Conversion Reaction Research Articles

Interplay Between Metal and Acid Sites Tunes the Catalytic Selectivity Over Pd/Nanodiamond Catalysts.

Metal and acid sites are two of the most crucial catalytically active components in heterogeneous catalysis. While variations in the size, morphology, and heterogeneity of metal species, or the manipulation of the strength, location, and density of acid sites, could significantly impact the catalytic performance, the combination and interplay between these sites are even more critical and have been a recent research focus. To achieve highly efficient and selective synergistic catalysis, it is desired to design a catalyst capable of orchestrating the sequential transformation of all reactants and intermediates at different active sites. In this study, we demonstrate that both acid and metal (Pd) sites can be introduced onto a nanodiamond@graphene (NDG) support particle through simple air oxidation and metal salt deposition-precipitation methods, respectively. The presence and assembly of these two catalytically active sites significantly alter the reaction network for the cyclohexanol conversion reaction. Under this strategy, the selectivity toward designated products─cyclohexene, phenol, and benzene─can be precisely tuned by the presence and patterning of these two sites on the nanodiamond particles. Specifically, we show that the catalyst with both acid sites and Pd ensemble sites, i.e., Pd/NDG, can efficiently convert cyclohexanol through consecutive dehydration and dehydrogenation reactions to form benzene with high selectivity (>80%). These findings underscore the potential of integrating metal and acid sites to design advanced catalysts with tailored reactivity and selectivity, paving the way for more efficient and versatile catalytic processes in industrial applications.

Constructing a Li2O/LiZn Mixed Ionic Electron Conductive Layer by Ultrasonic Spraying to Enhance Li/Garnet Solid Electrolyte Interface Stability for Solid-State Batteries.

Garnet-type Li6.25Ga0.25La3Zr2O12(LGLZO) is believed to be a promising solid electrolyte for solid-state batteries due to its high ionic conductivity, safety, and good stability toward Li. However, one of the most challenges in practical application of LGLZO is the poor contact between Li and LGLZO. Herein, a ZnO layer is prepared on the surface of LGLZO pellet by ultrasonic spraying. Then, a Li2O/LiZn mixed ionic and electron conductive (MIEC) layer is formed at the Li/LGLZO interface via the conversion reaction between ZnO and molten Li. Experiments and theoretical calculations reveal that this MIEC layer can simultaneously improve interface contact, optimize interfacial kinetics, and guide homogeneous Li deposition. As a result, the interface impedance decreases significantly to 36 Ω cm2, the critical current density (CCD) can reach as high as 2.15 mA cm-2, and the Li/ZnO@LGLZO/LiFePO4 all-solid-state cells stably cycle 100 times at 0.5 C. This simple and effective approach may provide a viable strategy for improving the cycle performance of solid lithium metal batteries.

Enhanced lithium-ion storage through anchoring nanocrystalline MoO2/C microspheres in rGO nanosheets: Boosting pseudocapacitance and facilitating rapid conversion

