Efficient Non-precious Metal Catalysts Research Articles

Efficient targeted acquisition 2,5-furandicarboxylic acid derived from 5-hydroxymethylfurfural over novel copper and vanadium oxide-functionalized catalysts

2,5-Furandicarboxylic acid (FDCA), which is recognized as a valuable alternative to petroleum-derived terephthalic acid and produce more bio-based polymers, has attracted considerable attention in recent years. Herein, a series of nitrogen-containing polymer nanosheets bearing Cu2+ and VO2+ (Cu2+-VO2+/PDVTA) were designed and displayed superior catalytic performance in the selective oxidation of 5-hydroxymethylfurfural (HMF) to FDCA. The catalyst was characterized by FT-IR, SEM, XPS, TG, UV–Vis DRS, PL, and ICP-AES analysis techniques. The effects of various reaction parameters, including the tert-butyl hydroperoxide dosage, temperature, and solvents on the HMF oxidation were systematically investigated, and the results were discussed in details. The Cu2+-VO2+/PDVTA catalyst achieved 100% conversion of HMF with 98.6% selectivity toward FDCA without the requirement for any basic additives under mild conditions (90 °C, 10 h), as well as has a good reusability. Coupling of the active sites of Cu2+ and VO2+ provide a synergistic effect for FDCA production. This study may provide a novel method for the development of efficient non-precious metal catalyst without addition of alkali additives, benefiting the valorization of furan-based compounds into high-valued chemicals in industrial processes.

Density functional theory-based screening of Ti4C3O2-loaded single atoms for efficient selective catalytic oxidation of formaldehyde

Indoor formaldehyde (HCHO) pollution poses a major risk to human health. Low-temperature catalytic oxidation is an effective method for HCHO removal. The high activity and selectivity of single atomic catalysts provide a possibility for the development of efficient non-precious metal catalysts. In this study, the most stable single-atom catalyst Ti–Ti4C3O2 was screened by density functional theory among many single atomic catalysts with two-dimensional (2D) monolayer Ti4C3O2 as the support. The computational results show that Ti–Ti4C3O2 is highly selective to HCHO and O2 in complex environments. The HCHO oxidation reaction pathways are proposed based on the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. According to the reaction energy and energy span models, the E-R mechanism has a lower maximum energy barrier and higher catalytic efficiency than the L-H mechanism. In addition, the stability of the Ti–Ti4C3O2 structure and active center was verified by diffusion energy barrier and ab initio molecular dynamics simulations. The above results indicate that Ti–Ti4C3O2 is a promising non-precious metal catalyst. The present study provides detailed theoretical insights into the catalytic oxidation of HCHO by Ti–Ti4C3O2, as well as an idea for the development of efficient non-precious metal catalysts based on 2D materials.

Synthesis of NbC@C(Nx) nanoparticles using DC arc discharge plasma for highly efficient oxygen reduction reaction

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(Nx) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N1.36) NPs showed an onset potential (Eonset) of 0.89 V (vs. RHE) and a half-wave potential (E1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (Eonset = 0.90 V, E1/2 = 0.80 V), and its diffusion-limited current density (JL) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (Te) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR.

Real-time diagnostic synthesis of nitrogen-doped carbon-coated VC@C(Nx) core-shell nanoparticles by DC arc plasma as efficient ORR electrocatalysts

The high complexity and cost of synthesis methods, along with the instability of catalytic activity, pose significant challenges in the search for viable non-precious metal alternatives to commercial Pt/C catalysts for oxygen reduction reaction (ORR). In this study, we employed a highly efficient and cost-effective method, namely, DC arc plasma, to synthesize carbon-coated vanadium carbide (VC@C) core-shell nanoparticles in a one-step process. The synthesized VC@C material was subsequently nitrogen-doped using urea as a nitrogen (N) source in a tube furnace, resulting in the formation of N-doped carbon-coated VC [VC@C(Nx)] catalysts for ORR electrocatalysis in alkaline media. Real-time optical emission spectroscopy (OES) analysis offers an in-depth comprehension of the energy states involved in the synthesis process of VC@C nanocrystalline powders. Highlighting the plasma states at various stages throughout the synthesis, provides a solid basis for dissecting the formation of VC@C nanoparticles and elucidating the intricate nature of their core-shell structures. Compared to the VC@C catalyst, the VC@C(N10) catalyst exhibited a significant improvement in both half-wave and onset potential, approaching the performance levels comparable to Pt/C catalysts. Moreover, VC@C(N10) demonstrated superior ORR kinetics, stability, and methanol tolerance. The exceptional performance of VC@C(N10) could be primarily attributed to the introduction of nitrogen doping, which generated more active sites and enhanced the synergistic cooperation between the VC core and the nitrogen-doped carbon shell. Additionally, the protective effect from the carbon shell prevented corrosion and oxidation of the VC core. This study represents a new exploration in the quest for the development of stable and efficient non-precious metal catalysts for ORR applications.

