Deposition Of Pt Nanoparticles Research Articles

Photoresponse dependence of WS2/Pt Schottky junction on the features of Pt nanoparticles

In this study, we delve into the photoresponsive characteristics of Schottky junctions fabricated through the deposition of Pt nanoparticles (NPs) onto multilayer WS2 sheets grown via chemical vapor deposition. Our analysis encompasses a comprehensive examination of the junction's morphology, structural attributes, and photophysical behavior. Of particular interest is the intricate relationship between the efficiency of hot electron injection and the specific properties of the Pt NPs, namely their density and size. Our findings reveal that Pt NPs effectively extinguish the photoluminescence of WS2, an outcome attributed to the efficient separation of photo-generated electron-hole pairs facilitated by the WS2/Pt Schottky junction. This process, however, does not significantly alter the electronic configuration of WS2. The modulation of exciton radiative decay is shown to be contingent upon the size and density of the Pt NPs, with an average size of 1.27 nm and density of 0.82/nm² yielding the most rapid exciton decay rate of 1.15 ns. This pronounced dependence of exciton dynamics on Pt NPs features can be attributed to the quenching effect exerted by densely packed Pt NPs, which also plays a pivotal role in the injection of hot electrons from Pt to WS2. The enhancement of internal photoemission is evidenced by a pronounced increase in near-infrared photoresponse within the 800–1000 nm range. Furthermore, the optimization of Pt NPs features leads to superior photoresponsive performance in the WS2/Pt Schottky junctions, manifesting as a responsivity of 280 A/W and a detectivity of 7.77 × 1012 Jones at a wavelength of 850 nm. This photoresponse's dependence on Pt NPs features underscores the dual mechanism governing photodetection in the WS2/Pt Schottky junction: a synergistic interplay between hot electron injection and the separation of photo-excited electron-hole pairs.

Naproxen electrooxidation using carbon paper electrodes modified with reduced graphene oxide and platinum nanoparticles

This research study investigates the electrooxidation of naproxen (NPX), an anti-inflammatory pharmaceutical, on modified carbon paper (CP) electrodes. Electrochemical modification of CP electrodes was accomplished with Pt or reduced graphene oxide (RGO)-Pt coatings, resulting in the production of electroactive electrodes. RGO coatings synthesized by cyclic voltammetry (CV) for 10 scans provided the optimal coverage for the CP electrode surface. The deposition of Pt nanoparticles (Pt NPs) on the electrodes (CP or CP-RGO) by CV produced a good electrode surface coverage with 20 synthesis scans. The voltammetric analysis of the electrodes in 230 mg/L NPX solution showed oxidation peaks around 1.0 to 1.2 V. Moreover, the inclusion of RGO in the coating led to an increase in the current density of these oxidation peaks and a decrease of the electrode electron transfer resistance as measured by electrochemical impedance spectroscopy.The electrolysis of NPX in different electrolytes (Na2SO4 and Na2SO4/NaCl) was conducted at 1.4 V, and the removal of NPX was analyzed using high-performance liquid chromatography. The CP-RGO-Pt electrode in Na2SO4/NaCl media showed the fastest NPX degradation kinetics, resulting in a 90 % degradation in only 90 min with low charge consumption (0.07 A·h·L-1). The smaller size of Pt NPs deposited on CP-RGO, as observed by field emission scanning electron microscopy and transmission electron microscopy, contributed to the higher electrochemical response in CV and a faster kinetic degradation of NPX.

Unique Self-Phosphorylating Polybenzimidazole of the 6F Family for HT-PEM Fuel Cell Application.

High-temperature polymer-electrolyte membrane fuel cells (HT-PEMFCs) are a very important type of fuel cells since they operate at 150-200 °C, making it possible to use hydrogen contaminated with CO. However, the need to improve the stability and other properties of gas-diffusion electrodes still impedes their distribution. Self-supporting anodes based on carbon nanofibers (CNF) are prepared using the electrospinning method from a polyacrylonitrile solution containing zirconium salt, followed by pyrolysis. After the deposition of Pt nanoparticles on the CNF surface, the composite anodes are obtained. A new self-phosphorylating polybenzimidazole of the 6F family is applied to the Pt/CNF surface to improve the triple-phase boundary, gas transport, and proton conductivity of the anode. This polymer coating ensures a continuous interface between the anode and proton-conducting membrane. The polymer is investigated using CO2 adsorption, TGA, DTA, FTIR, GPC, and gas permeability measurements. The anodes are studied using SEM, HAADF STEM, and CV. The operation of the membrane-electrode assembly in the H2/air HT-PEMFC shows that the application of the new PBI of the 6F family with good gas permeability as a coating for the CNF anodes results in an enhancement of HT-PEMFC performance, reaching 500 mW/cm2 at 1.3 A/cm2 (at 180 °C), compared with the previously studied PBI-O-PhT-P polymer.

