Long-Chain Molecular Crystals Antimony(III) Alkanethiolates Sb(SCnH2n+1)3 (n ≥ 12): Synthesis, Crystal and Electronic Structures, and Supramolecular Self-Assembly via Secondary Interactions.

Currently, there is not much success in solving the molecular and crystal structures of long-chain metal alkanethiolate complexes [M(SCnH2n+1)m] at the atomic level. Taking Sb(SC16H33)3 (1) as an example, we herein disclose the structural characteristics of long-chain trivalent antimony(III) alkanethiolates Sb(SCnH2n+1)3 (n ≥ 12) by single-crystal X-ray crystallography. Specifically, the Sb atom is three-coordinated by alkanethiolate ligands and a slightly distorted triangular pyramid SbS3 core is formed owing to the unique intramolecular stereochemistry of three alkyl chains, namely, two of them almost parallel aligning and the third chain extending alone around the SbS3 core. We further determine the conformation, spatial orientation and packing density of alkyl chains in 1 along with a comparison to those in other long-chain crystalline systems, and reveal the roles of intermolecular van der Waals and Sb···S secondary interactions in molecular self-assembly, which enables 1 to be a layer-structured molecular crystal with a monoclinic P21/c unit cell. The band structures and the atomic orbital contributions to the valence band maximum and conduction band minimum for 1 have also been evaluated by DFT calculations and rationally correlated with its optical absorption property. This study will help understand and discover new structures and structure-property relations of long-chain chemical systems.

A Regenerable Bi-based Catalyst for Efficient and Stable Electrochemical CO2 Reduction to Formate at Industrial Current Densities.

Renewable electricity shows immense potential as a driving force for the carbon dioxide reduction reaction (CO2RR) in production of formate (HCOO-) at industrial current density, providing a promising path for value-added chemicals and chemical manufacturing. However, achieving high selectivity and stable production of HCOO- at industrial current density remains a challenge. Here, we present a robust Bi0.6Cu0.4 NSs catalyst capable of regenerating necessary catalytic core (Bi-O) through cyclic voltammetry (CV) treatment. Notably, at 260 mA cm-2, faradaic efficiency of HCOO- reaches an exceptional selectivity to 99.23%, maintaining above 90% even after 400h, which is longest reaction time reported at industrial current density. Furthermore, in stability test, the catalyst was constructed by CV reconstruction to achieve stable and efficient production of HCOO-. In 20h reaction test, the catalyst has a rate of HCOO- production of 13.24mmol m-2 s-1, a HCOO- concentration of 1.91mol L-1, and an energy consumption of 129.80kWh kmol-1. In-situ Raman spectroscopy reveals the formation of Bi-O structure during the gradual transformation of catalyst from Bi0.6Cu0.4 NBs to Bi0.6Cu0.4 NSs. Theoretical studies highlight the pivotal role of Bi-O structure in modifying the adsorption behavior of reaction intermediates, which further reduces energy barrier for *OCHO conversion in CO2RR.

Clustering-Resistant Cu Single Atoms on Porous Au Nanoparticles Supported by TiO2 for Sustainable Photoconversion of CO2 into CH4.

Photocatalysts based on single atoms (SAs) modification can lead to unprecedented reactivity with recent advances. However, the deactivation of SAs-modified photocatalysts remains a critical challenge in the field of photocatalytic CO2 reduction. In this study, we unveil the detrimental effect of CO intermediates on Cu single atoms (Cu-SAs) during photocatalytic CO2 reduction, leading to clustering and deactivation on TiO2. To address this, we developed a novel Cu-SAs anchored on Au porous nanoparticles (CuAu-SAPNPs-TiO2) via a vectored etching approach. This system not only enhances CH4 production with a rate of 748.8 µmol ⋅ g-1 ⋅ h-1 and 93.1 % selectivity but also mitigates Cu-SAs clustering, maintaining stability over 7 days. This sustained high performance, despite the exceptionally high efficiency and selectivity in CH4 production, highlights the CuAu-SAPNPs-TiO2 overarching superior photocatalytic properties. Consequently, this work underscores the potential of tailored SAs-based systems for efficient and durable CO2 reduction by reshaping surface adsorption dynamics and optimizing the thermodynamic behavior of the SAs.

