Structure of Amorphous Selenium: Small Ring, Big Controversy.

Selenium (Se) discovered in 1817 belongs to the family of chalcogens. Surprisingly, despite the long history of over two centuries and the chemical simplicity of Se, the structure of amorphous Se (a-Se) remains controversial to date regarding the dominance of chains versus rings. Here, we find that vapor-deposited a-Se is composed of disordered rings rather than chains in melt-quenched a-Se. We further reveal that the main origin of this controversy is the facile transition of rings to chains arising from the inherent instability of rings. This transition can be inadvertently triggered by certain characterization techniques themselves containing above-bandgap illumination (above 2.1 eV) or heating (above 50 °C). We finally build a roadmap for obtaining accurate Raman spectra by using above-bandgap excitation lasers with low photon flux (below 1017 phs m-2 s-1) and below-bandgap excitation lasers measured at low temperatures (below -40 °C) to minimize the photoexcitation- and heat-induced ring-to-chain transitions.

π-Conjugation-Induced In Situ Nanoscale Ordering of Spiro-OMeTAD Boosts the Efficiency and Stability of Perovskite Solar Cells.

Spiro-OMeTAD hole transport materials typically exhibit an amorphous state in perovskite solar cells. However, the lack of structural ordering leads to weak intermolecular interaction, inferior carrier transfer, and poor stability in devices. Herein, we developed a π-conjugation-induced short-range ordering strategy to modulate the stacking order of spiro-OMeTAD during film formation. A clear molecular ordering at the nanoscale is observed, which enhances intermolecular π-π stacking in spiro-OMeTAD and enables effective carrier extraction and favorable energy level alignment. The nanoscale-ordered spiro-OMeTAD allows the achievement of perovskite solar cells with a champion efficiency of 25.37%, surpassing devices utilizing amorphous spiro-OMeTAD (23.52%). The unencapsulated device demonstrates enhanced operational stability by retaining 98% of its initial efficiency under continuous 1 sun equivalent illumination at 60 °C for 840 h. This work establishes a significant and valid modulation concept for the stacking order of organic transport materials, paving the way for the development of efficient and stable perovskite solar cells.

Alkali Metal Cations Induce Structural Evolution on Au(111) During Cathodic Polarization.

The activity of the electrocatalytic CO2 reduction reaction (CO2RR) is substantially affected by alkali metal cations (AM+) in electrolytes, yet the underlying mechanism is still controversial. Here, we employed electrochemical scanning tunneling microscopy and in situ observed Au(111) surface roughening in AM+ electrolytes during cathodic polarization. The roughened surface is highly active for catalyzing the CO2RR due to the formation of surface low-coordinated Au atoms. The critical potential for surface roughening follows the order Cs+ > Rb+ > K+ > Na+ > Li+, and the surface proportion of roughened area decreases in the order of Cs+ > Rb+ > K+ > Na+ > Li+. Electrochemical CO2RR measurements demonstrate that the catalytic activity strongly correlates with the surface roughness. Furthermore, we found that AM+ is critical for surface roughening to occur. The results unveil the unrecognized effect of AM+ on the surface structural evolution and elucidate that the AM+-induced formation of surface high-activity sites contributes to the enhanced CO2RR in large AM+ electrolytes.

Unveiling the Interfacial Species Synergy in Promoting CO2 Tandem Electrocatalysis in Near-Neutral Electrolyte.

The interfacial species-built local environments on Cu surfaces impact the CO2 electroreduction process significantly in producing value-added multicarbon (C2+) products. However, intricate interfacial dynamics leads to a challenge in understanding how these species affect the process. Herein, with ab initio molecular dynamics (AIMD) and finite element method (FEM) simulations, we reveal that the highly concentrated interfacial species, including the *CO, hydroxide, and K+, could synergistically promote the C-C coupling on the one-dimensional (1D) porous hollow structure regulated interfacial environment. The Cu-Ag tandem catalyst was then synthesized with the as-designed structure, exhibiting a high C2+ Faradaic efficiency of 76.0% with a partial current density of 380.0 mA cm-2 in near-neutral electrolytes. Furthermore, in situ Raman spectra validate that the 1D porous structure regulates the concentration of interfacial CO intermediates and ions to increase *CO coverage, local pH value, and ionic field, promoting the CO2-to-C2+ activity. These results provide insights into the design of practical ECR electrocatalysts by regulating interfacial species-induced local environments.

