Nanowire Catalysts Research Articles

Highly active nickel-loaded β-SiC nanowire catalysts for photocatalytic H2 production by water splitting

Developing a highly efficient water-splitting photocatalyst for hydrogen production under visible light is urgent. In this study, β-SiC nanowire photocatalysts loaded with 0.01–0.1 wt. % nickel were prepared. Their microstructure and hydrogen production activity were studied. The catalyst with 0.05 wt. % nickel and a sacrificial agent Na2S–Na2SO3 shows the highest hydrogen production rate of 375.4 µmol g−1 h−1 since the loaded nickel prohibits the recombination of photogenerated electron–hole pairs in the system, which enhances the photocatalytic activity.

Rational design of coaxial CdS@ZnO nanowire array for efficient photodegradation of organic pollutants

Herein, a novel coaxial CdS@ZnO nanowire array catalyst was synthesized by magnetron sputtering and hydrothermal method. The optimum photocatalytic composite was obtained by controlling the ratio of CdS and ZnO. Take methylene blue (MB) as the model, the CdS@ZnO nanowire array (CdS@ZnO-10) exhibited strong photocatalytic solid activity, and the highest adsorption and photodegradation rate of MB reached 90.38 % in 50 min and 99.13 % in 120 min under simulated sunlight illumination. The mechanism of the heterojunction interface affecting photocatalytic performance was studied. Therefore, the synthesis approach could offer new design and controllable construction of coaxial structure for organic dye pollutant degradation.

Phosphorus/sulfur co-doped heterogeneous NiCoPxSy nanoarrays boosting overall water splitting

In the large-scale implementation of renewable energy devices, the availability of stable and highly catalytic non-precious metal catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial. Meanwhile, integrating bifunctional electrocatalysts simultaneously on both the anode and cathode still faces challenges. To address this, a stepped preparation strategy was adopted on a nickel foam (NF) substrate to synthesize P, S co-doped NiCoPxSy nanowire array catalysts. The prepared NiCoPxSy catalysts demonstrated a small Tafel slope of 72.5 mV dec−1 for HER and 72.3 mV dec−1 for OER by requiring only 37 mV (326 mV) overpotential to achieve a current density of 10 mA cm−2 (50 mA cm−2). Moreover, when assembled into an electrolytic cell in 1 M KOH, the NiCoPxSy catalysts achieved a low voltage of 1.55 V at 10 mA cm−2 current density and exhibited long-term stability. The outstanding electrocatalytic performance can be attributed to the influence of doped anions on the electronic states and distribution among different atoms, which thereby positively affected the electrocatalytic activity. This research provides an effective method for designing innovative catalysts and paving the way to produce clean energy.

Durability of Pt nanowire supported on carbon nanotubes under simulated start-up/shut-down conditions for polymer electrolyte membrane fuel cells

The primary issue for the commercialization of proton exchange membrane fuel cells (PEMFCs) is the carbon corrosion of support and dissolution agglomeration of platinum nanoparticles under start-up/shut-down (SU/SD) conditions. Carbon nanotubes (CNTs)-supported Pt nanowire (PtNW) catalyst toward the ORR was synthesized via the soft template method. Electrochemical characterization demonstrated that the PtNW/CNTs showed higher activity than Pt/C because the anisotropy of the 1D structure strengthened its ability to transport electrons. An accelerated stressed test between 1.0 and 1.5 V for carbon corrosion was performed to examine durability at a single cell under practical SU/SD conditions. After 5000 cycles, the voltage drop was 0.142 V, and the voltage decay rate was 0.0284 mV cycle−1 for the PtNW/CNTs catalyst at 1600 mA cm−2; the voltage drop was 0.417 V, and the voltage decay rate was 0.0834 mV cycle−1 for the Pt/C catalyst at 1600 mA cm−2. The Pt/C catalyst demonstrated severe Pt nanoparticle aggregation and growth with a wide size distribution, whereas the PtNW/CNTs catalyst showed a slight variation. The PtNW/CNTs catalyst showed remarkable durability after 5000 SU/SD cycles. Consequently, PtNW/CNTs is a promising electrocatalyst, which can replace traditional Pt/C catalyst in PEMFCs.

