Multifunctional Electrocatalysts Research Articles

G-C3N4/Chlorocobaloxime Nanocomposites as Multifunctional Electrocatalysts for Water Splitting and Energy Storage.

Due to environmental contamination and the depletion of energy supplies, it is very important to develop low-cost, high-performance, multifunctional electrocatalysts for energy conversion and storage systems. Herein, we report the development of cost-effective modified electrodes containing g-C3N4/chlorocobaloxime composites (C1-C4) and their electrocatalytic behavior toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), followed by their energy-storage applications. A series of chlorocobaloximes {ClCo(dpgH)2B} with diphenylglyoxime (dpgH) and neutral bases (B) containing a carboxylic acid moiety (isonicotinic acid, pyridine-3,5-dicarboxylic acid, indole-2-carboxylic acid, and p-aminobenzoic acid) have been synthesized and characterized by spectroscopic techniques. The nanocomposites of g-C3N4/chlorocobaloximes are prepared and characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), particle size distribution analysis (PSA), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray analysis (EDAX) techniques. The composite coatings exhibit enhanced HER performance at lower overpotential and with a lower Tafel slope. When the water-splitting reactions are studied using 0.5 M H2SO4 and 0.5 M KOH as electrolytic solutions, the composite g-C3N4/C2 containing pyridine-3,5-dicarboxylic acid as a neutral base shows excellent HER activity with a lower overpotential of 173 mV at -10 mA cm-2 and OER activity with a lower overpotential of 303 mV. The HER reaction takes place through the Volmer-Heyrovský mechanism, where the desorption step is the rate-determining step. Among the synthesized nanocomposites, the nanocomposite g-C3N4/C2 shows higher efficiency toward both HER and OER reactions, with a lower Tafel slope of 55 mV dec-1 for HER and 114 mV dec-1 for OER than the other nanocomposites. The overall water-splitting studies of the composite g-C3N4/C2 in 0.5 M KOH indicate that the evolution of hydrogen and oxygen occurs constantly up to 120 h. The supercapacitance applications studied using cyclic voltammetry and charge-discharge studies indicate that the nanocomposite g-C3N4/C1 shows a good specific capacitance of 236 F g-1 at 0.5 A g-1 compared to others. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of electron-withdrawing carboxylic-acid-functionalized neutral bases present in cobaloximes, which increases electron mobility. The incorporation of a cobaloxime complex into a g-C3N4 nanosheet enhances the electrocatalytic behavior of the nanosheet, and its performance can further be fine-tuned by systematic variation in the structure of cobaloxime by changing the halide ion, dioxime, the neutral base ligand, or the substituent.

One-Dimensional, First-Row Transition Metal, Core-Shell Architectures as Multifunctional Electrocatalysts in Alkaline and Acidic Conditions

The development of practical electrocatalysts for fuel cells, electrochemical sensors, and batteries requires nanostructured architectures with high catalytic activity and good long-term durability. It is also essential that they have very low or even no platinum content. There has also been a recent emphasis on the importance of designing multifunctional catalysts with the ability to efficiently catalyze a wide-range of electrochemical reactions in both acidic and alkaline media. In light of these requirements, we have developed a solution-based synthetic method to prepare core-shell nanowires consisting of inexpensive and abundant first-row transition metals coated with precious metal shells. The core-shell motif enables a substantial quantity of platinum to be removed from the catalytically inactive core of the material, while also resulting in the ability to tune the activity of platinum through electronic and structural interactions between the two metals. The as-synthesized core-shell nanowires have a complex surface structure that brings together metal oxide and precious metal active sites that are active toward OER and result in a significant reduction in the overpotential for OER when compared with pure Pt and Co nanowires. In addition, we have developed an electrochemical process that selectively removes the metal oxide from the surface of the nanowires enabling the catalysts to be activated toward SOM oxidation in acidic media and ORR in alkaline media. For example, the activated core-shell nanowires display a 1.5-fold and a 4-fold increase in the specific activity and mass activity of methanol oxidation, respectively, relative to a pure platinum nanowire.

Ultrafine Pt NanoparticlesAnchored on 2D Metal-Organic Frameworks as Multifunctional Electrocatalysts for Water Electrolysis and Zinc-Air Batteries.