Engineering Interlayer Space and Composite of Square-Shaped V2O5 by PVP-Assisted Polyaniline Intercalation and Graphene for Aqueous Zinc-Ion Batteries.

V2O5 undergoes irreversible phase transition and collapse of layered structure during the Zn2+ insertion/extraction, which severely limits its application as a cathode for aqueous zinc-ion batteries (AZIBs). Herein, a synergistic strategy of conductive polyaniline insertion and graphene composite was proposed to boost the Zn2+ storage performance of the V2O5 cathode. A square-shaped polyaniline (PANI)-intercalated and graphene-composited vanadium oxide (GO/PANI-PVP/V2O5) structure was successfully synthesized via an in situ oxidation/insertion polymerization combined with a hydrothermal method. The results showed that PANI intercalation and the composite of graphene combined with layered V2O5, enabling reversible intercalation of Zn2+/H+. The insertion of conjugated PANI not only increases the lattice spacing of V2O5, providing a channel for rapid transport of Zn2+, but also increases the storage sites for charges through doping/dedoping processes and redox conversion reactions. GO/PANI-PVP/V2O5 delivers an excellent specific capacity (495 mA h g-1 at 0.1 A g-1), wonderful rate capability (208 mA h g-1 at 30 A g-1), and good cycling stability (93% after 4000 cycles). Our results provide a new approach for adjusting the valence states, interlayer spacing, and rational design of organic-inorganic compound materials for different functional materials.

CNT Composite ß-MnO2 with Fiber Cable Shape as Cathode Materials for Aqueous Zinc-Ion Batteries.

Rechargeable aqueous zinc-ion batteries (AZIBs) have developed into one of the most attractive materials for large-scale energy storage owing to their advantages such as high energy density, low cost, and environmental friendliness. Nevertheless, the sluggish diffusion kinetics and inherent impoverished conductivity affect their practical application. Herein, the ß-MnO2 composited with carbon nanotubes (CNT@M) is prepared through a simple hydrothermal approach as a high-performance cathode for AZIBs. The CNT@M electrode exhibits excellent cycling stability, in which the maximum specific discharge capacity is 259 mA h g-1 at 3 A g-1, and there is still 220 mA h g-1 after 2000 cycles. The specific capacity is obviously better than that of ß-MnO2 (32 mA h g-1 after 2000 cycles). The outstanding electrochemical performance of the battery is inseparable from the structural framework of CNT and inherent high conductivity. Furthermore, CNT@M can form a complex conductive network based on CNTs to provide excellent ion diffusion and charge transfer. Therefore, the active material can maintain a long-term cycle and achieve stable capacity retention. This research provides a reasonable solution for the reliable conception of Mn-based electrodes and indicates its potential application in high-performance AZIB cathode materials.

Modulating the electronic structure of ion phthalocyanine-based molecular catalysts for electrocatalytic nitrogen reduction: a DFT study.

The highly localized Fe d orbital in ion phthalocyanine (FePc)-based molecular catalysts significantly hinders their electrocatalytic nitrogen reduction reaction (eNRR) performance. Herein, we theoretically designed a series of FePc-based molecules with adjacent metal phthalocyanine sites to form an asymmetric delocalized electronic structure on Fe centers, promoting the catalytic activity and lowering the overpotential of the eNRR, as well as suppressing the hydrogen evolution reaction (HER) side reaction.

Fully Dispersed IrOx Atomic Clusters Enable Record Photoelectrochemical Water Oxidation of Hematite in Acidic Media.

Ir-based materials are still the benchmark catalysts for various reactions in acidic environment, but the high loading and low atom utilization limit their large-scale deployment. Herein, we report an effective strategy for implanting fully dispersed iridium-oxide atomic clusters onto hematite for boosting photoelectrochemical water oxidation in acidic solution. The resulting photoanode achieves a record-high photocurrent of 1.35 mA cm-2 at 1.23 V, corresponding to a mass activity of 172.70 A g-1 (3 times higher than electrodeposited control sample) and demonstrating the merits from the high atomic utilization of Ir. The systematically experimental and theoretical results reveal that the performance improvement correlates with the modulated electronic structure including the adjusted Fermi level and d-band center, which significantly enhances charge separation efficiency and promotes the conversion from intermediate *O into *OOH.

Lanthanide-Like Contraction Enables the Fabrication of High-Purity Selenium Films for Efficient Indoor Photovoltaics.

