High Electrochemical Surface Area Research Articles

MOF-Derived Urchin-like Co9S8-Ni3S2 Composites on Ni Foam as Efficient Self-Supported Electrocatalysts for Oxygen Evolution Reaction

Effective and inexpensive electrocatalysts are significant to improve the performance of oxygen evolution reaction. Facing the bottleneck of slow kinetics of oxygen evolution reaction, it is highly desirable to design the electrocatalyst with high activity, good conductivity, and satisfactory stability. In this work, nickel foam supported hierarchical Co9S8–Ni3S2 composite hollow microspheres were derived from in situ-generative MOF precursors and the subsequent sulfurization process by a simple two-step solvothermal method. The composite microspheres were directly grown on nickel foam without any binder, and nickel foam was used as the nickel source and support material. The morphology and constitution of the series self-supported electrodes were characterized by SEM, TEM, XRD, XPS, and Raman, respectively. The unique porous architecture enriched the electrode with sufficient active surface and helped to reactants and bubble evolved during electrochemical water oxidation. Through tuning the concentration of cobalt source and ligand, the content ratio of Co9S8 and Ni3S2 can be modulated. The heterostructures not only afford active interfaces between the phases but also allow electronic transfer between Co9S8 and Ni3S2. The optimized Co9S8-Ni3S2/NF-0.6 electrode with the highest electrochemical surface area and conductivity shows the best OER performance among the series electrodes in 1 M KOH solution. The overpotential of Co9S8-Ni3S2/NF-0.6 is only 233 mV when the current density is 10 mA cm−2, and corresponding Tafel slope is 116.75 mV dec−1. In addition, the current density of Co9S8-Ni3S2/NF-0.6 electrocatalyst hardly decreased during the 12 h stability measurement. Our approach in this work may provide the future rational design and synthesis of satisfactory OER electrocatalysts.

Rational design of dysprosium cobalt oxide decorated on flower-like molybdenum disulfide: Development of an electrochemical sensor for antipsychotic drug promazine

The construction of perovskite oxides and metal chalcogenide nanocomposites has been employed to develop electrochemical sensors with outstanding sensitivity and low detection limit. In this work, we have successfully synthesized dysprosium cobalt oxide (DCO) encapsulated with molybdenum disulfide (MS) via ultrasonication way, which is employed for the electrochemical determination of antipsychotic drug promazine (PMZ). The as-prepared DCO/MS nanocomposite was scrutinized by different techniques such as X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) analysis, field emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscope (HR-TEM). Further, the prepared nanocomposites were modified on a glassy carbon electrode (GCE) surface and electrochemical activity was inspected through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PB) with a potential window of 0.0–0.9 V. As a result, DCO/MS promotes superior electrochemical performance because of high electrochemical active surface area (0.396 cm2), good conductivity, and synergetic effect. The developed electrochemical sensor exhibits a broad linear range (0.002 – 695.6 μM) and the lowest detection limit of 0.005 µM, excellent sensitivity, repeatability, and reproducibility. Finally, the fabricated sensor was successively used for the real-time detection of PMZ in environmental and biological samples with feasible recoveries.

Self-supporting NiMo-Fe-P nanowire arrays as bifunctional catalysts for efficient overall water splitting.

Developing efficient bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts is beneficial for simplifying the design of electrolytic cells and reducing the cost of device manufacturing. Herein, a metal phosphide nanoarray (NiMo-Fe-P) electrocatalyst was designed by in situ ion exchange and low-temperature phosphating to promote overall water splitting in 1 M KOH. NiMo-Fe-P demonstrates superb HER and OER activities as reflected by the low overpotentials of 73.1 mV and 215.2 mV, respectively, at a current density of 10 mA cm-2. The addition of Fe changes the electronic structure of Ni, which is conducive to the chemisorption of oxygen-containing intermediates and reduces the energy barrier for water decomposition. Besides, the metal phosphide not only acts as the active site of the HER, but also improves the conductivity of the catalyst. Furthermore, nanowire arrays and the small particles generated on their surfaces provide a high electrochemical active surface area (ECSA), which was beneficial for the exposure of active sites. Attributed to these advantages, the cell voltage of the water electrolyzer constructed with NiMo-Fe-P as both the cathode and anode is only 1.526 V at 10 mA cm-2, and it maintains excellent stability for 100 h with near negligible changes in potential.