Regulating Complex Transition Metal Oxyhydroxides Using Ni3S2: 3D NiCoFe(oxy)hydroxide/Ni3S2/Ni Foam for an Efficient Alkaline Oxygen Evolution Reaction.

In electrochemical decomposition of water, the slow kinetics of the anodic oxygen evolution reaction (OER) is a challenge for efficient hydrogen production. Heterointerface engineering is a desirable way to rationally design electrocatalysts for the OER. Herein, we designed and fabricated a nanoparticle flower-like NiCoFe(oxy)hydroxide catalyst in situ grown on the surface of Ni3S2/NF to construct a heterojunction via combining hydrothermal and electrodeposition methods. The heterostructure exhibits a smaller overpotential of 254 mV at a large current density of 100 mA cm-2 in 1 M KOH than that of pristine NiCoFeOxHy/NF (356 mV) and Ni3S2/NF (471 mV). Tafel and electrochemical impedance spectroscopy further showed a favorable kinetics during electrolysis. The role of the substrate Ni3S2 was explored via density functional theory calculations. Our calculations found that SOx on the Ni3S2 surface is a strong nucleophilic group and the synergy effect between Fe and SOx could break *OOH to reduce the Gibbs energy. We also found that the contribution of SOx in sulfates to the OER activity could be negligible. Furthermore, a series of comparative samples were prepared to test this synergy effect. Our experiments indicated that the introduction of Ni3S2 is beneficial. The present contribution provides an important helpful insight into the design and fabrication of novel and highly efficient heterostructure electrocatalysts by introducing nucleophilic groups at the interface.

Crystalline-Dependent Discharge Process of Locally Enhanced Electrooxidation Activity on Ni2P.

The state-of-the-art transition-based electrocatalysts in alkaline media generally suffer from unavoidable surface reconstruction during oxygen evolution reaction measurements, leading to the collapse and loss of the crystalline matrix. Low potential discharge offers a gentle way for surface reconstruction and thus realizes the manipulation of the real active site. Nevertheless, the absence of a fundamental understanding focus on this discharge region renders the functional phase, either the crystalline or amorphous matrix, for the controllable reconstruction still undecidable. Herein, we report a scenario to employ different crystalline matrices as electrocatalysts for discharge region reconstruction. The representative low crystalline Ni2P (LC-Ni2P) possesses a relatively weak surface structure compared with highly crystalline or amorphous Ni2P (HC-Ni2P or A-Ni2P), which contributes abundant oxygen vacancies after the discharge process. The fast discharge behavior of LC-Ni2P leads to the uniform distribution of these vacancies and thus endows the inner interface with reactant activating functionality. A high increase in current density of 36.7% is achieved at 2.32 V (vs RHE) for the LC-Ni2P electrode. The understanding of the discharge behavior in this study, on different crystalline matrices, presents insights into the establishment of controllable surface reconstruction for an effective oxygen evolution reaction.

Polymer Photocatalysts Containing Segregated π-Conjugation Units with Electron-Trap Activity for Efficient Natural-light-driven Bacterial Inactivation.

Development of highly efficient and metal-free photocatalysts for bacterial inactivation under natural light is a major challenge in photocatalytic antibiosis. Herein, we developed an acidizing solvent-thermal approach for inserting a non-conjugated ethylenediamine segment into the conjugated planes of 3,4,9,10-perylene tetracarboxylic anhydride to generate a photocatalyst containing segregated π-conjugation units (EDA-PTCDA). Under natural light, EDA-PTCDA achieved 99.9 % inactivation of Escherichia coli and Staphylococcus aureus (60 and 45 min), which is the highest efficiency among all the natural light antibacterial reports. The difference in the surface potential and excited charge density corroborated the possibility of a built-in electron-trap effect of the non-conjugated segments of EDA-PTCDA, thus forming a highly active EDA-PTDA/bacteria interface. In addition, EDA-PTCDA exhibited negligible toxicity and damage to normal tissue cells. This catalyst provides a new opportunity for photocatalytic antibiosis under natural light conditions.