Multifunctional electrocatalysts are crucial to cost-effective electrochemical energy conversion and storage systems requiring mutual enhancement of disparate reactions. Embedding noble metal nanoparticles in 2D metal-organic frameworks (MOFs) are proposed as an effective strategy, however, the hybrids usually suffer from poor electrochemical performance and electrical conductivity in operating conditions. Herein, ultrafine Pt nanoparticles strongly anchored on thiophenedicarboxylate acid based 2D Fe-MOF nanobelt arrays (Pt@Fe-MOF) are fabricated, allowing sufficient exposure of active sites with superior trifunctional electrocatalytic activity for hydrogen evolution, oxygen evolution, and oxygen reduction reactions. The interfacial Fe─O─Pt bonds can induce the charge redistribution of metal centers, leading to the optimization of adsorption energy for reaction intermediates, while the dispersibility of ultrafine Pt nanoparticles contributes to the high mass activity. When Pt@Fe-MOF is used as bifunctional catalysts for water-splitting, a low voltage of 1.65V is required at 100mA cm-2 with long-term stability for 20h at temperatures (65°C) relevant for industrial applications, outperforming commercial benchmarks. Furthermore, liquid Zn-air batteries with Pt@Fe-MOF in cathodes deliver high open-circuit voltages (1.397V) and decent cycling stability, which motivates the fabrication of flexible quasisolid-state rechargeable Zn-air batteries with remarkable performance.

Construction of MnFe layer double hydroxide on biomass-derived carbon heterostructure for efficient electrocatalytic water splitting

In recent years, designing effective and stable non-metal electrocatalysts for water-splitting has received considerable attention. In this study, a bio-derived carbon/MnFe-layered double hydroxide (LDH) (MnFe–C) catalyst was synthesized by pyrolysis process followed by a hydrothermal method. The MnFe–C electrocatalyst showed outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities in 1 M KOH, with overpotentials of 120 and 280 mV at 10 mA cm−2 and smaller Tafel values of 86 and 92 mV dec−1, respectively. Furthermore, the MnFe–C electrocatalyst exhibited robust stability (50 h) for both the HER and OER in an alkaline medium. This remarkable water-splitting performance is ascribed owing to the synergistic effects of the heterostructure formation of MnFe-LDH and the bio-carbon. In addition, the electrocatalyst exhibited better electrical conductivity, faster electron transfer, and more surface-active sites, which collectively enhanced the overall electrocatalytic performance. Therefore, this study offers a dynamic approach to the development of efficient multifunctional electrocatalysts for alkaline water electrolyzers.

Tuning the electrocatalytic efficacy of nano-dumbbell shaped nickel selenide anchored cobalt telluride towards oxygen evolution

In the wake of environmental enigmas including global warming and the exhaustion of traditional hydrocarbon sediments, the usage of eco-friendly power generation is of paramount importance today. Alternatives to traditional fossil fuels such as hydrogen are clean, safe, and environmentally friendly. Moreover, hydrogen as a renewable energy source, as the only by product of burning hydrogen is water. Many electrochemical energy conversion methods rely on the oxygen evolution reaction (OER), but creating effectual, economical electrocatalysts for it has proven difficult. The multifunctional electrocatalyst, nickel selenide-anchored cobalt telluride, has been found to be effective in catalyzing oxygen evolution processes in alkaline medium. CoTe and NiSe, generated hydrothermally, exhibit promising electrocatalytic activity. However, their composite NiSe@CoTe, possesses higher OER durability. The presence of NiSe in the CoTe matrix responses a powerful OER responses due to the synergistic effect in alkaline environment. The NiSe@CoTe nanocomposite shows minimal Tafel value (39 mV/dec) and lower overpotential (247 mV) to attain a current density of 10 mA/cm2, whereas the pristine CoTe and NiSe needed higher overpotential to attain same current density. Following 16 h of utilizing the same catalyst, OER stability was maintained with 88 % current density retention.

Neighboring Platinum Atomic Sites Activate Platinum-Cobalt Nanoclusters as High-Performance ORR/OER/HER Electrocatalysts.

