Charge Transfer Reactions Research Articles

Interfacial States Cause Equal Decay of Plasmons and Hot Electrons at Gold-Metal Oxide Interfaces.

We compare the decay of plasmons and "conventional" hot electrons within the same series of gold/metal oxide interfaces. We found an accelerated decay of hot electrons at gold-metal oxide interfaces with decreasing band gap of the oxide material. The decay is accelerated by the increased phase space for electron scattering caused by additional interfacial states. Since plasmons decay faster within the same series of gold-metal oxide interfaces, we propose plasmons are able to decay into the same interfacial states as hot electrons. The similarity of plasmon damping to conventional hot electron decay implies that many classical surface analysis techniques and theoretical concepts are transferable to plasmonic systems. Our results support the mechanism of direct decay of plasmons into interfacial hot electron pairs but the utility of these interfacial states for charge transfer reactions remains to be investigated.

Effect of ball-milling time and Pd addition on electrochemical hydrogen storage performance of Co2B alloy

The Co2B alloy is synthesized by high temperature solid phase process. 5 wt% Pd is added to the Co2B alloy by ball milling at different milling time in order to enhance discharge performance of the raw alloy. The phase structure and surface morphology of these alloys is characterized by XRD and SEM. The discharge capacities of the alloy milled for 10 min and 30 min are higher than that of the raw alloy. However, the discharge capacity of the alloy milled for 1 h is lower than that of the raw alloy. The result of linear polarization and EIS shows that proper milling time and uniform distribution of palladium on the alloy surface can make the alloy electrode have excellent discharge capacity. Ball milling at appropriate time can make the palladium on the alloy surface uniformly distributed and the alloy particles do not aggregate, which increases the charge-transfer reaction rate and discharge capacity. The experimental results prove that the addition of palladium and proper ball milling can effectively improve the electrochemical hydrogen storage capacity of the Co2B alloy.

Investigating solid polymer and ceramic electrolytes for lithium-ion batteries by means of an extended Distribution of Relaxation Times analysis

Solid state electrolytes based on polymer or ceramic materials are a safe alternative to liquid electrolytes based on organic solvents. Yet their ionic conductivity does not meet the required specification for state-of-the-art lithium-ion batteries. Furthermore, their conductivity mechanisms and interfacial behavior are not fully understood, making in-depth electrical characterization necessary. The calculation of the Distribution of Relaxation Times from the impedance spectrum of an electrochemical component is a powerful approach to gain insight into the processes and mechanisms responsible for the electrical and electrochemical behavior. Here we introduce an extended Distribution of Relaxation Times to avoid error-prone preprocessing. This method includes non-resistive-capacitive elements in its impedance function to overcome the constraints usually limiting the Distribution of Relaxation Times. In this study we investigated solid polymer and ceramic electrolytes regarding their conductivity mechanisms, charge transfer mechanisms and interphase formation. While the materials all possess one major conductivity mechanism, significant differences in charge transfer and interphase behavior were observed. In the case of solid polymer electrolytes, poly (ethylene glycol) bottlebrush polymers were prepared using two different boron-based lithium salts. Additionally, solid polymer electrolytes based on triethylene glycol grafted onto a poly (glycidyl propargyl ether) backbone blended with lithium bis(trifluoromethanesulfonyl)imide were compared to a similar single-ion conducting solid polymer electrolyte with the bis(trifluoromethanesulfonyl)imide anion spatially fixed to the backbone by sequential co-click synthesis. For the ceramic electrolyte, Li5·6Al0·3La3Zr1·5Ta0·5O12 powder was synthesized via a mixed oxide route and the dense ceramic electrolytes layers were fabricated by the Powder Aerosol Deposition Method. The produced layers were post-treated at 400 °C and the influence of the thermal annealing atmosphere on the conductivity of the solid electrolytes was investigated. In this study, we present the feasibility of the extended Distribution of Relaxation Times for the characterization of the investigated materials. The time-dependent formation of an interphase layer in the polymer electrolytes is identified, separated from the charge transfer process and quantified. For the ceramic electrolyte, the influence of the annealing is depicted and the charge transfer reaction is detected.

