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Chemical doping is verified to be a promising strategy to regulate local electron distribution and further promote the poor intrinsic catalytic activity of graphdiyne. However, the current doping approach still faces problems such as precise doping for creating active sites and the destruction of graphdiyne skeleton calling for high temperature. Here, we achieved charge redistribution on graphdiyne surface through molecule functionalization. A p-type molecule–F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was introduced and the site-defined functionalization was accomplished. Theoretical calculations showed that the charge transfer ability is improved and graphdiyne becomes positively charged. The oxygen reduction electrocatalysis was conducted as a proof of principle, where the electronic states of sp hybridized C active site was tuned toward favorable reaction intermediates’ adsorption. Such work from both theoretical prediction and experimental validation, found that molecule functionalization is effective to promote the electrocatalytic oxygen reduction, which creates new possibilities for graphdiyne’s applications in different electrochemical reactions.

Electrochemical CO2 reduction (CO2R) is a sustainable way of producing carbon-neutral fuels, yet the efficiency is limited by its sluggish kinetics and complex reaction pathways. Developing active, selective, and stable CO2R electrocatalysts is challenging and entails intelligent material structure design and tailoring. Here we show a graphdiyne/graphene (GDY/G) heterostructure as a 2D conductive scaffold to anchor monodispersed cobalt phthalocyanine (CoPc) and reduce CO2 with an appreciable activity, selectivity, and durability. Advanced characterizations, e.g., synchrotron-based X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculation disclose that the strong electronic coupling between GDY and CoPc, together with the high surface area, abundant reactive centers, and electron conductivity provided by graphene, synergistically contribute to this distinguished electrocatalytic performance. Electrochemical measurements revealed a high FECO of 96% at a partial current density of 12 mA cm-2 in a H-cell and an FECO of 97% at 100 mA cm-2 in a liquid flow cell, along with a durability over 24 h. The per-site turnover frequency of CoPc reaches 37 s-1 at -1.0 V vs RHE, outperforming most of the reported phthalocyanine- and porphyrin-based electrocatalysts. The usage of the GDY/G heterostructure as a scaffold can be further extended to other organometallic complexes beyond CoPc. Our findings lend credence to the prospect of the GDY/G hybrid contributing to the design of single-molecule dispersed CO2R catalysts for sustainable energy conversion.

Understanding the interactions between metallic lithium (Li) and the anchoring sites/groups is essential for the design of stable host materials and artificial interphases in lithium metal batteries (LMBs). Here, we investigate the interactions of lithium with the polar organic functional groups in copper(II) hexadecafluorophthalocyanine (F16CuPc) and copper(II) phthalocyanine (CuPc) through the combination of in-situ X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based near-edge X-ray absorption fine structures (NEXAFS), and density functional theory (DFT) calculations. It is revealed that the highly polar C-F bonds can anchor the Li atom via ionic Li-F interaction around the outer aza bridge N atoms in F16CuPc, while Li tends to interact with the inner pyrrolic N atoms around the central Cu in CuPc. The central Cu(II) ions in both molecules are reduced to Cu(I) upon interaction with Li. Electrons are transferred from Li to the lowest unoccupied molecular orbitals (LUMO) of both F16CuPc and CuPc molecules, as revealed by the UPS and NEXAFS measurements. Our systematic study can shed light on the design of anode materials by adding polar functional groups for applications in lithium metal batteries (LMBs). Ministry of Education (MOE) The authors acknowledge the financial support from the Natural Science Foundation of China (U2032147), Singapore MOE Tier II grant R143-000-A29-112, and Academic Research Fund Tie I grant RG104/18.

Summary Aqueous electrochemical CO2 reduction (CO2R) on Cu can generate a variety of valuable fuels, yet challenges remain in the improvement of electrosynthesis pathways for highly selective fuel production. Mechanistically, understanding CO2R on Cu, particularly identifying the product-specific active sites, is crucial. Herein, we rationally designed and fabricated nine large-area single-crystal Cu foils with various surface orientations as electrocatalysts and identified the voltage- and facet-dependent CO2R selectivities. Operando grazing incidence X-ray diffraction (GIXRD) and electron back-scattered diffraction (EBSD) were applied to track the top-surface reconstructions of Cu, and we correlate the structural evolution with the change of product selectivities. We extracted three distinct structural descriptors, including crystal facet, atomic coordination number, and step-terrace angle, to reveal the intrinsic structure-function relationships and uniquely identify the specific product-producing sites for CO2R. Our work guides the rational design of Cu-based CO2R electrocatalysts and, more importantly, establishes a paradigm to understand the structure-function correlation in catalysis.

Electrocatalytic dinitrogen reduction reaction (N2RR) is an emerging route for ammonia synthesis at ambient conditions. Albeit the “π back-donation” process enables N2RR activity on transition metals with empty d-orbitals, given its dilemma in overcoming hydrogen evolution reaction (HER) competition, exploring p-block-element-based catalysts with relatively inferior HER activity is achievable for high selectivity. The challenge lies in designing rational structure to improve N2RR activity. Here, we synergistically integrate oxygen vacancy (VO) with hydroxyl on Bi4O5I2 (VO-Bi4O5I2-OH), which render this p-block-element-based material active to mimic “π back-donation” behavior because of sufficient vacant orbitals. In neutral media, the electrocatalytic N2RR performance of VO-Bi4O5I2-OH in terms of splendid faradic efficiency (32.4%) is superior to most of the prior reports using p-block-element-based catalysts. Our findings show a new strategy toward standout N2RR activity, which holds great potential in exploiting other p-block-element-based electrocatalysts. Ministry of Education (MOE) Accepted version Q.Y. acknowledges the funding support from Singapore MOE AcRF Tier 1 Grant Nos. RG113/15 and 2016-T1-002-065, and Tier 2 under Grant Nos. 2017-T2-2-069 and 2018-T2-01-010. The authors greatly thank the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore, for using their TEM, SEM, and XRD equipment.

In nanoparticle self-assembly, the current lack of strategy to modulate orientational order creates challenges in isolating large-area plastic crystals. Here, we achieve two orientationally distinct supercrystals using one nanoparticle shape, including plastic crystals and uniform metacrystals. Our approach integrates multi-faceted Archimedean polyhedra with molecular-level surface polymeric interactions to tune nanoparticle orientational order during self-assembly. Experiments and simulations show that coiled surface polymer chains limit interparticle interactions, creating various geometrical configurations among Archimedean polyhedra to form plastic crystals. In contrast, brush-like polymer chains enable molecular interdigitation between neighboring particles, favoring consistent particle configurations and result in uniform metacrystals. Our strategy enhances supercrystal diversity for polyhedra comprising multiple nondegenerate facets.