The lanthanide contraction involves a reduction in atomic radius among f-block elements below the expected level. A similar contraction is observed in group-16 elements. The atomic radius of Se (117 pm) is slightly larger than that of S (104 pm) arising from the presence of d electrons, compared to the significant increase in atomic radius from O (73 pm) to S. This lanthanide-like contraction contributes to Se's robust oxidative resistance. Here we report a selective oxidation strategy utilizing Se's strong antioxidative property to remove coexisting narrow-bandgap Te impurities from Se feedstocks. This strategy selectively oxidizes volatile Te impurities into involatile TeO2 that remains in the evaporation source, while only volatile Se deposits onto the substrate during the thermal-evaporation deposition process. This enables the fabrication of high-purity Se films possessing a wide bandgap of 1.88 eV, ideally suited to the optimal bandgap for indoor photovoltaics (IPVs). The resulting Se photovoltaics exhibit an efficiency of 20.1% under 1000-lux indoor illumination, outperforming market-dominant amorphous silicon and all types of lead-free perovskite IPVs. Unencapsulated Se devices show no efficiency degradation after 20,000 hours of storage in ambient atmosphere.

Facile Hydrogen-Bonding Assisted Crystallization Modulation for Large-area High-quality CsPbI2 Br Films and Efficient Solar Cells.

The thermally stable inorganic cesium-based perovskites promise efficient and stable photovoltaics. Unfortunately, the strong ionic bonds lead to uncontrollable rapid crystallization, making it difficult in fabricating large-area black-phase film for photovoltaics. Herein, we developed a facile hydrogen-bonding assisted strategy for modulating the crystallization of CsPbI2 Br to achieve uniform large-area phase-pure films with much-reduced defects. The simple addition of methylamine acetate in precursors not only promotes the formation of intermediate phase via hydrogen bonding to circumvent the direct crystallization of CsPbI2 Br from ionic precursors but also widens the film processing window, thus enabling to fabricate large-area high-quality phase-pure CsPbI2 Br film under benign conditions. Combining with stable dopant-free poly(3-hexylthiophene), the CsPbI2 Br solar cells achieve the record-high efficiencies of 18.14 % and 16.46 % for 0.1 cm2 and 1 cm2 active area, respectively. The obtained high efficiency of 38.24 % under 1000 lux illumination suggests its potential in indoor photovoltaics for powering the Internet of Things, etc.

Colloidal Zeta Potential Modulation as a Handle to Control the Crystallization Kinetics of Tin Halide Perovskites for Photovoltaic Applications.

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

Unconventional hcp/fcc Nickel Heteronanocrystal with Asymmetric Convex Sites Boosts Hydrogen Oxidation.

Developing non-platinum group metal catalysts for the sluggish hydrogen oxidation reaction (HOR) is critical for alkaline fuel cells. To date, Ni-based materials are the most promising candidates but still suffer from insufficient performance. Herein, we report an unconventional hcp/fcc Ni (u-hcp/fcc Ni) heteronanocrystal with multiple epitaxial hcp/fcc heterointerfaces and coherent twin boundaries, generating rugged surfaces with plenty of asymmetric convex sites. Systematic analyses discover that such convex sites enable the adsorption of *H in unusual bridge positions with weakened binding energy, circumventing the over-strong *H adsorption on traditional hollow positions, and simultaneously stabilizing interfacial *H2O. It thus synergistically optimizes the HOR thermodynamic process as well as reduces the kinetic barrier of the rate-determining Volmer step. Consequently, the developed u-hcp/fcc Ni exhibits the top-rank alkaline HOR activity with a mass activity of 40.6 mA mgNi -1 (6.3 times higher than fcc Ni control) together with superior stability and high CO-tolerance. These results provide a paradigm for designing high-performance catalysts by shifting the adsorption state of intermediates through configuring surface sites.

Regioselective Multisite Atomic-Chlorine Passivation Enables Efficient and Stable Perovskite Solar Cells.

