Crystal Orbital Hamilton Population Research Articles

Addressing the Activity and Selectivity Challenges for CO2 Reduction via Transition‐Metal‐Free Homo‐ and Hetero‐Biatomic Catalysts Embedded in Two‐Dimensional Networks

AbstractDesigning low‐cost and stable electrocatalysts with enhanced activity and selectivity for CO2 valorization to useful chemicals and fuels faces enormous challenges to address the pressing climate change concerns. Synergistic interactions between the atoms in double atom catalysts has emerged as a promising tool to tune and boost CO2 activation and reduction. In this work, we systematically designed highly stable transition‐metal‐free homo‐ and hetero‐biatomic catalysts based on Al, Be, B and Si supported on TCNQ monolayer for CO2 reduction to C1 products using dispersion corrected periodic density functional theory calculations. Our findings reveal that transition‐metal‐free homo‐and hetero‐biatomic TCNQ catalysts can effectively capture and activate the CO2 molecule with binding energies ranging from 0.09 to 2.35 eV. Extensive free energy calculations to screen the favourable reaction pathways to different C1 products (CO, HCOOH, CH3OH and CH4) demonstrate that Al2‐TCNQ, AlBe‐TCNQ and BeSi‐TCNQ stand out as potential candidates for catalyzing CO2RR to methanol in a selective manner, suppressing the competitive HER simultaneously. Remarkably, BeSi‐TCNQ shows the best catalytic activity towards CO2 reduction to methanol at record low limiting potential of −0.29 V with spontaneous desorption of the final product. From the in‐depth examination of the electronic structure details, integrated projected density of states and crystal orbital Hamilton populations are used to understand and rationalize the binding interactions between the adsorbed CO2 molecule and the homo‐ or hetero‐biatomic TCNQ catalysts. Moreover, the ΔG*COOH‐ΔG*CO2 and ΔG*HCOOH‐ΔG* OCHO/*COOH values are found to provide reasonable guidance to evaluate the overall CO2RR performance of homo‐ and hetero‐biatomic TCNQ catalysts, respectively. Therefore, our findings provide significant insights for designing transition metal‐free homo‐ and hetero‐biatomic catalysts with intriguing properties for improving CO2 utilization and conversion.

Theoretically exploring bioinspired enzyme-like [formula omitted] with organic ion axial ligand for electrocatalytic nitrate reduction to ammonia

Electrocatalytically driven reduction of nitrate (NO3−) from NO3−-laden wastewater to ammonia (NH3) has emerged as a promising complementary strategy to the energy-intensive Haber-Bosch process. Herein, based on density functional theory (DFT) calculations, 14 organic ionic groups are found to significantly improve the electrocatalytic reduction of NO3− to NH3 (eNO3RR-to-NH3) activity of typical M−N4−C (M = Fe, Co, and Ni) catalysts by axially ligating metal center, among which Ethyl thiolate axially ligated Co−N4−C exhibits the highest eNO3RR-to-NH3 activity with the limiting potential (UL) of -0.11 V. 4-Mercaptobenzoic acid and Thiophenolate axially ligated Fe−N4−C can inhibit the NN coupling reaction while having high eNO3RR-to-NH3 activity (UL = -0.16, -0.31 V, respectively) and thus have better NH3 selectivity. Furthermore, ΔGH*NO and ICOHP (integrated crystal orbital hamilton populations) between the 3d orbital of M and 2p orbital of N (*NO) atoms show remarkable volcano relationship for L−Fe−N4−C systems and linear relationship with R-Square of 0.83 occurs for L−Co−N4−C systems. There is an excellent linear relationship (R-Square is 0.88) between ICOHP and UL for the L−Co−N4−C systems. Hence, the ICOHP can work as an excellent thermodynamic activity descriptor for eNO3RR-to-NH3 over L−Co−N4−C catalysts. The three catalysts are concluded to be promising electrocatalysts for eNO3RR-to-NH3.

