Two-dimensional (2D) Ruddlesden-Popper perovskites have shown great potential for application in perovskite solar cells due to their appealing environmental stability. However, 2D perovskites generally show poor photovoltaic performance. Here, a new type of 2D perovskite using 2-thiophenemethylammonium (ThMA) as a spacer cation was developed and high photovoltaic performance as well as enhanced stability in comparison with its 3D counterpart was demonstrated. The use of the 2D perovskite (ThMA)(MA) PbI ( n = 3) in deposited highly oriented thin films from N, N-dimethylformamide using a methylammonium chloride (MACl) assisted film-forming technique dramatically improves the efficiency of 2D perovskite photovoltaic devices from 1.74% to over 15%, which is the highest efficiency for 2D perovskite ( n < 6) solar cells so far. The enhanced performance of the 2D perovskite devices using MACl as additive is ascribed to the growth of a dense web of nanorod-like film with near-single-crystalline quality, in which the crystallographic planes of the 2D MA PbI slabs preferentially aligned perpendicular to the substrate, thus facilitating efficient charge transport. This work provides a new insight into exploration of the formation mechanism of 2D perovskites with increased crystallinity and crystal orientation suitable for high-performance solar cells.

Enhancing the intrinsic activity and space time yield of Cu based heterogeneous methanol synthesis catalysts through CO2 hydrogenation is one of the major topics in CO2 conversion into value-added liquid fuels and chemicals. Here we report inverse ZrO2/Cu catalysts with a tunable Zr/Cu ratio have been prepared via an oxalate co-precipitation method, showing excellent performance for CO2 hydrogenation to methanol. Under optimal condition, the catalyst composed by 10% of ZrO2 supported over 90% of Cu exhibits the highest mass-specific methanol formation rate of 524 gMeOHkgcat−1h−1 at 220 °C, 3.3 times higher than the activity of traditional Cu/ZrO2 catalysts (159 gMeOHkgcat−1h−1). In situ XRD-PDF, XAFS and AP-XPS structural studies reveal that the inverse ZrO2/Cu catalysts are composed of islands of partially reduced 1–2 nm amorphous ZrO2 supported over metallic Cu particles. The ZrO2 islands are highly active for the CO2 activation. Meanwhile, an intermediate of formate adsorbed on the Cu at 1350 cm−1 is discovered by the in situ DRIFTS. This formate intermediate exhibits fast hydrogenation conversion to methoxy. The activation of CO2 and hydrogenation of all the surface oxygenate intermediates are significantly accelerated over the inverse ZrO2/Cu configuration, accounting for the excellent methanol formation activity observed.

Single-atom catalysts (SACs) have demonstrated superior catalytic performance in numerous heterogeneous reactions. However, producing thermally stable SACs, especially in a simple and scalable way, remains a formidable challenge. Here, we report the synthesis of Ru SACs from commercial RuO 2 powders by physical mixing of sub-micron RuO 2 aggregates with a MgAl 1.2 Fe 0.8 O 4 spinel. Atomically dispersed Ru is confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption spectroscopy. Detailed studies reveal that the dispersion process does not arise from a gas atom trapping mechanism, but rather from anti-Ostwald ripening promoted by a strong covalent metalsupport interaction. This synthetic strategy is simple and amenable to the large-scale manufacture of thermally stable SACs for industrial applications.

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Highly efficient and stable 2D/3D hybrid perovskite solar cells using 2‐thiophenemethylammonium (ThMA) as the spacer cation are successfully demonstrated. It is found that the incorporation of ThMA spacer cation into 3D perovskite, which forms a 2D/3D hybrid structure, can effectively induce the crystalline growth and orientation, passivate the trap states, and hinder the ion motion, resulting in improved carrier lifetime and reduced recombination losses. The optimized device exhibits a power conversion efficiency (PCE) of 21.49%, combined with a high VOC of 1.16 V and a notable fill factor (FF) of 81%. More importantly, an encapsulated 2D/3D hybrid perovskite device sustains ≈99% of its initial PCE after 1680 h in the ambient atmosphere, whereas the control 3D perovskite device drops to ≈80% of the original performance. Importantly, the device stability under continuous light soaking (100 mW cm−2) is enhanced significantly for 2D/3D perovskite device in comparison with that of the control device. These results reveal excellent photovoltaic properties and intrinsic stabilities of the 2D/3D hybrid perovskites using ThMA as the spacer cation.