Passivating defects using organic halide salts, especially chlorides, is an effective method to improve power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) arising from the stronger Pb-Cl bonding than Pb-I and Pb-Br bonding. However, Cl- anions with a small radius are prone to incorporation into the perovskite lattice that distorts the lead halide octahedron, degrading the photovoltaic performance. Here, we substitute atomic-Cl-containing organic molecules for widely used ionic-Cl salts, which not only retain the efficient passivation by Cl but also prevent the incorporation of Cl into the bulk lattice, benefiting from the strong covalent bonding between Cl atoms and organic frameworks. We find that only when the distance of Cl atoms in single molecules matches well with the distance of halide ions in perovskites can such a configuration maximize the defect passivation. We thereby optimize the molecular configuration to enable multiple Cl atoms in an optimal spatial position to maximize their binding with surface defects. The resulting PSCs achieve a certified PCE of 25.02%, among the highest PCEs for PSCs, and retain 90% of their initial PCE after 500 h of continuous operation.

Unconventional Bilateral Compressive Strained Ni-Ir Interface Synergistically Accelerates Alkaline Hydrogen Oxidation.

The alkaline hydrogen oxidation reaction (HOR) involves the coupling of adsorbed hydrogen (Had) and hydroxyl (OHad) species and is thus orders of magnitude slower than that in acid media. According to the Sabatier principle, developing electrocatalysts with appropriate binding energy for both intermediates is vital to accelerating the HOR though it is still challenging. Herein, we propose an unconventional bilateral compressive strained Ni-Ir interface (Ni-Ir(BCS)) as efficient synergistic HOR sites. Density functional theory (DFT) simulations reveal that the bilateral compressive strain effect leads to the appropriate adsorption for both Had and OHad, enabling their coupling thermodynamically spontaneous and kinetically preferential. Such Ni-Ir(BCS) is experimentally achieved by embedding sub-nanometer Ir clusters in graphene-loaded high-density Ni nanocrystals (Ni-Ir(BCS)/G). As predicted, it exhibits a HOR mass activity of 7.95 and 2.88 times those of commercial Ir/C and Pt/C together with much enhanced CO tolerance, respectively, ranking among the most active state-of-the-art HOR catalysts. These results provide new insights into the rational design of advanced electrocatalysts involving coordinated adsorption and activation of multiple reactants.

Evolution of Stabilized 1T-MoS2 by Atomic-Interface Engineering of 2H-MoS2 /Fe-Nx towards Enhanced Sodium Ion Storage.

Metallic conductive 1T phase molybdenum sulfide (MoS2 ) has been identified as promising anode for sodium ion (Na+ ) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic-interface engineering is employed for constructing 2H-MoS2 layers assembled on single atomically dispersed Fe-N-C (SA Fe-N-C) anode material that boosts its reversible capacity. The work-function-driven-electron transfer occurs from SA Fe-N-C to 2H-MoS2 via the Fe-S bonds, which enhances the adsorption of Na+ by 2H-MoS2 , and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS2 with the ferromagnetic spin-polarization of SA Fe-N-C occurs during the sodiation/desodiation process, which significantly enhances the Na+ storage kinetics, and thus the 1T/2H MoS2 /SA Fe-N-C display a high electronic conductivity and a fast Na+ diffusion rate.

Probing the Synergistic Effects of Mg2+ on CO2 Reduction Reaction on CoPc by In Situ Electrochemical Scanning Tunneling Microscopy.

We report herein the in situ electrochemical scanning tunneling microscopy (ECSTM) study on the synergistic effect of Mg2+ in CO2 reduction reaction (CO2RR) catalyzed by cobalt phthalocyanine (CoPc). ECSTM measurement molecularly resolves the self-assembled CoPc monolayer on the Au(111) substrate. In the CO2 environment, high-contrast species are observed in the adlayer and assigned to the CO2 adsorption on CoPc. Furthermore, the contrast of the CO2-bound complex is higher in Mg2+-containing electrolytes than in Mg2+-free electrolytes, indicating the formation of the CoPc-CO2-Mg2+ complex. The surface coverage of adsorbed CO2 is positively correlated with the Mg2+ concentration as the additive in electrolytes up to a plateau of 30.8 ± 2.7% when c(Mg2+) > 30 mM. The potential step experiment indicates the higher CO2 adsorption dynamics in Mg2+-containing electrolytes than without Mg2+. The rate constants of CO2 adsorption and dissociation in different electrolytes are extracted from the data fitting of statistical results from in situ ECSTM experiments.

Evaluation of prognostic staging systems of multiple myeloma in the era of novel agents.