Molten‐Salt‐Mediated Synthesis of an Atomic Nickel Co‐catalyst on TiO2 for Improved Photocatalytic H2 Evolution

AbstractAtomic co‐catalysts offer high potential to improve the photocatalytic performance, of which the preparation with earth‐abundant elements is challenging. Here, a new molten salt method (MSM) is designed to prepare atomic Ni co‐catalyst on widely studied TiO2 nanoparticles. The liquid environment and space confinement effect of the molten salt leads to atomic dispersion of Ni ions on TiO2, while the strong polarizing force provided by the molten salt promotes formation of strong Ni−O bonds. Interestingly, Ni atoms are found to facilitate the formation of oxygen vacancies (OV) on TiO2 during the MSM process, which benefits the charge transfer and hydrogen evolution reaction. The synergy of atomic Ni co‐catalyst and OV results in 4‐time increase in H2 evolution rate compared to that of the Ni co‐catalyst on TiO2 prepared by an impregnation method. This work provides a new strategy of controlling atomic co‐catalyst together with defects for efficient photocatalytic water splitting.

Molten-Salt-Mediated Synthesis of an Atomic Nickel Co-catalyst on TiO2 for Improved Photocatalytic H2 Evolution.

Atomic co-catalysts offer high potential to improve the photocatalytic performance, of which the preparation with earth-abundant elements is challenging. Here, a new molten salt method (MSM) is designed to prepare atomic Ni co-catalyst on widely studied TiO2 nanoparticles. The liquid environment and space confinement effect of the molten salt leads to atomic dispersion of Ni ions on TiO2 , while the strong polarizing force provided by the molten salt promotes formation of strong Ni-O bonds. Interestingly, Ni atoms are found to facilitate the formation of oxygen vacancies (OV) on TiO2 during the MSM process, which benefits the charge transfer and hydrogen evolution reaction. The synergy of atomic Ni co-catalyst and OV results in 4-time increase in H2 evolution rate compared to that of the Ni co-catalyst on TiO2 prepared by an impregnation method. This work provides a new strategy of controlling atomic co-catalyst together with defects for efficient photocatalytic water splitting.

Theoretical modelling of electrode overvoltage for an all-solid-state electrochemical device

Understanding the mechanism of electrode overvoltage generation is important for development of functional new all-solid-state electrochemical devices. The theory of electrode overvoltage developed for liquid-state electrochemical systems led to ambiguous causality when applied to solid-state systems. In this paper, the solid-state overvoltage is formulated from ionic transport theory in solids. The solid-state device was treated as an inhomogeneous thermodynamic system. Overvoltage was derived as a function of entropy production rate and found to be attributable to diffusion of neutral compounds in the electrodes. We discussed (1) measurement of the electrode overvoltage by the current interruption technique; (2) composite electrodes consisting of the electrolyte, electronic conductor, and active material; and (3) the problem on separation of charge transfer reaction process. Physical role of the electrode overvoltage was discussed on the basis of classical irreversible thermodynamics.

A novel Nb and Cu co-doped SrCoO3-δ cathode for intermediate temperature solid oxide fuel cells

The extensive explorations of potential cathode materials are prominently critical for the rapid development of high performance solid oxide fuel cells (SOFCs). Herein, we develop a novel Nb and Cu co-doped SrCoO3-δ (SCNC) cathode base on solid state reaction, which exhibits decent compatibility with gadolinium doped cerium oxide (GDC) electrolyte. The SCNC is successfully stabilized with cubic structure at room temperature when incorporating of small amount of high valence Nb5+. Meanwhile, the oxygen vacancy concentration of SCNC is efficiently improved with the addition of Cu. The Nb and Cu co-doping also substantially promotes the electronic conductivity, achieving 550 S cm−1 for the optical doped SrCo0.85Nb0.05Cu0.10O3-δ (SCNC10) at 400 °C. In addition, the polarization of SCNC is remarkably reduced, reaching as low as 0.021 Ω cm2 for SCNC10 at 700 °C. The activation energy for reaction is also significantly lowered to 0.78 eV. The reaction order m is deduced to be about 0.30, implying that the rate determination step for SCNC10 is the charge transfer reaction. The peak power density of the single cell reaches 780 mW cm−2 at 800 °C. All these outstanding performances demonstrate that SCNC is a promising cathode for SOFCs when operating at intermediate temperature (IT).

Anionic Redox Processes in Maricite- and Triphylite-NaFePO4 of Sodium-Ion Batteries.