Nanoarchitectonics and electrocatalytic properties of platinum nanoparticles in weak polyelectrolytes‐based multilayer thin films

AbstractIn this study, the electrocatalytic behavior of platinum (Pt) nanoparticles (NPs) in a novel multilayered thin film is investigated for proton exchange membrane fuel cells (PEMFC) applications. The multilayer thin films are assembled by the alternate deposition of branched polyethylenimine (BPEI) and poly(acrylic acid) (PAA) from aqueous solutions through a layer‐by‐layer (LbL) technique. Two extreme assembly pH conditions critically influence the films' physical and morphological characteristics, subsequently affecting their electrochemical behavior. Manipulation of the assembly pH modifies the charge density of the weak polyelectrolytes (BPEI and PAA), leading to variations in physical, structural, and electrochemical properties. The LbL thin films assembled at a pH of 9.5 for BPEI and 4.5 for PAA exhibit significantly greater thickness compared to the same film with all components deposited at pH 4.5. This is attributed to in‐and‐out diffusion of the partially charged polyelectrolytes with coiled polymeric conformation (BPEI at pH 9.5 and PAA at pH 4.5). As‐assembled LbL thin films are used as nanoreactors for the deposition of Pt NPs. The nanoscale control over polymeric conformation and charge density significantly influences electrocatalytic performance. 9.5BPEI/4.5PAA thin films exhibit higher electrocatalytic activity relative to 4.5BPEI/4.5PAA systems. This improved performance in 9.5BPEI/4.5PAA multilayers is ascribed to the fact that more carboxylic acid groups of PAA are coated in an exponentially grown behavior, which provides more active sites available for Pt NPs to be deposited. The multilayer thin films containing uniformly dispersed Pt NPs can be an attractive and advanced hybrid electrode material with great promise for the proton exchange membrane fuel cells.

Modification of nickel wire electrodes with platinum in the presence of copper ions via galvanic replacement reactions

In the galvanic replacement reaction between Ni wire and PtCl42- in an aqueous solution, the deposition of Pt nanoparticles (PtNPs) on Ni wire is generally unfavorable. However, the addition of Cu2+ into an aqueous solution of PtCl42- was found to promote the deposition of PtNPs effectively for the immersion of Ni wire. This promoted deposition of PtNPs on Ni wire could be confirmed by observing the electrocatalytic responses for ethanol oxidation, electrochemical impedance and the surface images. In addition, the EDS analysis showed that the deposited PtNPs did not contain Cu. The formation of PtNPs without containing Cu was also verified by observing the electrocatalytic properties of other alcohols. Although we had previously reported the stepwise modification of Pt on Ag-deposited Ni wire, the Cu2O-modified Ni wire was useless to allow the deposition of PtNPs in a similar stepwise treatment. Hence, the simple preparation using aqueous solutions containing both PtCl42- and Cu2+ can be proposed as a useful approach to modify PtNPs on Ni materials via galvanic replacement reactions.

Atomic layer deposition of Pt nanoparticles using dimethyl (N, N–dimethyl-3-butene-1-amine−N) platinum and H2 reactant and its application to 2D WS2 photodetectors

2D transition metal dichalcogenides (2D TMDCs) have thin and flexible structures and can be widely applied to nanoelectronics technology as a representative of 2D materials. Research studies on the surface functionalization of 2D TMDCs with nanoparticles have been actively conducted for fabrication of high-performance devices. Specifically, platinum (Pt) has attracted significant attention as a surface functionalization material in various applications, including photosensors, biosensors, and gas sensors due to its effective catalytic effect and excellent corrosion resistance. However, solution-based methods and PVD technologies, widely used for Pt nanoparticle synthesis, have difficulties forming fine particles dispersed on nanomaterials. Atomic layer deposition (ALD) is emerging as an advantageous method for forming nanoparticles, and dimethyl (N,N-dimethyl-3-buten-1-amine-N) platinum (DDAP) can overcome disadvantages of conventional ALD Pt precursors. In this study, we successfully synthesized Pt films using hydrogen as a new reactant in the DDAP-based ALD Pt process and evaluated formation of nanoparticles on SiO2/Si substrates. Subsequently, the ALD Pt-functionalized photodetector was fabricated with 2D WS2, a representative visible-light photodetector material, and improvement of photocurrent was confirmed by providing additional carriers via the localized surface plasmon resonance phenomenon. Furthermore, preferentially growing at high surface energy points, such as defects on WS2 nanosheets, can suppress the capture of photoexcited electrons by defects, consequently extending the carrier lifetime and preventing surface oxidation of the device. In the wavelength range of 500–1200 nm, the photoresponsivity of the ALD Pt-functionalized WS2 photodetector was improved more than 10–20 times compared to pristine WS2, and the response time was also noticeably improved. This study presents a novel approach to Pt functionalization using ALD, opening new possibilities for advanced nanodevice applications.