Exploration of sodium thiosulfate for leaching of cobalt-containing pyrite: A DFT study

The paper presents the theoretical calculation results of exploratory research relating to the leaching of cobalt-containing pyrite using sodium thiosulfate as a lixiviant. It is well known that density functional theory (DFT) calculations can qualitatively evaluate the exchange of matter and energy between the mineral system and the surroundings, which greatly expands the breadth and depth of leaching process. Thus, DFT method was used to determine the effectiveness of sodium thiosulfate (Na2S2O3) as a lixiviant for the leaching of cobalt-containing pyrite in this study. The analyses of DFT calculations illustrated that thiosulfate can be well adsorbed on the surface of cobalt-containing pyrite due to the formation of S-Fe and O-Co bonds between the S 3p orbital and O 2p orbital in sodium thiosulfate and the Fe 3d orbital and Co3d orbital in cobalt-containing pyrite. Analysis of crystal orbital Hamilton population (COHP) indicated that Fe-S and S-Co bonds became longer when the thiosulfate adsorbed on the surface of the cobalt-containing pyrite, resulting in the weakening of interactions between S and Fe or Co atoms. Overall, the findings suggested that sodium thiosulfate was a promising lixiviant，favored the dissolution of Fe and Co.

Parameter modulation on p-type doping of AlGaN nanowires

The p-type doping process during the growth of AlGaN nanowires directly influences the optoelectronic properties of the related devices. However, research on the p-type ionization mechanism in AlxGa1-xN nanowires remains limited. In this work, we utilize first principles calculations to investigate p-type doping in AlxGa1-xN nanowires under different structural variables (Al component, doping element, doping site, and doping concentration). Our results demonstrate that p-type doping in AlxGa1-xN nanowires is an endothermic process, and increased dopant concentration leads to a decrease in system stability. Moreover, we found that dopant atoms are easier to substitute for Ga atoms than Al atoms. Among the three doping elements (Zn, Be and Mg), Zn exhibits the most challenging doping difficulty, while Be shows the easiest doping process, with Mg falling in between. Crystal Orbital Hamilton Population (COHP) and bond population calculations reveal the mechanism for the variation in doping structure stability. Doping induces a rearrangement of energy level orbitals, resulting in changes in the band gap. Specifically, the valence band exhibits an overall upward trend crossing the Fermi level, showing the p-type conductive properties. Notably, a significant decrease in electron density near Mg and Be leads to the formation of p-type conductive properties. The changes in hole density and effective mass further confirm the formation of p-type conductivity after doping. Additionally, structures with lower Al composition exhibit higher doping ionization degrees. This study is expected to provide a theoretical basis for the growth, preparation, and application of optoelectronic devices based on p-type AlGaN nanowires.

A comparative study of structural, mechanical, electronic and optical properties of InTe monolayer & homo-bilayer

We have done a comparative study between InTe monolayer and van der Waals homo-bilayer. Four different stacking AA, AAʹ, AB, ABʹ are taken into consideration in which possible three stackings AAʹ, AB, ABʹ are considered for the calculations. The homo-bilayer is simulated for the 10ps via ab-intio molecular dynamics to ensure kinetic stability. The mechanical properties show that the InTe homo-bilayer is more elastic than its monolayer. The indirect to direct bandgap modulations are seen from the electronic properties. The Telluride atom has a major role in the electron transfer between the layer of the homo-bilayer. The Crystal Orbital Hamilton Populations calculation is done to observe the bonding nature. Enhancement is seen in the absorption coefficient of order 105 cm−1. The highest refractive index of 3.88 is observed in the visible region. Reflectivity increases in the visible and ultraviolet regions whereas the transmittivity decreases in homo-bilayer than monolayer.