Organic anode materials have attracted considerable interest owing to their high tunability by adopting various active functional groups. However, the interaction mechanisms between the alkali metals and the active functional groups in host materials have been rarely studied systematically. Here, a widely used organic semiconductor of perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) was selected as a model system to investigate how alkali metals interact with imide functional groups and induce changes in chemical and electronic structures of PTCDI. The interaction at the alkali/PTCDI interface was probed by in-situ X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based near edge X-ray absorption fine structure (NEXAFS), and corroborated by density functional theory (DFT) calculations. Our results indicate that the alkali metal replaces the hydrogen atoms in the imide group and interact with the imide nitrogen of PTCDI. Electron transfer induced gap states and downward band-bending like effects are identified on the alkali-deposited PTCDI surface. It was found that Na shows a stronger electron transfer effect than Li. Such a model study of alkali insertion/intercalation in PTCDI gives insights for the exploration of the potential host materials for alkali storage applications.

Graphene oxide/silica (GO/SiO2) multilayers could be successfully deposited onto a carbon fiber (CF) surface via a convenient and efficient layer-by-layer (LbL) self-assembly approach. It is possib...

Ion adsorption inside electrified carbon micropores is pivotal for the operation of supercapacitors. Depending on the electrolyte, two main mechanisms have been identified so far, the desolvation of ions in solvents and the formation of superionic states in ionic liquids. Here, it is shown that upon confinement inside negatively charged micropores, transition-metal cations dissolved in water associate to form oligomer species. They are identified using in situ X-ray absorption spectroscopy. The cations associate one with each other via hydroxo bridging, forming ionic oligomers under the synergic effect of spatial confinement and Coulombic screening. The oligomers display sluggish dissociation kinetics and accumulate upon cycling, which leads to supercapacitor capacitance fading. They may be dissolved by applying a positive potential, so an intermittent reverse cycling strategy is proposed to periodically evacuate micropores and revivify the capacitance. These results reveal new insights into ion adsorption and structural evolution with their effects on the electrochemical performance, providing guidelines for designing advanced supercapacitors. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by Singapore Ministry of Education Academic Research Fund Tier 2 (Grant No. MOE-T2EP10220-0005), Academic Research Fund Tier 1 (Grant No. RG104/18), Singapore National Research Foundation (Nanomaterials for Energy and Water Management CREATE Programme), Energy Innovation Research Programme (EIRP) (Grant No. NRF2015EWT-EIRP002-008), and French National Research Agency (Labex STORE-EX, Grant No. ANR-10-LABX-0076).

Free-standing metallic nanohole arrays (NAs) exhibit extraordinary benefits in combining nanofluidics and plasmonics in a single platform for flow-through plasmofluidic sensing. However, the sensing performance of NAs is usually limited by the low quality factor of the transmission peak, resulting from strong radiative damping. Here, we demonstrate a concept for high-performance plasmofluidic sensing based on the subradiant mode in free-standing metallic NAs. We show that the subradiant mode exhibits a good spectral resolution only when the dielectric media at the upper and lower metal surfaces are symmetric; otherwise, it easily emerges into other features present in the same spectral region. Therefore, free-standing NAs are particularly suitable for highly sensitive microfluidic sensing based on the subradiant mode. In addition, the subradiant mode exhibits a highly tunable frequency and refractive index sensitivity (RIS), depending strongly on the film thickness and periodicity and weakly on the hole r...

Surface defects in semiconductors have a significant role to tune the photocatalytic reactions. However, the dominant studied defect type is oxygen vacancy, and metal cation vacancies are seldom ex...

Inorganic single crystals with anisotropic structures usually suffer from high brittleness and stiffness. Flexible polymers are used to replace inorganic crystals, but the hot-stretching-induced orientation process is tedious, and oriented molecular chains tend to revert to random coils during aging. To overcome these obstacles and using the similarities between sub-1 nm nanowires (NWs) and linear polymers, we successfully fabricated anisotropic, transparent, flexible, and stable (ATFS) NW films with great potential for optical applications through a wet-spinning method. The NW films show birefringence, and their birefractive index is higher than that of many polymers. They also showed polarized absorption of UV light and anisotropic scattering of visible light. The integrated films composed of NWs and quantum dots showed good fluorescence polarization. The tedious synthesis of quantum rods and fabrication of oriented polymer films can thus be avoided.

The charge-transport properties of charge-transfer complexes (CTCs) play a key role in the potential applications toward novel optoelectronic devices. We have systematically studied the charge-transport properties of perylene-F4TCNQ CTCs with different stoichiometric ratios by first-principles calculations. Our calculated results showed that 1P1F4 (perylene-F4TCNQ 1:1) exhibits a higher charge-carrier mobility than 3P2F4 (perylene-F4TCNQ 3:2) due to the strong interlayer interactions in 3P2F4. Compared with the perylene-TCNQ CTC, the higher charge-carrier mobility in perylene-F4TCNQ CTC indicates that introducing fluorine atoms can enhance the charge-carrier mobility due to stronger intermolecular interactions. More importantly, the experimental measurements carried out with 1P1F4- and 3P2F4-based field-effect transistors are consistent with the theoretical predictions. Our study reveals that tuning the charge-transport properties in CTCs by controlling the stoichiometry between the donor and acceptor is a promising strategy in accelerating the development of high-performance organic electronic materials.

