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Exploring highly effective bifunctional electrocatalysts with surface structural advantages and synergistic optimization effects among multimetals is greatly important for overall water splitting. Herein, we successfully synthesized Pt-loaded NiFe-metal-organic framework nanosheet arrays grown on nickel foam (Pt-NiFe-MOF/NF) via a facile hydrothermal-electrodeposition process. Benefiting from large exposed specific surface, optimal electrical conductivity and efficient metal-support interaction endow Pt-NiFe-MOF/NF with highly catalytic performance, exhibiting small overpotential of 261 mV toward oxygen evolution reaction and 125 mV toward hydrogen evolution reaction at a current density of 100 mA cm-2 in alkaline medium. More significantly, the assembled water electrolyzer comprising the Pt-NiFe-MOF/NF//Pt-NiFe-MOF/NF couple demands a low cell voltage of 1.45 V to reach 10 mA cm-2. This work renders a viable approach to design dual-functional electrocatalysts with exceptional electrocatalytic activity and stability at high current density, showing the great prospect of water electrolysis for commercial application.
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2D nanodendrites (NDs) and nanosheets (NSs) have been regarded as efficient nanocatalysts for enhancing the electrocatalytic performance due to their low coordinated sites and abundant electrocatalytic centers. Nevertheless, it remains challenging to construct advanced NDs and NSs in a single reaction system. Herein, by tuning the volume ratios of mixed solvents, the reduction and diffusion rate of Sn2+ on Pd NSs template was rationally controlled to prepare PdSn NDs and PdSn NSs. Ascribed to the open 2D nanostructure, high specific surface area, and robust synergistic effect, the as-prepared PdSn NDs and PdSn NSs exhibited distinguished electrocatalytic activities for ethylene glycol oxidation reaction (EGOR) and ethanol oxidation reaction (EOR), as well as commendable electrocatalytic durability, which were far superior to the Pd NSs and commercial Pd/C. In addition, the PdSn NDs exhibited enhanced reaction kinetics because the characteristic branch structure exposed a high density of active sites. This work may provide significant guidance for preparing excellent nanocatalysts with various morphological features by simply optimizing the content of the coexisting solvents.
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By utilizing Metal-organic framework (MOF) materials as a base, constructing electrocatalysts with heterogeneous structures offers advantages for catalyzing water splitting. In this study, a hollow heterogeneous nanocatalyst, Ir-MIL-88A@NiFe-LDHs, was prepared by growing a layered double hydroxides (LDHs) shell on MIL-88A substrate. The catalyst shows excellent oxygen evolution reaction (OER) performance in a 1.0 M KOH solution, requiring only 217 mV overpotential to achieve a current density of 10 mA cm-2 with a Tafel slope of 62.18 mV dec-1, indicating significant electrocatalytic performance and reaction kinetics characteristics. Furthermore, long-term OER testing also demonstrates the catalyst's outstanding stability. Emphasizing the interfacial interaction between MOF and LDHs, as well as the synergistic effect among Ni, Fe, and Ir elements, the study highlights how these factors collaboratively control the local electronic structure of the hollow Ir-MIL-88A@NiFe-LDHs, resulting in an efficient MOF-derived electrocatalyst.
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Rational design of facile and low-cost efficient electrocatalysts for oxygen evolution reaction (OER) is crucial to solve the energy crisis. Benefiting from in situ self-reconstruction from metal-organic frameworks (MOFs) to (oxy)hydroxides in alkaline electrolytes, MOFs have become alternative OER catalysts. Thus, Fe-doped Co-MOF nanosheets (Co-MOF/Fe) were prepared and utilized straightforwardly as OER electrocatalysts. CoFe-layered bimetallic hydroxides (CoFe-LDHs) with abundant active sites are obtained from in situ conversion of Co-MOF/Fe after etching by the KOH electrolyte, which are generally actual active species. Meanwhile, the introduction of Fe ions will also produce a synergistic effect that greatly improves the electrocatalytic OER performance. The optimized catalyst (Co-MOF/Fe10) shows exceptional OER activity (η10 = 260 mV) and excellent durability over 50 h. The outstanding OER performance of Co-MOF/Fe10 can also be reflected in the two-electrode hydrolyzer (1.57 V at 10 mA cm-2). This study offers a pathway to probe the catalytic mechanism of MOFs and the rational construction of efficient MOF-derived catalysts.