The rational design of efficient and multifunctional electrocatalysts for energy conversion devices is one of the major challenges for clean and renewable energy transition. Herein, the local electronic structure of cobalt-platinum nanoclusters is regulated by adjacent platinum atomic site encapsulated in N-doped hollow carbon nanotubes (PtSA -PtCo NCs/N-CNTs) by pyrolysis of melamine-orientation-induced zeolite imidazole metal-organic frameworks (ZIF-67) with thimbleful platinum doping. The introduction of melamine can reactivate adjacent carbon atoms and initiate the oriented growth of nitrogen-doped carbon nanotubes. The systematic analysis suggests the significant role of thimbleful neighboring low-coordinated Pt─N2 in altering the localized electronic structure of PtCo nanoclusters. The optimized PtSA -PtCo NCs/N-CNTs-900 exhibit excellent hydrogen evolution reaction (HER)/oxygen evolution reaction (OER)/oxygen reduction reaction (ORR)/ catalytic performance reaching the current density of 10mA cm-2 in 1m KOH under the low 47 (HER) and 252mV (OER) overpotentials, and a high half-wave potential of 0.86 and 0.89V (ORR) in 0.1m KOH and 0.1m HClO4 , respectively. Remarkably, the PtSA -PtCo NC/N-CNT-900 also presents outstanding catalytic performances toward water splitting and rechargeable Zn-air batteries. The theoretical calculations reveal that optimal regulation of the electronic structure of PtCo nanoclusters by thimbleful neighboring Pt atomic reduces the reaction energy barrier in electrochemical process, facilitating the ORR/OER/HER performance.

Facile Synthesis of Nitrogen-Rich Porous Carbon/NiMn Hybrids Using Efficient Water-Splitting Reaction.

Proper design of multifunctional electrocatalyst that are abundantly available on earth, cost-effective and possess excellent activity and electrochemical stability towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are required for effective hydrogen generation from water-splitting reaction. In this context, the work herein reports the fabrication of nitrogen-rich porous carbon (NRPC) along with the inclusion of non-noble metal-based catalyst, adopting a simple and scalable methodology. NRPC containing nitrogen and oxygen atoms were synthesized from polybenzoxazine (Pbz) source, and non-noble metal(s) are inserted into the porous carbon surface using hydrothermal process. The structure formation and electrocatalytic activity of neat NRPC and monometallic and bimetallic inclusions (NRPC/Mn, NRPC/Ni and NRPC/NiMn) were analyzed using XRD, Raman, XPS, BET, SEM, TEM and electrochemical measurements. The formation of hierarchical 3D flower-like morphology for NRPC/NiMn was observed in SEM and TEM analyses. Especially, NRPC/NiMn proves to be an efficient electrocatalyst providing an overpotential of 370 mV towards OER and an overpotential of 136 mV towards HER. Moreover, it also shows a lowest Tafel slope of 64 mV dec-1 and exhibits excellent electrochemical stability up to 20 h. The synergistic effect produced by NRPC and bimetallic compounds increases the number of active sites at the electrode/electrolyte interface and thus speeds up the OER process.

Synthesis of High-Entropy-Alloy Nanoparticles by a Step-Alloying Strategy as a Superior Multifunctional Electrocatalyst.

High-entropy-alloy nanoparticles (HEA-NPs) have attracted great attention because of their unique complex compositions and tailorable properties. Further expanding the compositional space is of great significance for enriching the material library. Here, a step-alloying strategy is developed to synthesis HEA-NPs containing a range of strongly repellent elements (e.g., Bi-W) by using the rich-Pt cores formed during the first liquid phase reaction as the seed of the second thermal diffusion. Remarkably, the representative HEA-NPs-(14) with up to 14 elements exhibits extremely excellent multifunctional electrocatalytic performance for pH-universal hydrogen evolution reaction (HER), alkaline methanol oxidation reaction (MOR), and oxygen reduction reaction (ORR). Briefly, HEA-NPs-(14) only requires the ultralow overpotentials of 11 and 18mV to deliver 10 mA cm-2 and exhibits ultralong durability for 400 and 264h under 100mAcm-2 in 0.5m H2 SO4 and 1m KOH, respectively, which surpasses most advanced pH-universal HER catalysts. Moreover, HEA-NPs-(14) also exhibits an impressive peak current density of 12.6 A mg-1 Pt in 1m KOH+1m MeOH and a half-wave potential of 0.86V (vs RHE.) in 0.1m KOH. The work further expands the spectrum of possible metal alloys, which is important for the broad compositional space and future data-driven material discovery.