Exploring new hybridized catalysts for synergistically promoting the photocatalytic efficiency hold great challenges in solar-to-chemical energy conversion and environmental remediation. Hierarchical Zn2In2S5/Ti3C2(O, OH)x hybrids have been rationally constructed using Ti3C2(O, OH)x as a two-dimensional platform for in situ growth of flower-like Zn2In2S5 microsphere under anaerobically hydrothermal conditions. Upon exposure to visible light, the Zn2In2S5/Ti3C2(O, OH)x hybrids with the Ti3C2(O, OH)x content of 1.5% (by mass) had hydrogen generation yields of 12,983.8 μmol g−1, which was significantly better than that of pure Zn2In2S5. The apparent quantum efficiency reached 8.96% at 420 nm. Furthermore, the photocatalytic tetracycline removal rate was ˜1.25 times higher than that of pure Zn2In2S5, and can be further improved with the increase of temperature in the range of 35–55 °C. Excellent photocatalytic activity originated from the synergistic effects between visible-light-active Zn2In2S5 and conductive Ti3C2(O, OH)x for spatial electrical promotion. The photogenerated-electrons transfer efficiency from Zn2In2S5 to Ti3C2(O, OH)x was 33.0%. In accordance with spectroscopic, electrochemical, and density functional theory studies, we proposed that the interfacial-built-in quasi-alloying effect between ZIS and Ti3C2(O, OH)x culminated in notable charge redistribution, which thereby facilitated the spatial separation and transfer of photogenerated electron-hole pairs. This work revealed the underlying photo-excited charge transfer between metallic compound and semiconductor. Economic Development Board (EDB) Enterprise Singapore Ministry of Education (MOE) The authors gratefully acknowledge the financial support provided by the Singapore Ministry of Education Academic Research Funds Tier 2 (MOE2014-T2-2-074; ARC16/15) and Tier 1 (2015-T1-001-023; RG7/15), the GSK (GlaxoSmithKline) – EDB (Economic Development Board) Trust Fund, and the Joint Singapore-Germany Research Project Fund (SGP-PROG3-019). We also acknowledge funding from the Projects of the National Nature Science Foundation of China (No. 21776066, 51708195). Hou Wang, Yuanmiao Sun and Yan Wu contributed equally to this work.

Developing metal-free catalysts with high catalytic activity for oxygen evolution reaction (OER) is essentially important for energy and environment-related techniques. Compared with individual element doping, doping carbon materials with multiple heteroelements has more advantages for enhancing the OER performance. However, doped sites for the different atoms are highly uncontrollable under the reported methods, which hinder the deeper understanding on the relationship between structure and property, and also limit the enhancement of catalytic activity. Our latest research has reported a method to site-controlled introducing a new form of nitrogen atoms, i.e. sp-hybridized nitrogen (sp-N), into graphdiyne, showing its potential advantages in OER catalysis. Since the sites of sp-N atoms are defined in graphdiyne, and the doping sites for S atoms are well understood, the relative position between N and S can be further defined. It gives us a chance to understand deeply the mechanism in the N, S heteroelements doped metal-free catalyst. Experimental results present that the codoping of sp-N and S atoms brought an excellent OER performance with low overpotential and high current density owning to the effectively synergistic effect of the stereodefined heteroatoms. This work was supported by the National Key Research and Development Program of China (2016YFB0600903) and the National Natural Science Foundation of China (21590795, 21820102002), the Scientific Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201623), Queensland-Chinese Academy of Sciences Collaborative Science Fund (122111KYSB20170001), and Chinese Academy of Sciences (CAS) Interdisciplinary Innovation Team.

UiO-66(Ce)-encapsulated ruthenium nanoparticles (Ru@UiO-66(Ce)) was designed and used for dehydrogenation of primary amines to nitriles in water without any hydrogen acceptors and additives. Introduction of metal Ru to UiO-66(Ce) contributes to the formation of Lewis acid–base pairs on the catalyst owing to the metal–support interaction, acting as active sites for activation of amines and transfer of hydrogen. Ab initio calculation results further confirm the roles of Lewis acid–base pairs in the reaction.

We describe the design and modular synthesis of a library of substituted hexabenzoovalene derivatives (SHBO), along with the key precursor dinaphthopyrenes (3), highlighting the influence of a wide array of substituent variation on the photophysical properties via UV-vis absorption, fluorescence spectra and electrochemical methods. The results show that the cyclized hexabenzoovalenes present a stronger spectroscopic red-shift than the corresponding dinaphthopyrenes. X-ray diffraction analysis suggests that intermediate 3hx containing two nitro groups forms a trans-configuration with twisted structures. Our systematic investigation might provide a realistic design strategy to construct large one-dimensional and two-dimensional materials via bottom-up approaches.

Crystal phase engineering is a promising strategy to tune the catalytic performance of metal nanomaterials. Generally, the crystal phase effect on catalysis is ascribed to distinct surface atomic arrangements of catalysts with different crystal phases. Here we show that even for similar surfaces, such as the close-packed surfaces, different crystal phases have considerably different surface reactivities due to their distinct intrinsic surface strains. Using first-principles calculations, we find that the close-packed surfaces of hexagonal close-packed (HCP) and double HCP (4H) gold have significantly smaller intrinsic strains (∼1.3%) than those of face-centered cubic (FCC) gold (∼2.3%). These distinct intrinsic surface strains result in various oxygen adsorption energies and O2 dissociation barriers on these close-packed gold surfaces, and the dissociation of O2 on different crystal phases and surfaces follows the Bronsted–Evans–Polanyi principle.

Organic π-conjugated polymers (CPs) have been intensively explored for a variety of critical photocatalytic applications in the past few years. Nevertheless, CPs for efficient CO2 photoreduction have been rarely reported, which is mainly due to the lack of suitable polymers with sufficient solar light harvesting ability, appropriate energy level alignment and good activity and selectivity in multi-electron-transfer photoreduction of CO2 reaction. We report here the rational design and synthesis of two novel triphenylamine (TPA) based conjugated microporous polymers (CMPs), which can efficiently catalyze the reduction of CO2 to CO using water vapor as an electron donor under ambient conditions without adding any co-catalyst. Nearly 100% selectivity and a high CO production rate of 37.15 μmol h−1 g−1 are obtained for OXD-TPA, which is significantly better than that for BP-TPA (0.9 μmol h−1 g−1) as a result of co-monomer change from biphenyl to 2,5-diphenyl-1,3,4-oxadiazole. This difference could be mainly ascribed to the synergistic effect of a decreased optical band gap, improved interface charge transfer and increased CO2 uptake for OXD-TPA. This contribution is expected to spur further interest in the rational design of porous conjugated polymers for CO2 photoreduction. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Decentralized electrosynthesis of hydrogen peroxide (H2 O2 ) via oxygen reduction reaction (ORR) can enable applications in disinfection control, pulping and textile bleaching, wastewater treatment, and renewable energy storage. Transition metal oxides are usually not efficient catalysts because they are more selective to produce H2 O. Here, it is shown that divalent 3d transition metal cations (Mn, Fe, Co, Ni, and Cu) can control the catalytic activity and selectivity of columbite nanoparticles. They are synthesized using polyoxoniobate (K7 HNb6 O19 ·13H2 O) and divalent metal cations by a hydrothermal method. The optimal NiNb2 O6 holds an H2 O2 selectivity of 96% with the corresponding H2 O2 Faradaic efficiency of 92% in a wide potential window from 0.2 to 0.6 V in alkaline electrolyte, superior to other transition metal oxide catalysts. Ex situ X-ray photoelectron and operando Fourier-transformed infrared spectroscopic studies, together with density functional theory calculations, reveal that 3d transition metals shift the d-band center of catalytically active surface Nb atoms and change their interactions with ORR intermediates. In an application demonstration, NiNb2 O6 delivers H2 O2 productivity up to 1 molH2O2 gcat -1 h-1 in an H-shaped electrolyzer and can yield catholytes containing 300 × 10-3 m H2 O2 to efficiently decomposing several organic dyes. The low-cost 3d transition-metal-mediated columbite catalysts show excellent application potentials.

