Co─Mn Bimetallic Nanowires by Interfacial Modulation with/without Vacancy Filling as Active and Durable Electrocatalysts for Water Splitting.

Active and stable nonnoble electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are required for water splitting by sustainable electricity. Here, Mn bonded with O and P is incorporated to modulate Co3S4 and Co2P respectively to enhance the catalytic activity and extend the catalyst lifetime. Mn3O4 adjusts the electronic structure of Co3S4 and Co atom fills the oxygen vacancy in Mn3O4. The interfacial interaction endows Co3S4/Mn3O4 to a lower reaction barrier due to ideal binding energies for OER intermediates. Structure stability of active sites and enhanced Co─S bonds by Operando Raman spectroscopy and theoretical calculations reduce the dissolution of Co3S4/Mn3O4, resulting in a lifetime of 500 h at 50 mA cm-2 for OER. The modulation of Co2P by MnP weakens the interaction between Co sites and adsorbed H*, achieving a high activity under a large current for HER. The assembled electrolyzer affords 50 mA cm-2 at 1.58 V and exhibits a lifetime of 350 h at 50 mA cm-2. The calculations disclose the electron interaction for the activity and stability, as well as the enhanced conductivity. The findings develop new avenues toward promoting catalytic activity and stability, making Co─Mn bimetallic nanowires efficient electrocatalysts for nonnoble water electrolyzers.

Strong Interface Coupling Enables Stability of Amorphous Meta-Stable State in CoS/Ni3S2 for Efficient Oxygen Evolution.

Rational design of heterostructure catalysts through phase engineering strategy plays a critical role in heightening the electrocatalytic performance of catalysts. Herein, a novel amorphous/crystalline (a/c) heterostructure (a-CoS/Ni3S2) is manufactured by a facile hydrothermal sulfurization method. Strikingly, the interface coupling between amorphous phase (a-CoS) and crystalline phase (Ni3S2) in a-CoS/Ni3S2 is much stronger than that between crystalline phase (c-CoS) and crystalline phase (Ni3S2) in crystalline/crystalline (c/c) heterostructure (c-CoS/Ni3S2) as control sample, which makes the meta-stable amorphous structure more stable. Meanwhile, a-CoS/Ni3S2 has more S vacancies (Sv) than c-CoS/Ni3S2 because of the presence of an amorphous phase. Eventually, for the oxygen evolution reaction (OER), the a-CoS/Ni3S2 exhibits a significantly lower overpotential of 192 mV at 10 mA cm-2 compared to the c-CoS/Ni3S2 (242 mV). An exceptionally low cell voltage of 1.51 V is required to achieve a current density of 50 mA cm-2 for overall water splitting in the assembled cell (a-CoS/Ni3S2 || Pt/C). Theoretical calculations reveal that more charges transfer from a-CoS to Ni3S2 in a-CoS/Ni3S2 than in c-CoS/Ni3S2, which promotes the enhancement of OER activity. This work will bring into play a fabrication strategy of a/c catalysts and the understanding of the catalytic mechanism of a/c heterostructures.

Improvement of Perovskite Solar Cells Efficiency by Management of the Electron Withdrawing Groups in Hole Transport Materials: Theoretical Calculation and Experimental Verification.

Management of functional groups in hole transporting materials (HTMs) is a feasible strategy to improve perovskite solar cells (PSCs) efficiency. Therefore, starting from the carbazole-diphenylamine-based JY7 molecule, JY8 and JY9 molecules are incorporated into the different electron-withdrawing groups of fluorine and cyano groups on the side chains. The theoretical results reveal that the introduction of electron-withdrawing groups of JY8 and JY9 can improve these highest occupied molecular orbital (HOMO) energy levels, intermolecular stacking arrangements, and stronger interface adsorption on the perovskite. Especially, the results of molecular dynamics (MD) indicate that the fluorinated JY8 molecule can yield a preferred surface orientation, which exhibits stronger interface adsorption on the perovskite. To validate the computational model, the JY7-JY9 are synthesized and assembled into PSC devices. Experimental results confirm that the HTMs of JY8 exhibit outstanding performance, such as high hole mobility, low defect density, and efficient hole extraction. Consequently, the PSC devices based on JY8 achieve a higher PCE than those of JY7 and JY9. This work highlights the management of the electron-withdrawing groups in HTMs to realize the goal of designing HTMs for the improvement of PSC efficiency.

