Ruddlesden-Popper Research Articles

Enhancing photostability of 2D Ruddlesden–Popper perovskite via molecular acceptor passivation of metallic lead defects

Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites hold great potential for novel optoelectronic applications. However, their unconventional optoelectronic properties are often compromised by a vulnerability to light irradiation, which leads to the formation of metallic Pb (Pb0) defects. This study investigates the passivation mechanism of these Pb0 defects in phenylethylammonium lead iodide (PEA2PbI4) using a strong molecular acceptor, 2,2′-(perfluoronaphthalene-2, 6-diylidene) dimalononitrile (F6-TCNNQ). In situ x-ray photoelectron spectroscopy results demonstrate that F6-TCNNQ effectively removes the light-induced Pb0 states, leading to the recovery of photoluminescence intensity in photodegraded PEA2PbI4 samples and significantly improving the photostability of pristine PEA2PbI4. F6-TCNNQ protects the terrace edge of PEA2PbI4, which is the site of initial degradation, as evidenced by atomic force microscopy and scanning electron microscopy analyses. In situ ultraviolet photoelectron spectroscopy measurements confirm substantial electron transfer from Pb0 to F6-TCNNQ, causing the oxidation of Pb0 to Pb2+. Furthermore, the staggered energy level alignment prevents electron transfer from the valence band maximum of PEA2PbI4 to the lowest unoccupied molecular orbital of F6-TCNNQ, thereby preserving the pristine electronic structure of PEA2PbI4. These findings provide new insights into defect passivation in 2D RP perovskites and offer a design strategy for highly stable optoelectronic devices.

Synthesis of new oxygen deficient triple layered perovskite oxides LaSr3Fe3-xCrxO10-δ (x = 0.0, 0.2, and 0.5): Structural, optical, magnetic and photocatalytic properties

In the present study, new oxygen deficient triple layered Ruddlesden-Popper (RP) phases LaSr3Fe3-xCrxO10-δ (x = 0.0, 0.2, and 0.5) have been prepared via sol-gel procedure. The prepared n = 3 RP phases were characterized with various characterization techniques in order to visualize the effect of Cr3+ doping on structural, optical, magnetic and photocatalytic properties. Rietveld structural refinements showed that all the phases crystallized in the I4/mmm space group with tetragonal symmetry. Dominant anti-ferromagnetic (AFM) interactions (Fe3+―O―Fe3+ and Fe4+―O―Fe4+) were noticed in each of these oxygen deficient triple layered phases with presence of weak ferromagnetic (FM) interactions. The decline in the values of Neel temperature (TN) with Cr doping has been interpreted on the basis of increase in FM Fe3+―O―Cr3+ interactions. The energy band gap values (Eg) of all the synthesised oxygen deficient phases vary from 1.63 to 1.73 eV, which makes them excellent photocatalysts for dye decontamination. Furthermore, the photocatalytic performance of the prepared phases was assessed by utilizing rhodamine B (RhB) dye as model dye pollutant. It was found that LaSr3Fe2.5Cr0.5O9.17 photocatalyst showed excellent results in the removal of RhB dye. As a result, we were further encouraged to extend the degradation to some other organic dyes such as methylene blue (MB), methyl orange (MO) and their mixture (RhB + MB + MO).

Stable two-dimensional tin-based perovskites for warm-white light emitters

Two-dimensional (2D) Sn-based organic-inorganic hybrid perovskites are useful materials for white light emitters due to their super high fluorescence efficiency and higher stability when compared to their three-dimensional (3D) counterparts. Herein, 2D Ruddlesden-Popper (RP) perovskites (BA)2Sn(Br1-x Ix)4 (BA = n-butylammonium, x: 0–1) were prepared and regulated using halogen doping. As iodine content increased, the band gap of (BA)2Sn(Br1-xIx)4 was finely regulated from 2.35 eV to 2.0 eV, thereby tuning the photoluminescence from yellow to red with relatively high PLQY exceeding 40 %. The use of small amounts of Pb2+ to stabilize Sn2+ through the addition of PbO in the precursor solution resulted in high air- and photo stable (BA)2Pb0.1Sn0.9(Br–I)4 phosphors with bright yellow to red light. The mixture with (BA)2PbBr4 (blue light phosphor) followed by excitement by UV LED chips (285 nm) resulted in cold and warm white Sn–Br–I perovskite LEDs. The CIE coordinates and correlated color temperature (CCT) indicated Br0.4I0.6 LED as an ideal warm-white emitter with suitable CIE (0.352, 0.330) and CCT (4376.3 K). The prepared white LEDs showed high photo and air stability without significant luminescence decay (<5 % relative) under continuous UV light excitation over 200 min and exposure to air for 3 months.