Surface-structure tailoring of Dendritic PtCo nanowires for efficient oxygen reduction reaction

Platinum-based alloy nanowire catalysts demonstrates great promise as electrocatalysts to facilitate the cathodic oxygen reduction reaction (ORR) of proton exchange membrane fuel cells (PEMFCs). However, it is still challenge to further improve the Pt atom utilization of Pt based nanowires featuring inherent structural stability. Herein, a new structure of PtCo nanowire with nanodendrites was developed using CO-assistance solvent thermal method. The dendrite structure with an average length of about 7 nm are characterized by a Pt-rich surface and the high-index facets of {533}, {331} and {311}, and grows from the ultra-fine wire structure with an average diameter of about 3 nm. PtCo nanowires with nanodendrites developed in this work shows outstanding performance for ORR, in which its mass activity of 1.036 A/mgPt is 5.76 times, 1.74 times higher than that of commercial Pt/C (0.180 A/mgPt) and PtCo nanowires without nanodendrites (0.595 A/mgPt), and its mass activity loss is only 18% under the accelerated durability tests (ADTs) for 5k cycles. The significant improvement is attributed to high exposure of active sites induced by the dendrite structure with Pt-rich surface with the high-index facets and Pt-rich surface. This structure may provide a new idea for developing novel 1D Pt based electrocatalysts.

Controlling Surface Chemical Inhomogeneity of Ni2 P/MoNiP2 /MoP Heterostructure Electrocatalysts for Efficient Hydrogen Evolution Reaction.

Crystalline/amorphous phase engineering is demonstrated as a powerful strategy for electrochemical performance optimization. However, it is still a considerable challenge to prepare transition metal-based crystalline/amorphous heterostructures because of the low redox potential of transition metal ions. Herein, a facile H2 -assisted method is developed to prepare ternary Ni2 P/MoNiP2 /MoP crystalline/amorphous heterostructure nanowires on the conductive substrate. The characterization results show that the content of the MoNiP2 phase and the crystallinity of the MoP phase can be tuned by simply controlling the H2 concentration. The obtained electrocatalyst exhibits a superior alkaline hydrogen evolution reaction performance, delivering overpotentials of 20 and 76mV to reach current densities of 10 and 100mA cm-2 with a Tafel slope of 30.6mV dec-1 , respectively. The catalysts also reveal excellent stability under a constant 100h operation, higher than most previously reported electrocatalysts. These striking performances are ascribed to the optimized hydrogen binding energy and favorable hydrogen adsorption/desorption kinetics. This work not only exhibits the potential application of ternary Ni2 P/MoNiP2 /MoP crystalline/amorphous heterostructure nanowires catalysts for practical electrochemical water splitting, but also paves the way to prepare non-noble transition metal-based electrocatalysts with optimized crystalline/amorphous heterostructures.

Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C-C Cleavage in C2+ Alcohol Electro-oxidation Reactions.

Efficient C-C bond cleavage and oxidation of alcohols to CO2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO2. The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au1.0/Pt0.2 NWs have the largest percentage (∼75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C-C bond cleavage is indeed enhanced on the undercoordinated Pt-Au surface. Our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

In Situ Formation of CoP/Co3 O4 Heterojunction for Efficient Overall Water Splitting.

