Activity Of Pt Catalysts Research Articles

Enhancement of the ORR Activity and Durability of Pt/C by the Modification with Melamine and N-Containing Aromatic Compounds

The ORR activity and durability of Pt catalysts have to be enhanced for the wider spread of PEFCs. We pay special attention to possibility that surface modification of a Pt catalyst increases its ORR activity. On the Pt surface, Pt-OH species is stabilized too much by network structure of water molecules adsorbed there [1]. The overstabilization of Pt-OH impedes the ORR because this species is an intermediate of ORR. Then, we try to enhance the ORR activity by destabilizing Pt-OH. The perturbation of the water network would destabilize Pt-OH. We try to perturbate the water network by adding an external organic compound to enhance the ORR activity.We tested a wide variety of compounds as an enhancer of ORR of Pt. Although most of compounds tested exhibit no influence of inhibitory effects on the ORR, we found that certain kind of N-containing aromatic compounds -melamine (and tetraazaporphyrin)- enhance the ORR activity of Pt catalysts significantly [2-4]. With the addition of melamine, ORR activity at 0.9 V vs. RHE is increased by 1.6 times although the ECSA decreased (Fig. 1). The enhancement of the ORR activity is reasonably ascribed to the destabilization of Pt-OH, judging from the change of cyclic voltammograms of Pt/C after the addition of melamine.This melamine modification method is also applied for another highly active catalyst (Pt/Pd/C core-shell catalyst) to obtain a further activated catalyst. The mass activity of Pt/Pd/C core-shell catalyst increases by 2.4 times after melamine modification and reaches 3600 AgPt -1 at 0.9 V vs. RHE [5].Melamine also enhances the durability considerably. Under an accelerated durability test (ADT) (80 °C, 0.6 V (3s) - 1.0 V (3s), square wave, 10000 cycles), Pt/C undergoes severe degradation; the ECSA significantly decreases because of the increase in the size of Pt nanoparticles (Fig. 1). However, after the ADT in the presence of melamine, the decrease in ECSA is significantly suppressed [6]. This beneficial effect is due to the suppression of the increase in size of Pt nanoparticles. A melamine polymer (poly-melamine sulfonate)-modified Pt/C also exhibits higher durability than unmodified Pt/C [7]. The suppression of Pt-OH by melamine participates in the enhancement of the durability.In this talk, we introduce discovery of melamine as an ORR enhancer, effect of melamine on the ORR activity/durability of Pt/C, and mechanisms of functions of melamine.This paper is based on the results obtained from projects, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

(Poster Award - 2nd Place) Enhancement of ORR Activity of Pt Catalyst for PEFCs By Modification with Hydrogen-Bonded Organic Framework Composed of Melamine and Cyanuric Acid