Co-deposition of Co-Ni alloy catalysts from an ethylene glycol system for the hydrogen evolution reaction.

The preparation of active, stable and low-cost non-noble electrocatalysts for the hydrogen evolution reaction (HER) using the electrochemical water splitting process is crucial for the promotion of sustainable energy. In this study, Co-Ni alloys with various Co contents are prepared using a galvanostatic method and the co-deposition behavior of Co2+ and Ni2+ in ethylene glycol (EG) is reported. These results indicate that the presence of additional Ni2+ species can accelerate the Co-Ni co-deposition process and Co2+ species in the system can inhibit the reduction of Ni2+. Moreover, the two effects are improved with an increase in Ni2+ or Co2+ species concentration in the EG system, respectively. Chronoamperometry records show that the Co-Ni electro-crystallization mechanism is one of 3D instantaneous nucleation and growth. Moreover, the Co-Ni alloy with 59.46 wt% Co exhibits high electrocatalytic activity for HER with an overpotential of 133 mV at 10 mA cm-2 in 1 M KOH due to a high value of electrochemical active surface area (ECSA) (955.0 cm2). Therefore, the Co-Ni alloy electrocatalyst obtained from the EG system could be a promising candidate for practical hydrogen production.

The effect of iridium content in boron carbide-supported iridium catalyst on the activity and stability of proton exchange membrane water electrolyzer

One of the major obstacles to proton exchange membrane water electrolyzer (PEMWE) for large-scale applications is the cost of iridium for oxygen evolution reaction (OER). To resolve this issue, boron carbide-supported iridium catalysts are prepared by varying the iridium content from 10 to 60 wt%. Increasing the iridium content on the boron carbide support affects the physical properties of the catalysts and the electronic structure of iridium. At the content of 40%, Ir/B4C showed the highest catalytic activity mainly due to its high electrochemical surface area. 40%-Ir/B4C showed outstanding cell performance of 1.0 A/cm2 at 1.61 V with a loading of 0.5 mg⋅Ir/cm2 which has the same performance with 3.0 mg⋅Ir/cm2 of unsupported commercial catalyst. 40%-Ir/B4C also showed excellent durability in a half-cell as well as in a single cell. The presence of Ir (IV) and the metal-support interaction help 40%-Ir/B4C to be stable.

Optimization of Ascorbic Acid in the Synthesis of Cobalt Oxide for Enhanced Electrocatalytic Activity toward the Oxygen Evolution Reaction

In this work, we are reporting the combustion synthesis of Co3O4 nanoparticles (NPs) and investigation of the influence of the oxidizing agent [Co(NO3)2] and fuel content (ascorbic acid) on the microstructural and electrochemical characteristics of the NPs. Co3O4 NPs were prepared by varying the relative amount of cobalt nitrate to ascorbic acid in ratios of 1:0.5, 1:1, 1:2, and 1:4, and labeled as S1, S2, S3, and S4 respectively. X-ray diffraction data confirm the formation of the cubic phase of Co3O4, and transmission electron micrographs reveal the formation of fairly dispersed particles in the cases of samples S1 and S2 with average particle sizes of 24.5 ± 3.6 and 20.4 ± 1.2 nm and polydispersity indices of 14.7 and 6.5%, respectively. The X-ray photoelectron spectroscopy analysis reveals that the concentration of Co3+ ions at the surface of Co3O4 NPs increases from sample S1 to sample S2 and thereafter decreases in the case of samples S2 to S3, and S4. On the other hand, the oxygen vacancy decreases with an increase in the ascorbic acid content, that is, from sample S1 to sample S4, the oxygen vacancy decreases. Sample S1 having a high oxygen vacancy with low Co3+ possesses a low activity due to the decrease in conductivity caused by excess oxygen vacancies. Further, samples S3 and S4 showed low activity due to the low oxygen vacancy and low Co3+ content, having a low electrochemical surface area. Finally, sample S2 having the optimum oxygen vacancy with the highest Co3+ content showed the highest activity due to the high conductivity and the highest electrochemical surface area. The Tafel slope for sample S2 is found to be 54.46 mV/dec, denoting the highest activity. The electrochemical impedance analysis revealed that sample S2 exhibits the lowest polarization resistance during the oxygen evolution reaction test, showing enhanced kinetics for the oxygen evolution reaction.

