In recent decades, the environmental protection and long-term sustainability have become the focus of attention due to the increasing pollution generated by the intense industrialization. To overcome these issues, environmental catalysis has increasingly been used to solve the negative impact of pollutants emission on the global environment and human health. Supported platinum-metal-group (PGM) materials are commonly utilized as the state-of-the-art catalysts to eliminate gaseous pollutants but large quantities of PGMs are required. By comparison, single-atom site catalysts (SACs) have attracted much attention in catalysis owing to their 100% atom efficiency and unique catalytic performances towards various reactions. Over the past decade, we have witnessed burgeoning interests of SACs in heterogeneous catalysis. However, to the best of our knowledge, the systematic summary and analysis of SACs in catalytic elimination of environmental pollutants has not yet been reported. In this paper, we summarize and discuss the environmental catalysis applications of SACs. Particular focus was paid to automotive and stationary emission control, including model reaction (CO oxidation, NO reduction and hydrocarbon oxidation), overall reaction (three-way catalytic and diesel oxidation reaction), elimination of volatile organic compounds (formaldehyde, benzene, and toluene), and removal/decomposition of other pollutants (Hg 0 and SO 3). Perspectives related to further challenges, directions and design strategies of single-atom site catalysts in environmental catalysis were also provided.

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In this paper, the hydrothermal stability and catalytic activity of Pd@Ce0.5Zr0.5O2/Al2O3 catalyst with a core–shell structure were investigated for automobile three-way reactions and compared with those of Pd/Al2O3, Pd@CeO2/Al2O3, and Pd@ZrO2/Al2O3 catalysts. TEM, HRTEM, and EDS mapping analyses showed that the core–shell structure of Pd@Ce0.5Zr0.5O2 nanoparticles was intact after the hydrothermal treatment at 1050 °C for 5 h. Meanwhile, CO–DRIFT results suggested that the interface of Pd core and Ce0.5Zr0.5O2 shell acted as the active sites in the reaction of three-way catalysts. Additionally, XPS, FT-IR, and CO–DRIFT analyses demonstrated that a large amount of OH groups were present on the surface of Pd@Ce0.5Zr0.5O2/Al2O3 catalyst, which could accelerate the decomposition of carbonate species and reduce the activation energy of the catalytic reaction. This was an important reason for the Pd@Ce0.5Zr0.5O2/Al2O3 catalyst to keep the high catalytic activity after aging at high temperature.

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Due to the excellent photoelectric properties, lead halide perovskites have shown great application potential in photoelectric devices, especially in photovoltaic solar cells. [1] At present, the efficiency of perovskite solar cells (PSCs) has reached the level of classic crystalline silicon solar cells. Therefore, the research focus of PSCs is gradually shifting toward improving device stability and reducing production costs. [2,3] Among them, hole transport layer (HTL)-free carbon electrode-based PSCs (C-PSCs), which avoid the use of expensive hole transport materials and noble metal electrodes, are regarded as low-cost devices with a simple structure. [4][5][6][7][8][9][10][11][12][13][14] It is well known that the hydrophilic characteristic of the inorganic salt doped in the classical organic hole transport material (such as Spiro-OMeTAD) and the chemical reaction of the halogen with the metal electrode reduce the long-term stability of the corresponding device. [15,16] Therefore, C-PSCs can not only improve the stability of the device but also reduce the production cost, showing a superior commercial application prospect. [17][18][19][20] In terms of stability, methylamine (MA) is also a key factor limiting device stability due to its volatile characteristics. [21,22] Therefore, MA-free PSCs have received extensive attention in recent years. [14,[23][24][25][26][27][28] Currently, MA-free perovskites mainly include FAPbI 3 , CsPbI 3 , and Cs x FA 1-x PbI 3 with mixed cations. Because the ionic radius of FA þ (2.53 Å) is too large and Cs þ (1.88 Å) is too small, the lead iodine octahedral [PbI 6 ] can easily distort. [1] This causes the black phase of FAPbI 3 and CsPbI 3 to be thermodynamically unstable at room temperature, which limits their practical applications. The stability of the Cs x FA 1-x PbI 3 perovskite with mixed cations of FA þ and Cs þ has been significantly improved due to the complementarity of the tolerance factor, and it is also the most studied lightharvesting material in MA-free PSCs. [23,[29][30][31] According to literature reports, Cs x FA 1-x PbI 3 has good thermodynamic stability with a high Cs content between 40% and 60%. [32,33] This is mainly due to the optimized tolerance factor and entropy improvement for perovskite with these compositions. In addition, Cs x FA 1-x PbI 3 with high Cs content also has good application potential in tandem PSCs. [34] However, due to the large lattice mismatch and different phase-transition temperatures between FAPbI 3 and CsPbI 3 , it is difficult to prepare Cs x FA 1-x PbI 3 perovskites with high Cs content (>30%). [33][34][35]

Perovskite film with high crystal quality is fundamental to achieving high‐performance solar cells. A fast nucleation process is crucial to improving the crystallization quality. Here, we propose a self‐driven prenucleation strategy to achieve fast nucleation. This is realized through rational solvent design. The key characteristics of different solvents are systematically evaluated. Among them, formamide, with ultra‐high dielectric constant, low Gutman donor number, and a high boiling point, is selected as the co‐solvent. These unique characteristics render formamide a double‐face solvent that is a good solvent for formamidinium iodide (FAI) and CsI while a poor solvent for PbI2. As a result, formamide induces the self‐driven prenucleation of PbI2‐DMSO seeding crystals and accelerates the nucleation, improving the crystalline quality of perovskite film. The efficiency of the hole transport layer‐free carbon‐based perovskite solar cells is boosted beyond 19 % for the first time.

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