Introduction Improvement in ORR activity of Pt and Pt-based catalysts used in PEFCs for FCEVs is crucial for cost reduction and widespread commercialization [1]. We have reported that surface modification of Pt and Pt-based catalysts with melamine and its derivatives enhance ORR activity [2, 3]. However, it is concerned that melamine is easily washed out by water generated at the cathode in PEFCs because melamine is soluble in water (3.1 g/L). In this study, a hydrogen-bonded organic framework (HOF) composed of melamine (MEL) and cyanuric acid (CA) [4] was prepared to suppress the washing-out problem and investigated as a modifier of Pt catalyst loaded on mesoporous carbon (MPC) support. Experimental MPC (CNovel MH-18, SBET 1,334 m2/g, TOYO TANSO) was used as a carbon support for Pt catalyst. Pt/MPC (50 wt%) was prepared by an impregnation-thermal decomposition method using Pt(NO2)2(NH3)2 as a Pt source. Pt/MPC was modified as the following procedure. First MEL was impregnated within the Pt/MPC by ultrasonically dispersing 100 mg Pt/MPC catalyst and 10 mg MEL (10 wt.% to the catalyst) in 100 mL pure water, followed by drying using a rotary evaporator (MEL-Pt/MPC). Then MEL-Pt/MPC (110 mg) was dispersed in 100 mL water containing 10 mg CA and dried to obtain HOF-Pt/MPC. The catalyst was loaded on a glassy carbon (GC) RDE. CV of the catalyst was recorded in Ar-saturated 0.1 M HClO4 at 25oC at a scan rate of 50 mV/s and ORR activity was evaluated by LSV performed at 25oC in O2-saturated 0.1 M HClO4 at a scan rate of 10 mV/s on the positive sweep while rotating the GC disk electrode at 1,600 rpm. To investigate the stability of MEL and HOF on the electrode, the GC electrode after the initial measurements was immersed in 0.1 M HClO4 at 80oC for 1 h, followed by washing with pure water, and CV and LSV were measured in the same manner at 25oC. Results and Discussion Figure 1 shows the molecular structure of MEL-CA HOF [4]. Figures 2 and 3 show CVs and LSVs, respectively, for bare, MEL-, and HOF-Pt/MPC before the stability tests. For bare Pt/MPC in Fig. 2, peaks were observed around 0.05−0.4 V and 0.6−1.0 V, which are assigned to the adsorption/desorption of underpotential deposited hydrogen (Hupd) and Pt-oxide species formation/reduction, respectively. For MEL- and HOF-Pt/MPC, the HUPD peak area decreased slightly, while the onset potential for Pt-oxide formation was shifted positively in Fig. 2. As a result, ORR activity of MEL- and HOF-Pt/MPC was improved remarkably as shown in Fig. 3 (mass activity: 894 and 829 A/g, respectively, at 0.9 V). These results indicate that HOF has an enhancement effect for ORR activity similar to that of MEL modification. Figure 4 shows CVs for bare, MEL-, and HOF-Pt/MPC after the stability tests at 80oC for 1 h. In Fig. 4, the waves of Hupd and Pt-oxide of MEL-Pt/MPC became similar to those of bare Pt/MPC after the stability test, which indicated that MEL was washed out in the electrolyte solution. On the contrary, the HOF-Pt/MPC catalyst substantially retained the waves shapes before the stability test shown in Fig. 2. These results indicate that the HOF has higher stability against washing-out than MEL owing to a much lower solubility at 80°C. Figure 5 shows LSVs after the stability tests. The loss of activity of HOF-Pt/MPC (639 A/g) was smaller than MEL-Pt/MPC (553 A/g) owing to the suppression of washing-out, which is consistent with the results in Fig. 4. The results of single cell tests using bare Pt/MPC, MEL-Pt/MPC and HOF-Pt/MPC cathode catalysts will be presented at the meeting.This study was partly supported by NEDO, Japan.

High or Low Coordination: Insight into the Active Site of Pt Nanoparticles toward CO Oxidation.

The catalytic activity of metal nanoparticles (NPs) is highly dependent on the coordination environment of the surface sites. Understanding the role of different sites in reactions is essential for gaining insights into catalytic activity and the precise design of catalysts. Herein, we used first-principles calculation-based kinetic Monte Carlo simulations to investigate correlations between different sites on Pt NPs in CO oxidation reactions. Low-coordinated (LC) sites favor the CO adsorption and reaction, whereas the oxygen mainly adsorbs on high-coordinated (HC) sites and diffuses to LC sites for reaction at low temperatures. Compared with step-dominated and terrace-dominated structures, the step-terrace structures exhibit higher activities. This reveals that the catalytic performance is not simply determined by the sites where the reaction occurs but is dramatically affected by the kinetic synergies between different sites. A proper way to optimize the activity of Pt catalysts is to balance the LC and HC sites.

Structure and Reactivity of Metal-Oxide-Supported Noble Metal Nanoparticles: Electrooxidation of Simple Organic Molecules

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol, ethanol, formic acid and dimethyl ether. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.

Combining Highly Dispersed Amorphous MoS3 with Pt Nanodendrites as Robust Electrocatalysts for Hydrogen Evolution Reaction.

Surface modification of electrocatalysts to obtain new or improved electrocatalytic performance is currently the main strategy for designing advanced nanocatalysts. In this work, highly dispersed amorphous molybdenum trisulfide-anchored Platinum nanodendrites (denoted as Pt-a-MoS3 NDs) are developed as efficient hydrogen evolution electrocatalysts. The formation mechanism of spontaneous in situ polymerization MoS4 2- into a-MoS3 on Pt surface is discussed in detail. It is verified that the highly dispersed a-MoS3 enhances the electrocatalytic activity of Pt catalysts under both acidic and alkaline conditions. The potentials at the current density of 10mA cm-2 (η10 ) in 0.5msulfuric acid (H2 SO4 ) and 1mpotassium hydroxide (KOH) electrolyte are -11.5 and -16.3mV, respectively, which is significantly lower than that of commercial Pt/C (-20.2mV and -30.7mV). This study demonstrates that such high activity benefits from the interface between highly dispersed a-MoS3 and Pt sites, which act as the preferred adsorption sites for the efficient conversion of hydrion (H+ ) to hydrogen (H2 ). Additionally, the anchoring of highly dispersed clusters to Pt substrate greatly enhances the corresponding electrocatalytic stability.