In recent years, NaFePO4 has been regarded as one of the most promising cathode materials for next-generation rechargeable sodium-ion batteries. There is significant interest in the redox processes of rechargeable batteries for high capacity applications. In this paper, the redox processes of triphylite-NaFePO4 and maricite-NaFePO4 materials have been analyzed based on first-principles calculations and analysis of Bader charges. Different from LiFePO4, anionic (O2–) redox reactions are evidently visible in NaFePO4. Electronic structures and density of states are calculated to elaborate the charge transfer and redox reactions during the desodiation processes. Furthermore, we also calculate the formation energies of sodium extraction, convex hull, average voltage plateaus, and volume changes of Na1–x/12FePO4 with different sodium compositions. Deformation charge density plots and magnetization for NaFePO4 are also calculated to help understand the redox reaction processes.

The Role of Cation Vacancies in Electrode Materials for Enhanced Electrochemical Energy Storage: Synthesis, Advanced Characterization, and Fundamentals

AbstractThe incorporation of atomic scale defects, such as cation vacancies, in electrode materials is considered an effective strategy to improve their electrochemical energy storage performance. In fact, cation vacancies can effectively modulate the electronic properties of host materials, thus promoting charge transfer and redox reaction kinetics. Such defects can also serve as extra host sites for inserted proton or alkali cations, facilitating the ion diffusion upon electrochemical cycling. Altogether, these features may contribute to improved electrochemical performance. In this review, the latest progress in cation vacancies‐based electrochemical energy storage materials, covering the synthetic approaches to incorporate cation vacancies and the advanced techniques to characterize such vacancies and identify their fundamental role, are provided from the chemical and materials point of view. The key challenges and future opportunities for cation vacancies‐based electrochemical energy storage materials are also discussed, particularly focusing on cation‐deficient transition metal oxides (TMOs), but also including newly emerging materials such as transition metal carbides (MXenes).

Probing non-polarizable liquid/liquid interfaces using scanning ion conductance microscopy

The study of microscopic structure of a liquid/liquid interface is of fundamental importance due to its close relation to the thermodynamics and kinetics of interfacial charge transfer reactions. In this article, the microscopic structure of a non-polarizable water/nitrobenzene (W/NB) interface was evaluated by scanning ion conductance microscope (SICM). Using SICM with a nanometer-sized quartz pipette filled with an electrolyte solution as the probe, the thickness of this type of W/NB interface could be measured at sub-nanometer scale, based on the continuous change of ionic current from one phase to another one. The effects for thicknesses of the non-polarizable W/NB interfaces with different electrolyte concentrations, the Galvani potentials at the interface and the applied potentials on the probe were measured and systematically analyzed. Both experimental setups, that is an organic phase up and an aqueous down, and a reverse version, were employed to acquire the approach curves. These data were compared with those of an ideal polarizable interface under the similar experimental conditions, and several characteristics of non-polarizable interfaces were found. The thickness of a non-polarizable interface increases with the decrease of electrolyte concentration and the increase of applied potential, which is similar to the situation of a polarizable liquid/liquid interface. We also find that the Galvani potential across a non-polarizable interface can also influence the interfacial thickness, this phenomenon is difficult to observe when using polarizable interface. Most importantly, by the comparison of two kinds of liquid/liquid interfaces, we experimentally proved that much more excess ions are gathered in the space charge layer of non-polarizable interfaces than in that of polarizable interfaces. These results are consistent with the predictions of molecular dynamic simulations and X-ray reflectivity measurements.

Probing traps in the persistent phosphor SrAl2O4:Eu2+,Dy3+,B3+ - A wavelength, temperature and sample dependent thermoluminescence investigation