Effect of Polybenzimidazole Coating on Acetylene Black for Durability of Polymer Electrolyte Membrane Fuel Cell

One of the difficulties to retain Pt interfacial structure during PEMFC operation is arose from the high activity and large surface energy of the Pt nanoparticle, which facilitate i) Ostwald ripening, where the Pt particle size increases by a dissolution-redeposition process upon redox cycling and ii) agglomeration of Pt nanoparticles by sintering. These phenomena lead to the loss of Pt interfacial area and deteriorate the PEMFC performance. In addition, stability of carbon supports used as an electron conductive Pt supporting material is also essential to improve Pt stability since carbon corrosion catalyzed by Pt also takes place at a high potential (mainly over 1.0 V), which triggers the detachment of Pt and subsequent agglomeration. Thus, the use of durable carbon supports against the oxidation is crucial to increase the PEMFC durability. Since it is known that sp2 carbons are more thermodynamically stable than sp3 carbons upon oxidation, the use of highly graphitized carbons such as carbon nanotubes (CNTs) have been investigated to employ and it is proved that the use of such carbons mitigates the Pt agglomeration and thus enhance the PEMFC durability. However, an absence of the anchoring sites for Pt deposition on such graphitized carbon surface such as -OH and -COOH connected on sp3 carbons make the uniform deposition of Pt nanoparticles rather difficult. And it is pointed out that the weak interaction between the graphitized carbon surface and Pt nanoparticles often induces the sintering of Pt particles and, therefore the improvement of the Pt‒carbon interfacial strength will further improve the Pt stability. Although, general strategy to introduce anchoring sites for the highly graphitized carbons is to oxidize the surface by harsh chemical or physical treatments, such oxidation always involved the introduction of the sp3 sites and resulted in the decrease of the durability of carbon supports. We have developed smart method to introduce anchoring sites without creating sp3 carbons on the highly graphitized carbon surface, where the carbons are coated by polymer having anchoring sites for metal ions. In this method, polymer such as polybenzimidazole (PBI) is coated on the pristine (non-oxidized) carbons and can act as the anchoring site for the Pt deposition. Therefore, Pt can be deposited onto the surface of highly graphitized carbon such as CNTs without oxidizing the CNTs. Indeed, we reported that PEMFC having PBI-coated CNT as a carbon support showed excellent durability upon fuel cell accelerated durability test (ADT) between 1.0 ‒ 1.5 V. In that research, oxidized-CNT was used as a comparison since direct Pt deposition onto the pristine CNT was rather difficult and, in addition, we used the ADT protocol designed to degrade the carbon (1.0 – 1.5 V). Thus, we successfully demonstrated the advantage of the PBI coating to preserve inherent carbon durability but the effect of the PBI coating for the Pt stability was not investigated. We also demonstrated that the PBI-coating on Vulcan could enhance the durability of Vulcan-based PEMFC. However, in that research, PBI coating improved Vulcan stability mainly because the coverage of micropore of Vulcan decelerated the oxidation of the carbon surface during the ADT between 1.0 ‒ 1.5 V. Therefore, the effect of PBI coating for the stability of Pt particles was not observed. In this study, to clarify the effect of PBI coating for Pt stability and PEMFC durability, ADT between 0.6 ‒ 1.0 V designed to study Pt stability was applied for the PEMFC having PBI-coated carbons as a carbon support. Here, Acetylene Black (AB) was chosen as the carbon support since 1) AB shows high electrochemical stability due to their high crystallinity and Pt sintering triggered by the carbon corrosion during the ADT can be avoided and 2) direct Pt deposition on AB was possible and no oxidation pretreatment is necessary for the reference samples. As the result, we found that MEA employing PBI-coated AB shows only 8% decrease in the maximum power density, while MEA containing non-coated AB shows 34% decrease after the ADT. Structural analysis of the electrocatalysts after the ADT reveals that the PBI anchors both Pt nanoparticle and ionomer upon ADT and maintains their interfacial structure. We conclude that the polymer-coating method is promising both for the improvement of the durability and the activity of the PEMFC.