Elucidation of the mechanism of melamine adsorption on Pt(111) surface via density functional theory calculations.

The oxygen reduction reaction (ORR) activity of Pt catalysts in polymer electrolyte fuel cells (PEFCs) should be enhanced to reduce Pt usage. The adsorption of heteroaromatic ring compounds such as melamine on the Pt surface can enhance its catalytic activity. However, melamine adsorption on Pt and the consequent ORR enhancement mechanism remain unclear. In this study, we performed density functional theory calculations to determine the adsorption structures of melamine/Pt(111). Melamine was coordinated to Pt via two N lone pairs on NH2 and N- in the triazine ring, resulting in a chemisorption structure with slight electron transfer. Four types of adsorption structures were identified: three-point adsorption (two amino groups and a triazine ring: Type A), two-point adsorption (one amino group and a triazine ring: Type B), two-point adsorption (two amino groups: Type C), and one-point adsorption (one amino group: Type D). The most stable structure was Type B. However, multiple intermediate structures were formed owing to the conformational changes from the most stable to other stable adsorption structures. The resonance structures of the adsorbed melamine stabilise the adsorption, as increased resonance allows for more electron delocalisation. In addition, the lone-pair orbital of the amino group in the adsorbed melamine acquires the characteristics of an sp3 hybrid orbital, which prevents horizontal adsorption on the Pt surface. We believe that understanding these adsorption mechanisms will help in the molecular design of organic molecule-decorated Pt catalysts and will lead to the reduction of Pt usage in PEFCs.

Surface-functionalized three-dimensional MXene supports to boost the hydrogen evolution activity of Pt catalysts in alkaline media

Distinctive surface functional groups on 3D MXenes as Pt-supports are correlated with optimized Pt–H affinity and HER activity in alkaline media.

(Invited) Enhancing Oxygen Reduction Reaction Activities of Pt Catalysts By Atomic Layer Deposited Metal Oxides

The oxygen reduction reaction (ORR) posts a significant kinetic limit to hydrogen fuel cells, especially for polymer electrolyte membrane fuel cells (PEMFCs) operating at low temperatures. Highly active and durable electrocatalysts are required for reducing platinum group metal use and ensuring reliable device performance. The use of atomic layer deposition (ALD) and ALD transition metal oxides as dopants or templates are applied in controlled synthesis of highly active and durable Pt ORR catalysts. With density functional theory, these catalysts can also be designed with reliable theoretical guidance. The feasibility of their use in membrane electrode assemblies will be demonstrated.

Improved catalytic stability of Pt/TiO2 catalysts for methylcyclohexane dehydrogenation via selenium addition

To improve the catalytic activity of Pt catalysts for methylcyclohexane (MCH) dehydrogenation, which is utilized for hydrogen transportation, the effects of the addition of Se on the performance of Pt/TiO2 catalysts were investigated. In Se/Pt/TiO2 catalysts, even a small amount of Se addition (Se/Pt = 0.01) improved the catalyst stability. Se was highly dispersed on the Pt/TiO2 surface, without volatilizing in a reducing atmosphere at temperatures below 450 °C, and did not form an alloy with Pt. The analysis of adsorption-desorption characteristics revealed that the addition of Se promoted the desorption of products, including the main product, toluene. Moreover, an electron donation effect from Se to Pt was observed by FT-IR measurement after the reduction. The desorption characteristic caused by the electron donation effect suppressed the deterioration of the catalyst and allowed stable catalytic activity toward the MCH dehydrogenation reaction.

