Elsevier

Chemical Engineering Journal

Volume 358, 15 February 2019, Pages 1287-1295
Chemical Engineering Journal

Perovskite-type CsPbBr3 quantum dots/UiO-66(NH2) nanojunction as efficient visible-light-driven photocatalyst for CO2 reduction

https://doi.org/10.1016/j.cej.2018.10.120Get rights and content

Highlights

  • The CsPbBr3 QDs/UiO-66(NH2) nanocomposites have first been successfully fabricated.

  • The resultant nanocomposites exhibit excellent photoactivity on CO2 reduction.

  • The experimental system exhibits a high selectivity for CO generation.

  • The enhanced photocatalytic performance of the nanocomposites was discussed.

  • The reduction mechanism of the resultant nanocomposites was analyzed simply.

Abstract

Base-on the excellent optoelectronic properties, perovskite CsPbBr3 quantum dots (QDs) have been used on perovskite solar cells and LED devices, but little research has been focused on photochemical CO2 reduction due to their poor moisture stability. Coincidentally, metal-organic frameworks (MOFs) materials have received tremendous attention for sustainable clean energy and environmental remediation. However, the design of excellent performed MOFs is still indispensable. Therefore, the CsPbBr3 QDs/UiO-66(NH2) nanocomposites that combine the advantages of CsPbBr3 QDs and UiO-66(NH2) have been successfully designed and fabricated for the first time. Then we employ the nanocomposites as photocatalysts to convert CO2 to chemical fuels in nonaqueous media. The resultant nanocomposites exhibit significantly improved photocatalytic activity for CO2 reduction. When CsPbBr3 QDs content is 15 wt%, the amount of CO can reach 98.57 μmol·g−1. The remarkable photocatalytic performance could be ascribed to the improved electron extraction and transfer between UiO-66(NH2) and CsPbBr3 QDs, large accessible specific surface area and enhanced visible light absorption capacity. Moreover, the nanojunction shows excellent reusability for photocatalytic CO2 reduction. This work might supply new pathway to utilize halide perovskite QDs/MOF nanocomposite in energy conversion and environmental remediation.

Introduction

The superfluous consumption of fossil resources (coal, oil, natural gas), and excessive emission of carbon dioxide (CO2) have led to the imperious demand for sustainable clean energy and the greenhouse effect in current society [1], [2]. In addition to natural photosynthesis and underground mineralization, other efficient methods for CO2 valorization and fixation are significantly needed [3], [4]. Since the innovative discovery of Inoue group in the 1970s, artificial photocatalytic CO2 reduction provides an efficient pathway to ameliorate the environmental problem caused by the emission of CO2 [5], [6], [7]. Moreover, converting CO2 via photosynthesis can also partly fulfils the high value-added chemical fuels (e.g., CO, CH4, CH3OH, etc.). It goes without saying that the development of photocatalytic CO2 conversion technology is significant to solve environmental and energy issues in the future.

To date, amounts of semiconductor materials (e.g., TiO2, g-C3N4, CdS, SrTiO3-δ, etc.) have been developed for photocatalytic CO2 reduction [8], [9], [10], [11]. However, the search for an optimal candidate has not ceased until now. Recently, the organic-inorganic halide perovskite materials have caused great interest in optoelectronic applications, due to their wide absorption ranges, high extinction coefficients, and long electron-hole diffusion lengths [12], [13]. Within a few years, the photoelectric conversion efficiency has run up to 22.1% for perovskite solar cells [14]. Inspired by the achievements in solar cells, halide perovskite materials are strong candidates for performing efficient photosynthesis. Recently, Nam group first reported that methylammonium lead iodide powders could drive the photocatalytic HI splitting to H2 via precisely controlling the ion concentrations of I and H+ [15]. However, the inorganic halide perovskite CsPbBr3 quantum dots (QDs), as excellent optoelectronic materials for perovskite solar cells and light-emitting diode devices, have little been reported for photochemical CO2 conversion to chemicals due to their insufficient stability in the presence of moisture or polar solvent.