Revealing the Structure-Luminescence Relationship in Robust Sn(IV)-Based Metal Halides by Sb3+ Doping.

Low-dimensional hybrid metal halides are an emerging class of materials with highly efficient photoluminescence (PL), but the problems of poor stability remain challenging. Sn(IV)-based metal halides show robust structure but exhibit poor PL properties, and the structure-luminescence relationship is elusive. Herein, two Sn(IV)-based metal halides (compounds 1 and 2) with the same constituent ((C6H16N2)SnCl6) but different crystal structures have been prepared, which however show poor PL properties at room temperature due to the absence of active ns2 electrons. To improve materials' PL properties, Sb3+ with active 5s2 electrons was embedded into the lattice of Sn4+-based hosts. As a result, efficient emissions were achieved for Sb3+-doped compounds 1 and 2 with a maximum PL efficiency of 14.28 and 62%, respectively. Experimental and calculation results reveal that the smaller distorted lattice structure of the host could result in the blueshift of the emission from Sb3+. Thus, a tunable color from red to orange was realized. Benefiting from the broadband efficient emission from Sb3+-doped compound 2, an efficient white light-emitting diode with a high color rendering index of up to 92.3 was fabricated to demonstrate its lighting application potential. This work promotes the understanding of the influence of robust Sn(IV)-based host lattice on the PL properties of Sb3+, advancing the development of environmentally friendly, low-cost, and high-efficiency Sn(IV)-based metal halides.

Dual-Emissive γ-[Cu4I8]4- Enables Luminescent Thermochromism in an Organic-Inorganic Hybrid Copper(I) Halide.

A highly luminescent (C13H28N2)2Cu4I8 single crystal containing isolated γ-[Cu4I8]4- anionic cluster was synthesized without the use of unsaturated cations. To the best of our knowledge, compounds bearing such like anions are not dual-emitting under UV excitation. However, dual emission does occur in (C13H28N2)2Cu4I8. Moreover, the emission bands were found to be temperature-sensitive, allowing tuning of the emission colors from blue (0.19, 0.20) to green (0.33, 0.47) in the Commission International de L' Eclairage (CIE) chromaticity coordinates. Remarkably, the color could be restored on returning to the initial temperature, confirming an efficient and reversible luminescent thermochromic effect in (C13H28N2)2Cu4I8. The origin of this excellent optical performance is discussed, and the difference in the mechanism with the dual-emissive Cu(I) halide complexes is also elucidated. Overall, our work provides a promising way to achieve efficient luminescent thermochromism. The developed (C13H28N2)2Cu4I8 represents one of the viable alternatives for eco-friendly luminescent thermochromic materials.

Embedding Te4+ into Sn4+-Based Metal Halide To Passivate Structure Defects for High-Performance Light-Emitting Application.

Low-dimensional lead-halide hybrids are an emerging class of optical functional material but suffer the problems of toxicity and poor air stability. Among lead-free metal halides, tin(IV)-based metal halides are promising optoelectronic materials due to their robust structure and environmental friendliness. However, their photoluminescence (PL) properties are poor, and the underlying mechanisms are still elusive. Herein, a stable Sn4+-based halide hybrid, (C4H7N2)2SnCl6, was developed, which however exhibits poor PL properties at room temperature (RT) due to the lattice defects and the robust crystal structure. To enhance its PL efficiency, the Te4+ ion with a stereoactive 5s2 lone pair has been introduced into the lattice. As a result, Te4+-doped (C4H7N2)2SnCl6 displays broadband orange emission (∼640 nm) with a PL efficiency of ∼46% at RT. Interestingly, Te4+-doped (C4H7N2)2SnCl6 shows triple emission bands at 80 K, which could be due to the synergistic effect of the organic cations and the self-trapped state induced by Te4+. Additionally, high-performance white light-emitting diodes were prepared using Te4+-doped (C4H7N2)2SnCl6, revealing the potential of this material for lighting applications. This study provides new insight into the PL mechanism of Sn4+-based metal-halide hybrids and thus facilitates the design and development of eco-friendly light-emitting metal halides.

Relation Between Abnormal Spontaneous Brain Activity and Altered Neuromuscular Activation of Lumbar Paraspinal Muscles in Chronic Low Back Pain.