Channel Diameter Effect of Porous Carbon Microparticles on PEMFC Performance for Highly Active Ultra-Low Pt Catalysts

Proton exchange membrane fuel cells (PEMFCs) have received much attention as environmentally benign automotive power sources. PEMFCs can offer a large amount of electricity required for autonomous vehicles that battery-powered systems may not be able to provide. However, because PEMFC electrodes are based on expensive and scarce Pt catalysts, Pt minimization is necessary to expand the PEMFC market. To reduce Pt usage, various attempts have been made to increase the intrinsic activity of Pt catalysts, particularly at the cathode where the oxygen reduction reaction (ORR) occurs. Despite decades of progress, high ORR activity was typically reported in half-cell setups and frequently failed to show corresponding performance in single-cell. Catalysts with low Pt content perform poorly in the high-current density region because the thick catalyst layer limits mass transport.[1] In addition, low Pt loading catalysts typically suffer more in long-term operation.[2] As a result, it is critical to develop PEMFC catalysts with low Pt content that can facilitate mass transport while also exhibiting high durability.Herein, we report highly active and durable PtFe@C catalysts with ultra-low amounts of Pt (1 wt%) on channeled mesoporous carbon (CMC) particles. These CMC particles are designed to have continuous channels with open porosity and a large surface area, facilitating the mass transport behavior and maximizing cell performance. Block-copolymer particles (BCPs) with different molecular weights were used to fabricate CMC particles with pore diameters ranging from 13 to 63 nm. Two steps of pre-crosslinking and hyper-crosslinking were conducted prior to the carbonization step to preserve the porous internal structure of the BCP-based carbon support during high-temperature treatment. After depositing Pt onto the support by facile incipient wetness impregnation method followed by reduction, thin layers of carbon shell were observed to encapsulate the PtFe alloy nanoparticles.The channel diameter effect on the mass transport was studied in both half-cell and single-cell. Interestingly, from the cell performance obtained with varying channel diameters and different oxygen concentrations, we concluded that both reactant (proton and oxygen) supply and product (water) removal were greatly enhanced with larger channel size. With the largest channel diameter of 63 nm, initial mass activity in the single-cell was obtained to be 3.5 A mgPt -1, which is the highest value reported to date to the best of our knowledge. Cell performance under H2-air flow, which is the industrially relevant condition, surpassed the commercial 20 wt% Pt/C with only 1/20 of the Pt loading. The origin of enhanced cell performance upon enlarging the channel diameter was investigated by separating kinetic, ohmic (electronic and ionic charge transport), and mass transport overpotentials. Both the proton and oxygen transport resistance were confirmed to be reduced with larger channel size. Moreover, carbon shell protected Fe from getting leached out in an acidic environment, resulting in preserved catalyst structure and high durability. The outstanding performance of 51 kW/gPt in H2/air condition after 30,000 cycles of accelerated degradation tests (ADTs) was observed. This work will open a new paradigm to develop PEMFC catalysts with much higher activity and durability while simultaneously minimizing Pt use.

Sulphonated melamine polymer for enhancing the oxygen reduction reaction activity and stability of a Pt catalyst

• Poly(melamine) sulphonate enhances the oxygen reduction activity of Pt catalysts. • The enhancement of the activity persists even after a deterioration test at 79 °C. • The melamine polymer suppresses the degradation of Pt nanoparticles. Poly(melamine) sulphonate (Poly-MS) adsorbed on the surface of Pt nanoparticles enhanced the activity of Pt/C in the oxygen reduction reaction (ORR). This enhancement persisted even after an accelerated deterioration test (ADT) at 79 °C. Analysis of the particle size distribution using transmission electron microscopy (TEM) clearly showed that Poly-MS enhanced the stability of the Pt nanoparticles, enabling them to withstand the conditions of the ADT. These findings were supported by CO stripping voltammetry analysis.

Metal-organic frameworks derived RuP2 with yolk-shell structure and efficient performance for hydrogen evolution reaction in both acidic and alkaline media

Hydrogen generation from electrical water splitting has become a greatly increasing requirement for energy systems, however, highly effective and durable electrocatalysts towards universal-pH hydrogen evolution reaction (HER) remain a big challenge. Herein, we design and synthesize ruthenium di-phosphide (RuP2) confined in carbon layers (RuP2-C) with a unique yolk-shell structure (RuP2-C@RuP2-C) from MOF. As expected, it not only exceeds the HER activity of Pt catalysts, with very tiny overpotentials at 10 mA cm−2 (9 and 17 mV in 1.0 M KOH and 0.5 M H2SO4, individually), but also has high stability. Besides, it also exhibits a low overpotential (40 mV) close to Pt catalysts and high stability in 1.0 M PBS, indicating that RuP2-C@RuP2-C (RPC@RPC) owns outstanding HER performance at all pH values. Density functional theory (DFT) calculation results further unravel that the P-site on the surface of RPC@RPC possesses low hydrogen adsorption energy, beneficial for boosting the HER activity.