The thermal expansion coefficient (TEC) and thermal conductivity (k) of thermal fillers are key factors for designing thermal management and thermal protection composite materials. Due to its unique advantages, hexagonal boron nitride (h-BN) is one of the most commonly used thermal fillers. However, its TEC and k values are still unclear due to the inconsistency of characterization techniques and sample preparations. In this work, these disputes were addressed using the quasi-harmonic approximation (QHA) method and phonon Boltzmann transport equation (BTE) theory based on the density functional theory (DFT), respectively. The accuracy of our calculated TEC and k values was confirmed by previously reported experimental results, and the underlying physical principles were analyzed from the phonon behaviors. Our TEC results show that the h-BN has small in-plane negative value and large cross-plane positive value, which are −2.4×10−6 and 36.4×10−6 K−1 at 300 K, respectively. And the anisotropic TEC is mainly determined by the anisotropic isothermal bulk modulus and the low-frequency out-of-plane longitudinal phonon modes. We found that the convergence of cutoff radius and q-grid size have significant effect on the accuracy of k of h-BN. Our results show that the in-plane k is much higher than the cross-plane k, and the values at 300 K are 286.6 and 2.7 W m−1 K−1, respectively. The anisotropic phonon group velocity arising from the vibration behaviors of acoustic phonon modes should be primarily responsible for the anisotropic k. Our calculated TEC and k values will provide important references for the design of h-BN composite materials. This work was supported by the National Natural Science Foundation of China (51621091, 51225203, and 51672060), and the National Key Research and Development Program of China (2017YFB0310400).

Due to mechanical flexibility and low cost, heterojunctions consisting of graphene and small organic molecules are regarded as promising candidate materials for vertical organic field-effect transistors (VOFETs), where the charge carrier mobility perpendicular to the graphene plane is crucial to their performance. Herein, through density functional simulations, we find that the vertical charge carrier mobility of the heterojunctions can be greatly adjusted by tuning their π-π stacking distances. For the 6,13-dichloropentacene (DCP)/graphene heterojunctions, with the distance between the first DCP layer and graphene decreasing to below 2.4 A, the vertical electron mobility between DCP layers is improved dramatically while the vertical hole mobility is greatly reduced. The strong dependence of vertical charge carrier mobility on the distance between the first molecular layer and substrate for smaller values than the typical π-π stacking distance (3.3-3.8 A) was also observed in the perylenetetracarboxylic dianhydride (PTCDA)/graphene and DCP/hexagonal-BN heterojunctions, where the tendency is very different to that of the DCP/graphene heterojunction. Our simulation results enabled us to develop a new strategy to tune the vertical charge transport properties in molecule/graphene heterojunctions, which provides insights into developing efficient VOFETs.

Zwitterionic peptides are great candidates as antifouling coating materials in many biomedical applications. We investigated the structure and antifouling properties of surface-tethered zwitterionic peptide monolayers with different peptide chain lengths and charge distributions using a combination of surface plasma resonance, atomic force microscopy, and all atomistic molecular dynamics (MD) simulation techniques. Our results demonstrate that zwitterionic peptides with more zwitterionic lysine (K) and glutamic acid (E) repeating units exhibit better antifouling performance. The block charge distributions of the positive and negative charges in the peptides (having multiple positive charges next to the same amount of negative charges), although affecting the structure of the peptide molecules, do not significantly change the antifouling properties of the peptide monolayers in the solutions containing monovalent ions. However, divalent cations, Ca2+ and Mg2+, in solution can significantly alter the structure and lower the antifouling performance of the zwitterionic peptide monolayers, especially with the sequences of block charges. All atomistic MD simulations quantitatively reveal that the divalent cations in solution lead to more interchain electrostatic cross-links between peptide chains, especially for peptides with block charges, which causes dehydration of the zwitterionic peptides and diminishes their antifouling performances. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy. National Research Foundation (NRF) Accepted version This work was financially supported by the NTU-Northwestern Institute for Nanomedicine and the National Research Foundation, Prime Minister’s Office, Singapore, under the NRF Investigatorship (NRF-NRFI2017-07).

The chirality evolution from the molecular level to the macroscopic level remains elusive for inorganic hierarchical structures. Without adding any chiral ligands or dopants, we prepared the macroscopic helical assemblies of sub-1 nm nanowires through a facile evaporation-induced self-assembly process with 100% efficiency, benefiting from the self-adjustment and self-recognition of sub-1 nm nanowires. Furthermore, we observed circularly polarized luminescence signals from the helical assemblies composed of nanowires and achiral organic fluorescent dyes, stemming from chirality transfer from the helical assemblies to achiral organic molecules. Molecular dynamics simulations found that the chirality of nanowires played a key role in the formation of macroscopic helical assemblies. Our work clarifies the chirality evolution and transfer of inorganic nanomaterials in part without being studied previously. This work was supported by National Key R&D Program of China (2017YFA0700101, 2016YFA0202801) and NSFC (21431003). We are grateful to Jiawei Lv, Zhiyong Tang, Xiaoyu Liu, Xianju Liu, and Xiangxing Xu for their help in CD characterization and Xiaozeng Song and Lian Duan for providing DACT and TMD.