Mn-assisted Fe-electrocoagulation strategy for enhanced efficient arsenic removal and its mechanism

Electrocoagulation (EC) is a facile technique for removing arsenic (As) pollutants from different water matrices with high efficiency. In this work, a novel strategy of Mn-assisted Fe EC was developed to further enhance the removal efficiency of arsenite [As(III)] from wastewater. When 1 mM of MnCl2 was added to an Fe-EC system, the As removal efficiency reached 99.99%, and the residual concentration was only 9 μg/L, which is lower than the World Health Organization’s limit for drinking water. The characteristics of the generated flocs by four different EC processes in Fe, Fe-Mn, Fe-As, and Fe-Mn-As systems were investigated. The results showed that Mn2+ promoted the formation of FeOOH, FeOx, MnOx, FeHAsO4, and MnHAsO4 through low crystallinity and a high surface area. Density functional theory simulation and crystal orbital hamiltonian population confirmed that the generated Fe-Mn flocs had a greater adsorption affinity for As(III) and arsenate [As(V)]. The possible reactions in the EC processes and reaction mechanisms were also hypothesised. The current work provides meaningful insights into understanding the mechanisms of Mn-assisted Fe-EC systems, and further confirms its potential for practical applications in As pollution treatment.

Unleashing the impact of Nb-doped, single crystal, cobalt-free P2-type Na0.67Ni0.33Mn0.67O2 on elevating the cycle life of sodium-ion batteries

A synergistic stabilization effect in a Nb-doped P2-type single crystal cobalt-free layered oxide cathode material, offering remarkable cycling stability and high-power performance for Na-ion batteries have unveiled in this study. The introduction of Nb in the transition metal layer not only reduces the electronic band gap but also enhances electronic conductivity and mitigates ionic diffusion energy barriers. The induction of a robust Nb-O bond expedites electron and Na+ transfer, contributing to the stabilization of the host structure is further confirmed through the density functional theory calculations, including electron localization function (ELF) and crystal orbital Hamiltonian population (COHP). To the best of our knowledge, this study is the first to demonstrate a homogeneous distribution of niobium throughout the single crystal, specifically doped at the nickel site within the bulk, without inducing atomic-scale surface reorganization. The presence of single crystals improves various kinetic factors, demonstrating the profound correlation between structural defects and chemical proliferation, thereby reducing the evolution of oxygen gas. The P2-type Nb-doped single crystal cathode (Na0.67Ni0.31Mn0.67Nb0.02O2) exhibits remarkable capacity retention, >95 % after 100 cycles at 0.1 C and >90 % after an extended cycling of 2000 cycles at 1 C. Practical assessments in complete cell setups with a pre-sodiated hard carbon anode further validate the material's viability, showcasing capacity retention of over 93 % after 100 cycles in a coin cell and approximately 89 % in a pouch cell format. This comprehensive study establishes the transformative potential of Nb-doped single crystal cobalt-free P2-type layered oxide cathode materials, marking a significant advancement in sodium-ion battery technology.

Effect of phase transition on the piezoelectric properties of scandium-alloyed gallium nitride

In this study, the piezoelectric properties of scandium-alloyed gallium nitride (ScGaN), which is expected to be applied to microelectromechanical systems devices, are evaluated by first-principles calculations. The piezoelectric constant (d33) of GaN is found to increase by up to approximately 30 times upon the addition of 62.5 mol. % of Sc. The piezoelectric stress constant (e33) increases and the elastic constant (C33) decreases with increasing Sc content of ScGaN, driving the rise of d33. The improved piezoelectric properties of ScGaN compared with those of GaN are largely attributed to elastic softening, which is thought to be related to the transition from a wurtzite to hexagonal boron nitride (h-BN) structure driven by the change in bonding states between atoms caused by the addition of Sc to GaN. The crystal orbital Hamilton population analysis suggests that addition of Sc to GaN results in the combination of weaker Sc–N and Ga–N bonding, which makes the crystal structure unstable. This weakened bonding is thought to be the main cause of the destabilization of the wurtzite structure and transition to the h-BN structure of ScGaN. The elastic softening associated with this structural transition leads to the dramatic improvement in piezoelectric properties.