Nucleation and Crystallization in 2D Ruddlesden-Popper Perovskites using Formamidinium-based Organic Semiconductor Spacers for Efficient Solar Cells.

The conjugated organic semiconductor spacers have drawn wide attention in two-dimensional (2D) perovskites and formamidinium (FA) has been widely used as A-site cation in high-performance 3D perovskite solar cells (PSCs). However, the FA-based semiconductor spacers have rarely been investigated in 2D Ruddlesden-Popper (RP) perovskites. Here, we developed two FA-based spacers containing thieno[3,2-b]thiophene (TT) and 2,2'-bithiophene (BT) units, namely TTFA and BTFA, respectively, for 2D RP PSCs. The nucleation and crystallization kinetics of TTFA-Pb and BTFA-Pb from sol-gel to film were investigated using in situ optical microscopy and in situ grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. It is found that the TTFA spacer could reduce the energy barrier of nucleation and induces crystal vertical orientation of 2D perovskite by forming larger clusters in precursor solution, resulting in much improved film quality. Benefiting from the enlarged crystal grains, reduced exciton binding energy, and decreased electron-phonon coupling coefficient, the photovoltaic device based on (TTFA)2 MAn-1 Pbn I3n+1 (n=5) achieved a champion efficiency of 19.41 %, which is a record for 2D RP PSCs with FA-based spacers. Our work provides deep understanding of the nucleation and crystallization process of 2D RP perovskite films and highlights the great potential of FA-based semiconductor spacers in highly efficient 2D PSCs.

Nucleation and Crystallization in 2D Ruddlesden‐Popper Perovskites using Formamidinium‐based Organic Semiconductor Spacers for Efficient Solar Cells

AbstractThe conjugated organic semiconductor spacers have drawn wide attention in two‐dimensional (2D) perovskites and formamidinium (FA) has been widely used as A‐site cation in high‐performance 3D perovskite solar cells (PSCs). However, the FA‐based semiconductor spacers have rarely been investigated in 2D Ruddlesden‐Popper (RP) perovskites. Here, we developed two FA‐based spacers containing thieno[3,2‐b]thiophene (TT) and 2,2′‐bithiophene (BT) units, namely TTFA and BTFA, respectively, for 2D RP PSCs. The nucleation and crystallization kinetics of TTFA‐Pb and BTFA‐Pb from sol‐gel to film were investigated using in situ optical microscopy and in situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements. It is found that the TTFA spacer could reduce the energy barrier of nucleation and induces crystal vertical orientation of 2D perovskite by forming larger clusters in precursor solution, resulting in much improved film quality. Benefiting from the enlarged crystal grains, reduced exciton binding energy, and decreased electron‐phonon coupling coefficient, the photovoltaic device based on (TTFA)2MAn−1PbnI3n+1 (n=5) achieved a champion efficiency of 19.41 %, which is a record for 2D RP PSCs with FA‐based spacers. Our work provides deep understanding of the nucleation and crystallization process of 2D RP perovskite films and highlights the great potential of FA‐based semiconductor spacers in highly efficient 2D PSCs.

Spin Texture Sensitive Photodetection by Dion-Jacobson Tin Halide Perovskites.