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The fabrication of hollow nanoelectrocatalysts with multilayered heterogeneous interfaces, derived from metal-organic framework (MOF) materials, represents a highly efficient strategy that promotes the oxygen evolution reaction (OER). Within this research, we successfully synthesized a hollow nanobox of Ir-doped ZIF-67@CoFe PBA with bilayer heterointerfaces. The distinctive structure of Ir-ZIF-67@CoFe PBA provides a substantial number of active sites for reaction intermediates, resulting in improved utilization of precious metals. Furthermore, experimental results indicate the outstanding electrocatalytic performance of the optimized Ir-ZIF-67@CoFe PBA, as indicated by a mere 269 mV overpotential at 10 mA·cm-2, accompanied by a small Tafel slope of 80.1 mV·dec-1. Moreover, the Schottky junction formed between the heterojunction and Ir within Ir-ZIF-67@CoFe PBA accelerates the electron-transfer rate, contributing to its exceptional catalytic performance compared to that of a catalyst derived solely from ZIF-67. This distinctive feature of the catalyst holds tremendous application value.
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Metal-organic framework (MOF) has become a popular electrocatalyst for the oxygen evolution reaction (OER) because of its large specific surface area and adjustable porosity. Nevertheless, the electrochemical performance of MOFs has been greatly limited by poor intrinsic conductivity and catalytic activity. Herein, we report a Ce-doped nanoflower-like MOF material Ce@NiFe-MOF-5 via a facile ion competitive coordination effect and doping method. Benefiting from the nanoflower structure formed by the stacking of nanosheets, a large number of active sites can be exposed, which favors electron/mass transfer during water oxidation. The coordination substitution of Ce ions not only promoted an increase in the number of active sites on the surface of the nanosheets but also optimized the electronic structure of pristine NiFe-MOF. The well-designed Ce@NiFe-MOF-5 catalysts exhibited superior OER performance under basic conditions, which only required an overpotential of 258 mV at a current density of 10 mA cm-2 and a Tafel slope of 54.44 mV dec-1. Moreover, when Ce@NiFe-MOF-5 served as an anode and Pt/C as a cathode, the two-electrode system only needed 1.56 V to drive overall water splitting at 10 mA cm-2.
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The development of efficient and stable Pd-based electrocatalysts is extremely important to facilitate the development of catalysts for polyol oxidation reactions. To synthesize Pd-based catalysts with excellent catalytic performance, a series of PdAg porous nanowires (PdAg PNWs) with different elemental ratios was constructed by facile synthesis using a seed-mediated method. The synthesized PdAg PNWs have a rough surface and a porous one-dimensional structure, which optimize the specific surface area and surface area of catalysts, thereby providing more active sites for catalysts. PdAg PNWs benefited from the geometric effect of porous nanowires and the synergy between Pd and Ag, showing excellent catalysis (8243.0 and 4137.0 mA mgPd-1) for the ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). Among them, the optimal Pd62Ag38 PNWs show the highest catalytic activity (6.0 times and 3.9 times higher than Pd/C) and stability compared with Pd57Ag43 PNWs, Pd51Ag49 PNWs, and Pd/C for EGOR and GOR. At the same time, this porous one-dimensional structure also endows PdAg PNWs with faster electron transfer capabilities than Pd/C. This work will likely provide an effective strategy for constructing cost-effective catalysts.