Embedded metal inducing electron accumulation of multi-mesoporous pyridinic-N doped carbon for enhancing *COOH adsorption in electrochemical CO2 reduction

Nitrogen-doped carbon (NC) for carbon dioxide reduction reaction (CO2RR) are promising candidates. However, its selectivity and activity are limited by the undeveloped pore and limited electronic effect. Herein, we propose a strategy of three birds with one stone to utilize the embedded nickel for inducing electron-rich pyridinic-NC with multimodal porous structure based on the hard template assisted sacrificial template method. Nickel acts as sacrificial agent and inducer to facilitate the formation of mesoporous and reactive nitrogen species for capturing and activating reactants, respectively. Besides, we find that nickel as electron donor endows the NC with electron accumulation for participating actively in PCET reaction. The resultant Ni0.87-NC-1-AE exhibits an eminent FECO of 97.6 % with excellent activity and stability. In-situ Raman spectroscopy and the projected crystal orbital Hamilton populations (pCOHP) confirm the accumulation of *COOH and the stable adsorption of *COOH on the surface. What’s more, the well-designed experiments and DFT calculations accurately locate pyridinic-N as the active site, where the aggregated electrons donated by nickel significantly reduce the energy barrier of rate-determining step and promote the desorption of CO. This work provides an instructive perspective to construct advanced NC electrocatalysts with high mass transfer efficiency and high catalytic activity.

Hardness of surface hydroxyls and its pivotal role in the flotation of cassiterite from quartz via lead ions activation

Current research has trouble explaining the selective flotation mechanism realized by metal ions, which hinders the advancement of effective flotation techniques. In this work, the selective activation flotation of cassiterite from quartz with Pb2+ is taken as an example to illustrate the pivotal roles of surface hydroxyls in selective flotation. Accordingly, flotation, adsorption amount, and X-ray photoelectron spectroscopy (XPS) measurements and systematic first-principles calculations have been used to investigate the roles of hydroxyl groups on the selective adsorption of Pb2+. The obtained flotation, adsorption amount, and XPS test results consistently show that the Pb2+ can more strongly interplay with cassiterite than quartz resulting in selective flotation of cassiterite from quartz. The electron localization functional results illustrate that the electron localization of oxygen of Si-O bonds is stronger than the Sn-O bond resulting in the weaker electron migration ability (high hardness) of oxygen atoms of quartz than oxygen atoms of cassiterite. This makes the cassiterite surface hydroxyl groups less hard than quartz. Further crystal orbital Hamilton population and partial density of states show that the Pb2+ interacts with the oxygen atoms on cassiterite forming chemical bonds before and after the adsorption of benzohydroxamic acid (BHA). On the other hand, the interaction of Pb2+ with quartz is physical in the presence of BHA. The strong adsorption of Pb2+ on cassiterite makes it easier for BHA adsorption which accounts for the selective flotation of cassiterite from quartz. This work sheds new light on establishing a consistent and dependable theory that the hardness of surface hydroxyls is the original factor affecting the selective adsorption of metal ions on oxide mineral surfaces.

Spin-Steered Photosynthesis of H2O2 in Magnetic Single-Atom Modified Covalent Triazine Frameworks: A Density Functional Theory Study.

Covalent Organic Frameworks (COFs) demonstrate promising potential in the photocatalytic synthesis of H2O2 owing to favorable light absorption, superior charge separation, and considerable surface area. However, the efficiency of H2O2 photosynthesis is impeded by insufficient O2 adsorption sites and a high reaction barrier. In this work, various metal single atoms (Fe, Co, Ni) are introduced onto covalent triazine frameworks (CTFs) with N-N coordination sites to significantly enhance O2 adsorption and optimize H2O2 synthesis. Computational findings suggest that the presence of Fe, Co, and Ni not only enhances O2 adsorption but also exerts an influence on the reaction pathway of H2O2. Significantly, Fe exhibits a distinct advantage in modulating O2 adsorption through its unique electron spin state when compared to Co and Ni, as confirmed by crystal orbital Hamilton population (COHP) analysis. Additionally, this integration of metal atoms also improves light absorption and charge separation in CTFs. The study provides strategic insight into elevating H2O2 production by incorporating tailored metal single atoms into COFs.