(General Student Poster Award Winner, 2nd Place) Enhanced Oxygen Evolution Reaction Performance through Alkaline-Earth Metal Doped Fe-Rich Nano Dry-Petals: A Cost-Effective and Eco-Friendly Electrocatalyst Approach

The progress towards hydrogen production via electrolysis technologies rely on the advancement of economical, abundant, non-toxic, stable, and efficient non-precious metal catalysts for oxygen evolution reactions (OER). As the second most abundant metal on Earth, iron (Fe) offers a cost-effective alternative to more expensive OER catalysts derived from ruthenium (Ru), iridium (Ir), cobalt (Co) and nickel (Ni). However, Fe-based catalysts typically display limited OER activity. Here we present a unique strategy of introducing an alkaline-earth metal into Fe-rich crystal for the enhanced OER activity in alkaline condition. To achieve this, a facile method was developed to obtain a nano dry-petals structured M-FeOOH electrocatalyst. The optimized M-FeOOH electrocatalyst exhibits an impressively low overpotential of +259 mV at a current density of 10 mA cm-2 in 1.0 M KOH which was found to be superior to the pristine FeOOH electrode. Through a series of experiments and density functional theory (DFT) calculations, we reveal that the addition of an alkaline-earth metal to FeOOH as a dopant optimizes the electronic structure and free energy for adsorbed intermediates synergistically. As a result, the OER activity of the M-FeOOH electrocatalyst is significantly improved. Our results highlight the possibility of doping FeOOH OER catalysts using an affordable and eco-friendly approach, setting the stage for the development of advanced OER electrocatalysts.

Highly Durable Electrocatalyst with Low-Loading Pt-Co Dispersed over Graphene Nanofiber for Oxygen Reduction Reaction Under PEMFC Condition