Wavelength-dependent thermoluminescence (TL) experiments were performed on SrAl2O4:Eu, SrAl2O4:Eu,B, SrAl2O4:Eu,Dy and SrAl2O4:Eu,Dy,B polycrystalline samples. Excitation at 445 nm allows to selectively excite one of the two different Eu2+ ions substituting for Sr in the crystal, whereas excitation at 375 nm excites both Eu2+ ions. Incorporation of boron generates the deepest traps which contribute to the very long afterglow in this material, while dysprosium increases significantly (by a factor of about 4–8) the total number of traps involved in the afterglow of this persistent phosphor. Increasing the temperature at which the samples are irradiated (loaded) from 173 K to 248 K reveals that many new traps can only be occupied or activated at higher temperatures, leading to a strong increase of the integrated TL intensity, in particular for the Dy-containing samples. Boron does not appear to contribute to these thermally-activated traps significantly responsible for the long afterglow of SrAl2O4:Eu,Dy,B. The results of this study reveal that the diversity of traps leading to the long afterglow is much larger than previously reported in the literature. We propose that boron stabilizes F centers (which absorb in the far UV), while the presence of dysprosium induces an excitation-induced charge-transfer reaction Eu2+ + Dy3+ → Eu3+ + Dy2+. However, the principal traps responsible for the efficient afterglow are temperature-activated and appear to be associated with the green emitting Eu2+ ion on the Sr2 site coupled to a nearby dysprosium ion.

Glow discharge excitation and ionization of chromium, comparison with iron

Cr I and Cr II emission spectra from a Grimm-type glow discharge (GD) in argon and neon were analyzed. Intensities of strong resonance Cr I lines were corrected for self-absorption and population functions (experimental Boltzmann plots) of the Cr I system were established. A prevailing excitation mechanism in Cr I is the electron impact (EI) excitation. Cr II spectra in both discharges were described by transition rate (TR) diagrams, under the model of radiatively-dominated deexcitation. The contribution of cascade excitation was subtracted and the resulting net-TR diagrams of Cr II were analyzed. Unlike ionic spectra of some other transition elements, asymmetric charge transfer (ACT) between the ions of the discharge gas and ground state Cr atoms does not play a role in the excitation of the Cr II spectrum, because of the absence of suitable states in Cr II that would allow simultaneous conservation of energy and total angular momentum. Cr II states below ≈17 eV are populated largely by EI excitation from long-lived low Cr II states. In a neon discharge, ACT reactions between neutral neon metastables and doubly charged Cr ions and between neutral chromium and neon molecular ions were identified. The findings reported here were compared with the excitation of Fe I and Fe II systems at similar conditions. A well-known ‘hydrogen effect’, an enhancement of the Cr II line at 267.7165 nm in the presence of hydrogen in a GD plasma, was explained by charge transfer reaction between H+ ions and neutral chromium.

A novel contrast of the reactions of 2,4,6-trinitrotoluene (TNT) in atmospheric-pressure O2 and N2 plasma: Experimental and theoretical study

Negative-mode ion/molecule reactions of 2,4,6-trinitrotoluene (TNT) generated in atmospheric-pressure O2 and N2 corona discharge plasmas were studied. In the O2 plasma, charge transfer reaction, O2−• + TNT → O2 + TNT−•, was found as the major reaction channel. The proton abstraction reaction, O2−• + TNT → O2H• + [TNT − H+]−, was negligible, which is in sharp contrast to the formation of [DNT − H+] and [NT − H+] (DNT: 2,4-dinitrotoluene and NT: 2-nitrotoluene). TNT−• further reacts with O3 to form [TNT−NO•]− and [TNT−OH•]−. In atmospheric-pressure N2 plasma, TNT−• was detected as the dominant ion with no fragment ions.Adiabatic electron affinity (EA) of TNT was estimated by density functional theory (DFT) calculations as 2.08 eV. The precise mechanisms of the charge transfer, O2−• + TNT → TNT−• + O2, and TNT−• + O3 were examined by the frontier-orbital theory. The charge transfer may be attained by the specific O2−• coordination on the benzene ring of TNT. Reaction paths of [TNT + O3]−• leading to [TNT − OH•]− and [TNT − NO•]− were investigated by bimolecular reaction of TNT−• with O3. The formation of [TNT−NO•]− was found to be energetically more favorable than that of [TNT−OH•]−.

Anodic electrochemical mechanism and performance dominant factors of the VB2-air battery

The vanadium diboride air battery (VB2-air battery) is a primary battery with the highest intrinsic anode capacity of 4060 mAh g−1 and a theoretical open circuit potential of 1.55 V. So far, the studies of the battery are particularly limited by the elusive anodic electrochemical mechanism. In this work, the following new mechanism for the charge transfer reaction of the anode is proposed: VB2+12OH-→VO2++2BOH4-+2H2O+11e-. From the possible reactions of the anode, we conclude that the surface of the VB2 is not passivated during the battery's standing and discharging processes, which is further verified by specially designed experiments. The surface density of the active substance, the direct contact area of the active substance with the electrolyte, and the hydroxide ion concentration are considered as the dominant factors of the battery's discharge voltage and discharge capacity. A series of measurements on pouch cells have been conducted to ensure the direct proportion between the evolution tendency of charge transfer reaction and the concentration of the hydroxide ions.