Design of ZnSe-CoSe heterostructure decorated in hollow N-doped carbon nanocage with generous adsorption and catalysis sites for the reversibly fast kinetics of polysulfide conversion

Although lithium-sulfur batteries (LiSBs) are regarded as one of the most promising candidates for the next-generation energy storage system, the actual industrial application is hindered by the sluggish solid–liquid phase conversion kinetics, severe shuttle effect, and low sulfur loadings. Herein, a zeolitic imidazolate framework (ZIF) derived heterogeneous ZnSe-CoSe nanoparticles encapsulated in hollow N-doped carbon nanocage (ZnSe-CoSe-HNC) was designed by etching with tannic acid as a multifunctional electrocatalyst to boost the polysulfide conversion kinetics in LiSBs. The hollow structure in ZIF ensures large inner voids for sulfur and buffering volume expansions. Abundant exposed ZnSe-CoSe heterogeneous interfaces serve as bifunctional adsorption-catalytic centers to accelerate the conversion kinetics and alleviate the shuttle effect. Together with the highly conductive framework, the ZnSe-CoSe-HNC/S cathode exhibits a high initial reversible capacity of 1305.3 mA h g−1 at 0.2 C, high-rate capability, and reliable cycling stability under high sulfur loading and lean electrolyte (maintaining at 745 mA h g−1 after 200 cycles with a high sulfur loading of 6.4 mg cm−2 and a low electrolyte/sulfur ratio of 6 μL mg−1). Theoretical calculations have demonstrated the heterostructures of ZnSe-CoSe offer higher binding energy to lithium polysulfides than that of ZnSe or CoSe, facilitating the electron transfer to lithium polysulfides. This work provides a novel heterostructure with superior catalytic ability and hollow conductive architecture, paving the way for the practical application of functional sulfur electrodes.

Controlling the electronic structure of Fe-MOF electrocatalyst for enhanced water splitting and urea oxidation: A plasma-assisted approach

The design of high-performance electrocatalysts for water splitting and urea oxidation reactions requires effective regulation of their electronic structure and electrochemical surface area (ECSA). In this study, we developed an in-situ grown Fe-MOF electrocatalyst on Fe foam (FF) by using a combination of easy hydrothermal synthesis and advanced plasma technology (Fe-MOF/FF). By varying the plasma treatment time, we could tailor the surface morphology and electronic structure of the Fe-MOF/FF microrods. Meanwhile, density functional theory (DFT) calculations investigated the catalytic mechanism, revealing that plasma-treated Fe-MOF/FF has a lower energy barrier for water splitting and H* adsorption during the HER process, and higher catalytic activity for UOR. Additionally, the electronic density of optimized Fe-MOF/FF is significantly expanded near the Fermi level. Remarkably, our catalysts achieved exceptional activity in both water splitting and urea electrolysis, requiring only 1.54 V and 1.472 V, respectively, at 10 mA cm−2, with excellent stability. Our findings highlight the potential of plasma technology as a powerful tool for developing multifunctional electrocatalysts for clean energy and industrial wastewater treatment applications.

Defect-activated ternary carbon composite: A multifunctional electrocatalyst for efficient oxidation of water, urea, glucose, ORR, and zinc-air batteries

Designing a low-cost multifunction electrocatalyst that can synergistically catalyze multiple reactions in alkaline media while operative for long periods is of paramount importance for the hydrogen economy. Particularly, defect-activated electrocatalysts can significantly improve electrolytic performance by altering their chemical properties and electronic structures. However, developing defect-rich electrocatalysts with multiple active sites for efficient electro-oxidation of water remains challenging. In this respect, we present a straightforward strategy to design a defect-activated multifunctional ternary carbon composite by integrating graphene oxide (GO), Mxene (Mx), and graphitic carbon nitride (CN). Benefiting from the well-integrated 2D interfacial coupling of different carbon nanostructures, carbon composite has several advantageous properties including superior electric conductivity, higher specific surface area, activated surface defects, and highly accessible multicomponent surface-active sites. In addition, carbon composite exhibited macroporous 3D architecture for free migration of oxygen species and electrons. Accordingly, the carbon composite served as a multifunctional electrocatalyst in alkaline media, displaying superior electrolytic activities toward oxygen evolution reaction (OER), urea oxidation reaction (UOR), glucose oxidation reaction (GOR), and oxygen reduction reaction (ORR). Moreover, the Zn-air batteries (ZABs) fabricated with Zn anode and carbon composite as air-cathode demonstrated to have a high-power density, high discharge voltage, and excellent cycling stability in alkaline media. The exceptional electrolytic performance is attributed to the defect-rich interfaces and the synergistic interactions between the multi-components of carbon composite, which not only facilitate free accessible volume for rapid diffusion of oxygen-related species but also maintain the structural integrity during the reaction, thus allowing its comparable fast reaction kinetics. Overall, this work presents a simple and scalable strategy to design an efficient, stable, and eco-friendly multifunctional electrocatalyst that has the potential to be used in a wide range of applications in energy conversion and storage.