Proton exchange membrane fuel cell (PEMFC) has been demonstrated as a highly efficient energy conversion technology. The sluggish oxygen reduction reaction (ORR) at the fuel cell cathode requires 3 to 5 times more catalysts than the hydrogen oxidation reaction at the anode (1). Currently, platinum is still the catalyst material of choice. However, the heavy use of scarce Pt in the electrodes represents a major cost barrier to the commercialization of PEMFCs. Tremendous efforts have been dedicated to reduce or remove Pt usage through the development of Pt-transition metal catalysts, as highlighted recently by dealloyed PtNi (2), Mo-doped PtNi(3), and ordered PtCo (4); or through the development of transition metals-nitrogen-carbon based PGM-free catalysts (5, 6).In the fuel cell, catalysts should be highly dispersed over the electrode surface to be easily accessible by the reactants, especially at the high fuel cell current density where a large influx of O2 must be converted. For the Pt alloy catalyst of large crystallites, there won’t be enough crystallites available to spread over the electrode surface to encounter the incoming O2 if the total loading of platinum has to be maintained ultralow. Furthermore, unprotected Pt nano-alloys may lose their nanostructure and crystallinity from the dissolution and agglomeration during the ORR process. The PGM-free catalysts, on the other hand, have high catalytic site density with uniform distribution when prepared by homogenous precursors such as metal-organic framework or porous organic polymer, rendering them highly efficient in interacting with O2 flux. Their key drawback, however, is the poor stability operated under PEMFC condition.In this presentation, we will describe a method of preparing highly active yet stable electrocatalysts containing ultralow Pt content using polymer fiber containing cobalt zeolitic imidazolate framework as precursor. The new catalyst contains Pt-Co nanoparticels situated over the PGM-free catalystically active support (7,8). The ORR activities of the new catalyst was first tested in O2 saturated acidic electrolyte by rotating ring disk electrode (RRDE) before fabricated into the membrane electrode assembly (MEA) and evaluated under fuel cell operating condition. The synergistic catalysis between PtCo NPs and the PGM-free active substrate led to an unprecedented oRR performance in both RRDE and fuel cell. For example, the fuel cell test demonstrated a mess activity of 2.43 A/mgPt for the new catalysts and > 80% retention of the initial mass activity after 60000 continuous voltage cycles from 0.6 – 1.0 V.The characterizations of the fresh and the post-electrochemical test samples were investigated by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), x-ray absorption near-edge structure (XANES), extended x-ray absorption fine structure (EXAFS), transmission electron microscopy (TEM), Raman spectroscopy and BET surface analysis. We also performed DFT calculation on the ORR thermodynamic barriers over both Pt-Co NPs and PGM-free site as the descriptors for reaction pathway. The results reveal that the synergistic interaction between Pt-Co and PGM active substrate contribute significantly to both activity and durability enhancements.Acknowledgments:This work was supported by Argonne National Laboratory through Maria Goeppert Mayer Fellowship, US; Overseas Outstanding Youth Fund project, shanghai Jiao Tong university, Shanghai, China, State Key Laboratory of Metal Matrix Composites, shanghai Jiao Tong university, Shanghai, China. The works performed at Argonne National Laboratory’s Center for Nanoscale Materials and Advanced Photo Source, and Hydrogen research center, shanghai Jiao Tong university.Reference: H. A. Gasteiger, N. M. Markovic, Just a Dream-or Future Reality? Science 324, 48-49 (2009).B. Han et al., Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells. Energy & Environmental Science 8, 258-266 (2015).X. Huang et al., High-performance transition metal–doped Pt3Ni octahedra for oxygen reduction reaction. Science 348, 1230-1234 (2015).D. Wang et al., Structurally ordered intermetallic platinum-cobalt core-shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts. Nat Mater 12, 81-87 (2013).L. Chong et al., Investigation of Oxygen Reduction Activity of Catalysts Derived from Co and Co/Zn Methyl-Imidazolate Frameworks in Proton Exchange Membrane Fuel Cells. ChemElectroChem 3, 1541-1545 (2016).J. Shui, C. Chen, L. Grabstanowicz, D. Zhao, D. J. Liu, Highly efficient nonprecious metal catalyst prepared with metal-organic framework in a continuous carbon nanofibrous network. Proc Natl Acad Sci U S A 112, 10629-10634 (2015).L. Chong et al., Ultralow-loading platinum-cobalt fuel cell catalysts derived from imidazolate frameworks. Science, (2018).L. Chong et al., Highly durable fuel cell electrocatalyst with low-loading Pt-Co nanoparticles dispersed over single-atom Pt-Co-N-graphene nanofiber. Chem Catalysis 3, 100541.

Monometallic interphase synergistic Ni-based catalysts prepared by facile magnetron sputtering for efficient alkaline hydrogen evolution

The development of affordable, efficient and long-lasting electrocatalysts plays a vital role in advancing clean and renewable energy technologies. Ni-based materials have emerged as highly promising alternatives to noble metal for HER. However, existing Ni-based catalysts are generally constrained by complex composition, structure and preparation process, as well as poor stability caused by the weak bonding with the electrode substrate. Here, we prepared monometallic interphase synergistic Ni/NiO self-supported electrodes on Cu foam. The as-prepared Ni/NiO/CF-110 shows excellent HER activity, displaying a lower overpotential of 22 mV at 10 mA cm−2 and achieving nearly 100% Faradaic efficiency. Meanwhile, Ni/NiO/CF-110 exhibits robust stability, withstanding a chronopotentiometric test at 100 mA cm−2 over 100 h. The Ni/NiO/CF-110 was assembled into an alkaline electrolytic cell for water splitting, achieving 10 mA cm−2 with a remarkably low cell voltage of 1.4 V. The outstanding HER performance can be attributed to the synergistic effect of the monometallic phase Ni and NiO, the structural benefits of foam substrate, the good combination with substrate, and the optimal Ni/NiO ratio. This study proposes a novel and simple preparation strategy and provides guidance for developing highly efficient non-precious metal catalysts.