The electrochemical oxygen reduction reaction (ORR) mechanism was generally considered to be O₂→ OOH∗→ O∗→ OH∗→ H₂O (O∗ mechanism). This O∗ mechanism predicted reasonable ORR half-wave potential (E1/2) of Co/N/C but abnormally underestimated the one of Fe/N/C. Herein, we highlight an unconventional 2OH∗ ORR mechanism (O2→ OOH∗→ 2OH∗→ OH∗→ H2O), which was often ignored because the free energies (ΔG) of 2OH∗ and O∗ are equal, according to the famous scaling relation: 2ΔG(OH∗) = ΔG(O∗). This scaling relation is true for traditional catalysts with near-continuous active sites. We find a different scaling relation: ΔG(2OH∗) = ΔG(O∗) + 1.5 eV on single-atom catalysts (Me/N/C, Me = Fe, Co, etc.) and suggest that the 2OH∗ mechanism should not be overlooked. In consideration of both O∗ and 2OH∗ mechanisms, the ORR E₁/₂ values of Co/N/C and Fe/N/C are in good agreement with experimental results. This work reveals the structure dependence of ORR reaction mechanisms and scaling relations in single-atom catalysis, and it is also heuristic for other reactions, such as O₂ evolution and N₂ reduction on single-atom catalysts. Ministry of Education (MOE) We thank the financial support from Academic Research Fund Tier 1 (No. RG104/18) and the computing resources from National Supercomputing Centre Singapore.

The rational design of previously unidentified materials that could realize excellent electrochemical‐controlled optical and charge storage properties simultaneously, are especially desirable and useful for fabricating smart multifunctional devices. Here, a facile synthesis of a 1D π–d conjugated coordination polymer (Ni‐BTA) is reported, consisting of metal (Ni)‐containing nodes and organic linkers (1,2,4,5‐benzenetetramine), which could be easily grown on various substrates via a scalable chemical bath deposition method. The resulting Ni‐BTA film exhibits superior performances for both electrochromic and energy storage functions, such as large optical modulation (61.3%), high coloration efficiency (223.6 cm2 C−1), and high gravimetric capacity (168.1 mAh g−1). In particular, the Ni‐BTA film can maintain its electrochemical recharge‐ability and electrochromic properties even after 10 000 electrochemical cycles demonstrating excellent durability. Moreover, a smart energy storage indicator is demonstrated in which the energy storage states can be visually recognized in real time. The excellent electrochromic and charge storage performances of Ni‐BTA films present a great promise for Ni‐BTA nanowires to be used as practical electrode materials in various applications such as electrochromic devices, energy storage cells, and multifunctional smart windows., A 1D π–d conjugated coordination polymer (CCP) is successfully fabricated in which specific organic linker and metal ions are selected with the aim of increasing the density of redox active centers and enabling conductive paths for charge transport. Moreover, this CCP enables dual electrochromic and energy storage functionalities in an integrated smart device.

van der Waals heterojunctions (vdWHs) formed between 2D materials have attracted tremendous attention recently due to their extraordinary properties, which cannot be offered by their individual components or other heterojunctions. Intriguing electronic coupling, lowered energy barrier, intimate charge transfer, and efficient exciton separation occurring at the atomically sharp interface promise their applications in catalysis, which, however, are largely unexplored. Herein, we demonstrate a 0D/2D vdWH between 0D graphene quantum dots (GQDs) and 2D pristine graphene sheets, simply prepared by ultrasonication of graphite powder using GQDs as intercalation surfactant. Such an all-carbon Schottky-diode-like 0D/2D vdWH is employed for the emerging photoelectrochemical catalysis (water splitting) with high performance. The demonstrated low-cost and scalable bottom-up growth of heteroatom-doped GQDs will greatly promote their widespread applications. Moreover, the mechanisms underlying GQD growth and heterojunction-mediated catalysis are revealed both experimentally and theoretically. Accepted version

Active site number, water dissociation, and hydrogen adsorption free energy are the three main parameters for regulating the activity of electrocatalysts for hydrogen evolution reaction (HER) in alkaline media. However, at present, simultaneous modulations of these three parameters for alkaline HER still remain challenging. In this work, we take CoP as the model material and demonstrate that a metal and nonmetal dual-doping strategy can achieve simultaneous modulation of these three parameters by inducing lattice irregularity and optimizing the electronic configuration in CoP nanomaterials. Benefiting from the oxygen and copper dual-doping collective effect, the optimized O,Cu–CoP nanowire array electrode shows nearly 10-fold enhancement in catalytic activity for alkaline HER compared to a pure CoP nanowire electrode. Our work may provide a new concept to boost performance of nonprecious metal electrocatalysts for alkaline HER.

A silica-supported rhodium catalyst for the selective hydrogenation of phenol to cyclohexanone under mild conditions has been developed. As the Rh concentration on the catalyst increased from 0.5 to 15 wt%, the conversion (at phenol/Rh mole ratio 100/1) dropped whereas the initial selectivity to cyclohexanone increased. The direct hydrogenation to cyclohexanol occurred in parallel with partial hydrogenation to cyclohexanone. The negative correlation between selectivity and Rh dispersion suggests that direct hydrogenation occurs at low coordination sites whereas dissociation of phenol to phenoxy followed by hydrogenation to cyclohexanone takes place at higher coordinated terrace sites. DFT calculations revealed that the activation barrier for O–H bond cleavage is lower for phenol adsorbed on a Rh(1 1 1) flat surface than on small particles. By blocking the low coordination edge and step sites through grafting with (3-mercaptopropyl)trimethoxysilane, the cyclohexanone selectivity was improved from 82 to 93% at 100% conversion. The catalyst is active at room temperature and 1 atm H2 pressure and can be easily activated by in-situ reduction. MOE (Min. of Education, S’pore)

Optimizing the hydrogen adsorption on electrodes is one of the most effective strategies to promote the hydrogen evolution reaction (HER). In recent years, cobalt phosphides (CoP) have been identified as a promising catalyst for HER in acid. However, the hydrogen adsorption on CoP is strong and a considerable overpotential has to be applied to enable HER. Here, we report a strategy to weaken the hydrogen adsorption on CoP through an electron deficiency in CoP induced by Au@CoP core/shell structure. A weakened hydrogen adsorption is confirmed by the density functional theory (DFT) calculation. Au@CoP gave an overpotential (η) of 160 mV at the current density of 1 mA cm−2CoP, which is about 50 mV less than pure CoP. It also exhibited a turn-over frequency (TOF) value of 0.68 s−1 per active site at η = 150 mV, which is more than 4 times higher than CoP. The strategy reported here holds potential to be extended to other electrodes for optimizing their hydrogen adsorption for HER. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