Electrochemical water splitting is an environmentally friendly and effective energy storage method. However, it is still a huge challenge to prepare non-noble metal based electrocatalysts that possess high activity and long-term durability to realize efficient water splitting. Here, we present a novel method of low-temperature phosphating for preparing CoP/Co3 O4 heterojunction nanowires catalyst on titanium mesh (TM) substrate that can be used for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting. CoP/Co3 O4 @TM heterojunction showed an excellent catalytic performance and long-term durability in 1.0 M KOH electrolyte. The overpotential of CoP/Co3 O4 @TM heterojunction was only 257 mV at 20 mA cm-2 during the OER process, and it could work stably more than 40 h at 1.52 V versus reversible hydrogen electrode (vs. RHE). During the HER process, the overpotential of CoP/Co3 O4 @TM heterojunction was only 98 mV at -10 mA cm-2 . More importantly, when used as anodic and cathodic electrocatalyst, they achieved 10 mA cm-2 at 1.59 V. The Faradaic efficiencies of OER and HER were 98.4 % and 99.4 %, respectively, outperforming Ru/Ir-based noble metal electrocatalysts and other non-noble metal electrocatalysts for overall water splitting.

Self-Supported 3D PtPdCu Nanowires Networks for Superior Glucose Electro-Oxidation Performance.

The development of non-enzymatic and highly active electrocatalysts for glucose oxidation with excellent durability for blood glucose sensors has aroused widespread concern. In this work, we report a fast, simple, and low-cost NaBH4 reduction method for preparing ultrafine ternary PtPdCu alloy nanowires (NWs) with a 3D network nanostructure. The PtPdCu NWs catalyst presents significant efficiency for glucose oxidation-reduction (GOR), reaching an oxidative peak-specific activity of 0.69 mA/cm2, 2.6 times that of the Pt/C catalyst (0.27 mA/cm2). Further reaction mechanism investigations show that the NWs have better conductivity and smaller electron transfer resistance. Density functional theory (DFT) calculations reveal that the alloying effect of PtPdCu could effectively enhance the adsorption energy of glucose and reduce the activation energy of GOR. The obtained NWs also show excellent stability over 3600 s through a chronoamperometry test. These self-supported ultrafine PtPdCu NWs with 3D networks provide a new functional material for building blood glucose sensors and direct glucose fuel cells.

Preparation of porous carbon nanowires for hydrogen evolution reaction

Hydrogen for clean energy resources has attracted more and more attention, and water splitting for hydrogen production also has been widely studied. Electrocatalysis water splitting is considered the most efficient method for hydrogen production. In this work, we prepared a metal-free porous carbon nanowires catalyst with an electrostatic spinning method using granular poly styrol as the precursor and zinc chloride as the activating agent for forming a porous structure. The obtained catalysts exhibited a plentiful porous structure and an SSA value, which is beneficial for catalyzing hydrogen evolution reactions. The SSA is up to 329 m2 g−1, and the OP value at 10 mA·cm−2 is 386 mV. The materials presented good stability for hydrogen evolution reaction.

Rh-dispersed Cu nanowire catalyst for boosting electrocatalytic hydrogenation of 5-hydroxymethylfurfural

Electrocatalytic conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) presents a compelling strategy for the production of premium chemicals via the utilization of renewable energy sources. Exploring efficient catalytic systems to obtain highly selective BHMF has remained a giant challenge. A design strategy is proposed here to regulate active hydrogen (Hads) production in rhodium (Rh) nanoparticles grown on Cu nanowires (RhCu NWs) catalyst, which achieves a faradaic efficiency (FE) of 92.6% in the electrocatalytic reduction of HMF to BHMF at −20 mA cm−2 with no degradation in performance after 8 cycles. Kinetic investigations and electron spin resonance (ESR) spectroscopy reveal that the incorporation of Rh accelerates the water dissociation and facilitates the generation of Hads. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) further demonstrates that the Rh component boosts the proportion of ordered weakly hydrogen-bonded water molecules on the catalyst surface, which is much easier to dissociate. The construction of an interfacial Hads-rich environment promotes the HMF intermediates binding with Hads to BMHF, thereby suppressing the formation of undesired dimers. This work demonstrates the promise of altering the interfacial water environment as a strategy to boost the electrosynthetic properties of biomass-derived products toward value-added outcomes.