Enhancing electron interaction between Pt and support for superior electrochemical performance through atomic layer deposition of tungsten oxide

The stabilization of platinum (Pt) catalysts through strong metal-support interactions is crucial for their successful implementation in fuel cell applications. Tungsten oxide (WO3) has demonstrated excellent CO tolerance and has been recognized as a promising substrate for anchoring and stabilizing Pt nanoparticles (NPs). However, the limited specific surface area of conventional tungsten oxide restricts its effectiveness in dispersing noble metal NPs. In this study, we present a pioneering approach by employing atomic layer deposition (ALD) to create a WO3 interlayer between Pt NPs and a carbon substrate. Using nitrogen-doped carbon nanotubes (NCNT) as the foundation, WO3 nanoparticles (2–5 nm) were selectively synthesized, followed by the subsequent deposition of Pt NPs using a bottom-up approach. The Pt-WO3-NCNT catalyst, with a WO3 bridge layer effectively inserted between the active site and carbon support, has displayed a notable augmentation in electrocatalytic activity and notable stability when compared to commercial Pt catalysts in oxygen reduction reaction (ORR). The detailed microstructure and the enhanced electrochemical reaction mechanism of Pt-WO3-NCNT catalyst has been investigated by X-ray adsorption spectrum and density functional theory (DFT) calculations. This work presents an innovative approach for enhancing the stability of Pt catalysts through the utilization of the ALD technique.

Efficient deposition of Pt nanoparticles on TiO2 nanosheets by regulating the defect concentration: Strengthening MSI for enhancing dehydrogenation of dodecahydro-N-ethylcarbazole

Efficient deposition of Pt nanoparticles on TiO2 nanosheets by regulating the defect concentration: Strengthening MSI for enhancing dehydrogenation of dodecahydro-N-ethylcarbazole

Ultra-Small Ceria Nanocrystals at Carbon Surface Synthesized by Ultrasound Sonication: A Study of Highly Active Platinum-Cerium Bifunctional Catalysts for Methanol Oxidation and Oxygen Reduction

ABSTRACT Cerium (IV) oxide (called ceria) has gained a lot of interest from researchers due to its high oxygen storage capacity (1) and high tolerance toward CO-like intermediates of methanol oxidation reaction (MOR) (2,3). In our previous study (4), the ceria crystals were synthesized by the modified solvothermal synthesis with urea (5) and grain size of ceria was around 30 µm, even if the crystallite size was only 11 nm. However, even this huge grain-size CeOx particles contributed insignificantly to the catalytic synergetic effect of ceria at the PtCe catalysts toward MOR.The parameters influencing the deposition of Pt nanoparticles (NPs) on the ceria-carbon support by the ethylene glycol (EG) reduction method were investigated in previous study (4). It was found that the influence of energy supply methods on the reaction system needs to be simplified to control the nucleation and growth of Pt NPs better.Although the role of catalytically active components (Pt and CeOx) in catalyst is important, the structure of carbon support affects the catalytic behaviour of the catalyst significantly. The chromium carbide-derived carbon, noted as C(Cr-CDC), synthesized in our previous study (6) is active materials toward oxygen reduction reaction in 0.1 mol dm─3 KOH due to its high number of the active sites at the surface, large specific surface area, and unique micro-mesoporous structure. Therefore, it is a good support material for this study.The purpose of this study was to synthesize a ceria with small grain size, improve the activity of Pt NPs synthesized by tuning the parameters of EG reduction method, and compare the activity of the novel PtCe/C(Cr-CDC) materials and PtCe/C (commercial Ketjenblack carbon) materials.In detail, the ceria-carbon materials were synthesized firstly by ultrasound sonication method in the mixture of EG and sodium hydroxide solutions, called sonochemical method. Later, the Pt NPs were deposited onto the ceria-carbon materials by EG reduction method using the refluxing system. All the materials were characterized with thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) methods. All the PtCe/C materials were measured in the 3-electrode system in 0.5 mol dm─3 H2SO4 and in a mixture of 0.5 mol dm─3 H2SO4 + 1 mol dm─3 CH3OH to investigate the electrochemical behaviour and MOR activity, respectively.The results of XRD and SEM-EDX revealed that it was possible to synthesize the ultra-small ceria NPs by the sonochemical method. The crystallite size is smaller than 2 nm. EDX confirmed the presence of cerium in measuring areas, however, the grain size of ceria in ceria-carbon was too small to be revealed with SEM. The TGA confirmed that all cerium was deposited onto carbon with approximately 11 wt. % of the total ceria-carbon weight. Besides, XRD and TGA also confirmed the success of Pt deposition method. The electrochemical activity at PtCe/C materials revealed high electrochemically active surface area value (55-80 mPt 2 gPt −1). ACKNOWLEDGEMENT This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011) and Personal Research Grant PRG676. The SEM-EDX measurements were conducted using the NAMUR+ core facility funded by the Estonian Research Council (TT 13). REFERENCES E. Antolini and J. Perez, Int. J. Hydrog. Energy, 36, 15752–15765 (2011).S. Dai, J. Zhang, Y. Fu, and W. Li, New J. Chem., 42, 18159–18165 (2018).D. Y. Chung, K.-J. Lee, and Y.-E. Sung, J. Phys. Chem. C, 120, 9028–9035 (2016).H. Q. V. Nguyen, J. Nerut, H. Kasuk, M. Härmas, P. Valk, T. Romann, M. Koppel, P. Teppor, J. Aruväli, O. Korjus, O. Volobujeva, and E. Lust, J. Solid State Electrochem. (2022).S. B. Atla, M.-N. Wu, W. Pan, Y. T. Hsiao, A.-C. Sun, M.-J. Tseng, Y.-J. Chen, and C.-Y. Chen, Mater. Charact., 98, 202–208 (2014).H. Q. V. Nguyen, J. Nerut, H. Kasuk, V. Grozovski, T. Thomberg, I. Tallo, R. Palm, M. Koppel, T. Romann, R. Härmas, J. Aruväli, M. Külaviir, and E. Lust, Russ. J. Electrochem., 58, 781–797 (2022).