Cavitation regulated sonochemical synthesis of flexible self-supported CuO@PDA/CC electrode for highly sensitive glucose sensor

Sonochemical synthesis is recognized as a promising high-efficiency method for fabricating transition metal oxides (TMOs) based flexible self-supported electrodes as nonenzymatic glucose sensor. However, it is still a challenge to obtain TMOs self-supported electrodes with well-controlled TMOs nanostructure and desirable interfacial properties via a sonochemical approach because of the uncontrollability of transient cavitation. In this study, CuO@polydopamine (PDA) nanoparticles (NPs) are in situ grown onto carbon cloth (CC) to fabricate CuO@PDA/CC self-supported electrode via a sonochemical process. The sonochemically synthesized PDA not only stabilized the transient cavitation intensity, but also regulated the growth of CuO due to the strong chelating ability between Cu2+ and catechol groups from PDA. It is determined that the mean size of CuO@PDA NPs on the CuO@PDA/CC electrode is less than 100 nm with a narrow size distribution. Attributed to high electrochemical active surface area (4.61 mF cm−2) and low interface resistance (2.35 Ω), CuO@PDA/CC electrode displays excellent electrochemical performance as a glucose sensor with high sensitivity of 1.843 μA cm−2 mM−1 in a wide linear range up to 4.985 mM and excellent stability. This work provides a facile approach to fabricating the flexible self-supported electrodes with well-controlled nanostructure and desirable interfacial properties for high-performance electrochemical sensors via regulating the transient cavitation intensity in the sonochemical process.

Electrochemical Reduction of CO2 to C1 and C2 Liquid Products on Copper-Decorated Nitrogen-Doped Carbon Nanosheets.

Due to the significant rise in atmospheric carbon dioxide (CO2) concentration and its detrimental environmental effects, the electrochemical CO2 conversion to valuable liquid products has received great interest. In this work, the copper-melamine complex was used to synthesize copper-based electrocatalysts comprising copper nanoparticles decorating thin layers of nitrogen-doped carbon nanosheets (Cu/NC). The as-prepared electrocatalysts were characterized by XRD, SEM, EDX, and TEM and investigated in the electrochemical CO2 reduction reaction (ECO2RR) to useful liquid products. The electrochemical CO2 reduction reaction was carried out in two compartments of an electrochemical H-Cell, using 0.5 M potassium bicarbonate (KHCO3) as an electrolyte; nuclear magnetic resonance (1H NMR) was used to analyze and quantify the liquid products. The electrode prepared at 700 °C (Cu/NC-700) exhibited the best dispersion for the copper nanoparticles on the carbon nanosheets (compared to Cu/NC-600 & Cu/NC-800), highest current density, highest electrochemical surface area, highest electrical conductivity, and excellent stability and faradic efficiency (FE) towards overall liquid products of 56.9% for formate and acetate at the potential of -0.8V vs. Reversible Hydrogen Electrode (RHE).