A Hybrid Electrochemical Energy Storage Device Using Sustainable Electrode Materials

AbstractA new electrochemical energy storage device, comprising a faradaic rechargeable pseudo‐capacitor type electrode with a non‐faradaic rechargeable capacitor electrode, is successfully developed for potential applications in smart electric grids. Mapping new electrodes possessing both high energy and power densities as well as long cycle life is vital for the sustainable energy management. In this work, we present a new approach to design electrodes, fabricated from sustainable resources by hybridizing calcined eggshell capacitor anode with a mixed binary metal oxide pseudo‐capacitor cathode. Calcium carbonate (calcite), obtained from the biowaste‐derived eggshell, is an effective electrode material and operates via accumulation of ions on the electrode surface, providing a high discharge capacitance of 100 F/g through a non‐faradaic process. The calcite present in eggshells is found to be a valuable renewable resource which can be utilized for energy storage through suitable process design. Otherwise, such potentially useful materials (eggshells) are generally discarded as landfill. The mixed binary metallic oxide (NiO/Co3O4) showed a typical pseudocapacitive behaviour associated with both charge transfer reactions and electrostatic means provided a high discharge capacitance of 225 F/g. The fabricated prototype hybrid device provides an energy density 35 Wh/Kg at a power density 420 W/Kg. The charge storage characteristics of the hybrid device depend heavily on the current rate employed. The design and fabrication of new sustainable electrode materials provides an understanding of materials and their electrochemical performance in the high‐voltage window.

Electrochemical Inhibitory Effects of Non-edible Vegetable Oils on Low-Alloyed Low Carbon Steel in H2SO4

Corrosion inhibition mechanisms of Rubber, Neem and Jatropha seeds oils on low-alloyed low-carbon steel in 0.5 M·H2SO4 environment have been investigated herein. Potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron spectroscopy techniques were employed for the experimental process. The results obtained showed that inhibition efficiencies for Rubber, Neem and Jatropha seeds oils reached values of 99.957, 99.275 and 99.998%, respectively. The most shifts in corrosion potentials were > 85 and < 85 in positive directions for Rubber and Neem seeds oils, respectively, while Gibbs free energy of adsorption had values − 29.29 and − 15.06 and − 11.90 kJ/mol for Rubber, Neem and Jatropha seeds oils, respectively. Addition of oil inhibitors initiated formation of protective oxide films on substrate which contributed to increased inhibition efficiencies. The porosity of formed oxide film directly had impact on corrosion inhibition process as it led to localized reactions on substrate. Morphological examination of corroded substrates revealed that RSO was less prone to local corrosive attack. Inhibition efficiencies under the two electrochemical techniques employed corroborated, and corrosion inhibition occurred by retarding charge transfer reactions.

Carbon foam composites based on expanded graphite for electrochemical application

Polymer composites containing modified graphite structures as fillers have been successfully processed exhibiting attractive features for different applications. Carbon foams derived from polymer precursor is brittle and the addition of some reinforcement to produce them is of great interest not only to improve their mechanical properties, but also to use them for multifunctional purposes. Considering the advantages provided by different modified graphite structures added to polymer composites, including low price, ease of dispersion, good thermal stability, electrical conductivity, and mechanical properties, expanded graphite (EG) was chosen as filler for the carbon foams processing to produce reticulated vitreous carbon (RVC) composites. Poly(furfuryl alcohol) was used as the carbon matrix precursor and different amounts of EG were dispersed in the resin to impregnate the polyurethane foam template. The RVC_EG composites were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, compression test, and cyclic voltammetry. EG presence on RVC_EG composites showed synergic effects contributing to their crystallinity, compressive strength, and charge transfer reactions improvement as well as their specific electrochemical surface area increase. Therefore, the effectiveness of the resulting carbon composite was mainly attributed to the good interaction between EG and carbon matrix.