Template‐ and Surfactant‐Free Room Temperature Synthesis of Pt/C and Pt−Rh/C Nanowires/Nanoparticles for Ethanol Electro‐Oxidation

AbstractThe synthesis of Pt−Rh alloy nanowires (NWs) using straightforward methodologies remains a challenge. Here, carbon‐supported Pt and Pt−Rh nanowire catalysts were synthesised by chemical reduction at room temperature, without using surfactants or templates. The method of synthesis used yielded Pt/C NWs and a mixture of nanowires with some nanoparticles for the Pt−Rh/C catalysts (characterised using XRD, TEM, EDX, XPS, and XAS). The nanoparticles form due to differences in the surface energy and atomic radius between Pt and Rh. The binary NWs are found to be more active towards ethanol oxidation than the commercial Pt/C reference catalyst. Additionally, the Pt−Rh/C NW catalyst displays a specific activity 2.5‐fold higher than the Pt/C NWs and Pt/C reference catalysts after 15 min of chronoamperometric tests (at 0.5 V vs RHE). Thus, the synthesised carbon‐supported Pt NWs and Pt−Rh nanowires‐nanoparticles are promising alternatives for direct ethanol fuel cell anodes.

Photoassisted Strategy to Promote Glycerol Electrooxidation to Lactic Acid Coupled with Hydrogen Production

Electrocatalytic oxidation of glycerol (GLY; from a biodiesel byproduct) to lactic acid (LA; the key monomers for polylactic acid; PLA) is considered a sustainable approach for biomass waste upcycling and is coupled with cathodic hydrogen (H2) production. However, current research still suffer from issues of low current density and low LA selectivity. Herein, we reported a photoassisted electrocatalytic strategy to achieve the selective oxidation of GLY to LA over a gold nanowire (Au NW) catalyst, attaining a high current density of 387 mA cm-2 at 0.95 V vs RHE, together with a high LA selectivity of 80%, outperforming most of the reported works in the literature. We reveal that the light-assistance strategy plays a dual role, which can both accelerate the reaction rate through the photothermal effect and also promote the adsorption of the middle hydroxyl of GLY over Au NWs to realize the selective oxidation of GLY to LA. As a proof-of-concept, we realized the direct conversion of crude GLY that was extracted from cooking oil to attain LA and coupled it with H2 production using the developed photoassisted electrooxidation process, revealing the potential of this strategy in practical applications.

Transition Metal (Fe2O3, Co3O4 and NiO)-Promoted CuO-Based α-MnO2 Nanowire Catalysts for Low-Temperature CO Oxidation

As a toxic pollutant, carbon monoxide (CO) usually causes harmful effects on human health. Therefore, the thermally catalytic oxidation of CO has received extensive attention in recent years. The CuO-based catalysts have been widely investigated due to their availability. In this study, a series of transition metal oxides (Fe2O3, Co3O4 and NiO) promoted CuO-based catalysts supported on the α-MnO2 nanowire catalysts were prepared by the deposition precipitation method for catalytic CO oxidation reactions. The effects of the loaded transition metal type, the loading amount, and the calcination temperature on the catalytic performances were systematically investigated. Further catalyst characterization showed that the CuO/α-MnO2 catalyst modified with 3 wt% Co3O4 and calcined at 400 °C performed the highest CO catalytic activity (T90 = 75 °C) among the investigated catalysts. It was supposed that the loading of the Co3O4 dopant not only increased the content of oxygen vacancies in the catalyst but also increased the specific surface area and pore volume of the CuO/α-MnO2 nanowire catalyst, which would further enhance the catalytic activity. The CuO/α-MnO2 catalyst modified with 3 wt% NiO and calcined at 400 °C exhibited the highest surface adsorbed oxygen content and the best normalized reaction rate, but the specific surface area limited its activity. Therefore, the appropriate loading of the Co3O4 modifier could greatly enhance the activity of CuO/α-MnO2. This research could provide a reference method for constructing efficient low-temperature CO oxidation catalysts.