The organic spacer molecule is known to regulate the optoelectronic properties of two-dimensional (2D) perovskites. We show that the spacer layer thickness determines the nature of optical transitions, direct or indirect, by controlling the structural properties of the inorganic layer. The spin-orbit interactions lead to different electron spin orientations for the states associated with the conduction band minimum (CBM) and the valence band maximum (VBM). This leads to a direct as well as an indirect component of the transitions, despite them being direct in momentum space. The shorter chains have a larger direct component, leading to a better optoelectronic performance. The mixed halide Sn2+ Dion-Jacobson (DJ) perovskite with the shortest 4-C diammonium spacer outshines the photodetection parameters of those having longer (6-C and 8-C) spacers and the corresponding Ruddlesden-Popper (RP) phases. The DJ system with a 4-C spacer and equimolar Br/I embodies an unprecedentedly high responsivity of 78.1 A W-1 under 3 V potential bias at 485 nm wavelength, among the DJ perovskites. Without any potential bias, this phase manifests the self-powered photodetection parameters of 0.085 A W-1 and 9.9 × 1010 jones. The unusual role of electron spin texture in these high-performance photodetectors of the lead-free DJ perovskites provides an avenue to exploit the information coded in spins for semiconductor devices without any ferromagnetic supplement or magnetic field.

Influence of Organic Spacer Cation on Dark Excitons in 2D Perovskites

AbstractThe organic spacer cation plays a crucial role in determining the exciton fine structure in 2D perovskites. Here, magneto‐optical spectroscopy is used to gain insight into the influence of the organic spacer on dark excitons in Ruddlesden–Popper (RP) perovskites. Using modest magnetic field strengths (&lt;1.5 T), the optically forbidden dark exciton state can be identified and its emission properties significantly modulated via application of in‐plane magnetic fields, up to temperatures of 15 K. At low temperatures, an increase in collected photoluminescence efficiency of &gt;30% is demonstrated, signifying the critical role of the dark exciton state for light‐emitting applications of 2D perovskites. The exciton fine structure and the degree of magnetic‐field‐induced mixing are significantly impacted by the choice of organic spacer cation, with 4–methoxyphenylethylammonium (MeO‐PEA) showing the largest effect due to larger bright–dark exciton splitting. This study distinguishes between interior (bulk) and surface dark‐exciton emission, showing that bright–dark exciton splitting differs between the interior and surface. The results emphasize the significance of the organic spacer cation in controlling the exciton fine structure in 2D perovskites and have important implications for the development of optoelectronic technology based on 2D perovskites.

Self‐Configured Composites of Ruddlesden‐Popper Perovskite and Pr6O11 as Efficient and Durable Air Electrodes for Reversible Protonic Ceramic Electrochemical Cells

AbstractA breakthrough in the development of air electrodes is critical to minimizing the performance deterioration of reversible protonic ceramic electrochemical cells (R‐PCECs), which have demonstrated the potential to be the most promising electrochemical device for energy storage and conversion. Here, a Co‐doped Ruddlesden‐Popper (RP) perovskite with a nominal formula of Pr2Ni0.6Co0.4O4‐δ is reported, which is self‐configured into a composite of Pr4Ni1.8Co1.2O10‐δ (PNCO, 89.57 wt.%) and Pr6O11 (10.43 wt.%), suggested by the X‐ray diffraction refinement. The composite electrodes exhibit improved electrochemical activity with an area‐specific resistance of 0.33 Ω cm2 at 600 °C after being treated with wet air, due primarily to the raised surface exchange, bulk diffusion capabilities, and the increasing amount of Pr6O11 with catalytic activity. The R‐PCECs with the composite electrodes achieve a maximum power density of 1.32 W cm−2 and a current density of 3.09 A cm−2 at 1.3 V with acceptable Faradaic efficiencies at 650 °C. Furthermore, the composite electrodes show benign operational durability in fuel cell mode (‐0.5 A cm−2 for 167 h) and electrolysis mode (+0.5 A cm−2 for 176 h), and promising cycling stability (+/‐0.5 A cm−2) of 124 h at an interval of 2 h.