This study aimed to evaluate the existing staging systems for multiple myeloma (MM) in the real world. From January 2010 to June 2019, we retrospectively analyzed 859 newly diagnosed MM patients from two institutions. Clinical data including laboratory findings, imaging examinations and staging system were obtained by reviewing medical records. Survival distributions were estimated using the Kaplan-Meier curve analysis, and Cox proportional hazards model were used to identified risk factors. The overall survival (OS) of eligible patients was 61.0 months. The Revised International Staging System (R-ISS) had a larger receiver operating characteristic curve area (0.603) than both the International Staging System (0.573) and the Durie Salmon staging system (0.567). In the group receiving immunomodulatory agents-based regimens, the median OS was 92.0 months in R-ISS I, 63.0 months in R-ISS II and 18.0 months in R-ISS III (p < 0.0001). In the group receiving proteasome inhibitors-based regimens, the median OS was 102.0 months in R-ISS I, 63.0 months in R-ISS II and 22.0 months in R-ISS III (p < 0.0001). In different subgroups grouped according to age, hemoglobin (HGB), creatinine, and Ca, R-ISS also had a good stratification effect. Patients in R-ISS II, which accounted for 69.9% of all patients, were further analyzed. Univariate and multivariate Cox analyses revealed that age >65 years (p = 0.001), HGB < 100 g/L (p < 0.001), elevated LDH (p = 0.001), and Ca (p = 0.010) were independent predictors of worse prognosis within R-ISS II. To conclusion, R-ISS remains a valuable staging system in the real world of the novel drug era. However, patients classified as R-ISS II still have great heterogeneity.

Cobalt carbide nanoprisms for direct production of lower olefins from syngas.

Lower olefins-generally referring to ethylene, propylene and butylene-are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The 'Fischer-Tropsch to olefins' (FTO) process has long offered a way of producing lower olefins directly from syngas-a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

Interfacial Strain Engineering in Wide-Bandgap GeS Thin Films for Photovoltaics.

Wide-bandgap semiconductors exhibiting a bandgap of ∼1.7-1.9 eV have generated great interest recently due to their important applications in tandem solar cells as top cells and emerging indoor photovoltaics. However, concerns about the stability and toxicity especially in indoor application limit the choice of these materials. Here we report a new member of this family, germanium monosulfide (GeS); this material displays a wide bandgap of 1.7 eV, nontoxic and earth-abundant constituents, and high stability. We find that the little success of GeS solar cells to date is primarily attributed to the challenge in fabricating high-quality polycrystalline GeS films, wherein the high thermal expansion coefficient (α = 3.1 × 10-5 K-1) combined with high crystallization temperature (375 °C) of GeS induces large tensile strain in the GeS film that peels off GeS from the substrate. By introducing a high-α buffer layer between GeS and substrate, we achieve a high-quality polycrystalline GeS thin film that compactly adheres to substrate with no voids. Solar cells fabricated by these GeS films show a power conversion efficiency of 1.36% under AM 1.5G illumination (100 mW cm-2). The unencapsulated devices are stable when stored in ambient atmosphere for 1500 h. Their efficiencies further increase to 3.6% under indoor illumination of 1000 lux.

Multi-Phase Heterostructure of CoNiP/Cox P for Enhanced Hydrogen Evolution Under Alkaline and Seawater Conditions by Promoting H2 O Dissociation.

Hydrogen evolution reaction (HER) is a key step for electrochemical energy conversion and storage. Developing well defined nanostructures as noble-metal-free electrocatalysts for HER is promising for the application of hydrogen technology. Herein, it is reported that 3D porous hierarchical CoNiP/Cox P multi-phase heterostructure on Ni foam via an electrodeposition method followed by phosphorization exhibits ultra-highly catalytic activity for HER. The optimized CoNiP/Cox P multi-phase heterostructure achieves an excellent HER performance with an ultralow overpotential of 36 mV at 10 mA cm-2 , superior to commercial Pt/C. Importantly, the multi-phase heterostructure shows exceptional stability as confirmed by the long-term potential cycles (30,000 cycles) and extended electrocatalysis (up to 500 h) in alkaline solution and natural seawater. Experimental characterizations and DFT calculations demonstrate that the strong electronic interaction at the heterointerface of CoNiP/CoP is achieved via the electron transfer from CoNiP to the heterointerface, which directly promotes the dissociation of water at heterointerface and desorption of hydrogen on CoNiP. These findings may provide deep understanding on the HER mechanism of heterostructure electrocatalysts and guidance on the design of earth-abundant, cost-effective electrocatalysts with superior HER activity for practical applications.