Single atom surface engineering: A new strategy to boost electrochemical activities of Pt catalysts

Pt-based catalysts are widely applied in several catalytic electrochemical reactions for energy storage and conversion. The improvement of specific activity of Pt is typically achieved by introducing the transition metal to obtain the alloy structure. Different from the traditional alloy structure, herein, we report Pt catalyst modified with Co single atoms obtained by atomic layer deposition (ALD). The as-prepared catalysts show much higher mass activity and excellent stability compared to commercial Pt/C catalysts towards the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The atomic resolution TEM images and X-ray absorption spectroscopy (XAS) indicate the formation of atomically dispersed Co on Pt. First principle calculations reveal that the Co atom affects the electronic structure of the Pt catalysts, which resulted in the high HER and ORR performance. This work provides a new approach for the rational design of highly active and stable Pt-based catalysts, which hold great potential for application in various catalytic reactions.

CeO2‐TiO2 Hybid‐Nanotubes with Tunable Oxygen Vacancies as the Support to Confine Pt Nanoparticles for the Low‐Temperature Water‐Gas Shift Reaction

AbstractReducible oxides as supports have been demonstrated to improve the activity of Pt catalysts towards water‐gas shift (WGS) reaction. The Pt species anchored by the oxygen vacancies derived from these supports play as catalytic sites during low‐temperature WGS reaction. Herein, we introduced CeO2 to modify TiO2 nanotubes (TiO2NT) and prepared CeO2‐TiO2 hybid‐nanotubes ((CeO2)x(TiO2)1‐xNT, x=0.2, 0.4, 0.6) to confine Pt nanoparticles (NPs) as the efficient catalysts for the low‐temperature WGS reaction. Pt NPs confined in (CeO2)x(TiO2)1‐xNT catalysts exhibit higher WGS activity than that of the Pt NPs entrapped in pure TiO2NT (Pt‐in‐TiO2NT) and Pt/CeO2 catalysts throughout the entire reaction temperature range. Activity measurements coupled with the physicochemical characterization of catalysts suggest that the redox ability of PtOx species is positive correlated with WGS activity and oxygen vacancy adjacent to Pt (Pt‐Ov) serves as the active site for H2O dissociation and CO oxidation in WGS reaction.

A novel strategy to synthesize Pt/CNTs nanocatalyst with highly improved activity for methanol electrooxidation

Maximizing the activity of Pt catalysts for methanol oxidation (MOR) while minimizing adsorbed CO poisoning during MOR remains a major challenge. We have prepared Pt nanoparticles on multi-walled carbon nanotubes (MWCNTs)-supported catalysts in deep eutectic solvents (DES). These nanocatalysts are shown to be temperature dependent as the catalyst prepared at 80 °C (referred to Pt/CNTs-80) shows higher catalytic performance toward methanol (peak current: 1028.6 mA mg Pt −1 ) and better CO anti-poisoning capability (onset potential: 0.31 V, peak potential: 0.61 V) compared with Pt/CNTs-25 (synthesized in DES at 25 °C) (520.7 mA mg Pt −1 , 0.56 V, 0.64 V), Pt/CNTs-W (synthesized in water at 80 °C) (260.8 mA mg Pt −1 , 0.58 V, 0.66 V) and commercial Pt/C (177.8 mA mg Pt −1 , 0.63 V, 0.71 V). This study provides a suitable strategy for the preparation of high performance Pt-based electrocatalysts for the direct methanol fuel cell (DMFC).