Universal Intercalation/Alloying Hybrid Mechanism with -ICOHP Criterion in MAX Toward Steadily Ascending Lithium-Ion Batteries.

Profiting from the unique atomic laminated structure, metallic conductivity, and superior mechanical properties, transition metal carbides and nitrides named MAX phases have shown great potential as anodes in lithium-ion batteries. However, the complexity of MAX configurations poses a challenge. To accelerate such application, a minus integrated crystal orbital Hamilton populations descriptor is innovatively proposed to rapidly evaluate the lithium storage potential of various MAX, along with density functional theory computations. It confirms that surface A-element atoms bound to lithium ions have odds of escaping from MAX. Interestingly, the activated A-element atoms enhance the reversible uptake of lithium ions by MAX anodes through an efficient alloying reaction. As an experimental verification, the charge compensation and SnxLiy phase evolution of designed Zr2SnC MAX with optimized structure is visualized via in situ synchrotron radiation XRD and XAFS technique, which further clarifies the theoretically expected intercalation/alloying hybrid storage mechanism. Notably, Zr2SnC electrodes achieve remarkably 219.8% negative capacity attenuation over 3200 cycles at 1Ag-1. In principle, this work provides a reference for the design and development of advanced MAX electrodes, which is essential to explore diversified applications of the MAX family in specific energy fields.

Anisotropic phonon properties in SiP2 monolayer: A first-principles study

Recently, the micromechanical exfoliation method has effectively separated the two-dimensional (2D) SiP2 flake, which exhibits superior performance in field-effect transistors and photodetectors. In this paper, first-principles calculations were utilized to investigate the phononic properties of a SiP2 monolayer, which would be significant to explain the thermal deformation of 2D SiP2-based devices. We found that the acoustic phonon branches of SiP2 monolayer demonstrate significant in-plane anisotropy. The anisotropic ratios for the group velocities are 2.41 and 1.66 for the longitudinal and transverse acoustic modes, respectively. Meanwhile, the anisotropic ratio of the negative thermal expansion coefficient only considering the contribution from acoustic phonons is 0.14, while this ratio is ∼0.279 occurs at 120 K when both acoustic and optical phonons are taken into account. For the Raman-active optical phonons, the largest Grüneisen constant of these Raman-active phonons reaches 22.76, while the largest anisotropic ratio of phonon frequency is up to 2.16. To interpret this significant in-plane anisotropy, we calculated the electron density distribution, crystal orbital Hamilton populations (COHP) and interatomic force constants (IFCs), and found the maximal IFC in the x-direction is 5.79 times greater than y-direction, suggesting it as a major origin of the phononic anisotropy.

Density functional study of the electronic, bonding, elastic and infrared properties of tetragonal H2O2 ice

Hydrogen peroxide is one of the most important commercially used oxidant and exists widely in the environment. It crystallizes in a tetragonal phase via hydrogen bond at around −0.89 °C. However, many of its fundamental properties are still not well studied. To investigate systems containing hydrogen bond, van der Waals correction must be considered. In this work, we tested a series of local and non-local van der Waals corrections within the frame of density functional theory. The optPBE-vdW and the vdW-DF-CX functionals are found to be the best ones based on the relaxed lattice parameters. Then the electronic, bonding, elastic, infrared, piezoelectric and dielectric properties are studied and discussed. The results reveal that tetragonal H2O2 is an indirect band gap insulator. Bond critical point analysis, reduced density gradient analysis and crystal orbital Hamilton population analysis uncover that the H-O···H bonds are moderate hydrogen bonds, which contribute most to the formation of the crystal. The interactions between the O atoms of neighbouring H2O2 molecules also have a bit contribution. Elastic stability of tetragonal H2O2 is confirmed and its elastic anisotropy is illustrated by directional bulk and shear moduli. The vibrational modes at the Brillouin zone center are assigned, and their frequencies and eigen-displacements are calculated. Additionally, its infrared spectrum is simulated. Its Born effective charges, piezoelectric and dielectric coefficients are also obtained and discussed.