Multifunctional catalytic activity of Cu3N (001) surface: A first-principles study

Multifunctional catalysts that exhibit high catalytic performance for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) in a single material hold great promise for broad-spectrum applications, including overall water splitting, fuel cells, and metal–air batteries. In this first-principles study, Cu 3 N is computationally demonstrated as a multifunctional electrocatalyst for the HER, OER, and ORR owing to the unique coordination of N and Cu atoms on the (001) surface. Cu 3 N exhibits better HER catalytic activity than noble Pt-based catalysts. Furthermore, its OER and ORR catalytic activity is comparable to that of commercialized unifunctional catalysts, and its 4e – pathway selectivity is high during the ORR. The catalytic performance of the ORR is significantly improved by the introduction of vacancy defects. The integration of highly efficient HER, OER, and ORR catalytic performance in earth-abundant Cu 3 N not only opens an avenue for developing cost-efficient omnipotent catalysts but also facilitates advances in clean and renewable energy.

Hollow spherical LaNiO3 perovskite with superior multifunctional performances and durability for urea-assisted Zn-air batteries

Developing low-cost and effective catalysts for oxygen reduction reaction (ORR) and urea oxidation reaction (UOR) are highly desired in the urea-assisted Zn-air battery (UZAB) and urea splitting. Herein, a hollow spherical LaNiO3 perovskite (LNO-H) was prepared by a hydrothermal method for ORR/UOR, UZAB and urea splitting. The LNO-H exhibited excellent performances for UOR in 1 M KOH with 0.33 M urea (Ej10 = 1.41 V vs RHE) and ORR in 1 M KOH (E1/2 = 0.80 V vs RHE). Moreover, the LNO-H-based UZAB showed a remarkable cycling stability over 2100 h (6300 cycles) at 2 mA cm−2. In particular, the failure mechanisms of LNO-H-based UZAB were systematically investigated by analyzing the air cathode, Zn anode and the electrolyte. The failure of LNO-H-based UZAB at 2 mA cm−2 was mainly attributed to the formation of ZnO on the air electrode. Furthermore, K2CO3 on the surfaces of air electrode via the reaction of OH− with CO2was the crucial factor for the battery failure at 10 mA cm−2. Besides, LNO-H-based urea splitting required 1.42 V to achieve 10 mA cm−2. This work may help to rationally design other multifunctional electrocatalysts, and achieve urea-based energy conversion in future.

A multifunctional copper single-atom electrocatalyst aerogel for smart sensing and producing ammonia from nitrate

Despite modern chemistry's success in providing affordable fertilizers for feeding the population and supporting the ammonia industry, ineffective nitrogen management has led to pollution of water resources and air, contributing to climate change. Here, we report a multifunctional copper single-atom electrocatalyst-based aerogel (Cu SAA) that integrates the multiscale structure of coordinated single-atomic sites and 3D channel frameworks. The Cu SAA demonstrates an impressive faradaic efficiency of 87% for NH3 synthesis, as well as remarkable sensing performance with detection limits of 0.15 ppm for NO3- and 1.19 ppm for NH4+. These multifunctional features enable precise control and conversion of nitrate to ammonia in the catalytic process, facilitating accurate regulation of the ammonium and nitrate ratios in fertilizers. We thus designed the Cu SAA into a smart and sustainable fertilizing system (SSFS), a prototype device for on-site automatic recycling of nutrients with precisely controlled nitrate/ammonium concentrations. The SSFS represents a forward step toward sustainable nutrient/waste recycling, thus permitting efficient nitrogen utilization of crops and mitigating pollutant emissions. This contribution exemplifies how electrocatalysis and nanotechnology can be potentially leveraged to enable sustainable agriculture.