Construction of Single-Atom Catalysts for N, O Synergistic Coordination and Application to Electrocatalytic O2 Reduction.

Replacing expensive platinum oxygen reduction reaction (ORR) catalysts with atomically dispersed single-atom catalysts is an effective way to improve the energy conversion efficiency of fuel cells. Herein, a series of single-atom catalysts, TM-N2O2Cx (TM=Sc-Zn) with TM-N2O2 active units, were designed, and their catalytic performance for electrocatalytic O2 reduction was investigated based on density functional theory. The results show that TM-N2O2Cx exhibits excellent catalytic activity and stability in acidic media. The eight catalysts (TM=Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are all 4e- reaction paths, among which Sc-N2O2Cx, Ti-N2O2Cx, and V-N2O2Cx follow dissociative mechanisms and the rest are consistent with associative mechanisms. In particular, Co-N2O2Cx and Ni-N2O2Cx enable a smooth reduction in O2 at small overpotentials (0.44 V and 0.49 V, respectively). Furthermore, a linear relationship between the adsorption free energies of the ORR oxygen-containing intermediates was evident, leading to the development of a volcano plot for the purpose of screening exceptional catalysts for ORR. This research will offer a novel strategy for the design and fabrication of exceptionally efficient non-precious metal catalysts on an atomic scale.

N-doped porous carbon encapsulated Fe and Ni bimetal derived from MOFs as efficient oxygen reduction reaction catalysts for anion exchange membrane fuel cell

The anion exchange membrane fuel cell (AEMFC) represents a promising avenue in clean energy equipment. However, its practical application is limited due to the high cost of Pt-based catalysts. Therefore, it is necessary to develop cheap and efficient non-precious metal catalysts. Here in, we employed a simple one-step thermal strategy to synthesize N-doped porous carbon encapsulated Fe and Ni bimetal catalysts (FeNi-N-C-1-1-Ts, T = 900, 950, 1000, 1050 and 1100 ℃). Among these catalysts, FeNi-N-C-1-1-1000 exhibited the highest half-wave potential of 0.885 V, 5 mV higher than 20 wt% Pt/C (0.880 V). Furthermore, it demonstrated a dominant 4e- reduction pathway, exceptional durability and high resistance to methanol. These excellent performances were attributed to the synergistic effect of FeNi bimetallicaction, increased graphitic content, higher Fe/Ni-N4 content, larger BET surface area and the presence of mesoporous structures. Moreover, FeNi-N-C-1-1-1000 exhibited higher half-wave potential than Ni-N-C-1000 and Fe-N-C-1000 owing to the smaller particle size and larger BET surface area of FeNi-N-C after the doping of Ni into Fe-N-C. Finally, FeNi-N-C-1-1-1000 was employed as the cathode in the AEMFC with a loading of 2.0 mg·cm−2, resulting in the highest peak power density of 545 mW·cm−2, surpassing that of 20 wt% Pt/C (375 mW·cm−2) by 170 mW·cm−2.

Graphene-edge-supported iron dual-atom for oxygen reduction electrocatalysts.

Pyrolyzed Fe-N-C-based catalysts, particularly FeN4, are reported to show enhanced catalytic activity for some chemical reactions, particularly for the oxygen reduction reaction (ORR). Here, we present a computational study to investigate another pyrolyzed Fe-N-C-based catalyst, i.e. Fe2N6, adsorbed on graphene with special emphasis on the edges of graphene nanoribbons (both zig-zag and armchair configurations) as a candidate for Fe dual-atom catalysts (Fe-DACs). Utilizing density functional theory calculations along with microkinetic simulations, we investigate the influence of graphitic edges on the stability and ORR activity of Fe-DAC active sites. Our findings indicate that the presence of graphitic edges, particularly the zig-zag configuration, significantly lowers the formation energy of Fe-DAC active sites, making them more likely to form at the edges. Furthermore, several Fe-DAC active sites at graphitic edges exhibit exceptional ORR performance, surpassing the commonly employed FeN4 active site in SAC systems and even exceeding the benchmark Pt(111) surface. Notably, the (Fe2N6)o@z1 active site demonstrates outstanding performance in both associative and dissociative mechanisms. These results highlight the role of graphitic nanopores in enhancing the catalytic behavior of Fe-DAC active sites, providing valuable insights for designing efficient non-precious metal catalysts for ORR applications.