OBJECTIVE: To investigate the neural mechanism underlying functional reorganization and motor coordination strategies in patients with chronic low back pain (cLBP). DESIGN: A case-control study based on data collected during routine clinical practice. SETTING: This study was conducted at a university hospital. PARTICIPANTS: Fifteen patients with cLBP and 15 healthy controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Whole brain blood oxygen level-dependent signals were measured using functional magnetic resonance imaging and amplitude of low-frequency fluctuation (ALFF) method to identify pain-induced changes in regional spontaneous brain activity. A novel approach based on the surface electromyogram (EMG) system and fine-wire electrodes was used to record EMG signals in the deep multifidus, superficial multifidus, and erector spinae. RESULTS: In cLBP, compared with healthy groups, ALFF was higher in the medial prefrontal, primary somatosensory, primary motor, and inferior temporal cortices, whereas it was lower in the cerebellum and anterior cingulate and posterior cingulate cortices. Furthermore, the decrease in the average EMG activity of the 3 lumbar muscles in the cLBP group was positively correlated with the ALFF values of the primary somatosensory cortex, motor cortex, precuneus, and middle temporal cortex but significantly negatively correlated with the ALFF values of the medial prefrontal and inferior temporal cortices. Interestingly, the correlation between the functional activity in the cerebellum and the EMG activity varied in the lumbar muscles. CONCLUSIONS: These findings suggest a functional association between changes in spontaneous brain activity and altered voluntary neuromuscular activation patterns of the lumbar paraspinal muscles, providing new insights into the mechanisms underlying pain chronicity as well as important implications for developing novel therapeutic targets of cLBP.

Rational Design of a Super-Alkali Compound with Reversible Photoluminescence.

The zero-dimensional (0D) (H5O2)(C4H14N2S2)2BiCl8: Sb3+ single crystal is obtained by the cooling crystallization method. Surprisingly, this compound shows reversible photoluminescence (PL) upon H5O2+Cl- removal and insertion. To be specific, the release of H5O2+Cl- resulted in red-orange emission with a very low photoluminescence quantum yield (PLQY). While on the reuptake of it, a bright yellow emission with a nearly 10-fold increase of PLQY was observed. Density functional theory (DFT) calculations and temperature-dependent PL experiments reveal that significant [SbCl6]3- octahedron distortion induced by guest (H5O2+Cl-) removal at the ground state, especially at the excited state, is responsible for the disparate PL performance. Encouragingly, we also found that (C4H14N2S2)2BiCl7: Sb3+ exhibits a fast response (<3 s) to dilute hydrochloric acid with naked-eye perceivable PL color changes, rendering it a potential sensing material for hydrochloric acid.

Effect of the Host Lattice Environment on the Expression of 5s2 Lone-Pair Electrons in a 0D Bismuth-Based Metal Halide.

ns2-Metal halide perovskites have attracted wide attention due to their fascinating photophysical properties. However, achieving high photoluminescence (PL) properties is still an enormous challenge, and the relationship between the lattice environment and ns2-electron expression is still elusive. Herein, an organic-inorganic Bi3+-based halide (C5H14N2)2BiCl6·Cl·2H2O (C5H14N22+ = doubly protonated 1-methylpiperazine) with a six-coordinated structure has been successfully prepared, which, however, exhibits inferior PL properties due to the chemically inert expression of Bi3+-6s2 lone-pair electrons. After reasonably embedding Sb3+ with 5s2 electrons into the lattice of (C5H14N2)2BiCl6·Cl·2H2O, the host lattice environment induces the Sb-Cl moiety to change from the original five-coordinated to six-coordinated structure, thereby resulting in a broad-band yellow emission with a PL efficiency up to 50.75%. By utilizing the host lattice of (C5H14N2)2BiCl6·Cl·2H2O, the expression of Sb3+-5s2 lone-pair electrons is improved and thus promotes the radiative recombination from the Sb3+-3P1 state, resulting in the enhanced PL efficiency. This work will provide an in-depth insight into the effect of the local structure on the expression of Sb3+-5s2 lone-pair electrons.

Tailoring Photophysical Dynamics in a Hybrid Gallium-Bismuth Heterometallic Halide by Transferring from an Indirect to a Direct Band Structure.