Both crystalline and amorphous MoO2 exhibit distinct advantages for lithium-ion battery applications, with the former favoring lithium-ion intercalation and the latter undergoing complete lithiation via a conversion reaction. However, their sluggish lithium-ion insertion rates and inadequate charge transfer kinetics hinder their full potential. To address these challenges, we have developed a controllable approach that integrates liquid-phase dispersion of the HxMoO3/C and graphene oxides (GO) precursors followed by freeze-drying and low-temperature calcinations, aiming to merit the ionic conductivity of MoO2/C nanocrystallite and the electronic conductivity of reduce graphene oxides (rGO), respectively. This facile method yields bubble-sheet-like MoO2/C@rGO composites, where the quantitatively strategic incorporation of rGO can effectively mitigate recrystallization and surface oxidation of MoO2 nanocrystals. Furthermore, the approximately 70 % volume shrinkage of HxMoO3/C precursors into MoO2/C can create a flexible void space between the microspheres and the rGO coating for better accommodating volume variations during lithiation. Electrochemical measurements show that MoO2/C@rGO delivers high initial coulombic efficiency (ICE, e.g., up to 71.3 % at 100 mA g⁻¹), impressive rate performance (e.g., achieving 60 mA h g⁻¹ at 1 A g⁻¹, and 34.1 % retention from 0.1 to 2 A g⁻¹) and excellent cyclability (e.g., retaining 98.9 % of its capacity after 200 cycles) when employed as an intercalation-type anode material above 1.00 V (vs. Li/Li⁺). Remarkably, electrochemical analysis indicates that the capacitive contribution is dominant during high-rate applications (e.g., up to 73.06 % ratio at a scan rate of 0.50 mV s⁻¹), exhibiting a pseudocapacitive behavior. Additionally, MoO2/C@rGO exhibits enhanced ICE (e.g., up to 76.9 % at 100 mA g⁻¹), accelerated activation (e.g., achieving peak performance within 10 cycles at 100 mA g⁻¹), superior rate performance (e.g., achieving 446 mA h g⁻¹ at 2 A g⁻¹), and remarkable cyclability (e.g., maintaining 510 mA h g⁻¹ with 88.9 % capacity retention over 600 cycles at 1 A g⁻¹) when applied as a conversion-type anode material at between 1.00 and 3.00 V (vs. Li/Li⁺). To elucidate the mechanisms underlying the high-rate performance and the increased capacity, ex-situ XRD, ex-situ SEM, ex-situ TEM, and electrochemical analysis were carried out. No evident phase transition or material pulverization can be observed upon cycling above 1.00 V; therefore, the structural evolution is entirely single-phase or solid-solution, which accompanies with pseudocapacitive characteristic. However, the diffraction peaks downshift, the eminent of LixMoO2+δ, the pulverization, and the gradual amorphization of MoO2 can be observed upon cycling, indicating an sequential intercalation-to-conversion activation from a crystalline state to an amorphous state.

Assessment of four rhodium(I) complexes bearing SNS ligands for the catalytic reaction of chemical CO2 conversion to obtain cyclic carbonates

SNS pincer type ligands (L1-L4) were metallized with RhCl(PPh3)3, yielding new SNS type Rh(I) complexes. Different techniques, including 31P NMR, UV–Vis, XPS, mass, elemental analysis, molar conductivity, and FT-IR were used to analyze the synthesized compounds. According to the spectral data, the molecular structure of Rh(I) complexes has a four-coordinated square planar geometry around the metal center.The complexes’ lack of conductivity properties demonstrates their non-electrolyte nature in solution. The novel SNS-type Rh(I) complexes efficiently catalyzed the coupling of a variety of epoxides and CO2 to create cyclic carbonates in the presence of DMAP as a Lewis base. Diverse cyclic carbonates were also synthesized under ideal conditions with good to perfect yields (2 h, 1.6 MPa, and 100 °C). Following the discovery of new SNS-type Rh(I) catalysts with outstanding catalytic performance, epoxide, the impact of the reaction time, base, CO2 pressure, and temperature was examined for these catalysts. The complex L3-Rh and DMAP displayed the highest catalytic activity (89.6 %) and selectivity (99.4 %) for the coupling of CO2 and ECH under optimum conditions (100 °C, 2 h, and 1.6 MPa).

Candle flame generated Co and Fe single atoms supported in soot as novel host for lithium-sulfur batteries with excellent electrochemical performance

By simply introducing metal salts into paraffin, Co and Fe single atoms dispersed in candle soot (CS) can be directly collected from the flame of home-made candles without any byproducts. STEM, XRD and XANES analysis demonstrate that Co and Fe exist in single atom state. The prepared Co-CS and Fe-CS, with high specific area and excellent sulfur loading capability, can be used as innovative host for cathode to assemble Li-S pouch cells, and exhibit excellent electrochemical performance with higher specific capacities (approximately 1250 mAh/g at 0.1 C with 7.5 mg/cm² sulfur loading) and improved cycling stability (retaining about 63 % of capacity after 50 cycles) than bare CS host. Meanwhile, density functional theory (DFT) calculations demonstrate that Fe-CS/Co-CS decrease the energy barriers of conversion reactions from Li2S8 to Li2S due to the increased binding energy between Co-CS/Fe-CS and LiPSs, therefore effectively mitigating the polysulfides shuttle effect. Such a strategy holds promise for practical cell-level designs in Li-S batteries.