Enhancing the catalytic performance of Co-N-C derived from ZIF-67 by mesoporous silica encapsulation for chemoselective hydrogenation of furfural.

Developing Cr-free and non-noble metal catalysts with high activity, selectivity and durability for chemoselective hydrogenation of furfural to furfuryl alcohol is highly desirable yet challenging. In this study, we design a hollow mesoporous Co-N-C@mSiO2 nanostructure derived from ZIF-67 via the encapsulation-pyrolysis strategy. The Co-N-C@mSiO2 catalyst exhibits excellent catalytic performance in the furfural hydrogenation towards furfuryl alcohol with good stability, and is much better than the Co-N-C catalyst originating from plain ZIF-67 and other reported transition metal catalysts. Characterization methods and control experiments show that Co-Nx species rather than Co metal should be catalytically active sites for the above reaction. The enhanced performance is associated with abundant Co-Nx active sites, good mass transport, and the SiO2 shell protection. This work provides a novel and facile strategy for preparing highly efficient non-precious metal catalysts to replace Cr-based and noble metal catalysts for furfural hydrogenation.

Candied Haws-Like Fe–N–C Catalysts with Broadened Carbon Interlayer Spacing for Efficient Zinc–Air Battery

As efficient nonprecious metal catalysts for oxygen reduction reaction (ORR), Fe-N-C materials are one of the most promising alternatives to Pt-based catalysts for fuel cells and metal-air batteries. However, the intrinsically low density of key active sites like FeN4 moieties hampers their commercial applications. Herein, we provide a smart strategy to construct a candied haws-like Fe-N-C catalyst (CH-FeNC) with broadened carbon interplanar spacing (>4 Å), starting with trehalose as a structure-built brick coupled with a zinc-zeolite imidazole framework (ZIF-8) and polyaniline (PANI) and then followed by copyrolysis carbonization of them. The obtained CH-FeNC exhibits half-wave potentials of 0.92 and 0.90 V (vs RHE) before and after 10,000 cycles in 0.1 M KOH, which are superior to the 0.90 and 0.85 V obtained by commercial Pt/C for ORR. The power density of a homemade zinc-air battery equipped with the catalyst is up to 131 mW cm-2, greater than that of Pt/C (124 mW cm-2). The extended X-ray absorption fine structure (EXAFS) results and density functional theory (DFT) theoretical calculations reveal that there exists enriched zigzag or armchair edge-hosted FeN4 active sites, located at the abundant interface between carbon components in this composite. Furthermore, the unique broadened carbon interlayer spacing plays a key role in deciding the ORR rate in alkaline but not in acidic environments because there exists a fifth ligand of active Fe in the form of FeN4 centers coupled with SO42- and ClO4- from acids.

Single-atom Co-N-C catalysts for high-efficiency reverse water-gas shift reaction

Designing efficient non-precious metal catalysts for CO2 hydrogenation is a significant challenge. Cobalt-based catalysts often failed to catalyze the reverse water-gas shift (RWGS) reaction with high CO selectivity and stability. Herein, nitrogen-doped carbon (N-C) immobilized single-atom Co-N4 catalyst with 5% Co loading were prepared by anchoring strategy through regulating the cobalt species coordination structure. The stable single-atom catalyst achieves almost 100% CO selectivity and a high CO2 conversion of 52.4% at 500 °C during CO2 hydrogenation, while the 20% Co-N-C nanoparticle catalyst favored CH4 formation. The experiments and density functional theory (DFT) calculations revealed that atomically dispersed Co-N4 site followed the hydrogen-assisted pathway in which the intermediate COOH* was desorbed and dissociated into CO, whereas the Co nanoparticle catalysts mainly followed the direct dissociation. This study provided a new strategy for designing Co-based RWGS catalysts with excellent performance.