Recently, metal-organic frameworks (MOFs), have also received extensive attention due to their unique physicochemical properties, such as large specific surface areas, structural adaptivity and flexibility. Hence, they have been applied in adsorption, separation, nonlinear optical properties and catalysis and so forth [16], [17], [18], [19], [20]. They can act as catalysts themselves, using open metal sites, unsaturated metal centers and catalytically active organic linkers. In addition, Some MOFs can behave as semiconductors and act as a charge-carrier transport system by the photoexcitation of organic linkers or metal clusters [21], [22]. What’s more, extra active sites, such as photoactive metal species and semiconductor nanoparticles, can be also introduced into the host framework. In comparison with traditional semiconductor photocatalysts, the superiority of MOFs is that the narrow micropore distribution may lead to the formation of monodisperse photoactive anchored on MOFs, which is of high interest for catalytic activity and selectivity. More importantly, the host porous materials for photocatalytic reactions can also provide extra pathways for the migration of photogenerated electrons, and thus promote charge carrier separation, increasing the photocatalytic efficiency. In fact, the inorganic semiconductor/MOF nanojunction-type composites (e.g., CdS/MIL-100(Fe), Cd0.5Zn0.5S/ZIF-8) have been fabricated and show great advantages [23], [24]. As far as we know, the CsPbBr3 QD/UiO-66(NH2) heterojunction-type nanocomposites for photocatalytic CO2 reduction have not been investigated.

Hence, the typical halide perovskite CsPbBr3 QDs, UiO-66(NH2), and CsPbBr3 QDs/UiO-66(NH2) nanocomposites were designed and synthesized for photocatalytic CO2 reduction in the solution of slight H2O/ethyl acetate. As far as we know, this is the first report on artificial photocatalytic CO2 reduction base-on CsPbBr3 QDs/UiO-66(NH2) nanocomposite by coupling CsPbBr3 QDs with UiO-66(NH2). Furthermore, the reusability of CsPbBr3 QDs/UiO-66(NH2) nanocomposite for CO2 reduction is researched, the possible mechanism for the excellent photocatalytic performance of CsPbBr3 QD/UiO-66(NH2) nanocomposite is discussed simply. We hope that the work could inspire growing interest on the preparation of other high-performance CsPbBr3 QD/MOFs nanocomposite by coupling the advantage of CsPbBr3 QD and MOFs.

Section snippets

Raw materials

Lead(II) bromide (PbBr2, 99%, Aladdin-reagent), cesium carbonate (Cs2CO3, 99%, Aladdin-reagent), oleylamine (80–90%, Aladdin-reagent), oleic acid (97%, Aladdin-reagent), 1-octadecene (>95%, Aladdin-reagent), Zirconium chloride (ZrCl4, 98%, Aladdin-reagent) and 2-amino-1, 4-benzenedicarboxylic acid (>98%, TCI-reagent) were used as received without any further purification.

Preparation of CsPbBr3 quantum dots

The CsPbBr3 quantum dots (QDs) were fabricated by hot-injecting Cs-oleate solution into PbBr2 solution at 150 °C.

Structural characterization

Initially, the crystal structures of CsPbBr3 QDs, UiO-66(NH2) and CsPbBr3 QDs/UiO-66(NH2) nanocomposites were researched by powder X-ray diffraction (XRD). As depicted in Figs. 1 and S2, the sharp peaks of monodisperse CsPbBr3 QDs demonstrate that the CsPbBr3 QDs are highly crystallized and display a monoclinic perovskite crystal structure. The peaks at 2θ = 14.9, 21.1, 26.3, 30.4, 37.4 and 43.4° are ascribed to {1 0 0}, {1 1 0}, {1 1 1}, {2 0 0}, {2 1 1} and {2 0 2} crystal planes of CsPbBr3

Conclusions

In summary, high active CsPbBr3 QDs/UiO-66(NH2) nanocomposites have been successfully synthesized. The resultant nanohybrids exhibited significantly enhanced photocatalytic activity for CO2 reduction under visible light compared with pristine CsPbBr3 QDs and UiO-66(NH2). The optimum loading content of CsPbBr3 QDs is determined to be 15 wt%, and corresponding CO product rate is 98.57 mol·g−1. The remarkable enhanced photocatalytic activity can be ascribed to the fast charge separation and

Acknowledgements

This work was financially supported by the Key Project of Chinese National Programs for Research and Development (2016YFC0203800), the National Natural Science Foundation of China (51578288), Industry-Academia Cooperation Innovation Fund Projects of Jiangsu Province (BY2016004-09), Jiangsu Province Scientific and Technological Achievements into a Special Fund Project (BA2015062, BA2016055 and BA2017095), Top-notch Academic Programs Project of Jiangsu Higher Education Institutions, A Project by

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