Organizing nanoparticles into supercrystals comprising multiple structures remains challenging. Here, we achieve one assembly with dual structures for Ag polyhedral building blocks, comprising truncated cubes, cuboctahedra, truncated octahedra, and octahedra. We create two micro-environments in a solvent evaporation-driven assembly system: one at the drying front and one at the air/water interface. Dynamic solvent flow concentrates the polyhedra at the drying front, generating hard particle behaviors and leading to morphology-dependent densest-packed bulk supercrystals. In addition, monolayers of nanoparticles adsorb at the air/liquid interface to minimize the air/liquid interfacial energy. Subsequent solvent evaporation gives rise to various structurally diverse dual-structure supercrystals. The topmost monolayers feature distinct open crystal structures with significantly lower packing densities than their densest-packed supercrystals. We further highlight a 3.3-fold synergistic enhancement of surface-enhanced Raman scattering efficiency arising from these dual-structure supercrystals as compared to a uniform one., Crystals with multiple structures often perform special functions in nature, inspiring the creation of synthetic analogues. Here, the authors subject polyhedral nanoparticles to two self-assembly micro-environments to realize supercrystals with dual structures, in which the order of the surface layer differs from the bulk structure.

Nitrogen-doped graphenes (NG) fabricated through thermal annealing of graphene oxide (GO) and urea was applied to activate peroxymonosulfate (PMS) for sulfacetamide (SAM) degradation. The contents of reactive functional groups (graphitic N, pyridinic N, pyrrolic N, nitric oxide and C O) and catalytic performance of NG were delicately controlled by adjusting thermal annealing temperature. Thermal annealing temperature of ≥500°C was required to produce the NG endowed with catalytic activity for SAM degradation via PMS activation. NG600 (NG prepared at 600°C) with a high N doping level (16.0 wt%) and a most optimum amount of pyridinic N (38.4%N), pyrrolic N (31.8%N), graphitic N (25.9%N) and C O groups (43.7%O) exhibited the most outstanding catalytic activity to activate PMS. NG600 with the controlled N bonding configurations possessed a higher SAM degradation efficiency than NGs prepared via other optimized synthesis methods The specific surface area (SSA) contributed less significantly than N doping to the SAM degradation performance. Increments in the PMS dosage and catalyst loading were both conducive to the catalytic performance of NG. The presence of NO3− in the NG600/PMS system had a negligible influence on SAM degradation but Cl− and humic acid decreased the SAM degradation rate. Experiments using chemical scavengers and electron paramagnetic resonance (EPR) study revealed that SAM degradation process follows predominantly the radical pathway with sulfate radical (SO4 −) as the main reactive oxygen species over the non-radical pathway. Density functional theory (DFT) calculations suggest that graphitic N can facilitate PMS adsorption on the NG and SAM degradation. This study improves the understanding on the role of different surface N functional groups of NG in the PMS activation.

Exploring earth-abundant electrocatalysts to realize efficient oxygen evolution reaction (OER) is highly desired for developing sustainable electrochemical energy storage and conversion technologies. Herein, ultrathin single-crystalline Fe-doped nickel thiophosphate (NiPS3) nanosheets prepared in large scale by an easy solid-state method were demonstrated to be highly efficient OER electrocatalysts. The density functional theory (DFT) calculations reveal that the Fe-doping effectively decreases the energy barrier of OER path by reducing the binding of the oxygen-containing species on the surface of NiPS3. As such, the Fe-doped NiPS3 nanosheets show a low overpotential of 256 mV to reach a current density of 30 mA cm−2 and a small Tafel slope of 46 mV dec−1. To our knowledge, this is one of the best OER electrocatalysts in alkaline medium to date. The in-depth mechanism study demonstrates that the in-situ formed Fe-doped nickel oxides/hydroxides shell, resulting from the surface oxidation during the OER process, not only may serve as favorable electrocatalytic species but also improves the chemical stability of the Fe-doped NiPS3 in alkaline electrolyte. This work provides a new perspective for designing highly efficient OER electrocatalysts based on the ternary two-dimensional layered metal thiophosphates. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

The coupling of the localized surface plasma resonance (LSPR) between noble metals of Au, Ag and Cu and semiconductors of Cu2 xE (E ¼ S, Se, Te) opens new regime to design photothermal (PT) agents with enhanced PT conversion efficiency. However, it is rarely explored on fabricating of engineered dual plasmonic hybrid nanosystem for combinatory therapeutic-diagnostic applications. Herein, rattle-type Au@Cu2 xS hollow mesoporous nanoparitcles with advanced PT conversion efficiency are designed for cellular vehicles and chemo-photothermal synergistic therapy platform. The LSPR coupling between the Au core and Cu2 xS shell are investigated experimentally and theoretically to generate a PT conversion efficiency high to 35.2% and enhanced by 11.3% than that of Cu2 xS. By conjugating microRNA (miRNA) gene probe on the surface, it can realize the intracellular oncogenic miRNA detection. After loading of anticancer drug doxorubicin into the cavity of the Au@Cu2 xS, the antitumor therapy efficacy is greatly enhanced in vitro and in vivo due to the NIR photoactivation chemo- and photothermal synergistic therapy. The rattle-type metal-semiconductor hollow mesoporous nanostructure with efficient LSPR coupling and high cargo loading capability will be beneficial to future design of LSPR-based photothermal agents for a broad range of biomedical application. MOE (Min. of Education, S’pore) Accepted version

Because of their intrinsic geometric structure of vertices, edges, and facets, Platonic nanoparticles are promising materials in plasmonics and biosensing. Their position and orientation often play a crucial role in determining the resultant assembly structures at a liquid/liquid interface. Here, we numerically explored all possible orientations of three Platonic nanoparticles (tetrahedron, cube, and octahedron) and found that a specific orientation (vertex-up, edge-up, or facet-up) is more preferred than random orientations. We also demonstrated their positions and orientations can be quantitatively predicted when the surface tensions dominate their total interaction energies. The line tensions may affect their positions and orientations only when total interaction energies are close to each other for more than one orientation. The molecular dynamics simulation results were in excellent agreement with our theoretical predictions. Our theory will advance our ability toward predicting the final structures of Platonic nanoparticle assemblies at a liquid/liquid interface. MOE (Min. of Education, S’pore) Accepted version

In recent years, organic-based, especially carbonyl-based, Li-ion battery electrode materials have attracted great attention due to their low-cost, environmentally friendly nature and strong Li-ion bonding abilities. However, new research is required to further increase the electron mobility and cycling performance of organic materials. The performance of a high-carbonyl C6O6 molecule-functionalized graphene electrode for Li-ion batteries is investigated using the density functional theory. The binding energy calculations indicate that the C6O6 molecule is adsorbed on graphene via physisorption. C6O6@graphene maintains excellent electronic conductivity with 1 to 6 Li ions. By our statistical method, the reduced voltage of the C6O6@graphene cathode displays a voltage between 2.6 V and 1.5 V with 2 phases from 1 to 6 Li ions with energy density of approximately 155 mA h g−1. The results obtained reveal that C6O6@graphene is a promising electrode material for renewable Li-ion batteries.