In-situ evolution of bimetallic Fe/ Ni/ Co nanohybrids on MXene for improved electrocatalytic oxygen evolution reaction

Oxygen evolution reaction (OER) is a vital electrochemical reaction for sustainable energy generation technologies. Due to the sluggish kinetics, exploration for an efficient non-precious metal catalyst is essential. Bimetallic nanohybrids are potential electrocatalysts for the OER due to their pore structure, large surface area, and inevitably dispersed metal centers. This work reports the synthesis of three bimetallic Ni–Co (NCMX), Fe–Co (FCMX), and Fe–Ni (FNMX) nanohybrids onto MXene for effective OER activity. An improved OER activity is observed on a plastic chip electrode (PCE) loaded with electrocatalysts. Among the synthesized electrocatalysts, NCMX exhibits excellent OER performance with an overpotential of 220 mV and a small Tafel slope of 94 mV/dec in a basic electrolyte (1 M KOH). The 3D MXenes framework promotes strong interaction with efficient charge transfer between the nanohybrids and MXene. Results demonstrate a promising recommendation for designing high-performance MXene-supported bimetallic nanohybrid electrocatalysts.

Surface engineering of flower-like Co-N-C on carbon paper for improved overall water splitting

Designing efficient non-precious metal catalysts with superior activity and stability for water splitting has been the pursuit of researchers. The purpose of this work is to investigate the influence of 2-amino terephthalic acid on the surface engineering of flower-like Co-N-C for improved water splitting in an alkaline solution. The flower-like Co-N-C grown on carbon paper (Co-N-C/CP) were fabricated by a facile hydrothermal and subsequent annealing process. When the ratio of Co2+ and 2-amino terephthalic acid reaches 1:2 in the precursors, the resultant Co-N-C/CP exhibits the overpotential of 181 mV and 290 mV at 10 mV cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Furthermore, the Co-N-C/CP (1:2)||Co-N-C/CP(1:2) water splitting systems deliver a current density of 10 mA cm−2 at 1.56 V. After 1500 cycles, the required voltage for water splitting still maintains at 1.57 V. The outstanding electrocatalytic properties are attributed to the tuning electron structure on the surface of Co-N-C, which promotes the charge transfer and chemical mass transport during water splitting in an alkaline solution. This study provides a new opportunity to develop highly efficient cobalt-based catalysts for enhanced water splitting.

Bimetallic NiMo oxides coupled with 3D CuxO nanorods for efficient overall water splitting

Development of efficient non-precious metal catalysts for water electrolysis is imperative in the area of energy conversion. Herein, transition-metal oxide catalyst of CuxO@NiO-MoO2 nanorods with three-dimensional core–shell nanostructures was constructed by a facile route. The CuxO@NiO-MoO2 NRs supplies a high electrochemical active area, thus exposing more active centers in full contact with the electrolyte. The fast charge transfer between the nanorods and nanoparticles and the synergistic effect among the bimetals enable the catalyst to show superior catalytic performance. CuxO@NiO-MoO2 NRs requires the overpotentials of 65 mV for hydrogen evolution reaction (HER) at 10 mA cm−2 and 321 mV for oxygen evolution reaction (OER) at 50 mA cm−2. Meanwhile, the catalyst also shows satisfactory performance at the high current densities of 100 and 200 mA cm−2 for HER, requiring overpotentials of only 152 and 192 mV, respectively. Moreover, the CuxO@NiO-MoO2 NRs needs a voltage of 1.54 V to achieve 10 mA cm−2 as a water electrolyzer. This study provides a promising route for preparing bifunctional catalysts via the rational design of interfaces and nanostructure arrays.