High-Throughput Screening of Sulfur Reduction Reaction Catalysts Utilizing Electronic Fingerprint Similarity.

The catalytic performance is determined by the electronic structure near the Fermi level. This study presents an effective and simple screening descriptor, i.e., the one-dimensional density of states (1D-DOS) fingerprint similarity, to identify potential catalysts for the sulfur reduction reaction (SRR) in lithium-sulfur batteries. The Δ1D-DOS in relation to the benchmark W2CS2 was calculated. This method effectively distinguishes and identifies 30 potential candidates for the SRR from 420 types of MXenes. Further analysis of the Gibbs free energy profiles reveals that MXene candidates exhibit promising thermodynamic properties for SRR, with the protocol achieving an accuracy rate exceeding 93%. Based on the crystal orbital Hamilton population (COHP) and differential charge analysis, it is confirmed that the Δ1D-DOS could effectively differentiate the interaction between MXenes and lithium polysulfide (LiPS) intermediates. This study underscores the importance of the electronic fingerprint in catalytic performance and thus may pave a new way for future high-throughput material screening for energy storage applications.

Understanding the electronic and structural effects in ORR intermediate binding on anion-substituted zirconia surfaces.

For oxygen reduction reaction (ORR), the surface adsorption energies of O* and OH* intermediates are key descriptors for catalytic activity. In this work, we investigate anion-substituted zirconia catalyst surfaces and determine that adsorption energies of O* and OH* intermediates is governed by both structural and electronic effects. When the adsorption energies are not influenced by the structural effects of the catalyst surface, they exhibit a linear correlation with integrated crystal orbital Hamiltonian population (ICOHP) of the adsorbate-surface bond. The influence of structural effects, due to re-optimisation slab geometry after adsorption of intermediate species, leads to stronger adsorption of intermediates. Our calculations show that there is a change in the bond order to accommodate the incoming adsorbate species which leads to stronger adsorption when both structural and electronic effects influence the adsorption phenomena. The insights into the catalyst-adsorbate interactions can guide the design of future ORR catalysts.

Theoretical study of NH3 , H2 S, and HCN adsorption enhancement on defective graphene-supported Cu19 clusters.

Recent studies have shown that graphene-supported metal clusters can enhance catalytic reactivity compared with corresponding metal clusters. In this study, the adsorptions of NH3 , H2 S, and HCN on Cu19 and defective graphene-supported Cu19 clusters are investigated using plane-wave density functional theory. The results reveal the three gas molecules can be adsorbed on three types of top sites of Cu atoms, respectively. The adsorption energies of the corresponding adsorption sites on the defective graphene-supported Cu19 clusters are all increased compared with those on the Cu19 clusters. The orbital-resolved, crystal orbital Hamilton population analysis demonstrates that the larger the integrated crystal orbital Hamilton population, the stronger the adsorption between the gas molecule and the bonded Cu atom. The center of antibonding states on the defective graphene-supported Cu19 is shifted upward relative to Fermi level compared to the corresponding one on pure Cu19 , which explains the enhanced adsorption energy on defective graphene-supported Cu19. In addition, the closer d-band center to the Fermi level on the defective graphene-supported Cu19 indicates a stronger adsorption capacity than on pure Cu19 .

Surface Electronic Properties-Driven Electrocatalytic Nitrogen Reduction on Metal-Conjugated Porphyrin 2D-MOFs.

Two-dimensional (2D) metal organic framework (MOF) or metalloporphyrin nanosheets with a stable metal-N4 complex unit present the metal as a single-atom catalyst dispersed in the 2D porphyrin framework. First-principles calculations on the 3d-transition metals in M-TCPP are investigated in this study for their surface-dependent electronic properties including work function and d-band center. Crystal orbital Hamiltonian population (-pCOHP) analysis highlights a higher contribution of the bonding state in the M-N bond and antibonding state in the N-N bond to be essential for N-N bond activation. A linear relationship between ΔGmax and surface electronic properties, N-N bond strength, and Bader charge has been found to influence the rate-determining potential for nitrogen reduction reaction (NRR) in M-TCPP MOFs. 2D Ti-TCPP MOF, with a kinetic energy barrier of 1.43 eV in the final protonation step of enzymatic NRR, shows exclusive NRR selectivity over competing hydrogen reduction (HER) and nitrogenous compounds (NO and NO2). Thus, Ti-TCPP MOF with an NRR limiting potential of -0.35 V in water solvent is proposed as an attractive candidate for electrocatalytic NRR.