Gold nanoparticles decorated covalent organic polymer as a bimodal catalyst for total water splitting and nitro compound reduction

The design and construction of a bimodal catalyst with magnificent performance and high stability is a debatable one for total water splitting and nitro compound reduction. Herein, we report the synthesis of a covalent organic polymer network based on 1,4-phenylenediamine based covalent organic polymer (PD-COP) and its decoration with Au nanoparticles (Au NPs) as well as their confirmation using various analytical and surface techniques. The electrocatalytic activity toward total water-splitting reaction (OER and HER) in KOH solution (1.0 M) was investigated. In addition, the reduction of aromatic nitro compounds (4-nitrophenol (4-NP) and 2-nitroaniline (2-NA)) was carried out in the presence of NaBH4. Among the different electrocatalysts (PD-COP, Au@PD-COP-I, Au@PD-COP-II, Au@PD-COP-III and Au@PD-COP-IV) studied in this work, the Au@PD-COP-II demands a low overpotential of 288 mV and 184 mV to attain a 50-mA/cm2 geometrical current density with a lowest Tafel slope value of 56 and 85 mV/dec for OER and HER respectively. From the OER and HER phenomenal activity, a two-electrode system was constructed, and it needs a cell voltage of 1.615 V to conquer a current density of 10 mA/cm2 with outstanding stability for 34 h. The high electroactivity of Au@PD-COP-II may be allied with the presence of innumerable redox-active sites and high electrochemical active surface area (ECSA) towards effective water electrolysis. Further, the catalytic activity performed towards the reduction of 4-NP to 4-aminophenol (4-AP) and 2-NA to o-PDA (o-phenylenediamine), Au@PD-COP-II showed good catalytic activity with a reduction time of 20 and 14 min respectively.

On the optimal cathode catalyst layer for polymer electrolyte fuel cells: Bimodal pore size distributions with functionalized microstructures

A high advancement has been achieved in the design of proton exchange membrane fuel cells (PEMFCs) since the development of thin-film catalyst layers (CLs). However, the progress has slowed down in the last decade due to the difficulty in reducing Pt loading, especially at the cathode side, while preserving high stack performance. This situation poses a barrier to the widespread commercialization of fuel cell vehicles, where high performance and durability are needed at a reduced cost. Exploring the technology limits is necessary to adopt successful strategies that can allow the development of improved PEMFCs for the automotive industry. In this work, a numerical model of an optimized cathode CL is presented, which combines a multiscale formulation of mass and charge transport at the nanoscale(∼10nm)and at the layer scale(∼1μm). The effect of exterior oxygen and ohmic transport resistances are incorporated through mixed boundary conditions. The optimized CL features a vertically aligned geometry of equally spaced ionomer pillars, which are covered by a thin nanoporous electron-conductive shell. The interior surface of cylindrical nanopores is catalyzed with a Pt skin (atomic thickness), so that triple phase points are provided by liquid water. The results show the need to develop thin CLs with bimodal pore size distributions and functionalized microstructures to maximize the utilization of water-filled nanopores in which oxygen transport is facilitated compared with ionomer thin films. Proton transport across the CL must be assisted by low-tortuosity ionomer regions, which provide highways for proton transport. Large secondary pores are beneficial to facilitate oxygen distribution and water removal. Ultimate targets set by the U.S. Department of Energy and other governments can be achieved by an optimization of the CL microstructure with a high electrochemical surface area, a reduction of the oxygen transport resistance from the channel to the CL, and an increase of the catalyst activity (or maintaining a similar activity with Pt alloys). Carbon-free supports (e.g., polymer or metal) are preferred to avoid corrosion and enlarge durability.