Effects of Mesoporosity and Conductivity of Hierarchically Porous Carbon Supports on the Deposition of Pt Nanoparticles and Their Performance as Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media.

The structural characteristics of supports, such as surface area and type of porosity, affect the deposition of electrocatalysts and greatly influence their electrochemical performance in fuel cells. In this work, we use a series of high surface area hierarchical porous carbons (HPCs) with defined mesoporosity as model supports to study the deposition mechanism of Pt nanoparticles. The resulting electrocatalysts are characterized by several analytical techniques, and their electrochemical performance is compared to a state-of-the-art, commercial Pt/C system. Despite the similar chemical composition and surface area of the supports, as well as similar amounts of Pt precursor used, the size of the deposited Pt nanoparticles varies, and it is inversely proportional to the mesopore size of the system. In addition, we show that an increase in the size of the catalyst particles can increase the specific activity of the oxygen reduction reaction. We also report on our efforts to improve the overall performance of the above electrocatalyst systems and show that increasing the electronic conductivity of the carbon support by the addition of highly conductive graphene sheets improves the overall performance of an alkaline fuel cell.

Platinum nanoparticle modulated titania electronic structure descriptors for selective photocatalytic CO2 conversion

Modulation of the electronic structure of TiO2 nanorod array (NR), which governs the selectivity for the photocatalytic CO2 conversion, is demonstrated by the deposition of Pt nanoparticles (NPs) with various configurations. In-situ X-ray absorption near edge structure (XANES) measurements suggest that the active sites for the photocatalytic reaction are located on the surface of TiO2 NRs, but not on the Pt NPs, because the photocharge transfer from TiO2 NRs to Pt NPs is inefficient. The t2g/eg orbital ratio and dz2/dx2-y2 orbital ratio of TiO2 acquired from Ti L3-edge spectra of the Pt NP/TiO2 NR photocatalysts, which are strongly influenced by the feature of the deposited Pt NPs, are respectively well-correlated to the experimental selectivity of H2 and CH4 for photocatalytic CO2 conversion as well as the density functional theory calculated adsorption energies of H atom and CO molecule on the TiO2 surface. The Pt NPs thus play a crucial role as a promoter rather than as a cocatalyst. Besides the adsorption energies of H and CO on TiO2, the t2g/eg and dz2/dx2-y2 ratios of Ti 3d unoccupied state can be the electronic structure-based descriptors of TiO2 heterostructures for photocatalytic CO2 conversion to distinguish between H2 evolution and CH4 formation.