Self-supported nickel sulfide derived from nickel foam for hydrogen evolution and oxygen evolution reaction: effect of crystal phase switching.

Designing and fabricating economically viable, high active and stable electrocatalysts play an important role for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Crystal phase is the crucial factor that governs the electrochemical property and electrocatalytic reaction pathways. Here, a one-step nickel foam derived sulfidation method was presented to synthesize self-supported NiS2 and Ni3S2. The crystal phase-dependent chemical properties related to electrocatalytic behavior were evaluated by a series of advanced characterization and density functional theory calculations. Overall, the self-supported Ni3S2 shows high electrochemical activity towards both HER and OER in alkaline conditions, which afford the current density of 10 mA cm-2 with overpotentials of 245 mV for OER and 123 mV for HER, respectively. When employed the self-supported Ni3S2 as the bifunctional electrocatalysts for overall water splitting, the entire device provides the current density of 10 mA cm-2 at 1.61 V. These results indicate that the electrocatalytic properties can be exert greater improved by controlling the crystal phase, offering the prospect for advanced materials design and development.

Discharge-Induced Enhancement of the Oxygen Evolution Reaction.

The fundamental understanding of the surface reconstruction induced by the applied potential is of great significance for enhancing the oxygen evolution reaction (OER). Here, we show that a previously overlooked discharge current in the low applied potential region also leads to in situ electrochemical activation of a nitrogen-doped nickel oxyhydroxide surface. We exploit the fact that doping of heteroatoms weakens the surface structure, and hence, a weak discharge current originating from the capacitive nature of nickel oxyhydroxide has a strong structure-reforming ability to promote the formation of nitrogen and oxygen vacancies. The current density at 1.4 V (vs. Hg/HgO) can dramatically increase by as much as 31.3 % after discharge in the low applied potential region. This work provides insight into in situ enhancement of the OER and suggests that the low applied potential region must be a primary consideration in evaluating the origin of the activity of electrocatalysts.

A NIR-Responsive Phytic Acid Nickel Biomimetic Complex Anchored on Carbon Nitride for Highly Efficient Solar Hydrogen Production.

A challenge in photocatalysis consists in improving the efficiency by harnessing a large portion of the solar spectrum. We report the design and realization of a robust molecular-semiconductor photocatalytic system (MSPS) consisting of an earth-abundant phytic acid nickel (PA-Ni) biomimetic complex and polymeric carbon nitride (PCN). The MSPS exhibits an outstanding activity at λ=940 nm with high apparent quantum efficiency (AQE) of 2.8 %, particularly λ>900 nm, as it outperforms all reported state-of-the-art near-infrared (NIR) hybrid photocatalysts without adding any noble metals. The optimum hydrogen (H2 ) production activity was about 52 and 64 times higher with respect to its pristine counterpart under the AM 1.5 G and visible irradiation, respectively, being equivalent to the platinum-assisted PCN. This work sheds light on feasible avenues to prepare highly active, stable, cheap NIR-harvesting photosystems toward sustainable and scalable solar-to-H2 production.

Ink-Assisted Synthetic Strategy for Stable and Advanced Composite Electrocatalysts with Single Fe Sites.

The oxygen evolution reaction is critical to the efficiency of many energy technologies that store renewable electricity in chemical form. However, the rational design of high-performance and stable catalysts to drive this reaction remains a formidable challenge. Here, a facile ink-assisted strategy to construct a series of stable and advanced composite electrocatalysts with single Fe sites for permitting seriously improved performance characteristics is reported. As revealed by a suit of characterization techniques and theoretical methods, the improved electrocatalytic performance and stability can be attributed to the unique coordination states of Fe in the form of distorted FeO4 C and the interfacial effect in the composite system that optimize and stabilize single Fe sites in changing to better configurations for intermediates adsorption. The findings provide a novel strategy to in-depth understanding of practical guidelines for the electrocatalyst design for energy conversion devices.