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Rational design and construction of well-defined hollow heterostructured nanomaterials assembled by ultrathin nanosheets overtakes crucial role in developing high-efficiency oxygen evolution reaction (OER) electrocatalysts. Herein, a reliable metal-organic framework-mediated and cation-exchange strategy to tune the geometric structure and multicomponent heterostructures has been proposed for the fabrication of hollow CoWO4-Co(OH)2 hierarchical nanoboxes assembled by rich ultrathin nanosheets. Benefiting from the hierarchical hollow nanostructure, the CoWO4-Co(OH)2 nanoboxes offer plenty of metal active centers available for reaction intermediates. Moreover, the well-defined nanointerfaces between CoWO4 and Co(OH)2 can function as the bridge for boosting the efficient electron transfer from CoWO4 to Co(OH)2. As a consequence, the optimized CoWO4-Co(OH)2 nanoboxes can exhibit outstanding electrocatalytic performance toward OER by delivering 10 mA cm-2 with a low overpotential of 280 mV and a small Tafel slope of 70.6 mV dec-1 as well as outstanding electrochemical stability. More importantly, this CoWO4-Co(OH)2 heterostructured nanocatalyst can couple with Pt/C to drive overall water splitting to achieve 10 mA cm-2 with a voltage of 1.57 V.
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Pd- and Pd-based catalysts have emerged as potential alternatives to Pt- and Pt-based catalysts for numerous electrocatalytic reactions, particularly fuel cell-related reactions, including the anodic fuel oxidation reaction (FOR) and cathodic oxygen reduction reaction (ORR). The creation of Pd- and Pd-based architectures with large surface areas, numerous low-coordinated atoms, and high density of defects and edges is the most promising strategy for improving the electrocatalytic performance of fuel cells. Recently, 2D Pd-based nanomaterials with single or few atom thickness have attracted increasing interest as potential candidates for both the ORR and FOR, owing to their remarkable advantages, including high intrinsic activity, high electron mobility, and straightforward surface functionalization. In this review, the recent advances in 2D Pd-based nanomaterials for the FOR and ORR are summarized. A fundamental understanding of the FOR and ORR is elaborated. Subsequently, the advantages and latest advances in 2D Pd-based nanomaterials for the FOR and ORR are scientifically and systematically summarized. A systematic discussion of the synthesis methods is also included which should guide researchers toward more efficient 2D Pd-based electrocatalysts. Lastly, the future outlook and trends in the development of 2D Pd-based nanomaterials toward fuel cell development are also presented.
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The core@shell structure dimension of the Pd-based nanocrystals deeply impacts their catalytic properties for C1 and C2 alcohol oxidation reactions. However, the precise simultaneous control on the synthesis of core@shell nanocrystals with different shell dimensions is difficult, and most synthesis on Pd-based core@shell nanocatalysts involves the surfactants participation by multiple steps, thus leads to limited catalytic properties. Herein, for the first time, a facile one-step surfactant-free strategy is developed for shell dimension reconstruction of PdAu@Pd core@shell nanocrystals by altering volume ratios of mixed solvents. The Pd-based sunflower-like (SL) and coral grass-like (CGL) nanocrystals are obtained with different 2D hexagonal nanosheet assembles and 3D network shells, respectively. Benefitting from the clean surface shell of 2D ultrathin nanosheets structure, high atom utilization efficiency, and robust electronic effect. The PdAu@Pd SL achieves the ascendant methanol/ethanol/ethylene glycol oxidation reaction (MOR/EOR/EGOR) activities, much higher than Pd/C catalysts, as well as the improved antipoisoning ability. Notably, this one-step construction shell dimension of PdAu@Pd core@shell catalysts not only provide a significant reference for the improvement of surfactant-free synthetic routes, but also shed light on the advanced engineering on shell dimensions in core@shell nanostructures for electrocatalysis and so forth.