Atomic substitution engineering-induced domino synergistic catalysis in Li-S batteries

Atomic substitution engineering is considered as effective strategy to activate the basal plane of molybdenum disulfide (MoS2) which has been demonstrated effective catalytic cathode in lithium-sulfur (Li-S) batteries. Rationally designing atomic substitution structure is vital to figure out the origin of catalytic activity in doped-MoS2 based catalytic cathodes. Herein, an “adjacent period, adjacent group” atomic substitution engineering is constructed to investigate the role of foreign atoms in sulfur redox reaction, and reveal the origin of catalytic activity. Theoretical calculations reveal that the real active sites are the S atoms adjacent to the doped atoms. It has been demonstrated that Nb atomic substitution acts as an initiator to trigger a “Domino Effect” of activating the S sites, enhancing the adsorption ability, facilitating the conversion reaction of sulfur species, and accelerating the Li+ diffusion. Enlightened by the theoretical guidance, Nb-doped MoS2 ultrathin nanosheets assembled hollow nanotubes (Mo1-xNbxS2 HNTs) are fabricated as efficient “adsorption-conversion” sulfur hosts, which exhibit high initial discharge capacities (1163 mAh g−1 at 0.2 C, 971 mAh g−1 at 0.5 C). An initial capacity of 613 mAh g−1 could be achieved under high sulfur loading (3.13 mg cm−2) and lean electrolyte (5.6 μL mg−1). This work provides pivotal guidance to design highly efficient catalytic cathodes for advanced Li-S batteries.

Electrochemical synthesis and carbon doping of nanostructured iron fluorides from the selection of metal current collectors in lithium-ion batteries

The use of materials that rely on conversion reactions as electrodes in lithium-ion batteries is extensively investigated due to their potential for enhanced capacity compared to traditional electrode materials. Iron fluorides, in particular, present a promising alternative in terms of specific capacity. However, these materials often face challenges related to low intrinsic conductivity. This issue is typically addressed in the literature by doping the active material with carbon particles and reducing the particle size of the active material. This study explores the feasibility of directly integrating conductive carbon from the substrate into the fluoride-based active material during the synthesis process. The synthesis employs a simple anodic method conducted directly on the chosen metallic substrate, which then functions as the current collector in the devices. This approach simplifies the synthesis process, reduces processing time, and eliminates the need for additives and binders at the conventional active material-current collector interface. Two FeF3 layers were electrochemically synthesized on steel substrates with different carbon contents. These layers were evaluated as cathode-active materials for rechargeable lithium-ion batteries. The influence of carbon on the conductivity of the conversion layer was assessed using Electrochemical Impedance Spectroscopy (EIS) with a model based on conductive porous electrodes. Morphological and thickness analyses of the layers showed a strong correlation between increased pore size and layer thickness and the carbon content in the metallic substrate. The optimal performance was observed with the layer on the substrate with higher carbon content. The electrochemical performance of the active material was further evaluated using electrochemical impedance spectroscopy and galvanostatic tests in pouch cells. The conversion layers derived from carbon steel exhibited reduced resistivity and enhanced specific capacitance and cyclability compared to layers formed on pure iron.