Non-Enzymatic Electrochemical Detection of Hydrogen Peroxide and Glucose through Using Copper(II) and Platinum(II) Complexes with Tridentate Ligand – Platinum Nanoparticles – Graphene Oxide Composite

Two complex compounds [Cu(L)Cl2] (Cu-L) and [Pt(L)Cl]Cl (Pt-L) containing tridentate ligand (L = 2,6-bis(benzimidazol-2-yl)−4-hydroxypyridine) were prepared. After the successful immobilization of Cu-L and Pt-L on graphene oxide (GO), the electrochemical deposition of Pt nanoparticles was carried out on the modified surface. The resulting electrodes were demonstrated to possess exceptional electrocatalytic features towards the detection of H2O2, and glucose as indicated by the improvement in the cathodic peak response and a favourable shift in the reduction potential of each two reagents. The sensing devices exhibited promising electrochemical performance for the non-enzymatic measurement of H2O2, ranging from 0.01 mmol l−1 to 5 mmol l−1, and a considerably low LOD of 0.063 μmol l−1 and 0.113 μmol l−1 for Cu-L and Pt-L modified-GO decorated with Pt nanoparticles, respectively. Both sensors also showed exceptional sensitivity in the detection of glucose, with LOD of 0.054 μmol l−1 and 0.065 μmol l−1 in the concentration range of 0.01 mmol l−1 to 2 mmol l−1. The fabricated sensors also demonstrated decent sensitivity, long-term durability, and minimal interference capability. They were also tested for their ability to identify H2O2 and glucose in the actual biological fluid, demonstrating their practical use in routine H2O2 and glucose detection.

Insight into the LED-induced deposition of Pt nanoparticles on a graphite matrix: Unravelling the photodeposition processes on materials different than semiconductors

A novel LED-assisted photodeposition process was used for the photoreduction of platinum nanoparticles on the exfoliated graphite surfaces. The photodeposition process on graphite was presented for the first time. It was found that the exfoliated graphite/Pt is graphite flakes with platinum nanocrystalline being homogeneously deposited on the surface of the carbon matrix. The mechanism of Pt photodeposition was based on the initial adsorption of Pt(IV) ions on the surface of the expanded graphite, and the reduction of Pt under the influence of UV radiation. Electrochemical measurements demonstrated that the EG/Pt composite exhibited good catalytic activity in the reaction of methanol electro-oxidation. The tested electrode maintained a high activity despite poisoning the Pt catalyst with intermediate products of methanol oxidation. This confirms that the LED-assisted photodeposition process can be an element of a novel approach for the synthesis of graphite-based materials for direct methanol fuel cells.

Enhancing the photocatalytic properties of doped TiO2 nanowires grown by seed-assisted thermal oxidation

In the present paper, an investigation of the structural, optical, and photo-catalytical properties of TiO2 nanowires (NWs) was conducted. The NWs were synthesized on a Si substrate by thermal oxidation of a thick (4 µm) Ti film covered by a thin (∼ 5 nm) Au film. The annealing process at 750 °C produced a 1.7 μm thick NWs TiO2 layer over a 3 μm thick TiO2 film. Characterization techniques show that TiO2 NWs are in rutile phase and have gold nanoparticles on top. Fe-doped TiO2 NWs were synthesized to increase photoactivity in the visible range. The doping was performed using an unusual strategy, that is, implanting Fe+ ions into the Ti layers before the growth of the TiO2 NWs. The defectiveness introduced by the ion implantation is avoided and precise control of the doping is achieved. The photocatalytic properties were studied by following the degradation of methylene blue. In order to increase the photo-degradation rate under UV light of undoped NWs, two different strategies have been followed: 1) deposition of Pt nanoparticles on the front or on the rear side of the samples, and 2) thermal annealing in a reductive environment. A three-fold activity enhancement is obtained and discussed. Photocatalytic activity in the visible range was also measured for the Fe-doped samples, showing good activity, which was further improved by using the same strategies implemented under UV irradiation.

Ultrathin Ultralow-Platinum Catalyst Coated Membrane for Proton Exchange Membrane Fuel Cells.

