (2023) 2300038.

[31]

Z. Cui, P. Wang, Y. Wu, et al., Appl. Catal. B: Environ. 310 (2022) 121375.

[32]

H. Li, B. Zhu, S. Cao, et al., Chem. Commun. 56 (2020) 5641–5644.

[33]

X.D. Li, Y.F. Sun, J.Q. Xu, et al., Nat. Energy 4 (2019) 690–699.

[34]

M. Wang, M. Shen, X. Jin, et al., ACS Catal. 9 (2019) 4573–4581.

Appendix

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Year 2024 volume 35 Issue 11

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doi: 10.1016/j.cclet.2024.109700

Receive Date：2023-11-09
Online Date：2025-11-26
Published：2024-11-15

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Received：2023-11-09
Revised：2023-11-30
Accepted：2024-01-03

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^a School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, China

^b Institute for Agro-food Standards and Testing Technology, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China

^c School of Chemistry and Chemical Engineering, Hainan University, Haikou 570228, China

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表12种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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Fig. 1 (a) TEM and (b) HRTEM images of Cs₂CuBr₄ PQDs. (c) TEM and (d) HRTEM images of mesoporous CuO framework. (e) TEM and (f) HRTEM images of the CCB/CuO heterojunction. (g) EDX element mapping analysis of the CCB/CuO heterojunction.

Fig. 2 XPS spectra of CuO, Cs₂CuBr₄, and CCB/CuO heterojunction: (a) Full survey, (b) Cs 3d, (c) Br 3d, (d) Cu 2p, (e) Cu 2p, and (f) O 1s spectra in CuO, Cs₂CuBr₄, and CCB/CuO heterojunction. (g) ESR spectra of CuO, Cs₂CuBr₄, and CCB/CuO heterojunction; Calculated work functions of (h) CuO and (i) Cs₂CuBr₄.

Fig. 3 Surface potential distribution changes of (a-c) CuO and (d-f) CCB/CuO heterojunction under dark and light conditions (ΔCPD = CPD_light - CPD_dark). (g) Scheme illustrating the charge transfer mechanism of the CCB/CuO p-n heterojunction.

Fig. 4 Photocatalytic CO₂ reduction tests: (a) Yields of CO and CH₄ from photocatalytic reaction over CuO, Cs₂CuBr₄, and CCB/CuO heterojunctions with different loading amounts of Cs₂CuBr₄; (b) Comparison of R_electron for photocatalytic CO₂ reduction over CuO, Cs₂CuBr₄, and CCB/CuO heterojunctions; (c) Photocatalytic CO₂ reduction tests under different conditions; (d) GC–MS spectra of the photocatalytic product over CCB/CuO using ¹³CO₂ as carbon source; (e) Recycling tests of the CCB/CuO heterojunction; (f) Long-term photocatalytic tests of CCB/CuO; (g) In-situ DRIFTS of CO₂ photoreduction over CCB/CuO with increasing irradiation time; (h) Proposed reaction pathway of CO₂ photoreduction over CCB/CuO; (i) Schematic illustration of the mechanism of photocatalytic CO₂ reduction over the CCB/CuO heterojunction.

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