Constructing Dual Schottky Junctions for High‐Performance Zinc Anode

AbstractAqueous zinc ion batteries provide new solutions for achieving environmentally friendly and safe energy storage devices. Unfortunately, the further application is hampered by the growth of zinc dendrites caused by uneven zinc deposition, hydrogen evolution and other side interfacial reactions at the zinc anode. Herein, a multifunctional Bi‐Bi2O3 hybrid artificial interface layer is constructed on the surface of the zinc anode using an in situ conversion reaction. Among them, the Bi‐Bi2O3 Schottky structure not only significantly accelerates the migration of Zn2+ through its built‐in electric field, but also effectively improves the hydrogen evolution barrier (ΔGH*), thereby suppressing side reactions. Moreover, the Schottky contact formed between the interface layer and the metal zinc interface also regulates the electronic distribution state on the zinc surface and optimizes the deposition process of Zn2+, ensuring a more uniform and orderly zinc deposition process. Based on the synergistic effect of dual Schottky junctions, symmetric batteries achieve stable cycling for 2000 h under the conditions of 1.0 mA cm−2 and 1.0 mAh cm−2. The full cell assembled with α‐MnO2 as the cathode maintains capacity of 112.7 mAh g−1 after 1000 cycles at 1 A g−1 with a capacity retention rate of 84%.

Boosting the phosphorus uptake of La2(CO3)3·8H2O based adsorbents via sodium addition: Relationship between crystal structure and adsorption capacity

Excess phosphate contents in water bodies triggers eutrophication, which posts significant challenges to the aquatic ecosystem. Lanthanum-carbonate based adsorbents exhibit excellent phosphate binding properties for remediating eutrophication. However, they suffer from significant adsorption-capacity loss (>85 %) at high pH. Little has been done on understanding this behavior for improving the phosphorus adsorption of lanthanum-carbonate adsorbents in alkaline environments (e.g. eutrophic water bodies). Here, we discover that La2(CO3)3·8H2O, when produced by a conversion reaction from NaLa(CO3)2·xH2O, exhibits high phosphate adsorption capacity in a wide pH window. Under alkaline conditions (e.g. pH = 10), its adsorption capacity decreases by only 8 % compared to the value under neutral pH. By isolating three different lanthanum-carbonate based compounds and analyzing their molecular structures, we find that the trace amount of Na+ residual in our La2(CO3)3·8H2O alters the chemical environment surrounding the La3+ ions, which may significantly boost the phosphate uptake at high pH. Our results provide molecular insights for further tuning the material structure of phosphate adsorbents to achieve robust performances.

Carbonaceous catalyst boosting conversion kinetics of Na2S in Na-ion batteries

Conversion-type metal sulfide anode with high theoretical capacity has received increasing attention in Na-ion batteries (SIBs), but the irreversible conversion of Na2S intermediate in charging process usually engenders low rate capability and poor cycling stability. Herein, guided by DFT calculation, a new-type carbonaceous graphitic carbon nitride (g-CN) catalyst is first reported to boost conversion kinetics of Na2S intermediate to pristine MoS2 in SIBs. Notably, the large chemisorbed energy, high selectivity and low catalytic energy barrier of g-CN catalyst can ensure its affluent charge transfers to Na2S intermediate, which chemically anchor and decompose Na2S intermediate for catalyzing its reversible conversion. Moreover, the microfluidic strategy is developed to enhance the mass diffusion of g-CN catalyst precursors into MoS2 skeleton for facilitating their subsequently covalent bonding process. The covalent bonding of g-CN catalyst on 1T-MoS2 (1T-MoS2/g-CN) superlattice with strong interfacial interaction via C-Mo bond can greatly promote Na+-storage kinetics of MoS2 in discharging process and reversible conversion reaction of Na2S intermediate to pristine MoS2 in following charging process, which is further evidenced by DFT calculation and in-situ characterizations. Consequently, the 1T-MoS2/g-CN superlattice reveals superb rate capacity and excellent cycling stability.

Versatile Organometallic Synthesis of 0D/2D Metal@Germanane Nanoarchitectonics for Electrochemical Energy Conversion Applications.