Ruddlesden–Popper Sr4Ir3O10 perovskite: A new family for water splitting driven by interlayer oxygen migration

Ruddlesden–Popper (R-P) layered perovskites offer a new possibility for efficient water splitting due to their periodically packed rock-salt and perovskite layers along the c-axis in crystallographic. Herein, a novel R-P Sr4Ir3O10 oxide with a dynamic characteristic of short-range oxygen migration between the SrO rock-salt monolayer and SrIrO3 perovskite multilayers were fabricated. It shows lower Fermi level around the redox potential level of O2/H2O, which enables an interstitial oxygen assisted lattice oxygen evolution mechanism to improve OER performance with low overpotential of 205 and 278 mV at 10 and 100 mA/cm2 in acidic environment. In practical proton exchange membrane (PEM) device, the Sr4Ir3O10 can sustain more than 50 h without obvious decay at 10 mA/cm2, steming from a cascade migration of oxygen species from adsorbed water to interstitial oxygen and then lattice oxygen. This may open a new door to developing high-performance R-P perovskites for application in PEM water electrolysis.

A Self-Powered UV Photodetector With Ultrahigh Responsivity Based on 2D Perovskite Ferroelectric Films With Mixed Spacer Cations.

Self-powered photodetectors (PDs) have the advantages of no external power requirement, wireless operation, and long life. Spontaneous ferroelectric polarizations can significantly increase built-in electric field intensity, showing great potential in self-powered photodetection. Moreover, ferroelectrics possess pyroelectric and piezoelectric properties, beneficial for enhancing self-powered PDs. 2D metal halide perovskites (MHPs), which have ferroelectric properties, are suitable for fabricating high-performance self-powered PDs. However, the research on 2D metal halide perovskites ferroelectrics focuses on growing bulk crystals. Herein, 2D ferroelectric perovskite films with mixed spacer cations for self-powered PDs are demonstrated by mixing Ruddlesden-Popper (RP)-type and Dion-Jacobson (DJ)-type perovskite. The (BDA0.7 (BA2 )0.3 )(EA)2 Pb3 Br10 film possesses, overall, the best film qualities with the best crystalline quality, lowest trap density, good phase purity, and obvious ferroelectricity. Based on the ferro-pyro-phototronic effect, the PD at 360nm exhibits excellent photoelectric properties, with an ultrahigh peak responsivity greater than 93 A W-1 and a detectivity of 2.5 × 1015 Jones, together with excellent reproducibility and stability. The maximum responsivities can be modulated by piezo-phototronic effect with an effective enhancement ratio of 480%. This work will open up a new route of designing MHP ferroelectric films for high-performance PDs and offers the opportunity to utilize it for various optoelectronics applications.

A Comprehensive Study of Electronic, Optical, and Thermoelectric Characteristics of Cs2PbI2Br2 Inorganic Layered Ruddlesden-Popper Mixed Halide Perovskite through Systematic First-Principles Analysis.

In this research, we present a comprehensive study on the influence of layer-dependent structural, electronic, and optical properties in the two-dimensional (2D) Ruddlesden-Popper (RP) perovskite Cs2PbI2Br2. Employing first-principles computations within the density functional theory method, including spin orbit coupling contribution, we examine the impact of various factors on the material. Our results demonstrate that the predicted 2D-layered RP perovskite Cs2PbI2Br2 structures exhibit remarkable stability both structurally and energetically, making them promising candidates for experimental realization. Furthermore, we observe that the electronic band gap and optical absorption coefficients of Cs2PbI2Br2 strongly depend on the thickness variation of the layers. Interestingly, Cs2PbI2Br2 exhibits a notable absorption coefficient in the visible region. Using a combination of density functional theory and Boltzmann transport theory, the thermoelectric properties were forecasted. The calculation involved determining the Seebeck coefficient (S) and other associated thermoelectric characteristics, such as electronic and thermal conductivities, as they vary with the chemical potential at room temperature. These findings open up exciting opportunities for the application of this 2D RP perovskite in solar cells and thermoelectric devices, owing to its unique properties.