MoSe2 and NiCo2O4/NiO Based HybridNanostructure as Novel Electrocatalyst for High Performance Rechargeable Zinc-Air Battery

Efficient air electrocatalysts are needed to develop eco-friendly rechargeable Zinc-air (Zn-air) batteries for renewable energy storage. Here, we investigate the electrocatalytic activity of hydrothermally synthesized MoSe2, NiCo2O4/NiO and NiCo2O4/NiO-MoSe2 hybrid nanostructure by performing oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) studies. The NiCo2O4/NiO-MoSe2 hybrid nanostructure (Tafel slope∼ 54 mV decade−1) shows best electrocatalytic activity and stability for OER study among synthesized electrocatalysts. Further, the oxygen reduction behaviors of prepared catalysts have been observed in oxygen saturated electrolyte solution. The excellent electrocatalytic activity of hybrid nanostructure can be associated with its high electrochemical active surface area, number of active sites and possibly due to the presence of selenium vacancies and edges in MoSe2. Furthermore, we demonstrate Zn-air batteries with these electrocatalysts as air cathode, showing open circuit potential of 1.42 V, the specific capacity of 1023 mA h gZn−1 and energy density of 1195 W h kgZn−1, with high durability for hybrid nanostructure-based Zn-air battery. To the best of our knowledge, this is the first study demonstrating pristine MoSe2 and NiCo2O4/NiO-MoSe2 hybrid nanostructure-based cathodes for Zn-air batteries with excellent specific capacity and energy density.

The preparation of bifunctional Co-N co-doped carbon with bamboo-like hollow tubular as an efficient electrocatalyst for oxygen reduction and methanol oxidation reaction

• Bamboo-like hollow tubular Co-N-C was prepared by direct pyrolysis method. • The Co-N-C catalyst exhibits a high specific surface area. • The Pt@Co-N-C has a high electrochemical surface area. • The Co-N-C and Pt@Co-N-C exhibit excellent ORR and MOR activity and stability. Catalysts with distinguished properties and stability are very important for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) of fuel cells. Herein, we describe a convenient and efficient preparation means to synthesize a bamboo-like hollow tubulous structure Co-N co-doped carbon material (Co-N-C) via a late-model of Co-Imace coordinated compound as the precursor by direct pyrolysis. Additionally, Pt nanoparticles supported by Co-N-C catalysts (Pt@Co-N-C) were prepared using the ethylene glycol reduction procedure. The obtained catalyst exhibited an excellent electro-catalytic property for ORR in alkaline media, which possessed a more positive half-wave potential (0.868V) than commercial Pt/C (0.852V). Moreover, the Co-N-C maintained preeminent long-term stability (91.6 %) after the 21000s and also owned a stronger methanol resistance than Pt/C. The obtained Pt@Co-N-C electrocatalyst exhibited higher MOR activity (96.3 mA cm -2 ), which is 1.6 times greater than that of Pt/C, benefiting from the high electrochemical surface area of Pt@Co-N-C (68 m 2 g -1 ). Furthermore, the Pt@Co-N-C exhibited lower onset potentials, higher I f /I b ratios, and well long-term stability than Pt/C.

Rational engineering of metal–organic coordination networks into facet‐controlled phosphides for overall water splitting

AbstractAlthough transition metal phosphide electrocatalysts display unique electronic structure that serves as functional centers for hydrogen evolution reaction, the synthesis of this class of materials for oxygen evolution remains a challenge due to the complex multielectron transfer pathways and sluggish reaction kinetics. This study details an in‐situ modification and transformation of cyanide‐bridged nickel‐iron (CN‐NiFe) organometallic hybrid into the preferential Fe2P phase with prevailing exposed faceted active centers by leveraging on the facile coordinate cleavage dynamics and compound reactivity of labile metal organic coordination frameworks. The resultant transition metal phosphide attains high electrochemical surface area, low Tafel slope, and low overpotential for the oxygen evolution reaction, while also demonstrating bifunctional electrocatalytic performance for overall water splitting. Comprehensive experimental studies and density functional theory calculations reveal that the exceptional catalytic activity originates from the transformation of framework metallic sites into preferential active sites allows an optimal adsorption of oxygen evolution reaction intermediates.image

A highly stable Tungsten-Doped TiO2-Supported platinum electrocatalyst for oxygen reduction reaction in acidic media