Hydrogen-terminated 2D-Germanane (2D-GeH), a germanium-based 2D material akin to graphene, is receiving enormous attention owing to its predicted optoelectronic characteristics. However, experimental research of 2D-GeH is still in an early stage, and therefore its real implementation for task-specific applications will depend on the correct development of suitable chemical functionalization methods. Herein, a general and straightforward organometallic (OM) approach is provided for the robust functionalization of 2D-GeH with different 0D noble metal nanoparticles (M-NPs), resulting in 0D/2D M@GeH nanoarchitectonics. As a proof-of-principle, 0D/2D Pt@GeH and Au@GeH nanoarchitectonics have been successfully synthesized, characterized, and explored as unconventional electrocatalysts for boosting energy conversion reactions. While the hydrogen evolution reaction activity was evaluated for Pt@GeH, the oxygen reduction reaction was interrogated for Au@GeH. Interestingly, the implanted catalytic features of M-NPs yielded to 0D/2D M@GeH nanoarchitectonics with enhanced energy conversion activity comparing to pristine 2D-GeH counterpart. This work proves the suitability of 2D-GeH as unconventional substrates to stabilize nobleM-NPs, and the versatility of the OM approach for the custom design of a new family of 0D/2D M@GeH nanoarchitectonics to expand the implementation of monoelemental 2D materials as promising electrocatalysts in energy conversion field and beyond.

Crystallographic Dimensionality Determines the Electrochemical Reaction Mechanism in Alkali Transition-Metal Chlorides.

Intense research efforts on transition metal chalcogenides (oxides and sulfides), pnictides (nitrides and phosphides), and fluorides have demonstrated the complex, intertwined effects of structural and chemical changes on their electrochemical response leading to intercalation, conversion, or displacement reactions when reacting with lithium. Prior efforts largely left halides unexplored due to their heightened solubility in classical liquid electrolytes. In this work, we employ superconcentrated electrolytes to demonstrate the composition- and structure-dependent electrochemical reactivity of A2MCl4 compounds (A = Li or Na and M = Cr, Mn, Fe, and Co). Comparing four lithiated compounds, we demonstrate that they all undergo conversion reactions when reacting with 2 Li+ per formula unit, associated with large polarization and limited cycling ability. Nevertheless, combining in situ XRD with post-mortem XPS and STEM/EDS analysis, we demonstrate that Li2CoCl4 first reacts with one Li+ following a displacement reaction providing a reversible capacity of 125 mAh g-1. This reaction is enabled by the formation of a Li6CoCl8 intermediate, which shares a similar anionic framework with pristine Li2CoCl4, ensuring the topotactic insertion of Li+ balanced by the Co2+/Co0 redox couple and the formation of metallic Co nanoparticles. Comparing these compounds, we propose that two criteria are necessary to trigger the displacement reaction in A2MCl4 compounds: the presence of 1D chains of edge-sharing octahedra to favor electronic delocalization and the availability of a metal-deficient intermediate. Screening numerous A2MCl4 compounds, we demonstrate the universality of these design principles, which extend to Na-ion materials by demonstrating a low-polarization, reversible displacement reaction for Na2MnCl4.

Adsorbate Resonance Induces Water-Metal Bonds in Electrochemical Interfaces.

This study delves into the intricate interactions between surface-near species, OH and H2O, on electrodes in electrochemical interfaces. These species are an inevitable part of many electrocatalytic energy conversion reactions such as the oxygen reduction reaction. In our modeling, we utilize high statistics on a dataset of complex solid solutions with high atomic variability to show the emergence of H2O-metal covalent bonds under specific conditions. Based on density functional theory (DFT) calculations ofadsorption energies onmany thousands of different surface compositions, we provide a quantifiable physical understanding of this induced water covalency, which is rooted in simple quantum mechanics. Directional hydrogen bonding between surface-near H2O and OH, enables surface bonding electrons to delocalize mediatedby near-symmetrical adsorbate resonance structures. The different adsorbate resonance structures differ by surface coordination explaining the induced H2O-metal bonding.

Adsorbate Resonance Induces Water‐Metal Bonds in Electrochemical Interfaces

AbstractThis study delves into the intricate interactions between surface‐near species, OH and H2O, on electrodes in electrochemical interfaces. These species are an inevitable part of many electrocatalytic energy conversion reactions such as the oxygen reduction reaction. In our modeling, we utilize high statistics on a dataset of complex solid solutions with high atomic variability to show the emergence of H2O‐metal covalent bonds under specific conditions. Based on density functional theory (DFT) calculations of adsorption energies on many thousands of different surface compositions, we provide a quantifiable physical understanding of this induced water covalency, which is rooted in simple quantum mechanics. Directional hydrogen bonding between surface‐near H2O and OH, enables surface bonding electrons to delocalize, mediated by near‐symmetrical adsorbate resonance structures. The different adsorbate resonance structures differ by surface coordination explaining the induced H2O‐metal bonding.