Probing the origin of transition metal carbide VC for oxygen reduction reaction: A DFT study

The development of oxygen reduction reaction (ORR) electrocatalysts with high activity, high stability and low-cost is still a grand challenge. Transition metal carbides (TMCs)-based catalysts have been reported as one species of oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) trifunctional catalyst with high efficient and favorable stability. Particularly, TMCs exhibit excellent ORR activity in electrochemical catalysis, even be profitable comparable with Pt in some situations, but the clarification of the intrinsic catalytic mechanism of VC remains a challenge. Herein, the potential performance of VC system on the ORR by using the first-principles calculation method based on density functional theory and quantum mechanics. The results showed that both end-on and side-on adsorptions on the surface of VC system all possess have satisfactory ORR catalytic activity. In this study, our work proposed a reasonable design scheme for the development of multifunctional electrocatalysts with the conversion and storage of renewable energy, and provided a new possibility for the application of TMCs.

Mixed phase nanoarchitectonics of NiS@SnS@Ni3Sn2S2 as a tetrafunctional catalyst for dye-sensitized solar cells, supercapacitors, and water splitting applications

The development of low-cost, high-efficiency multifunctional electrocatalysts is an ongoing concern, and it is critical for future energy-related devices. Mixed-phase NiS@SnS@Ni3Sn2S2 nanostructures are synthesized by facile microwave approach and are used as an electrocatalyst for the reduction of tri-iodide to iodide (I3−/I−) in dye-sensitized solar cells (DSSCs), asymmetric supercapacitors, and overall water-splitting applications. Further, the performances have been improved by adding multi-walled carbon nanotubes (MWCNT). For assessing the crystalline structure, phase, size, shape, porosity, and composition, several analytical tools are employed. The electrochemical outcomes show that NiS@SnS@Ni3Sn2S2/MWCNT counter electrode assisted DSSC cell delivered the highest efficiency of 6.0 % and found to be an efficient electrode for supercapacitors, evidencing a large specific capacitance (766 F g−1 at 1 A g−1), an outstanding energy density of 85.2 W h kg−1 at an ultra-high-power density of 3600 W kg−1 and cycling stability (94 % after 10,000 cycles at 15 A g−1). Furthermore, the optimized NiS@SnS@Ni3Sn2S2/MWCNT catalyst demonstrates better oxygen and hydrogen evolution reaction. The combination of different phases and shapes in the catalysts can provide a synergistic effect as well as good surface active sites along with a carrier transfer path, resulting in efficient I3− reduction, higher specific capacitance and energy density, superior cycling stability, and low over-potential, thus making NiS@SnS@Ni3Sn2S2/MWCNT hybrid as an efficient tetrafunctional electrocatalyst for energy gadgets.

Enhanced Polysulfide Trapping and Conversion by Amorphous-Crystalline Heterostructured MnO2 Interlayers for Li-S Batteries.

The practical application of lithium-sulfur batteries (LSBs) is still hindered by several technical issues, including severe polysulfide shuttling and sluggish redox kinetics, which reduces the sulfur utilization and further results in low energy density. Herein, amorphous-crystalline heterostructured MnO2 (ACM) prepared through a simple calcination process was employed as the functional interlayer to play a double role as effective trapper and multifunctional electrocatalyst for LSBs. ACM not only combines the strong sulfur chemisorption of the amorphous MnO2 (AM) and fast Li+ transportation of the crystalline MnO2(CM) but also accelerates the interface charge transfer at the amorphous/crystalline interfaces. The LSBs with such unique interlayer exhibited an excellent rate performance of 1155.5 mAh·g-1 at 0.2 C and 692.9 mAh·g-1 at 3 C and a low decay rate of 0.071% per cycle over 500 cycles at 0.5 C. Even for a high sulfur loading of 5 mg·cm-2 at 0.1 C, a high capacity retention of 92.3% could also be achieved after 100 cycles. The concept of amorphous-crystalline heterostructures prepared by crystallization regulation might also be used for other electronic devices and catalyst designs.