Sustainable Anionic Redox by Inhibiting Li Cross-Layer Migration in Na-Based Layered Oxide Cathodes.

The irrational utilization of an anionic electron often accompanies structural degradation with an irreversible cation migration process upon cycling in sodium-layered oxide cathodes. Moreover, the insufficient understanding of the anionic redox involved cation migration makes the design strategies of high energy density electrodes even less effective. Herein, a P3-Na0.67Li0.2Fe0.2Mn0.6O2 (P3-NLFM) cathode is proposed with the in-plane disordered Li distribution after an in-depth remolding of the Li ribbon-ordered P3-Na0.6Li0.2Mn0.8O2 (P3-NLM) layered oxide. The disordered Li sublattice in the transition metal slab of P3-NLFM leads to the dispersed |O2p orbitals, the lowered charge transfer gap, and the suppressed phase transition at high voltages. Then the enhanced Mn-O interaction and electronic stability are disclosed by the crystal orbital Hamilton population (COHP) analysis at high voltage in P3-NLFM. Furthermore, ab initio molecular dynamics (AIMD) simulation suggests the order/disorder of the transition metal layer is highly correlated with the stability of the Li sublattice. The cross-layer migration and loss of Li in P3-NLM are suppressed in P3-NLFM to enable the high reversibility upon cycling. As a result, the P3-NLFM delivers a high capacity of 163 mAh g-1 without oxygen release and an enhanced capacity retention of 81.9% (vs 42.9% in P3-NLM) after 200 cycles, which constitutes a promising approach for sustainable oxygen redox in rechargeable batteries.

Overall Spontaneous Water Splitting for Calcium Bismuthate Ca(BiO2)2: Flexible-Electronic-Controlled Band Edge Position and Adsorption-Site-Modulated Bond Strength.

Eco-friendly photocatalysts for water splitting, highly efficient in oxygen/hydrogen evolution reactions, hold great promise for the storage of inexhaustible solar energy and address environmental challenges. However, current common photocatalysts rarely exhibit both H2 and O2 production performances unless some regulatory measures, such as strain engineering, are implemented. Additionally, the extensive utilization of flexible electronics remains constrained by their high Young's modulus. Herein, on the basis of density functional theory calculations, we identify a novel spontaneous oxygen-producing two-dimensional Ca(BiO2)2 material, which can efficiently regulate the electronic structures of the surface active sites, optimize the reaction pathways, reduce the reaction energy barriers, and boost the overall water-splitting activity through biaxial strain modulation. In detail, an unstrained Ca(BiO2)2 monolayer not only possesses a suitable band gap value (2.02 eV) to fulfill the photocatalytic water-splitting band edge relationships but also holds favorable transport properties, excellent optical absorption across the visible light spectrum, and spontaneous oxygen production under neutral conditions. More excitingly, under application of a 7% biaxial tensile strain modulation with an ideal biaxial strength of 32.35 GPa nm, the Ca(BiO2)2 monolayer not only maintains its structural integrity but also exhibits a completely spontaneous reaction for photocatalytic hydrogen precipitation with superior optical absorption. This can primarily be attributed to the substantial reduction of the potential barrier through strain engineering as well as the weakening of bond energy resulting from changes of the adsorption site as calculated by crystal orbital Hamiltonian population analysis. This flexible stretchable electronic modulated the photocatalyst behavior and bond energy of O-Bi and O-Ca interactions, offering outstanding potential for photocatalytic water spontaneous oxygen and hydrogen evolution among all of the reported metal oxides, and is more likely to become a promising candidate for future flexible electronic devices.