Electrochemical activation of MnS as an efficient conversion-type Cu2+ storage electrode

Electrochemical activation can turn inactive materials into active materials in situ for energy storage facilely, controllably and efficiently, which makes metal sulfides feasible for Cu2+ storage based on electrochemical activated into CuS. Among common heavy metal sulfides, MnS has the highest solubility product and high Cu2+ adsorption and exchange rate in the copper removal by vulcanization in nickel electrolytic anodic solution. Here, MnS is electrochemical activated in situ in aqueous Cu-ion battery, and the effects of crystal structure and particle size on the electrochemical activation of MnS were revealed. The results show that both α, γ-MnS can be electrochemical activated, and activation cycling number is related to the particle size of MnS. When the MnS particle size is ball-milled small enough (1–2 μm), MnS will be completely transformed into CuS during the first discharge process, and then CuS↔Cu2S will participate in the reversible conversion reaction for copper storage. When the MnS particle size is larger (> 10 μm), the α-MnS electrode capacity gradually increases and becomes stable after 30 cycles, and the capacity remains at 458.6 mAh g–1 after 300 cycles.

Formation of C2 and C3 hydrocarbons through photocatalytic CO2 conversion on vertical Bi2WO6 nanosheets

In contrast to conventional nanostructured photocatalysts that only catalyze the conversion of CO2 into C1 compounds of CO and CH3OH, in this study, the Bi2WO6 nanosheets are deliberately grown to form a unique vertical configuration for achieving superior photocatalytic CO2 conversion in the production of additional C2/C3 hydrocarbons, such as HCOOCH3, CH3CHO, and CH3COCH3. These products can serve as high-caloric-value fuels and chemical feedstocks, contributing to sustainability by potentially replacing fossil fuels. The vertical Bi2WO6 nanosheets predominantly expose (010) crystal planes to the CO2 atmosphere. By modifying the nanosheet to display a jagged porous feature that exposes a higher proportion of edge surfaces perpendicular to the main exposure faces, the resulting vertical porous Bi2WO6 nanosheets catalyze the formation of additional hydrocarbons, including CH4 and CH3CH2CHO. This enhancement further strengthens the sustainability merit of this photocatalytic process. To support these experimental findings, density functional theory calculations verify the enhanced photocatalytic activity of a characteristic edge face, the Bi2WO6 (100) plane, compared to the Bi2WO6 (010) plane in the conversion of CO2 and H2O into hydrocarbons requiring multielectron transfer. This study highlights the effectiveness of the vertical Bi2WO6 nanosheets, primarily featuring exposed (010) crystal planes along with additional exposed edge faces, in promoting sustainable CO2 conversion reactions for the production of C2/C3 hydrocarbons involving multielectron transfer processes.

Entropy-Modulated Short-Chain Cathode for Low-Temperature All-Solid-State Li-S Batteries.

All-solid-state Li-S batteries (ASSLSBs) due to high theoretical energy density and exceptional safety are highly desirable for electric aircraft. However, as the flight altitude rises, the low-temperature performance is hampered by inadequate practical capacity. Here, we discover that low-temperature sulfur utilization is constrained by the multi-step endothermic conversion reaction. By introducing multi-chalcogen to modulate the local entropy, a short-chain molecule cathode is designed to shorten the reduction pathways and enhance low-temperature discharge capacity. Furthermore, the mismatched lithiation lattice of the short-chain cathode reduces the decomposition energy barriers, thus enhancing low-temperature charge/discharge reversibility. The designed short-chain cathode exhibits high cathode utilization (99.4 %) and cycling stability (400 cycles, 92.2 % retention) at room temperature, as well as delivers excellent discharge capacity (579.6 mAh g-1, -40 °C) and cycling performance (100 cycles, 98.4 % retention, 394.9 Wh kg-1electrode, -20 °C) at low temperature. This study presents new opportunities to stimulate the development of low-temperature ASSLSBs.