Low-dimensional lead-free metal halides have emerged as novel luminous materials for solid-state lighting, remote thermal imaging, X-ray scintillation, and anticounterfeiting labeling applications. However, the influence of band structure on the intriguing optical property has rarely been explored, especially for low-dimensional hybrid heterometallic halides. In this study, we have developed a lead-free zero-dimensional gallium-bismuth hybrid heterometallic halide, A8(GaCl4)4(BiCl6)4 (A = C8H22N2), that is photoluminescence (PL)-inert because of its indirect-band-gap character. Upon rational composition engineering, parity-forbidden transitions associated with the indirect band gap have been broken by replacing partial Ga3+ with Sb3+, which contains an active outer-shell 5s2 lone pair, resulting in a transition from an indirect to a direct band gap. As a result, broadband yellow PL centered at 580 nm with a large Stokes shift over 200 nm is recorded. Such an emission is attributed to the radiative recombination of an allowed direct transition from triplet 3P1 states of Sb3+ based on experimental characterizations and theoretical calculations. This study provides not only important insights into the effect of the band structure on the photophysical properties but a guidance for the design of new hybrid heterometallic halides for optoelectronic applications.

Realizing Efficient Emission in Three-Dimensional CsCdCl3 Single Crystals by Introducing Separated Emitting Centers.

Hitherto, three-dimensional (3D) perovskite single crystals with a low exciton binding energy generally possess inferior photoluminescence (PL) performance due to the spatially unconfined nature of excitons. In this work, 3D CsCdCl3 single crystals with multiple emissions from self-trapped excitons (STEs) have been developed, which unsurprisingly exhibit a discouraging PL quantum yield (PLQY) of ∼4.8%. To improve the luminescence efficiency, Mn2+ and Sn2+ are introduced into the lattice as dopants, respectively. By embedding Mn2+ ion into CsCdCl3, the long Mn-Mn distance enables the resultant material to produce an intense orange emission (∼100% PLQY) from the d-d orbital transition (4T1-6A1) of Mn2+. Intriguingly, the embedded Sn2+ triggers the formation of Jahn-Teller-like STEs that induces a subsequent deep red emission with a PLQY of ∼28.22%, which is quite high for 3D bulk perovskites. Such a remarkable PL efficiency is attributed to the distinctive bonding mode of CsCdCl3 that encourages the expression of the Sn 5s2 lone pair. Furthermore, a white-light-emitting diode (WLED) is also fabricated with Mn2+-doped CsCdCl3 to show its potential in lighting application. This work paves a new avenue to improve the luminescence performance of bulk 3D perovskite materials.

The study of intramolecular decay and intermolecular energy transfer for phosphorescent organic light-emitting devices.

Due to the huge potential of organic light-emitting diodes (OLEDs) in optical display devices, the exciton utilization of devices should be elucidated comprehensively to achieve a high external quantum efficiency (EQE). In this study, theoretical calculations of intramolecular excited state decay and intermolecular excitation energy transfer (EET) were conducted to investigate the differences in EQE between the two studied systems. Compared to the PtOO7-based system (using PtOO7 as the guest and 26mCPy as the host), the greater EQE of the PtON7-based system (using PtON7 as the guest and 26mCPy as the host) was mainly governed by the stronger energy transfer efficiency, with a secondary role being played by the higher photoluminescence quantum yield of the emitter. We confirmed that the different triplet EET (TEET) rates mainly contribute to the difference in the energy transfer efficiency between two studied systems, where the higher TEET rate from 26mCPy to PtON7 can be attributed to the restrained structural deformation of PtON7 and the desirable energy gap in the energy transfer process. Our calculations indicated that the electronic structure can evidently affect the intramolecular excited state decay and intermolecular excitation energy transfer. In addition, considering the environmental effects on the emission spectra of the emitters, the simulated spectra were consistent with the experimental measurements, which indicated that our descriptions of electronic structures are accurate; furthermore, an effective description of the molecular environment should be obtained. Our computational protocol successfully explored the relationship between the electronic structures, intramolecular excited state decay, and intermolecular excitation energy transfer, which can provide a deep understanding for the design and development of high-quality OLEDs from a molecular perspective.

Revealing practical specific capacity and carbonyl utilization of multi-carbonyl compounds for organic cathode materials.