2D perovskites, such as 2D Ruddlesden-Popper (RP) and 2D Dion-Jacobson (DJ) perovskites, have attracted much attention owning to their better structure and environmental stability compared with their 3D analogs. [12][13][14][15][16] However, the efficiencies of 2D PSCs are still much lower than that of state-of-theart 3D PSCs. One strategy to combine the advantages of the high stability of 2D perovskite and high efficiency of 3D perovskite is developing the 2D/3D hybrid perovskites by embedding a highly stable 2D perovskite into a 3D perovskite matrix. So far, the 2D/3D hybrid perovskites has shown great promise in high performance PSCs, which may promote the commercial application of this technology. [17][18][19][20][21] In 2017, Snaith et al. reported that the introducing of n-butylammonium (BA) cations into a mixed-cation 3D perovskite using a one-step deposition method achieved an average stabilized PCE of ≈17.5% with a 1.61-eV-bandgap perovskite. [19] In 2019, 2-thiophenemethylammonium (ThMA) was used as organic spacer to construct the 2D/3D perovskite. It was found that the ThMAI could assist the perovskite crystal growth and orientation, achieving a high efficiency of 21.49% with significantly improved film and device stability. [20] Huang et al. reported that incorporating 0.83 molar percent phenethylammonium chloride (PEACl) into perovskite inks enables highly crystalline formamidine (FA)-alloyed perovskites with extraordinary optoelectronic properties and achieving a high efficiency of 22.0%. [22] Due to the abundant and inevitable defects generated during film fabrication, the quality of the solution-processed perovskite films play a very important role for their photovoltaic properties and device stability. Although some excellent works have been done to improve the PCE and stability by developing different organic spacers, [19][20][21][22][23][24] the crystal nucleation and growth mechanism of 2D/3D perovskite is still not very clear and is largely unexplored. Moreover, the development of efficient crystal growth regulation strategies and understanding the crystallization kinetics in 2D/3D perovskite films are the path to high performance PSCs for future commercial application.In this work, we demonstrate the fabrication of high-quality 2D/3D hybrid perovskite by crystal growth regulation with 2D (NpMA) 2 PbI 4 perovskite. A 2D (NpMA) 2 PbI 4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) were introduced to the PbI 2 precursor respectively to modulate the crystal growth in 2D/3D perovskite film using a two-step deposition method. The cross-section scanning electron microscopy Reducing the electronic defects in perovskite films has become a substantial challenge to further boost the photovoltaic performance of perovskite solar cells. Here, 2D (NpMA) 2 PbI 4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) are separately introduced into the PbI 2 precursor solutions to regulate the crystal growth in a 2D/3D perovskite film using a two-step deposition method. The (NpMA) 2 PbI 4 modul...

Developing high-performance electrocatalysts for the ethanol oxidation reaction (EOR) is critical to the commercialization of direct ethanol fuel cells. However, current EOR catalysts suffer from high cost, low activity, and poor durability. Here we report the preparation of PdBi-Bi(OH) 3 composite nanochains with outstanding EOR activity and durability. The incorporation of Bi can tune the electronic structure and downshift the d-band center of Pd while the surface decoration of Bi(OH) 3 can facilitate the oxidative removal of CO and other carbonaceous intermediates. As a result, the nanochains manifest an exceptional mass activity (5.30 A mg Pd −1 , 4.6-fold higher than that of commercial Pd/C) and outstanding durability (with a retained current density of ∼1.00 A mg Pd −1 after operating for 20 000 s). More importantly, the nanochain catalyst can be reactivated, and negligible activity loss has been observed after operating for 200 000 s with periodic reactivation, making it one of the best EOR catalysts.

The dominated hole transport material (HTM) used in state-ofthe-art perovskite solar cells (PSCs) is Spiro-OMeTAD, which needs to be doped to improve its conductivity and mobility. The inevitable instability induced by deliquescent dopants and the necessary oxidation process in air hinders the commercialization of this technology. Here, an alloy strategy using two conjugated polymers with highly similar structures but different crystallinities for dopant-free HTM and high-performance PSCs has been demonstrated. We found that the polymeric packing and crystallinity of a polymer alloy could be regulated finely by blending the polymer PM6 and our developed polymer PMSe, which exhibits a shorter π−π stacking distance due to the improved planarity of the polymer backbone with strong CO•••Se noncovalent interactions. The structure−property relationship of the polymer alloy is investigated by theoretical and experimental analyses. The optimized PSCs using the polymer alloy HTM without any ionic dopants feature an excellent power conversion efficiency of 24.53% and a high open circuit voltage (V OC ) of 1.19 V with much improved stability. This efficiency is much higher than that of the control device using doped Spiro-OMeTAD HTM (PCE = 22.54%). Our work provides a very effective strategy to design and construct dopant-free hole transport materials for highly efficient perovskite solar cells and other applications.