Porous rare earth-transition metal bimetallic oxide nanoparticles oxygen electrocatalyst for rechargeable Zinc-air battery

BackgroundThe design and preparation of efficient nonprecious metal catalysts for the ORR, it is still a big challenge in alkaline media. Therefore, there is a need to develop an efficient electrocatalyst to meet the current problems such as energy scarcity in society MethodsIn this experiment, a series of bimetallic oxide nanoparticle catalysts (SmFeOx@CN) with fairly good morphology, which combine the advantages of rare earths and transition metal oxides, were successfully prepared by using silica dioxide as an encapsulated template and later removed. Significant findingsThe bimetallic oxide nanoparticle catalyst produces redox activity that is comparable to that of commercial platinum-carbon catalysts and shows excellent stability, power and energy densities. This excellent performance is owed to the concerted effect of bimetallic oxide nanoparticles and the special electronic layer structure of rare earths.

Metal - organic frameworks derived Ni5P4/NC@CoFeP/NC composites for highly efficient oxygen evolution reaction

As an efficient non-precious metal catalyst for the oxygen evolution reaction (OER), phosphides suffer from poor electrical conductivity, so it is still a challenge to reasonably design their structures to further improve their conductivity and OER performances. Here, we present a novel Ni5P4/N-doped carbon@CoFeP/N-doped carbon composite (Ni5P4/NC@CoFeP/NC) as electrocatalysts for OER. This elaborate structure consists of Ni5P4/NC derived from Ni-MOF and CoFeP/NC derived from CoFe-Prussian blue analog MOF (Co-Fe PBA). The cube-like CoFeP/NC are scattered and uniformly coated on the sheet of Ni5P4/NC flowers. Among them, NC can enhance the conductivity of phosphides, while CoFeP/NC can increase the electrochemical active area, which benefit the properties of Ni5P4/NC@CoFeP/NC. Notably, the Ni5P4/NC@CoFeP/NC catalyst possesses outstanding OER performances with a low overpotential of 260 and 303 mV at a current density of 10 and 100 mA·cm−2, an ultra-low Tafel slope of 31.1 mV·dec-1 and excellent stability in 1 M KOH. XPS analysis shows that proper chemical composition promotes the oxidation of transition metal species and the chemisorption of OH–, thus accelerating the OER kinetics. Therefore, this work provides a hopeful method for designing and preparing transition metal phosphide/carbon composite as OER electrocatalysts.

Engineering nickel vacancies in NiCo LDH nanoarrays accelerates hydrogen evolution and oxygen evolution reactions.

Exploring efficient bifunctional electrocatalysts is crucial for constructing water splitting systems. In this work, a bifunctional catalyst, NiCo layered double hydroxide (LDH) nanosheets with nickel vacancies, was fabricated by a hydrothermal and chemical etching method, which requires 195 and 227 mV overpotentials for HER and OER to achieve 10 mA cm-2 and exhibited sustained activity for 100 h with almost no degradation. This study provides a new idea for the rational design of efficient non-precious metal catalysts with defects for water splitting.

Iron and nitrogen doped carbon derived from ferrocene and ZIF-8 as proton exchange membrane fuel cell cathode catalyst

H2-O2 proton exchange membrane fuel cells (PEMFCs), one of the applications of hydrogen energy with specific energy density of 143 MJ/kg, might be a promising alternative to replace the use of fossil energy. The key to accelerate the application of PEMFCs is to design an efficient non-precious metal catalyst to lower the overpotential of the cathode oxygen reduction reaction (ORR). Herein, we developed a novel iron and nitrogen doped carbon (FeNC) catalyst using ferrocene as iron source, ZIF-8 as organic framework as well as the main carbon source. The regular morphology of ZIF-8 and ferrocene can prevent active sites from agglomeration, resulting a homogenous distribution of Fe, N and C. Moreover, the high specific area, porous structure and abundant catalytic Fe and N species gave rise to the ORR performance of the catalyst. As a result, the as-prepared FeNC catalyst showed an onset and half-wave potential of 0.95 V and 0.78 V in 0.1 M HClO4 with 1600 rpm, respectively. The catalysts were also applied in a PEMFC as the cathode catalysts with an open circuit voltage of more than 0.9 V and a maximum power density of 601 mW/cm2. Additionally, the as-prepared FeNC-1:30 catalyst showed a current density of 380 mA/cm2 at 0.7 V, which outperformed other as-prepared catalysts.