Organic carbonyl compounds are regarded as promising candidates for next-generation rechargeable batteries due to their low cost, environmentally benign nature, and high capacity. The carbonyl utilization is a key issue that limits the practical specific capacity of multi-carbonyl compounds. In this work, a combination of thermodynamic computation and electronic structure analysis is carried out to study the influence of carbonyl type and carbonyl number on the electrochemical performance of a series of multi-carbonyl compounds by using density functional theory (DFT) calculations. By comparing discharge profiles of six tetraone compounds with different carbonyl sites, it is demonstrated that pentacene-5,7,12,14-tetraone (PT) with para-dicarbonyl and pyrene-4,5,9,10-tetraone (PTO) with ortho-dicarbonyl undergo four-lithium transfer while the other four compounds with meta-dicarbonyl fragments show only two-lithium transfer during the discharge process. By further increasing the carbonyl number, the electrochemical performance of molecules with similar para-dicarbonyl sites to PT can not be strongly improved. Among all the studied multi-carbonyl compounds, triphenylene-2,3,6,7,10,11-hexaone (TPHA) and tribenzo[f,k,m]tetraphen-2,3,6,7,11,12,15,16-octaone (TTOA) with similar ortho-dicarbonyl sites to PTO exhibit the best electrochemical performance due to simultaneous high specific capacity and high discharge voltage. Our results offer evidence that conjugated multiple-carbonyl molecules with ortho-dicarbonyl sites are promising in developing high energy-density organic rechargeable batteries.

Theoretical analysis of oxygen reduction reaction activity on single metal (Ni, Pd, Pt, Cu, Ag, Au) atom supported on defective two-dimensional boron nitride materials.

A single atom supported by two-dimensional material is a suitable candidate for an oxygen reduction reaction (ORR) to replace Pt-based catalysts. In this work, new promising single-atom catalysts (SACs) with precise metal-nitrogen coordination (M-N) were investigated, where a single transition metal atom (M = Ni, Pd, Pt, Cu, Ag, Au) was supported by experimentally available defective two-dimensional boron nitride materials (M/BN) with a boron vacancy. ORR performance is predicated by the volcano plot, which indicates that those M/BN catalysts offer optimized binding strength of *OH species exhibiting high ORR activity. Moreover, only a direct 4e- pathway occurs on Ni/BN, Pd/BN and Pt/BN with only d valence electrons of a single metal atom. As an example, Pd/BN catalyzes ORR via a direct 4e- pathway with a small reaction barrier of 0.42 eV, which is smaller than that of Pt-based catalysts (0.79 eV). This high activity is attributed to precise M-N3 coordination in the M/BN catalysts. This work is expected to provide useful insight for development of novel high-efficiency SACs for ORR.

A single-atom catalyst of cobalt supported on a defective two-dimensional boron nitride material as a promising electrocatalyst for the oxygen reduction reaction: a DFT study.

Single-atom catalysts present extraordinary catalytic performance towards various reactions. In this work, the possibility of single Co atoms supported by the experimentally available defective two-dimensional boron nitride material (2D-BN) with boron vacancies (Co/BN) as a potential catalyst for the oxygen reduction reaction (ORR) was investigated by density functional theory. Co/BN has a similar active center to the cobalt nitride species, which have been proved to be effective ORR catalysts. It is found that Co atoms bind with the defective 2D-BN strongly to ensure the stability of Co/BN. Moreover, all of the ORR intermediates can be adsorbed on Co/BN. Especially, the HOOH species is found to be unstable and decomposes into two OH species immediately, suggesting that the ORR process occurs on Co/BN only through a direct 4e- pathway. Along the favorable pathway, the reduction of O2 to OOH is the rate-limiting step with a largest activation barrier of 0.30 eV and the maximum free energy change is 0.82 eV. Co/BN exhibits competitive ORR activity with that of CoN3 embedded graphene and Pt-based catalysts. These results should be enlightening to understand the ORR mechanism on Co/BN and design novel single-atom catalysts for the ORR and other electrocatalysis reactions.

Exploring the electrochemical properties of hole transporting materials from first-principles calculations: an efficient strategy to improve the performance of perovskite solar cells.

Perovskite solar cells (PSCs) have been achieved with impressively dynamic improvement in power conversion efficiency (PCE), becoming the hottest topic in photovoltaics. One of the hot topics is to develop inexpensive and efficient hole transporting materials (HTMs). In the present work, we systematically investigated the impact of different atoms in the heteromerous structure on the performance of perovskite solar cells. In addition, the influence of the structural modification of the HTM molecular building blocks was also revealed. To further understand the relationship between the charge-transport properties and the structural modification, the electronic properties, reorganization energy, and hole transporting properties of a series of organic hole transporting materials were investigated using first-principles calculations combined with Marcus theory. Moreover, the orientation function µΦ (V, λ, r, θ, γ; Φ) was applied to quantitatively evaluate the overall carrier mobility of HTMs in PSCs. It is revealed that this model predicts the hole mobility of HTMs correctly. The calculated results indicate that hole transporting materials with heteroatoms and larger dimensional structures show higher hole mobility, which may significantly improve the photovoltaic performance of PSCs.