Impact of dehydrogenation on the methanol oxidation reaction occurring on carbon nanotubes supported Pt catalyst with low Pt loading

The electro-catalytic methanol oxidation reaction (MOR) has received considerable research attention due to its importance in the development of direct methanol fuel cells. In this study, the dehydrogenation step in MOR was investigated using low levels of platinum (Pt) which supported on carbon nanotubes as a catalyst. The concentration of H+ had a significant effect on the MOR activity of Pt catalysts supported by carbon nanotubes (Pt/CNTs), indicating that the dehydrogenation process was a critical step in MOR for Pt/CNTs with low Pt loading. Furthermore, the effects of Pt particle size and the distance between the Pt particles were investigated. We suggested a hypothesis: for the Pt catalyst with large particle size, only a few particles were needed for dehydrogenation to proceed; for the Pt catalyst with small particle size, many Pt particles were needed to form a network for the dehydrogenation reaction, but when the Pt particles were close enough, only a few Pt particles were needed. Our study provided insight into the electro-catalytic activity of Pt/CNTs from a mechanistic perspective.

(Invited) Enhancement of Oxidation of Dimethyl Ether through Applicationof Metal-Oxide-Supported Noble Metal Catalytic Nanoparticles: Comparison to Behavior of Other Simple Organic Fuels

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.We pursue a concept of utilization of zirconia nad mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of dimethyl ether relative to methanol, formic acid and ethanol. Among important issues is incorporation of additional metal (e.g. Rh or Pt) nanostructures capable of weakening, or even breaking, the C-C and C-O bonds in the ethanol and dimethyl ether molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol and dimethyl ether are partitioned (at Rh, Pt or Pd) to methanolic residues and further oxidized at PtRu cannot be excluded.

Three-dimensional mesoporous PtM (M = Co, Cu, Ni) nanowire catalysts with high-performance towards methanol electro-oxidation reaction and oxygen reduction reaction.

Alloying with transition elements is proven to be an effective way to improve the methanol electro-oxidation reaction (MOR) and oxygen reduction reaction (ORR) activities of Pt catalysts for direct methanol fuel cells (DMFCs). Through a process of rapid solidification and two-step dealloying, we have successfully fabricated three-dimensional mesoporous PtM (M = Co, Cu, Ni) nanowire catalysts, which show much enhanced electrocatalytic properties towards MOR and ORR in comparison with the commercial Pt/C catalyst. Electrochemical tests indicate that alloying with Cu presents the best ORR activities, the half-wave potential of which is 42 mV positively shifted compared with the commercial Pt/C (0.892 V vs. RHE). Meanwhile, the PtM nanowire catalysts also possess good CO tolerance as well as stability for 10 000 cycles of cyclic voltammetry scanning. This convenient preparation method is promising for the development of high performance electrocatalysts for MOR and ORR in DMFCs.

Improved electrocatalytic activity of Pt catalyst supported on core–shell CMs@NiO for methanol oxidation

The as-prepared Pt catalyst supported on core–shell CMs@NiO for the methanol oxidation with the extraordinary electrocatalytic performance and durability.

Ultralow Loading (Single‐Atom and Clusters) of the Pt Catalyst by Atomic Layer Deposition Using Dimethyl ((3,4‐η) N,N‐dimethyl‐3‐butene‐1‐amine‐N) Platinum (DDAP) on the High‐Surface‐Area Substrate for Hydrogen Evolution Reaction

AbstractSingle‐atom Pt catalyst has seen a tremendous surge in the research community in very recent times. The minimum loading of such precious metal catalysts on high surface area substrates with effective performance toward catalyzing a reaction is indeed of great importance. Here, an alternative way is demonstrated to perform an ultralow loading of Pt catalyst by atomic layer deposition (ALD) using dimethyl ((3,4‐η) N,N‐dimethyl‐3‐butene‐1‐amine‐N) platinum precursor (C8H19NPt). The ultralow loading of Pt catalyst is performed on highly porous nitrogen–carbon‐powder coated carbon cloth (NC–CC) substrates by varying the number of ALD cycles (2 to 60), and their performance in electrochemical hydrogen evolution reaction (HER) is evaluated. The inductively coupled plasma‐optical emission spectrometry provides the exact mass of the Pt catalyst, whereas, the transmission electron microscopy images confirm the uniform and homogeneous dispersion of platinum single‐atoms and clusters (with an average size of <1 nm for ten ALD cycles) on the NC–CC substrate. It is further found that the mass activity of Pt catalyst (per microgram of Pt) toward HER is extraordinarily high for less number of ALD cycles (two and five), whereas, the overall performance (current density per geometrical area) becomes more and more improved with increasing the ALD cycles.