Pressure-Induced Superconductivity and Flattened Se6 Rings in the Wide Band Gap Semiconductor Cu2I2Se6.

The two major classes of unconventional superconductors, cuprates and Fe-based superconductors, have magnetic parent compounds, are layered, and generally feature square-lattice symmetry. We report the discovery of pressure-induced superconductivity in a nonmagnetic and wide band gap 1.95 eV semiconductor, Cu2I2Se6, with a unique anisotropic structure composed of two types of distinct molecules: Se6 rings and Cu2I2 dimers, which are linked in a three-dimensional framework. Cu2I2Se6 exhibits a concurrent pressure-induced metallization and superconductivity at ∼21.0 GPa with critical temperature (Tc) of ∼2.8 K. The Tc monotonically increases within the range of our study reaching ∼9.0 K around 41.0 GPa. These observations coincide with unprecedented chair-to-planar conformational changes of Se6 rings, an abrupt decrease along the c-axis, and negative compression within the ab plane during the phase transition. DFT calculations demonstrate that the flattened Se6 rings within the CuSe layer create a high density of states at the Fermi level. The unique structural features of Cu2I2Se6 imply that superconductivity may emerge in anisotropic Cu-containing materials without square-lattice geometry and magnetic order in the parent compound.

Ionothermal Synthesis of Metal Chalcogenides M2Ag3Sb3S7 (M = Rb, Cs) Displaying Nonlinear Optical Activity in the Infrared Region.

Two interesting non-centrosymmetric metal chalcogenides, Rb2Ag3Sb3S7 and Cs2Ag3Sb3S7, were synthesized by an ionothermal approach. Crystals of compounds Rb2Ag3Sb3S7 and Cs2Ag3Sb3S7 possess isomorphic configuration, consisting of two-dimensional (2D) anionic networks ∞[Ag3Sb3S7]2-, which are split by alkali-metal M+ cations. The band gaps are 2.11 and 2.02 eV for Rb2Ag3Sb3S7 and Cs2Ag3Sb3S7, respectively. Second-harmonic generation (SHG) studies revealed that Rb2Ag3Sb3S7 affords a powder SHG performance of ∼0.5 × AgGaS2 with type-I phase matching, while Cs2Ag3Sb3S7 shows a slightly stronger SHG performance of ∼0.6 × AgGaS2 with type-I phase matching. Both compounds possess broad transparency ranges (∼0.6-20 µm), suggesting their potential as infrared (IR) nonlinear optical (NLO) materials. The laser damage thresholds (LDTs) of both Rb2Ag3Sb3S7 and Cs2Ag3Sb3S7 are about 2.3 × AgGaS2. The calculated birefringence indexes Δn are 0.1885 and 0.1944 at 1.064 µm, respectively, which are sufficiently large enough to achieve phase matching. Theoretical studies using density functional theory have been implemented to further understand the relationship between their NLO properties and band structures.

Facile Syntheses of Ba2[B4O7(OH)2] and Na[B5O7(OH)2](H2O) Borate Salts Exhibiting Nonlinear Optical Activity in the Ultraviolet.

Two novel noncentrosymmetric metal borates, Ba2[B4O7(OH)2] (1) and Na[B5O7(OH)2](H2O) (2), have been obtained by hydrothermal and surfactant-thermal means. Compound 1 consists of novel one-dimensional borate chains formed by B3O9 and B3O8 rings, assembled into a three-dimensional (3D) framework by Ba2+ cations. The structure of 2 exhibits double-helical chains constructed from B5O10 primary building units, which are interconnected via Na+ cations and H-bonding interactions to generate a 3D framework. Second-harmonic-generation (SHG) measurements show that 1 shows a phase-matching powder SHG response of ∼2.2 × KH2PO4 (KDP), while 2 exhibits a weak SHG response. The cutoff edges of 1 and 2 are ∼242 and ∼221 nm, respectively, which suggests that they are potential ultraviolet nonlinear optical (NLO) materials. Band structures and NLO properties have also been theoretically studied.