What accounts for the color purity of tetradentate Pt complexes? A computational analysis.

In order to improve the texture of human visual perception and broaden the range of certain optical applications, many phosphorescent complexes exhibiting narrow emission spectra have been prepared through reasonable molecular design. For example, by adding a particular group such as tert-butyl (tbu) to a suitable position of PtON1 and PtON7, the peak width of a relevant vibronic band caused by the specific vibrational normal modes could be dramatically restrained in the emission spectra at room temperature. For the purpose of finding an effective approach to replace the trial-and-error manner, the microscopic mechanism of such high color purity was elucidated by computational investigation. In this study, we aim to identify the reason that causes sharp emission associated with the relevant vibrational normal modes. Here, these modes can be labeled to the emission peak by the vibrationally resolved emission spectra. Based on the displacement vectors of relevant normal modes and the vibrationally resolved spectra, the most possible reason for the higher color purity is that tbu in a specific location can restrain the structural deformation between the first triplet excited state (T1) and the ground state (S0). That is to say, the relevant Huang-Rhys factor (Sk) of specific vibrational modes would be decreased. For these compounds, the total bandwidth and the height of the intermediate and high-frequency regions which are in direct proportion to Sk would be decreased to obtain the higher color purity by tbu in a particular position. What is more, the best position for tbu in order to suppress the structural deformation was also considered. In the meantime, radiative (kr) and nonradiative (knr) decay rates of T1 were investigated to seek the effective phosphorescent complexes.

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations.

Solar emission produces copious nitrosonium ions (NO(+)) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO(+) is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO(+)(H2O)4 and pentahydrate NO(+)(H2O)5-are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO(+)(H2O)4 exhibits a chain-like structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO(+)(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO(+)(H2O)4 and NO(+)(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation.

Theoretical study on the origin of activity for the oxygen reduction reaction of metal-doped two-dimensional boron nitride materials.

Two-dimensional boron nitride (2D-BN) materials doped with metallic atoms are suitable candidates for the oxygen reduction reaction (ORR) to replace Pt-based catalysts. In this study, a series of model 2D-BN materials doped with metallic atoms were designed to uncover the relationship between ORR activity and metallic dopants. A volcano curve correlation was derived between ORR overpotential and the adsorption free energy values of *OH. Only the doped structures, located at the top of the volcano curve, exhibit optimized activity. Through analyzing the dynamic results, the ORR was found to occur only via the 4e- pathway on Co doped 2D-BN materials with the activation energy of 0.30 eV, which is lower than that achieved with the state-of-the-art Pt-based catalysts (0.79 eV). Furthermore, based on the calculations of electronic structure properties, we find that the small highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap is more beneficial to the 4e- pathway and prove that the binding strength between metallic atoms-doped 2D-BN materials and oxygenated intermediates is regulated by the HOMO of the metallic dopant consisting non-bonding or delocalized orbitals. These results provide an effective method to facilitate the design of new BN-based materials with high electrocatalytic performances besides the ORR performance.

π-Bridge modification of thiazole-bridged DPP polymers for high performance near-IR OSCs.

Thiophene-bridged and thiazole-bridged diketopyrrolopyrrole (DPP) polymers for near-infrared (near-IR) photovoltaic applications have been investigated via density functional theory (DFT) and Marcus charge transfer theory. Compared with thiophene-bridged DPP polymers, thiazole-bridged polymers have higher ionization potentials (IPs) but poorer optical absorption and worse charge transport capability. Different beneficial substituents replaced the hydrogen atoms (H) on the thiazole rings for the sake of reversing the disadvantages of thiazole-bridged DPP polymers and making these compounds better near-infrared absorbing materials. In order to gain deep insight into the impact of π-bridge modification on the photoelectronic properties of DPP polymers, their electronic structures, absorption capabilities, intramolecular charge transfer properties and charge transport performances have been analyzed. The calculated results reveal that π-bridge modification is a feasible way to improve the light-absorbing capability, electron excitation properties and charge transport performance of thiazole-bridged DPP polymers. It is expected that π-bridge modification can also work for other polymers containing π-bridge units. We hope that our research efforts will be helpful in the designing of new near-IR absorbing materials and could motivate further improvement of organic solar cells.