Effect of Phosphorus Modulation in Iron Single-Atom Catalysts for Peroxidase Mimicking.

Fe-N-C single-atom catalysts (SACs) exhibit excellent peroxidase (POD)-like catalytic activity, owing to their well-defined isolated iron active sites on the carbon substrate, which effectively mimic the structure of natural peroxidase's active center. To further meet the requirements of diverse biosensing applications, SAC POD-like activity still needs to be continuously enhanced. Herein, a phosphorus (P) heteroatom is introduced to boost the POD-like activity of Fe-N-C SACs. A 1Dcarbon nanowire (FeNCP/NW) catalyst with enriched Fe-N4 active sites is designed and synthesized, and P atoms are doped in the carbon matrix to affect the Fe center through long-range interaction. The experimental results show that the P-doping process can boost the POD-like activity more than the non-P-doped one, with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can greatly enhance POD-like activity initially, but its effect becomes insignificant with increasing amount of P. As a proof of concept, FeNCP/NW is employed in an enzyme cascade platform for highly sensitive colorimetric detection of the neurotransmitter acetylcholine.

Enabled Efficient Ammonia Synthesis and Energy Supply in a Zinc-Nitrate Battery System by Separating Nitrate Reduction Process into Two Stages.

The aqueous electrocatalytic reduction of NO3 - into NH3 (NitrRR) presents a sustainable route applicable to NH3 production and potentially energy storage. However, the NitrRR involves a directly eight-electron transfer process generally required a large overpotential (<-0.2 V versus reversible hydrogen electrode (vs. RHE)) to reach optimal efficiency. Here, inspired by biological nitrate respiration, the NitrRR was separated into two stages along a [2+6]-electron pathway to alleviate the kinetic barrier. The system employed a Cu nanowire catalyst produces NO2 - and NH3 with current efficiencies of 91.5 % and 100 %, respectively at lower overpotentials (>+0.1 vs. RHE). The high efficiency for such a reduction process was further explored in a zinc-nitrate battery. This battery could be specified by a high output voltage of 0.70 V, an average energy density of 566.7 Wh L-1 at 10 mA cm-2 and a power density of 14.1 mW cm-2 , which is well beyond all previously reported similar concepts.

Enabled Efficient Ammonia Synthesis and Energy Supply in a Zinc–Nitrate Battery System by Separating Nitrate Reduction Process into Two Stages

AbstractThe aqueous electrocatalytic reduction of NO3−into NH3(NitrRR) presents a sustainable route applicable to NH3production and potentially energy storage. However, the NitrRR involves a directly eight‐electron transfer process generally required a large overpotential (&lt;−0.2 V versus reversible hydrogen electrode (vs. RHE)) to reach optimal efficiency. Here, inspired by biological nitrate respiration, the NitrRR was separated into two stages along a [2+6]‐electron pathway to alleviate the kinetic barrier. The system employed a Cu nanowire catalyst produces NO2−and NH3with current efficiencies of 91.5 % and 100 %, respectively at lower overpotentials (&gt;+0.1vs. RHE). The high efficiency for such a reduction process was further explored in a zinc‐nitrate battery. This battery could be specified by a high output voltage of 0.70 V, an average energy density of 566.7 Wh L−1at 10 mA cm−2and a power density of 14.1 mW cm−2, which is well beyond all previously reported similar concepts.

Thermal Annealing Induced Surface Oxygen Vacancy Clusters in α-MnO2 Nanowires for Catalytic Ozonation of VOCs at Ambient Temperature.