Dopamine-modified cobalt spinel nanoparticles as an active catalyst for the acidic oxygen evolution reaction.

The development of efficient non-noble metal electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions remains a critical challenge. Herein, we report a N-doped carbonaceous component-engineered Co3O4 (NCEC) catalyst synthesized via the sol-gel method. Dopamine hydrochloride (DA)-derived nitrogen-doped carbonaceous components were found to boost the OER performance of Co3O4. The optimized catalyst can reach an overpotential as low as 330 mV in 1 M H2SO4 at a current density of 10 mA cm-2 and maintains a good long-term stability of 60 hours. In particular, we found that the thermodynamic overpotential was inversely proportional to the content of oxidized N and pyridinic N, whereas it was directly proportional to the pyrrolic-N content. Our experiments and density functional theory (DFT) calculations confirm that the optimized catalyst exhibits enhanced charge transfer and the oxidized N species on Co3O4 is responsible for the high catalytic activity. Our study suggests that the performance of NCEC in acidic media can be further optimized by enhancing the content of oxidized N species.

Well-defined diatomic catalysis for photosynthesis of C2H4 from CO2.

Owing to the specific electronic-redistribution and spatial proximity, diatomic catalysts (DACs) have been identified as principal interest for efficient photoconversion of CO2 into C2H4. However, the predominant bottom-up strategy for DACs synthesis has critically constrained the development of highly ordered DACs due to the random distribution of heteronuclear atoms, which hinders the optimization of catalytic performance and the exploration of actual reaction mechanism. Here, an up-bottom ion-cutting architecture is proposed to fabricate the well-defined DACs, and the superior spatial proximity of CuAu diatomics (DAs) decorated TiO2 (CuAu-DAs-TiO2) is successfully constructed due to the compact heteroatomic spacing (2-3 Å). Owing to the profoundly low C-C coupling energy barrier of CuAu-DAs-TiO2, a considerable C2H4 production with superior sustainability is achieved. Our discovery inspires a novel up-bottom strategy for the fabrication of well-defined DACs to motivate optimization of catalytic performance and distinct deduction of heteroatom synergistically catalytic mechanism.

Modulating Electron Transfer between Pt and MOF Support through Pd Doping Promotes Nanozyme Catalytic Efficiency.

Electron transfer is considered to be a typical parameter that affects the catalytic activity of nanozymes. However, there is still controversy regarding whether higher or lower electron transfer numbers are beneficial for improving the catalytic activity of nanozymes. To address this issue, we propose the introduction of Pd doping as an important electron regulation strategy to tune electron transfer between Pt and ZIF-8 carriers (PtxPd1@ZIF-8). We observe a volcano-shaped relationship between the electron transfer number and catalytic activity, reaching its peak at Pt4Pd1@ZIF-8. Mechanism studies indicate that as the electron transfer number from Pt to ZIF-8 carriers increases, the d-band center of the active site Pt increases, reducing the occupancy of antibonding states and enhancing the adsorption capacity of the key intermediate (*O). However, a further increase in the adsorption of *O energy makes it difficult to desorb and participate in the next reaction, thus exhibiting volcanic activity. The optimized Pt4Pd1@ZIF-8 nanozyme is applied to develop an immunoassay for the detection of zearalenone, achieving a detection limit of 0.01 µg/L, which is 6 times higher than that of the traditional enzyme-linked immunosorbent assay. This work not only reveals the potential regulatory mechanism of electron transfer on the catalytic activity of nanozymes but also improves the performance of nanozyme-based biosensors.

Crystalline-dependent surface reconstruction at low applied potential region for enhanced oxygen evolution reaction.