Revealing direct atomic structure and electrostatic maps of the Ruddlesden-Popper faults in LaNiO3 perovskite

Ruddlesden-Popper (RP) faults in perovskites as one type of the anti-phase boundaries provide a versatile platform to manipulate the magnetic, conducting, and magnetoresistance properties in the complex oxides. Local fine structure at the boundaries containing light atoms is a key factor to understand the underlying structure-function relationship due to their interfaces mediated effects. In this work, the atomic structure, chemical distribution and electronic structure of typical RP faults in perovskite LaNiO3 and its epitaxial nanocomposite films on a SrTiO3 substrate were systematically investigated combining high-resolution scanning transmission electron microscopy (STEM) and density functional theory (DFT) calculations. Integrated differential phase contrast (iDPC) STEM imaging results demonstrate a NiO2-x-(LaO-LaO)-NiO2-x atomic configuration with content fluctuations of oxygen at the RP faults. Atomic electronic energy loss spectroscopy results and DFT calculations illustrate that Ni cations have mixed valence of Ni2+, Ni3+ at the RP faults accompanying with oxygen environment fluctuations affected by the non-stoichiometric bonding. This study offers a comprehensive route to explore intriguing chemical structures and physical properties in the homointerface structure at the atomic level.

Photoexcitation Control of Excitation Relaxation in Mixed‐Phase Ruddlesden‐Popper Hybrid Organic‐Inorganic Lead‐Iodide Perovskites

AbstractThe electronic states and exciton binding energies of layered Ruddlesden‐Popper (RP) metal‐halide perovskites can be tailored through changes of their chemical composition, yielding multi‐phase systems with complex energy cascades. Ultrafast photoexcitation relaxation with transfer dynamics into domains of increasing layer number has been reported for these materials. Here, ultrafast optical spectroscopy is used to report an unexpected excitation energy dependence of photoexcitation relaxation dynamics in mixed‐dimensional benzylammonium cesium lead iodide RP perovskite (BeA2CsPb2I7) thin films, which gives rise to spectrally broadband luminescence over the visible region. Using transient absorption and photoluminescence spectroscopy it is found that excitations, which are formed in the n = 2 RP‐phase after photoexcitation with ≈0.2 electron volt excess energy, transfer to higher layer number RP‐phases on unexpectedly slow timescales of tens of picoseconds. Further, it is observed that such excitations are initially optically passive. Notably, luminescence occurs under these conditions from multiple RP‐phases with optical bandgaps across the visible range, yielding broadband luminescence. The results hold potential for realization of broadband white‐light emitters and other light‐emitting devices.

Jahn–Teller distortion in Sr2FeO4: group-theoretical analysis and hybrid DFT calculations

We present theoretical justification for distorted Ruddlesden–Popper (RP) phases of the first-order by using hybrid density functional theory (DFT) calculations and group-theoretical analysis. We, thus, demonstrate the existence of the Jahn–Teller effect around an Fe^{4texttt {+}} ion in Sr_{2}FeO_{4}. On the calculation side, we have established a combination of Wu–Cohen (WC) exchange and Perdew-Wang (PW) correlation in a three-parameter functional WC3PW, giving the most accurate description of Sr_{2}FeO_{4} from the comparison of three hybrid DFT functionals. Self-consistently obtained Hartree–Fock exact exchange of 0.16 demonstrates consistent results with the experimental literature data. Importantly, we explain conditions for co-existing proper and pseudo-Jahn–Teller effects from the crystalline orbitals, symmetry-mode analysis and irreps products. Moreover, phonon frequency calculations support and confirm the results of symmetry-mode analysis. In particular, the symmetry-mode analysis identifies a dominating irreducible representation of the Jahn-Teller mode (X2+) and corresponding space group (SG) of ground state structure (SG Cmce model). Therefore, the usually suggested high-symmetry tetragonal crystal structure (SG I4/mmm model) is higher in energy by 121 meV/f.u. (equivalent to the Jahn-Teller stabilization energy) compared with the distorted low-symmetry structure (SG Cmce model). We also present diffraction patterns for the two crystal symmetries to discuss the differences. Therefore, our results shed light on the existence of low-symmetry RP phases and make possible direct comparisons with future experiments.