Catalytic ozonation has gained considerable interest in volatile organic compound (VOC) elimination due to its mild reaction conditions. However, the low activity and mineralization rate of VOCs over catalysts hinder its practical application. Herein, a series of α-MnO2 nanowire catalysts were prepared via thermal annealing treatment at various temperatures to tailor defect species. Numerous characterization techniques were used and combined to investigate the relationship between activity and microstructure. PALS and XAFS indicated that more unsaturated manganese and oxygen vacancies, especially surface oxygen vacancy clusters, were produced in α-MnO2 under the optimal high calcination temperature. As a result, MnO2-600 was found to exhibit the best-ever performance in toluene conversion (95%) and mineralization rate (89.5%) at 20 °C, making it a promising candidate for practical use. The roles of these defects in manipulating the reactive oxygen species of α-MnO2 were clarified by quantifying the amounts of reactive oxygen species by quenching experiments and density functional theory calculations. 1O2 and ·OH species generated in the vicinity of oxygen vacancy clusters, especially the dimer oxygen vacancy cluster, were identified as key oxygen species in the abatement of toluene. This study provides a facile method to engineer the microstructure of MnO2 by means of the manipulation of oxygen vacancies and an in-depth understanding of their roles in the catalytic ozonation of VOC.

Vacancy-Defective Cobalt Nitride Nanostructures for Sonocatalytic Hydrogen Production Using Various Water Resources

The cavitation effect, as a kind of geochemical phenomenon, widely exists under intense hydrodynamic circumstances, turbulent streams, earthquakes, or waterfalls and anywhere else where a shear force abruptly breaks the continuity of liquid surfaces. The development of an efficient and cheap sonocatalyst is hence one of the effective ways to utilize the cavitation effect to harness energy. In this study, we use a flower-like cobalt nitride nanowires catalyst with rich nitrogen-vacancy nanostructures to achieve efficient sonocatalytic hydrogen production in various water resources. In pure water, an exceptional sonocatalytic hydrogen generation rate of 28.5 μmol g–1 h–1 is delivered by the flower-like cobalt nitride nanowires. More interestingly, hydrogen peroxide, a high-value oxidation product, is also detected in the liquid phase after ultrasonic wave vibrations. Due to the acid/alkali resistance and corrosion resistance of the transition metal nitrides (TMNs), cobalt nitride nanowires can also produce hydrogen in acidic water, alkaline water, seawater, and wastewater. Enriched active sites in cobalt nitride nanowires greatly promote the recombination of radicals generated by the implosion of cavitation bubbles, which promotes sonochemical reaction efficiency. In addition, the cobalt nitride nanowire catalyst displays excellent stability and reusability during the sonochemical catalytic reaction. The findings are anticipated to be useful for further research on transition metal nitride materials as prospective sonocatalysts for energy conversion and environmental remediation.

Platinum-Cobalt Nanowires for Efficient Alcohol Oxidation Electrocatalysis.

The compositions and surface facets of platinum (Pt)-based electrocatalysts are of great significance for the development of direct alcohol fuel cells (DAFCs). We reported an approach for preparing ultrathin PtnCo100-n nanowire (NW) catalysts with high activity. The PtnCo100-n NW alloy catalysts synthesized by single-phase surfactant-free synthesis have adjustable compositions and (111) plane and strain lattices. X-ray diffraction (XRD) results indicate that the alloy composition can adjust the lattice shrinkage or expansion of PtnCo100-n NWs. X-ray photoelectron spectroscopy (XPS) results show that the electron structure of Pt is changed by the alloying effect caused by electron modulation in the d band, and the chemical adsorption strength of Pt is decreased, thus the catalytic activity of Pt is increased. The experimental results show that the activity of PtnCo100-n for the oxidation of methanol and ethanol is related to the exposed crystal surface, strain lattice and composition of catalysts. The PtnCo100-n NWs exhibit stronger electrocatalytic performance for both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The dominant (111) plane Pt53Co47 exhibits the highest electrocatalytic activity in MOR, which is supported by the results of XPS. This discovery provides a new pathway to design high activity, stability nanocatalysts to enhance direct alcohol fuel cells.