Alkaline water electrolysis is apreferred technology for large-scale green hydrogen production. For most active transition metal-based catalysts during anodic oxygen evolution reaction (OER), the atomic structure of the anodic catalysts' surface often undergoes reconstruction to optimize the reaction path and enhance their catalytic activity. The design and maintenance of highly active sites during this reconstruction process remain critical and challenging for most OER catalysts. In this study, we explored the effects of crystal structures in pre-catalysts on surface reconstruction at low applied potential. Through experimental observation and theoretical calculation, we found out that catalysts with specific crystal structures exhibit superior surface remodeling ability, which enables them to better adapt to the conditions of the oxygen evolution reaction and achieve efficient catalysis. The discharge process enables the formation of abundant phosphorus vacancies on the surface, which in turn affects the efficiency of the entire oxygen evolution reaction. The optimized crystal structure of the catalyst results in an increase as high as 58.5 mA/cm2 for Ni5P4, which is twice as high as that observed for Ni2P. These results provide essential theoretical foundations and technical guidance for designing more efficient catalysts for oxygen evolution reactions.

Designing 2D carbon dot nanoreactors for alcohol oxidation coupled with hydrogen evolution.

The coupled green energy and chemical production by photocatalysis represents a promising sustainable pathway, which poses great challenges for the multifunction integration of catalytic systems. Here we show a promising green photocatalyst design using Cu-ZnIn2S4 nanosheets and carbon dots as building units, which enables the integration of reaction, mass transfer, and separation functions in the nano-space, mimicking a nanoreactor. This function integration results in great activity promotion for benzyl alcohol oxidation coupled H2 production, with H2/benzaldehyde production rates of 45.95/46.47 mmol g-1 h-1, 36.87 and 36.73 times to pure ZnIn2S4, respectively, owning to the enhanced charge accumulation and mass transfer according to in-situ spectroscopies and computational simulations of the built-in electrical field. Near-unity selectivity of benzaldehyde is achieved via the effective separation enabled by the Cu(II)-mediated conformation flipping of the intermediates and subsequent π-π conjugation. This work demonstrates an inspiring proof-of-concept nanoreactor design of photocatalysts for coupled sustainable systems.

Cations induced in situ electrochemical amorphization for enhanced oxygen evolution reaction.

Surface reconstruction is widely existed on the surface of transition metal-based catalysts under operando oxygen evolution reaction (OER) condition. The design and optimize the reconstruction process are essential to achieve high electrochemical active surface and thus facilitate the reaction kinetics, whereas still challenge. Herein, we exploit electrolyte engineering to regulate reconstruction on the surface of Fe2O3 catalysts under operando OER conditions. The intentional added cations in electrolyte can participate the reconstruction process and realize a desirable crystalline to amorphous structure conversion, contributing abundant well-defined active sites. Spectroscopic measurements and density functional theory calculation provide insight into the underlying role of amorphous structure for electron transfer, mass transport, and intermediate adsorption. With the assistant of Co2+ cations, the enhanced current density as large as 17.9 % can be achieved at 2.32 V (vs RHE). The present results indicate the potential of electrolyte engineering for regulating the reconstruction process and provide a generalized in-situ strategy for advanced catalysts design.

Structural, electronic, and linear optical properties of organic photovoltaic PBTTT-C14 crystal.

Poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (PBTTT-C14) is an important electro-optical polymer, whose three-dimensional crystal structure is somewhat ambiguous and the fundamental electronic and linear optical properties are not well known. We carried out first-principles calculations to model the crystal structure and to study the effect of side-chains on the physical structure and electronic properties. Our calculations suggest that the patterns of side-chain has little direct effect on the valence band maximum and conduction band minimum but they do have impact on the bandgap through changing the π-π stacking distance. By examining the band structure and wave functions, we conclude that the fundamental bandgap of the PBTTT-C14 crystal is determined by the conduction band energy at the Q point. The calculations indicate that the bandgap of PBTTT-C14 crystal may be tunable by introducing different side-chains. The significant peak in the imaginary part of the dielectric function arises from transitions along the polymer backbone axis, as determined by the critical-point analysis and the large optical transition matrix elements in the direction of the backbone.