Selenophene-Based 2D Ruddlesden-Popper Perovskite Solar Cells with an Efficiency Exceeding 19.

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites have emerged as attractive candidates for high-performance perovskite solar cells (PSCs) thanks to their superior environmental and structural stability. However, 2D RP PSCs exhibit larger exciton binding energy due to the dielectric mismatch between the organic and inorganic layers, resulting in poorer photovoltaic performance compared to their 3D analogs. Here, we developed a selenophene-based spacer, namely, 2-selenophenemethylammonium (SeMA), for stable and efficient 2D RP PSCs. The 2D perovskite film using methylammonium (MA) as the A-site cation (nominal n = 5) shows excellent film quality with large grain size and a preferred vertical orientation relative to the substrate. Furthermore, we have successfully demonstrated the effectiveness of a predeposition transport layer (PDTL) consisting of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in passivating surface defects of the perovskite film and inducing densification of the upper PCBM electron transport layer. This densification promotes efficient extraction and transport of electrons. The optimized PSCs based on 2D RP perovskite using MA as A-site cation (nominal n = 5) achieved a power conversion efficiency (PCE) of 17.25%, which was further boosted to 19.03% when using formamidinium (FA) as A-site cation. This represents a record PCE of 2D RP PSCs by using the selenophene-based spacer. Moreover, these 2D RP PSCs significantly improve thermal, moisture, and light stability. Our results provide significant implications for the synergistic strategy of developing selenophene-based spacers and device engineering methods for achieving highly efficient and stable 2D RP perovskite solar cells.

Regulating Phase Distribution of Dion-Jacobson Perovskite Colloidal Multiple Quantum Wells Toward Highly Stable Deep-Blue Emission.

Metal halide perovskite colloidal quantum wells (CQWs) hold great promise for modern photonics and optoelectronics. However, current studies focus on Ruddlesden-Popper (R-P) phase perovskite CQWs that contain bilayers of monovalent long-chain alkylamomoniums between the separated perovskite octahedra layers. The bilayers are packed back-to-back via weak van der Waals interaction, resulting in inferior charge carrier transport and easier decomposition of perovskite. This report first creates a new type of perovskite colloidal multiple QWs (CMQWs) in the form of Dion-Jacobson (D-J) structure by introducing an asymmetric diammonium cation. Furthermore, the phase distribution is optimized by the synergistic effect of valeric acid and zwitterionic lecithin, finally achieving pure deep-blue emission at 435nm with narrow full width at half maximum. The diammonium layer in D-J perovskite CMQWs features extremely short width of only ≈0.6nm, thereby contributing to more effective charge carrier transport and higher stability. Through the continuous photoluminescence (PL) measurement and corresponding theoretical calculation, the higher stability of D-J perovskite CMQWs than that of R-P structural CMQWs is confirmed. This work reveals the inherent superior stability of D-J structural CMQWs, which opens a new direction for fabricating stable perovskite optoelectronics.

Regulation of phase arrangement in 2D ruddlesden-popper perovskite films via anti-solvent method for efficient solar cells

Recently, quasi-two-dimensional RP(Ruddlesden-Popper)-based perovskite solar cells have attracted a wide range of research interest. However, two-dimensional layered perovskites have disordered phase distribution and multi-quantum well structure that are adversely to charge transport and extraction, resulting in the inability to obtain relatively satisfactory photoelectric conversion efficiency (PCE). Here, we fabricated an 2D RP perovskite solar cell with reversely graded phase arrangement by friendly antisolvent method, and obtained the PCE of 14.45%. The dependence of efficiency on device architecture according to the vertical growth direction is further revealed and discussed. To investigate the effect of different antisolvents on crystal orientation and phase arrangement of GA-based 2D RP perovskites, we applied IPA as antisolvent and found that IPA not only significantly improved the surface roughness, quality and crystallinity of 2D perovskites but also reduce or even eliminate lower-n (n = 1, 2) phases and improve the vertical orientation of 2D phases in perovskites films, thereby improving charge transport and extraction. In the end, we achieved a champion PCE of 15.80%. These findings provide an effective guidance for developing GA-based organic spacers toward highly efficient and stable 2D PSCs with less quantum confinement.