The carbon-supported platinum electrocatalyst’s severe carbon corrosion issue in acidic media limits the widespread application of proton exchange membrane fuel cells (PEMFCs). Therefore, exploring novel noncarbon supports with improved corrosion resistance is needed to resolve this problem. This research presented tungsten-modified titanium dioxide (W-doped TiO2) support for the Pt catalyst toward the oxygen reduction reaction (ORR). W-doped TiO2 showed a higher surface area and more Ti3+ defect sites and oxygen vacancies than the undoped TiO2 support, which enhanced strong metal support interaction for the deposited Pt catalyst. Furthermore, the high ORR activity of the Pt/W-doped TiO2 catalyst was demonstrated using a high electrochemical surface area of 44.1 m2/gPt and mass activity value of 41.22 A/gPt for electrochemical performance in 0.1 M HClO4. Moreover, the rotating ring-disk electrode measurement of the Pt/W-doped TiO2 catalyst under acidic conditions showed a four-electron pathway with an ultrasmall peroxide yield of 0.42 %. Particularly, the durability test showed that the Pt/W-doped TiO2 had a remarkable stability compared to commercial catalysts. Therefore, this study provides a promising pathway to improve the stability of Pt-based catalysts for PEMFCs.

Spinel-structured CuCo2O4 with a mixed 1D/2D morphology for asymmetric supercapacitor and oxygen evolution electrocatalyst applications

Transition metal oxides with multifunctional properties have attracted attention for use in various electro-catalytic applications, but their weak electroactive centers have severely limited their commercialization. In the present study, we describe an efficient bifunctional material whose structural morphology makes it both an effective oxygen evolution reaction (OER) electrocatalyst and a reliable power source for supercapacitor (SC) electrodes. We successfully fabricated spinel-structured CuCo2O4 consisting of a mix of one-dimensional (1D) nanorods and two-dimensional (2D) nanoplates using precipitation followed by hydrothermal treatment and calcination. For comparison purposes, CuO nanoplates and Co3O4 nanorods were synthesized individually, and their multifunctional features were examined. The synthesized mixed-morphology CuCo2O4 delivered an excellent electrochemical performance for SC and OER electrocatalyst applications. The mixed-morphology CuCo2O4 produced a specific capacity of 561 C g−1 (1122 F g−1) at 1 A g−1 and exhibited a superior rate capability and excellent stability, with 92% retention of capacity after 5000 cycles at 30 A g−1 in a three-electrode cell. In addition, a fabricated asymmetric supercapacitor device (CuCo2O4//activated carbon) delivered an energy density of 47.6 W h kg−1 and a power density of 1280 W kg−1, with outstanding long-term cyclic stability. Furthermore, the prepared CuCo2O4 had a low Tafel slope, a high electrochemical surface area, and excellent long-term durability. Therefore, mixed-morphology CuCo2O4 holds significant promise for use in SC and OER catalyst applications. Moreover, this study offers a useful method for preparing multifunctional materials.

Comparative study for electrochemical and Single-Cell performance of a novel MXene-Supported Platinum–Ruthenium catalyst for Direct methanol fuel cell application