Catalyst coated membrane (CCM) is the core component of proton exchange membrane fuel cells and is routinely fabricated by spraying Pt/C slurriesonto membrane, resulting in low activity and thick catalyst layer (CL, 5-10µm) with an unaffordable Pt loading of 0.2-0.4mg cm-2 and a large mass transfer resistance at cathode. Highly active ultrathin ultralow-Pt CL (UUCL) is urgently required, but remains rare. Herein, wet-chemical direct growth of UUCLs on both sides of membrane to achieve integrated ultrathin ultralow-Pt catalyst coated membranes (UUCCMs) with a cathodic CL thickness of 79.7 ± 15.0nm and a Pt loading of 20.2 ± 1.6µg cm-2 is reported. The key to this unique fabrication is the release of proton from membrane to regioselectively initiate the growth of interconnected Pd nanoneedle clusters array on membrane, followed by high-density deposition of Pt nanoparticles on Pd (Pt/Pd UUCLs). The single cell of UUCCMs exhibits the highest mass peak power density of 59.9W mgPt,Cathode -1 in the literature. The exceptional activity originates from high electrochemically active surface area, remarkable oxygen reduction reaction activity closely correlated with strain, and electronic effect at Pt/Pd interface, as well as improved mass transfer and optimal water management.

Catalytic Activity for ORR of Pt Supported on Ordered Mesoporous Carbon with Network Structure

IntroductionIn order to realize carbon neutrality, working toward becoming a hydrogen-based society using renewable energy is essential, and hydrogen fuel cell vehicles will be one of the key devices. For further widespread deployment of fuel cell vehicles, cost reduction and performance enhancement of polymer electrolyte fuel cell (PEFC) systems are urgently needed. Recently, Pt/C-based electrocatalysts using mesoporous carbon as a support material have attracted attention, because well-designed mesopores can act as “accessible pores,” in which direct contact between ionomer and Pt surface is avoided, while the transport of protons, oxygen and generated water is not suppressed. Ordered mesoporous carbon (OMC) with a uniform nanopore structure is one of the ideal candidate materials for a catalyst support with accessible pores. However, with conventional synthesis methods, the typical OMC primary particle size is on the order of micrometers, and mass transport within the nanopores could be a difficult issue. In the present study, we focused on the development of OMC nanoparticles with a network structure. By use of nonionic surfactant micelles with phenol-formaldehyde resole resin as a carbon source, we obtained OMC nanoparticles with a novel hierarchical network structure (ns-OMC). To the best of our knowledge, there are no reports of the synthesis of ordered mesoporous carbon nanoparticles with a rigid network structure. In this study, in addition to the effect of synthesis conditions on the ns-OMC structure, a newly developed technique for the selective deposition of Pt nanoparticles within the ns-OMC nanopores, and the ORR activity of the Pt/ns-OMC catalysts, will be discussed in detail.ExperimentalNs-OMC powder was synthesized with resol-nonionic surfactant micelles as a carbon source and structure directing agent. Resol-F127 (nonionic surfactant) micelles were synthesized by mixing phenol, formaldehyde, water and F127 with sodium hydroxide. After hydrothermal treatment of the mixture, the resulting solid was filtered and washed thoroughly and dried under vacuum. The obtained powder was carbonized at 700 ºC followed by annealing at 1000 ºC. Pt was deposited on the ns-OMC powder by the reverse micelle and colloid techniques. Cyclic voltammetry and linear sweep voltammetry were carried out in N2-saturated and O2-saturated 0.1 M HClO4 solution at 25 ºC using the conventional rotating disk electrode (RDE) technique. Potential step cycling measurements simulating load cycling between 0.6 V and 1.0 V vs. RHE were carried out according to the FCCJ protocol. Coating of the catalyst on a glassy carbon disk substrate was carried out by an electrospray (ES) coating technique developed by our group [1]. N2 adsorption measurement at liquid nitrogen temperature was carried out. The morphology of the Pt/ns-OMC was observed by scanning transmission electron microscope (STEM).Results and discussionAs seen in the STEM images of the ns-OMC powder (Figure 1), the network structure formed by connection of OMC primary nanoparticles to form developed macropores is clearly observed. The OMC nanoparticles were tightly connected via a thick necking structure. The primary particle size of the OMC and neck thickness were controllable via the resol-F127 micelle concentration and the temperature during the hydrothermal treatment. Highly ordered nanopores were observed on the surface of the OMC particles, with a pore size of ca. 5 nm and an interpore distance of ca. 8 nm. The nanopores and the network structure were stable even after high temperature annealing at 1400 ºC. The BET specific surface area for the ns-OMC annealed at 1000 ºC was 814 m2 g-1, and the BJH pore size distribution curve of the ns-OMC showed a mesopore peak at 4.5 nm, which is in good agreement with the STEM observation. When Pt was deposited on the ns-OMC support, most of the Pt particles, with diameters of 4 to 5 nm, were dispersed on the support and, interestingly, located inside or right above the nanopore entrances. Careful STEM measurements revealed that the Pt particles were not deposited deeply within the OMC nanopores, but most were deposited at relatively shallow positions. RDE measurements revealed that the Pt/ns-OMC catalysts showed higher specific activity and mass activity for the ORR and much higher stability for the ECSA values during potential step cycling measurements in comparison with a commercial Pt/CB catalyst. The higher catalytic activity and durability observed for the Pt/ns-OMC catalyst may be due to a near-ideal distance between neighboring Pt particles deposited on the novel support. Aggregation and sintering of the Pt particles were successfully suppressed due to the nanopore structure.[1] S. Cho, K. Tamoto and M. Uchida, Energy Fuels, 34, 14853 (2020).Acknowledgement: This work was supported by the ECCEED’30-FC project from NEDO. Figure 1