Rational Microstructure Design on Metal–Organic Framework Composites for Better Electrochemical Performances: Design Principle, Synthetic Strategy, and Promotion Mechanism

AbstractMetal–organic frameworks (MOFs) simultaneously containing metal ions and organic ligands have recently shown great potential for application in energy storage and conversion fields due to their controllable conversion into carbon materials or various metal species, which often exhibit superior electrochemical performance as electrode materials for energy storage and conversion. Nevertheless, the electrochemical energy storage performance of MOF derivatives can still be further enhanced through building composites with other functional materials. It is of great significance in developing new strategies of fabricating MOF composites to achieve electrode materials with improved charge transfer and electrochemical redox reaction kinetics. In this review, the novel design and strategies of MOF composites with various functional components are focused on, including carbon‐based materials (carbon nanotubes, graphene, etc.), metal oxides, 3D conductive substrates, polymeric materials, and the second MOFs and metal salts, especially their derivatives for energy storage and conversion fields. The key factors for controllable synthesis of various MOF composites and electrochemical performance enhancement mechanisms are discussed in detail. It is expected that this review will provide new inspiration for the development of MOF derivatives for energy storage and conversion.

Porous spherical NiO@NiMoO4@PPy nanoarchitectures as advanced electrochemical pseudocapacitor materials

In this work, a rational design and construction of porous spherical NiO@NiMoO4 wrapped with PPy was reported for the application of high-performance supercapacitor (SC). The results show that the NiMoO4 modification changes the morphology of NiO, and the hollow internal morphology combined with porous outer shell of NiO@NiMoO4 and NiO@NiMoO4@PPy hybrids shows an increased specific surface area (SSA), and then promotes the transfer of ions and electrons. The shell of NiMoO4 and PPy with high electronic conductivity decreases the charge-transfer reaction resistance of NiO, and then improves the electrochemical kinetics of NiO. At 20Ag−1, the initial capacitances of NiO, NiMoO4, NiO@NiMoO4 and NiO@NiMoO4@PPy are 456.0, 803.2, 764.4 and 941.6Fg−1, respectively. After 10,000 cycles, the corresponding capacitances are 346.8, 510.8, 641.2 and 904.8Fg−1, respectively. Especially, the initial capacitance of NiO@NiMoO4@PPy is 850.2Fg−1, and remains 655.2Fg−1 with a high retention of 77.1% at 30Ag−1 even after 30,000 cycles. The calculation result based on density function theory shows that the much stronger Mo-O bonds are crucial for stabilizing the NiO@NiMoO4 composite, resulting in a good cycling stability of these materials.

2D tremella-like Co6Al2CO3(OH)16•4H2O in-situ growing on 1D rod-shape ZnFe2O4 to accelerate the surface reaction kinetics for photoelectrochemical water splitting

ZnFe2O4 films applied for photoelectrochemical (PEC) water splitting is still confronted with some challenges like long distance of charge transfer and slow surface reaction kinetics. Herein, ZnFe2O4 films are initially modified by controlling morphology via regulating iron source during the hydrothermal process. A series of measurements demonstrate that one-dimensional (1D) rod-like ZnFe2O4 films possess a better PEC performance (0.11 mA cm−2 at 1.23 V vs. RHE) than that of petal-like ZnFe2O4 films (0.07 mA cm−2 at 1.23 V vs. RHE). Furthermore, the slow surface reaction kinetics of ZnFe2O4 nanorods (NRs) is accelerated by in-situ growing two-dimensional (2D) tremella-like layered double hydroxide Co6Al2CO3(OH)16•4H2O (denoted as CoAl-LDH) through a fugacious hydrothermal method. The photocurrent density of ZnFe2O4/CoAl-LDH is 0.60 mA cm−2 at 1.23 V vs. RHE, which is 5.45 times than that of ZnFe2O4 NRs. Notably, the onset potential of ZnFe2O4/CoAl-LDH is left shifted about 0.19 V–0.77 V vs. RHE compared with ZnFe2O4 NRs (0.96 V vs. RHE). This is ascribed to Co species providing active sites to capture holes for water oxidation reaction and Al species offering the support for layer skeleton. This is a first exemplification of optimizing ZnFe2O4 films for PEC water splitting through tuning morphology and depositing layered double hydroxides, it is meaningful to perceive and conceive efficient PEC devices in the future.