Assuntos
Nanopartículas , Paládio , Catálise , Etanol , SolventesRESUMO
Optimizing the electronic and synergistic effect of hybrid electrocatalysts based on Pt and Pt-based nanocatalysts is of tremendous importance towards a superior hydrogen evolution performance under both acidic and alkaline conditions. However, developing an ideal Pt-based hydrogen evolution reaction (HER) electrocatalyst with moderated electronic structure as well as strong synergistic effect is still a challenge. Herein, we fabricated boron (B)-doped PtNi nanobundles by a two-step method using NaBH4 as the boron source to obtain PtNi/Ni4 B3 heterostructures with well-defined nanointerfaces between PtNi and Ni4 B3 , achieving an enhanced catalytic HER performance. Especially, the PtNi/Ni4 B3 nanobundles (PtNi/Ni4 B3 NBs) can deliver a current density of 10â mA cm-2 at the overpotential of 14.6 and 26.5â mV under alkaline and acidic media, respectively, as well as outstanding electrochemical stability over 40â h at the current density of 10â mA cm-2 . Remarkably, this approach is also universal for the syntheses of PtCo/Co3 B and PtFe/Fe49 B with outstanding electrocatalytic HER performance.
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Pt-based catalysts with core@shell structures are widely used in alcohol oxidations due to their excellent catalytic performance. In this work, we synthesized a series of core@shell PtAuAg@PtAg hollow nanodendrites (HNDs) with different compositions by a simple seed-mediated method. The PtAuAg@PtAg HNDs with a hollow core and dendritic shell exhibit excellent catalytic performance for ethylene glycol oxidation reaction (EGOR) and methanol oxidation reaction (MOR). Among these, Pt38Au29Ag33 HNDs have the highest mass activity (12364.0 mA mgPt-1/3278.0 mA mgPt-1) for EGOR and MOR, which is 4.2 times and 5.3 times higher than that of commercial Pt/C (2941.0 mA mgPt-1/617.6 mA mgPt-1), respectively. More importantly, after successive cyclic voltammetry tests, the retained mass activities of Pt38Au29Ag33 HNDs are 3913.8 mA mgPt-1 and 348.3 mA mgPt-1, which are much higher than that of commercial Pt/C as well. The excellent catalytic performance of PtAuAg@PtAg HNDs can be attributed to the structure of HNDs, which can greatly increase the surface area and active sites, as well as the electronic and synergistic effects among Pt, Au, and Ag. This research may provide new ideas for the development of high-efficiency hollow catalytic materials for EGOR and MOR.
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Photoelectrocatalytic nanomaterials are promising for direct alcohol fuel cells, but the construction of high-efficiency catalysts remains difficult. We herein successfully synthesized three-dimensional (3D) PdM nanosheet assemblies (PdM NSAs, M = Au, Ag, and Cu) through a seed-mediated growth method, which displayed a typical 3D nanoflower morphology assembled from many two-dimensional ultrathin nanosheets. Due to the open 3D structure and the synergistic and electronic effects between Pd and Ag, the optimized PdAg NSAs showed the highest mass activity (9378 mA mg-1) for the ethylene glycol oxidation reaction. More interestingly, when irradiated with visible light, the mass activity increased to 14â¯590 mA mg-1, 12.1 times higher than that of the commercial Pd/C (1205 mA mg-1). In addition, the as-obtained catalysts also showed better long-term durability than that of the commercial Pd/C under the condition of with or without visible-light illumination. This work highlights the utilization of light energy in designing excellent photoelectrocatalysts to promote the photoelectrocatalytic performance of anode catalysts for fuel cells.