Unraveling the Enhanced Electrochemical Performances of Nickel Aluminum Sulfide Lattices for Overall Water Splitting and as Counter Electrode Materials for Dye-Sensitized Solar Cells

The development of a high-performance precious metal-free multifunctional electrocatalyst for overall water splitting is a promising sign for future energy research. Here, a new strategy has been followed for the synthesis of novel-structured binary metal chalcogenide electrocatalysts, such as nickel aluminum sulfide (NiAl2S4) or nickel aluminum selenide (NiAl2Se4) spinels. The new chalcogenides, NiAl2S4 or NiAl2Se4, were confirmed by different physicochemical characterizations. Using a 316 stainless steel (SSL) mesh electrode as a three-dimensional conducting substrate, the electrocatalytic overall water splitting reaction was studied. Here, NiAl2S4 spinel outperformed the other metal chalcogenide in terms of electrocatalytic activity and charge transport in the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and overall water splitting in alkaline medium. Moreover, NiAl2S4 spinel provided the finest electrocatalytic efficiencies compared to other benchmark electrocatalysts with minimized overpotentials, such as 47 or 290 mV for HER or OER, respectively, to reach the current density of 20 mA cm–2. In overall water splitting studies, a two-electrode system was formulated to show a very low potential of 1.54 V at a current density of 20 mA cm–2. Further, the prepared NiAl2S4 electrocatalyst-loaded 316 SSL electrode demonstrated excellent durability in HER, OER, and overall water splitting reactions. The obtained Faradaic efficiency was 97%, which is due to the two-dimensional sheet-like morphology of NiAl2S4, enabling a high active surface area for efficient water electrolysis. Furthermore, NiAl2S4 spinel performed well as a counter electrode (CE) material in dye-sensitized solar cells, with an efficiency of 5.02% compared to Pt (5.38%) on the fluorine-doped indium tin oxide electrode.

A high-performance self-supported multifunctional NF@Pt electrocatalyst for overall water splitting and rechargeable zinc-air battery

Developing multifunctional electrocatalysts has been a lasting challenge. Herein, with dual surface guiding agents NaI and PVP, uniformly dispersive Pt nanoclusters on self-supported nickel foam (NF@Pt-1) has been fabricated with low Pt loading. The obtained NF@Pt-1 performs excellently in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting and rechargeable zinc-air battery. The NF@Pt-1 exhibits low HER overpotentials of 32.8 mV in alkaline solution and 50 mV in acidic solution at 10 mA cm−2. At a high current density of 100 mA cm−2, the overpotential for HER in alkaline solution is only 72.3 mV. The OER overpotential of NF@Pt-1 is 307 mV at 20 mA cm−2. All of these drive a 1.575 V overall water splitting potential. In rechargeable zinc-air battery, the recharging polarization voltage is only 0.869 V, 0.107 V smaller than that of the battery constructed with Pt/C. The excellent performances and the wide range of applications would be ascribed to the highly dispersion of Pt nanoclusters on self-support nickel foam under proper guiding effect of dual surface guiding agents. This work has explored an effective route for fabricating multifunctional electrocatalysts with relatively high performance-cost ratio.

Manifolding active sites and in situ/operando electrochemical-Raman spectroscopic studies of single-metal nanoparticle-decorated CuO nanorods in furfural biomass valorization to H2 and 2-furoic acid

Here, CuO nanorods fabricated via pulsed laser ablation in liquids were decorated with Ir, Pd, and Ru NPs (loading ∼7 wt%) through pulsed laser irradiation in the liquids process. The resulting NPs-decorated CuO nanorods were characterized spectroscopically and employed as multifunctional electrocatalysts in OER, HER, and the furfural oxidation reactions (FOR). Ir–CuO nanorods afford the lowest overpotential of ∼345 mV (HER) and 414 mV (OER) at 10 mA cm−2, provide the highest 2-furoic acid yield (∼10.85 mM) with 64.9% selectivity, and the best Faradaic efficiency ∼72.7% in 2 h of FOR at 1.58 V (vs. RHE). In situ electrochemical-Raman analysis of the Ir–CuO detects the formation of the crucial intermediates, such as Cu(III)-oxide, Cu(OH)2, and Irx(OH)y, on the electrode–electrolyte surface, which act as a promoter for HER and OER. The Ir–CuO || Ir–CuO in a coupled HER and FOR-electrolyzer operates at ∼200 mV lower voltage, compared with the conventional electrolyzer and embodies the dual advantage of energy-saving H2 and 2-furoic acid production.