Entropy‐Modulated Short‐Chain Cathode for Low‐Temperature All‐Solid‐State Li−S Batteries

AbstractAll‐solid‐state Li−S batteries (ASSLSBs) due to high theoretical energy density and exceptional safety are highly desirable for electric aircraft. However, as the flight altitude rises, the low‐temperature performance is hampered by inadequate practical capacity. Here, we discover that low‐temperature sulfur utilization is constrained by the multi‐step endothermic conversion reaction. By introducing multi‐chalcogen to modulate the local entropy, a short‐chain molecule cathode is designed to shorten the reduction pathways and enhance low‐temperature discharge capacity. Furthermore, the mismatched lithiation lattice of the short‐chain cathode reduces the decomposition energy barriers, thus enhancing low‐temperature charge/discharge reversibility. The designed short‐chain cathode exhibits high cathode utilization (99.4 %) and cycling stability (400 cycles, 92.2 % retention) at room temperature, as well as delivers excellent discharge capacity (579.6 mAh g−1, −40 °C) and cycling performance (100 cycles, 98.4 % retention, 394.9 Wh kg−1electrode, −20 °C) at low temperature. This study presents new opportunities to stimulate the development of low‐temperature ASSLSBs.

Fueling the future of clean energy with self‐supported layered double hydroxides‐based electrocatalysts: A step toward sustainability

AbstractAmid the ongoing transition toward renewable fuels, the self‐supported layered double hydroxides (LDHs) are envisioned as propitious electrocatalysts for reinvigorating the electrocatalysis realm, thereby facilitating environmental remediation and bolstering sustainable global energy security. Exploiting appealing attributes such as unique lamellar structure, abundant active sites, tunable intercalation spacing and compositional flexibility, LDHs boast remarkable activity, selectivity and stability across diverse energy‐related applications. By virtue of addressing the technological and time prominence of excavating their renaissance, this review first encompasses the facile state‐of‐the‐art synthetic approaches alongside intriguing modification strategies, toward deciphering the authentic structure–performance correlations for advancing more robust and precise catalyst design. Aside from this, heterostructure engineering employing diversified ranges of coupling materials is highlighted, to construct ground‐breaking binder‐free LDHs‐based heterostructures endowing with unprecedented activity and stability. Subsequently, the milestone gained from experimental research and theoretical modeling of this frontier in multifarious electrocatalytic applications, including HER, OER, UOR, AOR, seawater splitting and other fundamental conversion reactions is rigorously unveiled. As a final note, a brief conclusion is presented with an outline of future prospects. Essentially, this review aspires to offer enlightenment and incite wise inspiration for the future evolution of innovative and resilient next‐generation catalysts.image

Recent Progress in Situ Application of H2O2 Produced via Catalytic Synthesis.

Industrial production of H2O2 requires lots of energy and causes environmental pollution. Moreover, in subsequent applications, much economic loss could be produced during the transportation process of H2O2 and its dilution process. Therefore, it is highly desirable for in situ application of H2O2. In recent years, catalytic synthesis of H2O2, e. g., direct catalytic synthesis, electrocatalytic synthesis, and photocatalytic synthesis, has attracted more and more attention because the continuous and low-concentration H2O2 produced by catalytic synthesis can be directly used for the oxidation of organic compounds, effectively avoiding the shortcomings of the current industrial route. Here, we briefly reviewed the latest processes for the catalytic production of H2O2 via various routes. On this basis, we summarized and discussed the in situ application of H2O2 in typical organic conversion reactions, including the ammoximation of ketones, the oxidation of alcohols, the oxidation of C-H bonds, and the oxidation of olefins. Some in situ coupling reactions have shown excellent performance with high conversion and selectivity, and the economic cost has been significantly reduced. Finally, the shortcomings of the in situ utilization of H2O2 in coupling reactions were analyzed, and some strategies for promoting the efficiency of the H2O2 application in organic synthesis were proposed.