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Developing high-performance and cost-efficient catalysts toward oxygen evolution reaction (OER) is an important but daunting task due to the sluggish kinetics hindered by the four-electron transfer process. Herein, an advanced class of ultralow Ru-doped NiCo-MOF hollow porous nanospheres (denoted as Ru@NiCo-MOF HPNs) has been reported in this work. Benefiting from the high porosity and large surface area of the metal-organic frameworks (MOFs) and optimized electronic properties by Ru doping, the as-prepared Ru@NiCo-MOF HPNs exhibit superior performance for water oxidation with the overpotential of only 284 mV to reach a current density of 10 mA·cm-2 in alkaline electrolyte, as well as a small Tafel slope of 78.8 mV·dec-1, outperforming the NiCo-MOF HPNs (358 mV) and commercial RuO2 catalyst (326 mV). The incorporation of Ru in NiCo-MOF HPNs enables a stable OER activity for at least 39 h. Moreover, we have probed the interaction between the content of Ru and OER performance, impressively, Ru@NiCo-MOF HPNs with 13.5 atom % Ru doping (denoted as Ru@NiCo-MOF-4) exhibited the highest OER activity with the excellent mass activity of 310 mA·mg-1 at an overpotential of 284 mV. Besides, a two-electrode cell with Ru@NiCo-MOF-4 as the anode and commercial Pt/C catalyst as the cathode also demonstrated outstanding electrocatalytic overall water splitting performance with a cell potential of merely 1.57 V to deliver a current density of 10 mA·cm-2.
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Although great progress in pursuing high-performance catalysts for advanced electrocatalysis has been made, the design of high-efficiency electrocatalysts continues to be a huge challenge for commercializing electrochemical energy technologies. Herein, a three-dimensional (3D) hierarchical assembly nanostructure consisting of ultrathin Ir-doped Pd nanosheets has been well designed, which could serve as a bifunctional electrocatalyst for advanced hydrogen evolution reaction (HER) and liquid fuel electrooxidation. In particular, the optimized Pd83.5Ir16.5 nanocatalyst displays excellent electrocatalytic HER performance with an overpotential of only 73 mV at 10 mA cm-2 along with excellent stability. More importantly, it can also show outstanding electrocatalytic performance for liquid fuel oxidation with a mass activity of 4326.1 mA mgmetal-1 for ethylene glycol oxidation reaction. Mechanistic study reveals that the highly porous 3D nanostructure, the modulation of electronic structure after the introduction of Ir, not only guarantees a high level of exposure of surface active sites and smooth charge transfer but also generates the new active centers for facilitating the adsorption of H2O and recombination of H*, thereby dramatically increasing the intrinsic activity of electrocatalysis.
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Hollow nanostructures with intricate interior and catalytic effects have been the focus of researchers in energy conversion and storage. Although tremendous efforts have been made, the fabrication of well-defined hollow nanostructures has been rarely reported due to the limitations of the synthetic methods. Herein, we have proposed a general synthetic strategy for the construction of V-doped CoMx (M = P, S, O) nanoboxes (NBs), where the doped V effectively modifies the electronic structure of CoMx to provide a favorable surface electrochemical environment for the adsorption of reaction intermediates (*O, *OH, and *OOH), leading to a significant enhancement in electrocatalytic performance. More importantly, the hollow nanostructures can expose abundant surface active areas and promote the chemical adsorption of reactants and intermediates, greatly contributing to the promotion of electrocatalytic performance. Impressively, the optimal V-doped CoS2 NBs show excellent electrocatalytic oxygen evolution reaction (OER) performance with an overpotential of only 290 mV at 10 mA cm-2, along with outstanding overall water-splitting performance. This work supplies pivotal insights for constructing high-performance OER catalysts on the basis of electronic and geometric engineering.