Interface engineering of Ruddlesden–Popper perovskite/CeO2/carbon heterojunction for rechargeable zinc-air batteries

The development of noble metal-based bifunctional electrocatalysts is the key to driving the sluggish oxygen reduction/evolution reaction (ORR/OER) for rechargeable zinc-air battery applications. There is an urgent need to design and construct robust and cost-efficient bifunctional electrocatalysts. Herein, an interface engineering strategy of Ruddlesden–Popper (RP) perovskite/CeO2/carbon heterojunction with core–shell nanostructures is described. Ce-based metal–organic framework derived CeO2-C nanosheets are decorated on the surface of RP type perovskite Pr3Sr(Ni0.5Co0.5)3O10−δ (PSNC) nanofibers. Benefiting from the favorable conductivity, abundant oxygen vacancies and strong interfacial coupling, the hierarchical CeO2-C/PSNC electrode delivers a half-wave potential of 0.78 V (ORR), and an OER overpotential of 370 mV at 10 mA cm−2, respectively. A liquid rechargeable zinc-air battery (ZAB) assembled with CeO2-C/PSNC electrocatalysts as the air cathode exhibits a peak power density of 161 mW cm−2 and a long-term cycling life over 219 h. In addition, the CeO2-C/PSNC-based all-solid-state cable-type ZAB provides a high open-circuit voltage (∼1.44 V), good flexibility and durability. Our study opens a new insight into the design of efficient electrocatalysts for rechargeable ZABs by constructing hierarchical heterojunctions.

Systematic first-principles investigation of electronic, optical and thermoelectric properties of all-inorganic layered ruddlesden-popper mixed halide perovskite Cs2SnI2Br2

Report on systematic study of the impact of layer dependent structural properties, electronic structures and optical characteristics on the two-dimensional (2D) Ruddlesden–Popper (RP) perovskite Cs2SnI2Br2 using first principles computation within the density functional theory method including a spin orbit coupling contribution. Our results reveal that the predicted 2D-layered RP perovskite Cs2SnI2Br2 are structurally and energetically stable which can be realized in experiments. It is also shown that the band gap and optical absorption characteristics of the 2D-layered RP perovskite Cs2SnI2Br2 are dependent on thickness variation. Interestingly, Cs2SnI2Br2 exhibited an interesting absorption coefficient in the visible region. The transport equations were solved in order to evaluate the effect of the Sn based 2D-layered RP perovskite on thermoelectric performance. It is found that Cs2SnI2Br2 has lower thermal conductivity and higher electrical conductivity for T = 300 K. In addition, Cs2SnI2Br2 is expected to get the highest figure of merit. This result provides an outstanding opportunity for this 2D RP perovskite with potential applications in solar cells and thermoelectric applications.

Exsolution-enhanced reverse water-gas shift chemical looping activity of Sr2FeMo0.6Ni0.4O6-δ double perovskite

This study investigates the structural evolution and redox characteristics of the double perovskite Sr2FeMo0.6Ni0.4O6-δ (SFMN) during hydrogen (H2) and carbon dioxide (CO2) redox cycles and explores the material performance in the Reverse Water-Gas Shift Chemical Looping (RWGS-CL) reaction. In-situ and ex-situ X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM) studies reveal that H2 reduction at temperatures above 800 °C leads to the exsolution of bimetallic Ni-Fe alloy particles and the formation of a Ruddlesden-Popper (RP) phase. A core–shell structure with Ni-Fe core and a perovskite oxide shell is formed with subsequent redox cycles, and the resulting material exhibits better performance and high stability in the RWGS-CL process. Thermogravimetric (TGA) and Temperature Programmed Reduction (TPR) and Oxidation (TPO) analyses show that the optimal reduction and oxidation temperatures for maximizing the CO yield are around 850 °C and 750 °C respectively, and that the cycled material is able to work steadily under isothermal conditions at 850 °C.