Novel nitrogen-doped porous molybdenum carbide (α-MoC1−x and β-Mo2C) architectures were prepared using Mo-based metal–organic frameworks (MOFs) as the precursor. The synthesized molybdenum carbides consist of numerous nanocrystals organized into micro-sized rods with interpenetrating mesoporous-channels and macroporous-tunnels along the axial direction. When employed as the cathode catalyst for Li-O2 batteries, this dual pore configuration offers abundant active sites for the electrochemical reaction and many nucleation sites for the discharge product of Li2O2; hence, decent performances were obtained. Among the two synthesized molybdenum carbides, the α-MoC1−x electrode stands out as being better due to its lower charge transfer resistance (395.8 Ω compared to 627.9 Ω) and better O2 adsorption (binding energy of −1.87 eV of α-(111)-Mo compared to −0.72 eV of β-(101)-Mo). It delivered a high full discharge of 20 212 mA h g−1 with a discharge voltage of 2.62 V at 200 mA g−1. A good cycling stability was also obtained: i.e. 100 stable cycles with a fixed capacity of 1000 mA h g−1 (at a current density of 200 mA g−1) with a charging voltage of 4.24 V and maintaining a respectable round-trip efficiency of ∼70%. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

To control the process of cation exchange (CE) in a multielemental system, a detailed understanding of structural changes at the microscopic level is imperative. However, the synthesis of a multielemental system has so far relied on the CE phenomenon of a binary system, which does not necessarily extend to the higher-order systems. Here, direct experimental evidence supported by theoretical calculations reveals a growth model of binary Cu–S to ternary Cu–Sn–S to quaternary Cu–Zn–Sn–S, which shows that cations preferentially diffuse along a specific lattice plane with the preservation of sulfuric anionic framework. In addition, we also discover that, unlike the commonly accepted structure (P63mc), the metastable crystal structure of Cu–Zn–Sn–S phase possesses fixed Sn occupancy sites. By revealing the preferential nature of cations diffusion and growth mechanism, our work provides insight into controlling the stoichiometry and phase purity of novel multielemental materials. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version We acknowledge financial support from National Research Foundation (NRF), Singapore, through the Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) and Nanomaterials for Energy and Water Management (SHARE NEW) CREATE program. L.H.W. thanks the funding support from Singapore Ministry of Education, Tier 2 (2016-T2-1-030). S.L. acknowledges the funding support from Singapore Ministry of Education Tier 1 (107/15). H.Z. thanks the funding support from U.S. DOE BES Materials Sciences and Engineering Division Under Contract No. KC22ZH. X.Y.L. thanks the funding support from Singapore Ministry of Education, Tier 1 (RG21/16) and Tier 2 (MOE2016-T2-1- 043) grants.. The work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank Fiona Doyle for lending us her synthetic laboratory in University of California Berkeley (UCB), Song Chengyu and Karen Bustilo for their help and assistance on TEM, and Matthew P. Sherburne for nanoparticle growth discussion.

We herein report aqueous fabrication of well-defined Au@Cu2–xE (E = S, Se) core@shell dual plasmonic supraparticles (SPs) for multimodal imaging and tumor therapy at the in vivo level. By means of a modified self-limiting self-assembly based strategy, monodisperse core@shell dual plasmonic SPs, including spherical Au@Cu2–xS SPs, Au@Cu2–xSe SPs, and rod-like Au@Cu2–xS SPs, are reliably and eco-friendly fabricated in aqueous solution. Due to plasmonic coupling from the core and shell materials, the as-prepared hybrid products possess an extremely large extinction coefficient (9.32 L g–1 cm–1 for spherical Au@Cu2–xS SPs) at 808 nm, which endows their excellent photothermal effect. Furthermore, the hybrid core@shell SPs possess the properties of good biocompatibility, low nonspecific interactions, and high photothermal stability. So, they show favorable performances for photoacoustic imaging and X-ray computed tomography imaging as well as photothermal therapy of tumors, indicating their application potential...

Shape-controlled polyhedral particles and their assembled structures have important applications in plasmonics and biosensing, but the interfacial configurations that will critically determine their resultant assembled structures are not well-understood. Hence, a reliable theory is desirable to predict the position and orientation of a polyhedron at the vicinity of a liquid/liquid interface. Here we demonstrate that the free energy change theory can quantitatively predict the position and orientation of an isolated octahedral nanoparticle at a liquid/liquid interface, whose vertices and facets can play crucial roles in biosensing. We focus on two limiting orientations of an octahedral nanoparticle, vertex up and facet up. Our proposed theory indicates that the surface wettability (hydrophilic/hydrophobic ratio) of the nanoparticle determines its most stable position and the preferred orientation at a water/oil interface. The surface wettability of an octahedron is adjusted from extremely hydrophobic to extremely hydrophilic by changing the amount of charge on the Ag surface in molecular dynamics (MD) simulations. The MD simulations results are in excellent agreement with our theoretical prediction for an Ag octahedral nanoparticle at a hexane/water interface. Our proposed theory bridges the gap between molecular-level simulations and equilibrium configurations of polyhedral nanoparticles in experiments, where insights from nanoparticle intrinsic wettability details can be used to predict macroscopic superlattice formation experimentally. This work advances our ability to precisely predict the final structures of the polyhedral nanoparticle assemblies at a liquid/liquid interface. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds, defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. This successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.

Regulating the interfacial interaction between fillers and matrices is crucial for fabricating high-performance polymer composites. In this research, a functionalized core–shell hybrid silica@graphene oxide was produced by the charge attraction method, and then added to a trans-1,4-polyisoprene matrix as a neoteric filler to obtain a brand-new silica@graphene oxide/trans-1,4-polyisoprene polymer nanocomposite. The hybrid incorporation simultaneously improved the fracture toughness, mechanical strength and heat resistance of the nanocomposites. We examined the thermal, mechanical and shape memory properties of the nanocomposites via methodical measurements from the microscale to the macroscale. The experimental results demonstrated that, compared with other samples, the nanocomposite sample with 1.0 wt% silica@graphene oxide exhibited the best mechanical and thermal performance, and the fabricated nanocomposites showed good shape memory properties. This new and feasible approach is likely to enable a new strategy for the design of interfaces for developing nanocomposites with high performance.