Three dimensional Ti3C2Tx and rGO hybrid supported Pt catalyst for the high performance hydrogen evolution reaction

The effective electrocatalysts for hydrogen evolution reaction (HER) in alkaline aqueous is critical point to reduce energy losses for water electrolysis. Here, a highly active and stable electrochemical catalyst of platinum (Pt) nanoparticles loaded on three-dimensional Ti3C2Tx-reduced graphite oxide (rGO) hybrid support (Pt/Ti3C2Tx-rGO3D) has been developed for hydrogen evolution reaction (HER). The large surface of 3 D support provides an adequate site for deposition of Pt nanoparticles, leading to superior HER activity with low overpotential about 41 mV and better stability than Pt/C. This study offers a hybrid support for the development of highly active electrocatalysts for hydrogen evolution reaction.

Noble Metals Deposited LaMnO3 Nanocomposites for Photocatalytic H2 Production.

Due to the growing demand for hydrogen, the photocatalytic hydrogen production from alcohols present an intriguing prospect as a potential source of low-cost renewable energy. The noble metals (Ag, Au, Pd and Pt) deposited LaMnO3 nanocomposites were synthesized by a non-conventional green bio-reduction method using aqueous lemon peel extract, which acts as both reducing and capping agent. The successful deposition of the noble metals on the surface of LaMnO3 was verified by using powder XRD, FTIR, TEM, N2-physisorption, DR UV-vis spectroscopy, and XPS techniques. The photocatalytic activity of the synthesized nanocomposites was tested for photocatalytic H2 production under visible light irradiation. Different photocatalytic reaction parameters such as reaction time, pH, catalyst mass and reaction temperature were investigated to optimize the reaction conditions for synthesized nanocomposites. Among the synthesized noble metal deposited LaMnO3 nanocomposites, the Pt-LaMnO3 nanocomposite offered superior activity for H2 production. The enhanced photocatalytic activity of the Pt-LaMnO3 was found as a result from low bandgap energy, high photoelectrons generation and enhanced charge separation due to deposition of Pt nanoparticles. The effective noble metal deposition delivers a new route for the development of plasmonic noble metal-LaMnO3 nanocomposites for photocatalytic reforming of aqueous methanol to hydrogen.

NiMoO4 nanorods derives carbon layers wrapped NiCo alloy decorated with Mo2C platinum-based catalyst for efficient methanol electrooxidation

To the aim of accelerate the methanol oxidation reaction (MOR), rationally designing novel MOR catalyst is highly desired. Hence, NiCo alloy resides in carbon layers decorated with Mo2C platinum-based catalyst (Pt/NiCo-Mo2C@NDC) is fabricate. For the fabrication, NiMoO4 nanorods (NRs) are firstly coated with CoZn-ZIF and then subjected to anneal treatment and NaBH4 reduction procedure. In the system, CoZn-ZIF serves as the sacrificial template and reducing agent, rendering bifunctional effect: CoZn-ZIF provides doped nitrogen sources, which are beneficial to the overall conductivity and deposition of Pt nanoparticles. Besides, it could act as the carbon sources for the reaction formation of the Mo2C during high temperature calcination, which delivers the excellent co-catalytic effect. Meanwhile, NiCo alloy can be fabricated during the annealing treatment and alter the structure properties of the catalyst, showing the Ni content-depended electrochemical performance. Therefore, the catalyst exhibits remarkable electrocatalytic activity and stability. Moreover, we also focus on the structure-activity relationships to provide insight into the effect of alloy and molybdenum carbide on catalytic activity.