The large amount of 4-nitrophenol (4-NP) wastewater produced by the chemical industry has received increased concern over the growing risk of environmental pollution. The ability to catalyze the reduction of highly concentrated 4-NP wastewater is highly desirable for the practical treatment of industrial wastewater, yet it remains a significant challenge. Herein, we report Pd nanoparticle-decorated 3D-printed hierarchically porous TiO2 scaffolds (Pd/TiO2 scaffolds) for the efficient reduction of highly concentrated 4-NP wastewater (2 g·L–1, ∼14.38 mM). The millimeter-sized interconnected channels in the scaffolds are conducive to rapid mass and ion transportation; meanwhile, the abundant micrometer- and nanometer-sized pores on the surface of the scaffolds offer adequate anchoring sites for Pd nanoparticles. The turnover frequency of the hierarchically porous Pd/TiO2 scaffold (16 layers) is up to 2.69 min–1, which is 1063 times higher than that of the Pd/TiO2-bulk material with the same size (0.00253 min–1). Importantly, no obvious deactivation of the catalytic activity is observed even after 20 cycles of catalytic reduction of 4-NP, showing excellent catalytic stability and reusability. Our strategy of loading the nanostructured catalyst on 3D-printable hierarchically porous structures put forward a flexible and versatile approach for boosting the catalytic performance of the catalysts, including catalytic activity, stability, and reusability, which can help promote their practical application in industry.
Hexagonal NaYF4:Yb3+,Tm3+@SiO2 upconversion nanoprism-mixed SiO2 passivation layers are introduced into hole-transport-layer free carbon-based perovskite solar cells to improve the power conversion efficiency. This layer on the top of the TiO2 scaffold has multiple functions: (i) upconversion units could transform near-infrared photons to visible region and thus extend the absorption range; (ii) nanoprisms act as light-scattering centers to prolong light-transmission distance and enhance light harvesting; (iii) SiO2 capping layer could suppress charge recombination at the interface of perovskite/TiO2 through passivation effect. The champion efficiency of our carbon-based device with an optimal amount of upconversion nanoprisms is 14.47%, which is 16.1% higher than that of the reference (12.46%). In addition, our unencapsulated solar cells exhibit good stability against moisture and thermal stressing in ambient condition. We also demonstrated another application of our device as a self-powered photodetector with NIR-sensitive features.
Metal amine halide perovskite solar cells (PSCs), as a promising next generation photovoltaic device , have undergone an unexpected swift growth in the past decade. However, the practical application of PSCs is still facing the challenge of improving efficiency and stability, and the interfacial defects at mesoporous scaffolds is the crucial bottleneck need to be solved. Here, to heal defects and enhance performance, we implement four advantageous designs, i.e. low-temperature processing, rare-earth ion doping, brookite TiO 2 scaffolds, and SnO 2 blocking layer. As a result, the binder-free and sinter-free processing generates a single crystalline phase , evenly distributed, mesoporous Sc 3+ doped brookite TiO 2 scaffold, which induces a uniform coverage, void-less and high-quality perovskite layer. The favorable energy level alignment, diminished defects and carrier recombination improve the performance of the device. Consequently, the PSC based on Sc 3+ tailored brookite TiO 2 scaffold achieves a power conversion efficiency of 21.75% with hysteresis-free and excellent UV stability.
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