• Novel formulation of bimetal embedded on MXene structure. • Latest two dimensional materials with ceramic and metal-like category. • Comparative study on electrochemical and DMFC single cell performance. • Promising anodic electrocatalyst for methanol oxidation reaction. • High electrochemical surface area and intrinsic activity leads to high performance. Direct methanol fuel cell (DMFC) is one of the reliable sources of energy owing to numerous benefits it offers and its suitability for portable electronic applications. Therefore, this study aims to overcome the main issues confronting anodic electrocatalyst part by introducing the novel formulation of platinum–ruthenium (PtRu) bimetal into the 2D Ti 3 C 2 T x structure to boost the electrocatalytic activity and single-cell performance. A comparative study for electrochemical measurement and DMFC performance is conducted between as-synthesized electrocatalyst PtRu/Ti 3 C 2 T x and two other electrocatalysts, PtRu/C and Pt/C. This comparative study between electrocatalyst revealed that PtRu/Ti 3 C 2 T x exhibits the highest electrochemical surface area (55 m 2 g -1 ), electrocatalytic and intrinsic activity (449 mA mg PtRu −1 / 1.36 mA cm ECSA −2 ), carbon monoxide tolerance (1.56), and smallest charge-transfer resistance (2.66 Ω) compared with other electrocatalysts. Furthermore, the validation by DMFC single-cell test showed that PtRu/Ti 3 C 2 T x electrocatalyst improves the performance almost 70 % compared to the Pt/C electrocatalyst. This excellent electrochemical and single-cell performance of PtRu/Ti 3 C 2 T x electrocatalyst validates its potential to be one of the promising candidates for the anodic electrocatalyst in DMFC application.

Enhanced Ageing Performance of Sulfonic Acid-Grafted Pt/C Catalysts.

Chemical functionalization of carbon support for Pt catalysts is a promising way to enhance the performance of catalysts. In this study, Pt/C catalysts grafted with various amounts of phenylsulfonic acid groups were prepared under mild conditions. The influence of sulfonic acid groups on the physiochemical characteristics and electrochemical activities of the modified catalysts were studied using X-ray diffraction, X-ray photoelectron spectroscopy, a transmission electron microscope, and cyclic voltammetry (CV). The presence of the chemical groups enhanced the hydrogen adsorption onto/desorption off the Pt surface during the CV cycling. In contrast, the hydrogen peaks of the grafted catalysts increased after 500 CV cycles, especially for Pt (111) facets. The highest electrochemical surface area (ECSA) after the aging test was obtained for the catalyst with 18.0 wt.% graft, which was ca. 87.3% higher than that of the non-functionalized Pt catalyst. In the density functional theory (DFT) calculation, it was proven that SO3H adsorption on the crystalline was beneficial for Pt stability. The adsorption energy and bond distance of the adsorbed SO3H on Pt (110), (100), and (111) surfaces were calculated. All the stable configurations were obtained when O from S-O single bond or S was bound to the Pt surface, with the adsorption energy following the trend of (111)F > (100)H > (110)H. This result was consistent with the ECSA experiment, which explained the high electrochemical stability of the sulfonic acid groups-grafted Pt/C catalyst.

High Surface Area 3D Copper Nanowire Networks for High-Throughput Electrochemical CO2 Reduction

An attractive solution towards net-zero carbon emission is the electrocatalytic CO2 reduction with its ability to convert the greenhouse gas CO2 with renewable electricity and appropriate catalytic materials to useful chemicals and fuels to store energy. Depending on the number of electrons transferred a variety of oxygenates and hydrocarbons can be obtained. Among used catalytic materials, such as metals, alloys or composites, copper has shown the unique property to electrocatalytically convert CO2 into a wide variety of valuable C2+ products such as ethylene or alcohols.Apart from the high potential to reshape our carbon economy the electrocatalytic CO2 reduction is still in its early development stage compared to the more mature water electrolysis, with high-throughput operation at practical current densities as well as long-term stability of the catalysts being only scarcely demonstrated. Additionally, selectivity towards high-value (beyond C1) products using copper catalysts has proven to be challenging and many research efforts are directed towards improving product selectivity. For this purpose, mainly nanostructured porous Cu electrodes either based on randomly ordered nanoparticles loaded on porous (carbon-based) supports or low-surface area metal foams, meshes or felts with high porosity are commonly used. While the former electrode architecture typically shows poor long-term stability with often weak adhesion between the nanoparticles and the porous support, the latter electrodes have a low electrochemical surface area and hence are not suitable for high-throughput CO2 reduction at high current densities.In this work we present novel high-surface area porous copper electrodes, so-called copper nanomeshes, that are regular 3D-networks of interconnected Cu nanowires. These unique few µm-thin electrodes show a large surface area enhancement (compared to planar Cu) by a factor of ~80, while providing a high porosity of ~70% together with sufficient mechanical stability, an important aspect towards their practical implementation in electrocatalytic flow cells. Cu nanomesh electrodes with a thickness of 4µm were fabricated through electrochemically plating in 3D-porous anodic aluminum oxide templates and show a mixed surface texture of (111), (100) and (110) Cu. We demonstrate the high potential toward high-throughput CO2 electrolysis of these novel electrodes in comparison to planar copper electrodes in various CO2-containing electrolyte solutions. The CO2 reduction product analysis showed a significant difference in selectivity between planar (polycrystalline or with preferential 111 or 200 texture) and the polycrystalline Cu nanomesh electrodes with CO or C2H4 as major reduction products depending on the potential applied. The beneficial effect of the high electrochemical surface area was demonstrated by a significant increase in the current density on the nanostructured Cu electrodes. Additionally, we characterized the copper nanomesh electrodes before, during and after CO2 reduction with complementary techniques to gain insights on the reaction mechanism and on the electrode stability. Figure 1