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The research on exploring advanced electrocatalysts that coupled with structural coherence and fast mass/electron transport characteristics, and maximized electrocatalytic redox activity is extremely urgent for the oxygen evolution reaction (OER), a key process for water dissociation, but it still challenging. Herein, we demonstrate a templated-engaged strategy for the fabrication of highly open and defect-rich Mn-doped Cu(OH)2 hexagonal nanorings (denoted as Mn-doped Cu(OH)2 HNs) by employing Mn(OH)2 hexagonal nanoplates as a sacrificial template. As a result of the successful doping of Mn into Cu(OH)2, the as-prepared Mn-doped Cu(OH)2 HNs possess rich defects and a modified electronic structure, which contribute to the exceptional property as a catalyst for OER electrocatalysis. More importantly, by coupling nickel foam (NF) supported Mn-doped Cu(OH)2 HNs as the anode electrode, NFs supported Pt/C as cathode electrode, a potential of only 1.62 V is needed to drive the water electrolysis to reach the current density of 10 mA cm-2, comparable to the commercial IrO2//Pt/C couple.
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Designing and elaborating cost-efficient Pd-based electrocatalysts for direct ethanol fuel cells is thought to be a significant approach to obliterating the challenge of large-scale practical application of fuel cells. Herein, our group creates a novel class of one-dimensional (1D) PdRhTe nanotubes (NTs) by using H2PdCl4 and RhCl3 as metal precursors and Te nanowires (NWs) as the reductant and sacrificial template. Strikingly, the as-obtained PdRhTe ternary nanomaterials with a unique 1D nanotube structure display a high specific activity of 6.53 mA cm-2 and a mass activity of 2039.2 mA mg-1 for the ethanol oxidation reaction (EOR) in alkaline media, which are 1.25 (1.6) and 1.77 (8.0) times those of PdTe/C and (Pd/C), respectively. More significantly, further electrochemical measurements such as CA and successive CV confirm that the optimized PdRhTe NTs display desirable durability and negligible activity decay. Taking advantage of physicochemical characterizations and electrochemical measurements, we reasonably reveal that the outstanding electrocatalytic performances are derived from the unique geometric structure and synergistic effect. The introduction of Rh facilitates the cleavage of C-C bonds, increasing the self-stability of PdRhTe NTs. In general terms, this work should provide new orientations to synthesize cost-efficient electrocatalysts by a sacrificial template method.
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Well-defined noble metal nanomaterials are attractive as catalysts for various applications because of abundant surface-active sites. However, the shape-controlled synthesis of high-performance Pt-based nanocatalysts remains a forbidden challenge. We herein demonstrate a versatile approach for realizing the systemically controlled syntheses of bimetallic Pt-Cu nanocrystals (NCs) from concave nanocubes (CNCs), to excavated nanocubes, to tripods via simply switching the amount of glycine (reducing agent). These Pt-Cu nanostructures supply a desirable platform for carrying out the structure-dependent electrocatalytic studies in the liquid fuel electro-oxidation. Impressively, all of the Pt-Cu NCs show high activity and outstanding durability for alcohol oxidation. In particular, the Pt-Cu CNCs display unprecedent high activity toward MOR and EOR, which are found to be 2041.1 and 5760.9 mA mg-1 in mass activity, 7.9- and 11.5-folds greater than the commercial Pt/C catalysts, respectively, showing a promising class of electrocatalysts for fuel cells. This work sheds great promise for optimizing the electrochemical catalysis by precisely modulating the structure of catalysts.
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Plasmonic photocatalyst has attracted significant attention due to its valuable theoretical study and promising practical applications in solar cells, functional composites, and sensors. Herein, an interesting RGO-C3N4-supported AuAg core-Au shell (AuAg@Au) nanocomposite has been reported. Due to the surface plasmon resonance (SPR) of AuAg@Au and the accelarated electron transfer and separation of charge carriers induced by the fascinating RGO-C3N4 substrate, the newly-generated AuAg@Au/RGO-C3N4 nanomaterials show a strong photo-electrochemical response under visible-light irradiation. The AuAg@Au/RGO-C3N4 photocatalyst demonstrated an excellent photo-electrochemical performance with a broad concentration linear range of 0.064-780.904 µM and a low detection limit of 0.022 µM, high stability, and good selectivity when applied in the determination of dopamine (DA) under visible-light irradiation.