Though plasmonic effect is making some headway in the energy harvesting realm, its fundamental charge transfer mechanism to a large extent is attributed to the hot-carrier generation at the contact interface. Herein this work attempts to elucidate the physical origin of light induced plasmo-pyroelectric enhancement based on charge density manipulation on surface state in the vicinity of the metal-ferroelectric contact interface. More importantly, by tuning the band bending, it is shown that the charge density on the surface state of a hybrid plasmo-pyroelectric (BaTiO3 -Ag) nanosystem can be manipulated and largely increased under the resonant blue light illumination (363 nm). It is also demonstrated that owing to this effect, the spatial pyroelectric activity of a hybrid plasmo-pyroelectric nanosystem governs 46% enhancement in pyroelectric coefficient. This research highlights the optically regulated charge density in plasmo-pyroelectric nanosystems, which could pave a new avenue for energy harvesting/conversion devices with distinguished advantages in wireless, photonic-controlled, localized, and dynamic stimulation.

Electronic structure greatly determines the band structures and the charge carrier transport properties of semiconducting photocatalysts and consequently their photocatalytic activities. Here, by simply calcining the mixture of graphitic carbon nitride (g-C3 N4 ) and sodium borohydride in an inert atmosphere, boron dopants and nitrogen defects are simultaneously introduced into g-C3 N4 . The resultant boron-doped and nitrogen-deficient g-C3 N4 exhibits excellent activity for photocatalytic oxygen evolution, with highest oxygen evolution rate reaching 561.2 µmol h-1 g-1 , much higher than previously reported g-C3 N4 . It is well evidenced that with conduction and valence band positions substantially and continuously tuned by the simultaneous introduction of boron dopants and nitrogen defects into g-C3 N4 , the band structures are exceptionally modulated for both effective optical absorption in visible light and much increased driving force for water oxidation. Moreover, the engineered electronic structure creates abundant unsaturated sites and induces strong interlayer C-N interaction, leading to efficient electron excitation and accelerated charge transport. In the present work, a facile approach is successfully demonstrated to engineer the electronic structures and the band structures of g-C3 N4 with simultaneous introduction of dopants and defects for high-performance photocatalytic oxygen evolution, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.

The inorganic halide perovskite CsPbI3 has shown great promise for efficient solar cells, but the instability of its cubic phase remains a major challenge. We present a route for stabilizing the cubic α-phase of CsPbI3 through the control of vacancy defects. Analysis of the ionic chemical potentials is performed within an ab initio thermodynamic formalism, including the effect of solution. It is found that cation vacancies lead to weakening of the interaction between Cs and PbI6 octahedra in CsPbI3, with a decrease in the energy difference between the α- and δ-phases. Under I-rich growth conditions, which can be realized experimentally, we predict that the formation of cation vacancies can be controlled. Other synthetic strategies for cubic-phase stabilization include the growth of nanocrystals, surface capping ligands containing reductive functional groups, and extrinsic doping. Our analysis reveals mechanisms for polymorph stabilization that open a new pathway for structural control of halide perovskites. This work is supported as part of the fundamental research project “Design of Innovative Functional Materials for Energy and Environmental Application” (no. 2016-20) funded by the State Committee of Science and Technology, DPR Korea. The work in the UK has been supported by the Royal Society and the Leverhulme Trust.

Using density functional theory calculations, we explore the structural, electronic, and optical properties of the inorganic Ge-based halide perovskites AGeX3 (A = Cs, Rb; X = I, Br, Cl) that can possibly be used as light absorbers. We calculate the lattice parameters of the rhombohedral unit cell with an R3m space group, frequency-dependent dielectric constants, photoabsorption coefficients, effective masses of charge carriers, exciton binding energies, and electronic band structures by use of PBEsol and HSE06 functionals with and without SOC effect. We also predict the absolute electronic energy levels with respect to the external vacuum level by using the (001) surfaces with AX and GeX2 terminations, demonstrating their strong dependence on the surface terminations. The calculated results are found to be in reasonable agreement with the available experimental data for the cases of CsGeX3, while for the cases of RbGeX3 they are predicted for the first time in this work. We reveal that replacement of Cs with Rb can offer reasonable flexibility in optoelectronic properties matching for solar cell design and optimization, while X anion exchange gives rise to large changes. This work was supported as part of the fundamental research project “Design of Innovative Functional Materials for Energy and Environmental Application” (No. 2016-20) funded by the State Committee of Science and Technology, DPR Korea. Computation was done on the HP Blade System C7000 (HP BL460c) that is owned by Faculty of Materials Science, Kim Il Sung University.

Heterostructures with abundant phase boundaries are compelling for surface-mediated electrochemical applications. However, rational design of such bifunctional electrocatalysts for efficient hydrogen and oxygen evolution reactions (HER and OER) is still challenging. Here, due to the well-matched lattice parameters, we easily achieved the epitaxy of two-dimensional ternary nickel thiophosphate (NiPS3) nanosheets with in-grown dinickel phosphide (Ni2P) through an in situ growth strategy. Density functional theory calculations reveal that the NiPS3/Ni2P heterojunction significantly decreases the kinetic barrier for hydrogen adsorption and accelerates electron transfer due to the built-in electric field at the epitaxial interfaces. The significantly improved electrocatalytic performance is shown to be closely related to the epitaxial interfacial area rather than the amount of secondary phase. Notably, the resultant NiPS3/Ni2P heterostructures enable an overall water splitting electrolyzer to achieve 50 mA cm–2 at a lower bias of 1.65 V compared to that for the pristine NiPS3 alone (2.02 V) and even the benchmark Pt/C//IrO2 electrocatalysts (1.69 V). MOE (Min. of Education, S’pore) Accepted version

Catechol adhesives are limited to two-part curing designs. For the first time, a one-pot catechol adhesive is demonstrated with multiple modes of external activation: self-curing, electrocuring, substrate, and two-part curing. Lap shear adhesion (50 kPa) and viscoelastic properties demonstrate that electrocuring is noninferior to two-part curing methods. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Published version