In-situ corrosion induced Zr-doped Ni/Fe (oxy)hydroxide layer on Ni-Fe foam realizing efficient electrocatalysis for oxygen evolution reaction

The synthesis of efficient and economical electrocatalysts for oxygen evolution reactions (OER) by the energy-saving approach has far-reaching significance for the production of hydrogen by water electrolysis. Herein, a facile route was proposed to prepare Zr-doped Ni/Fe (oxy)hydroxide layer grown on Ni-Fe foam (Zr-NiFe(OH)x/NFF) by chloride ions in-situ corrosion strategy in “NaCl-ZrOCl2” mixed solution. The smooth NFF surface was effectively transformed into a rough multimetallic (oxy)hydroxide nanosheet with high electrochemical specific surface area and strong bonding to the substrate, resulting in excellent interface performance for mass transfer and charge transfer. Specifically, the incorporation of Zr4+ regulated the electronic environment around the Ni/Fe center, as a result, adsorption energies were optimized and the inherent OER activity of active sites was enhanced. The Zr-NiFe(OH)x/NFF self-supporting electrode exhibited outstanding OER electrocatalytic activity where low overpotentials of 211 and 245 mV were obtained to achieve 10 and 100 mA cm−2 respectively, along with impressive durability for 40 h. This work provides a simple strategy for low-cost and mass production of the robust OER self-supporting electrocatalysts.

Enhanced electro-activity of nickel phosphide by pre-treatment for efficient hydrogen sulfide elimination

Electrochemical sulfide oxidation is a promising approach for sulfide removal from wastewater or biogas due to low energy and chemical consumption. In this work, nickel phosphide was facilely electrodeposited on stainless steel (SS/Ni-P) and comprehensively evaluated as anode catalyst for sulfide oxidation. Electrochemical property analysis suggested that SS/Ni-P had low polarization resistance (109.10 Ω) and high electrochemical active surface area (Cdl = 1.3 mF/cm2). The sulfide removal efficiency of SS/Ni-P achieved 95.00 ± 3.55 % at 1.42 V vs RHE within 48 h, which was 2.60 times and 3.62 times of that by SS/Ni and SS anodes, respectively. The first order kinetic rate constant of SS/Ni-P for sulfide removal was 0.0315 ± 0.0061 h-1, superior than that of the reported single nickel atom based catalyst with stainless steel substrate. Pre-treating SS/Ni-P under a constant external potential for 10 s further improved the electroactivity on sulfide oxidation due to the enhancement of the electrochemical active surface area by 46.56%. Further analysis of the chemical state changes during the sulfide oxidation process revealed that the Ni from Ni-P was the real active center, which formed Ni-S precursors to promote polysulfide formation. This work provided a highly efficient sulfide oxidation anode material for sulfide containing wastewater and biogas treatment.