mA mgPt Research Articles

Synthesis of highly efficient Cu-PtRu ternary metal catalyst for methanol oxidation

Development of remarkably catalytic activity and CO resistance catalyst has become a focus for methanol oxidation. In this study, the irregular polyhedral of Cu was synthesized by simple electrochemical deposition method. Then Pt-Ru alloy nanoclusters were uniformly deposition on Cu polyhedra to prepare Cu-PtRu ternary alloy materials. The morphology and structure of the ternary alloy were studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). Electrochemical results showed that Cu-PtRu exhibited favorable catalytic capacity and high CO resistance for methanol oxidation. In various proportion of Pt-Ru, Cu-Pt5.2Ru1 showed the highest electrocatalytic activity (638.2 mA mgPt−1) for methanol oxidation, which was 2.2 and 2.84 folds relative to commercial Pt/C (Pt wt.20%) and PtRu/C (Pt wt.30%), respectively. Therefore, Cu-Pt5.2Ru1 might be used as a novel structure electro-catalyst for methanol oxidation.

PtCoFe Intermetallic Alloy Catalyst Derived from PtFe@CoO with High Stability for Oxygen Reduction Reaction

AbstractPlatinum‐based ordered alloy catalysts possess higher intrinsic activity in oxygen reduction reactions (ORR). High‐temperature annealing during ordered alloy formation frequently results in larger nanoparticles, and the strategy for obtaining ordered alloys at 600 °C is still undefined. Herein, an ordered Fe‐doped PtCo catalyst (O‐PtCoFe/C) with a size of sub‐4 nm was prepared at 600 °C derived from PtFe@CoO. CoO can generate oxygen vacancies by H2 reduction, lowering the atomic migration barrier and serving as a protective layer to inhibit nanoparticle migration. Experimental analyses showed the formation of O‐PtCoFe/C and electron‐rich Pt atoms due to Pt, Co, and Fe, which was advantageous for ORR performance. The mass activity of the prepared catalyst for ORR was 382.8 mA mgPt−1, which is 5.4 times greater than Pt/C. After 10000 potential cycles, the half‐wave potential was only negatively shifted by 10 mV. In PEMFC (proton exchange membrane fuel cells) tests, the O‐PtCoFe/C showed only 3 % decay after 3000 cycles, whereas the Pt/C showed a significant loss (18.4 %). This work provides an effective method for preparing ordered PtCo alloys for fuel cell cathode catalysts at 600 °C.

A high-performance and anti-sulfur poisoning oxygen reduction reaction catalysts derive from molybdenum-doping on PtCo alloy nanoparticles surface

During the operation of fuel cell vehicles, sulfur dioxide (SO2) as a primary air pollutant can be transported to the cathode of the fuel cell with the air, leading to poisoning of the cathodic Pt-based catalyst, and subsequently, causing performance degradation and even shutdown. Therefore, there is an urgent need for SO2-tolerant Pt-based catalysts to mitigate poisoning in the cathodic oxygen reduction reaction (ORR). Herein, we report a carbon-supported Mo doped PtCo alloy catalyst with high-performance and anti-sulfur poisoning, termed as Mo-PtCo/C. Detailed investigations demonstrate that the Co in PtCo alloy nanoparticles (NPs) greatly promote ORR activity but do little to improve the SO2-tolerance. However, the PtCo alloy NPs doped with Mo not only exhibit a higher ORR activity, but also a superior SO2 poisoning resistance and a superior recovery performance. The optimal Mo-PtCo/C catalyst demonstrates a high initial mass activity of 871.0 mA mgPt−1, which is higher than that of the PtCo/C catalyst (initial value=558.8 mA mgPt−1) and 6.6 times higher than that of the commercial Pt/C (20 wt.% Pt, initial value=174.6 mA mgPt−1), along with a low mass activity loss of 36.19% after SO2 poisoning, which is much lower than 82.4% of the PtCo/C catalyst and 81.3% of the commercial Pt/C. More importantly, it is revealed that MoO3 formed on the PtCo NPs surface after Mo doping helps to reduce the electrooxidation potentials of SO2 to the operating potential of the fuel cell, thereby markedly boosting SO2-tolerance. Furthermore, the fuel cells test also confirmed that MoO3 improved the SO2-tolerance of the Mo-PtCo/C catalysts.

Space Confinement to Regulate Ultrafine CoPt Nanoalloy for Reliable Oxygen Reduction Reaction Catalyst in PEMFC.

A Co-based zeolitic imidazolate framework (ZIF-67) derived catalyst with ultrafine CoPt nanoalloy particles is designed via a two-step space confinement method, to achieve a robust oxygen reduction reaction (ORR) performance for proton exchange membrane fuel cell (PEMFC). The core-shell structure of ZIF-67 (core) and SiO2 (shell) is carefully adjusted to inhibit the agglomeration of Co nanoparticles. In the subsequent adsorption-annealing process, the in situ formed graphene shell on the surface of Co nanoparticles further protects metal particles from coalescence, leading to the ultrafine CoPt nanoalloy (average diameter is 2.61nm). Benefitting from the high utilization of Pt metal, the mass activity of CoPt nanoalloy catalyst reaches 681.8mA mgPt -1 at 0.9V versus RHE according to the rotating disk electrode test in 0.1m HClO4 solution. The CoPt nanoalloy-based PEMFC provides a high maximum power density of 2.22W cm-2 (H2 /O2 ) and 0.923W cm-2 (H2 /air). Simultaneously, itshows good stability in the long-time dynamic test at low humidity, due to the robust CoPt@graphene core-shell nanostructure. This work provides a viable strategy for designing Pt-based nanoalloy catalysts with ultrafine metal particles and high stability.

Efficient Electrooxidation of Ethanol on Annular Cu@Pt–Ru Ternary Metal Catalyst

Many efforts have been made to develop efficient electrocatalysts for ethanol fuel cells. However, the commonly used Pt‐based catalysts still have some shortcomings, such as low catalytic activity, severe CO poisoning, and poor stability. Herein, the preparation of Cu@Pt–Ru catalysts with high activity against CO poisoning by using an electrochemical method is reported. Because of its interatomic electronic effects, the Cu@Pt6.98Ru1 catalyst exhibits high electrocatalytic performance for the ethanol oxidation reaction. The mass activity reaches 641 mA mgPt−1, which are 2.9, 5.13, and 8.8 times those of CuPt, PtRu/C, and Pt/C catalysts, respectively. The specific activity reaches 3.19 mA cm−2, which are 1.77, 2.06, and 2.4 times those of CuPt, PtRu/C, and Pt/C catalysts, respectively. The catalytic activity remains relatively high after 2000s. The results have proven that the successful introduction of Cu and Ru into the Pt lattice would improve the catalytic activity and stability and increase its ability to resist CO poisoning of the catalyst.

Self-supporting trimetallic PtAuBi aerogels as electrocatalyst for ethanol oxidation reaction

The creation of anodic ethanol oxidation reaction catalysts with superior all-around performance for direct ethanol fuel cells (DEFCs) has continued to attract the attention of researchers. An ultrathin trimetallic PtAuBi aerogel with branching, rough-surfaced 1D nanowires that self-assemble into a 3D porous network structure has been created in this study. It has a mass activity (MA) of 8045 mA mgPt−1 in an alkaline medium, which is 7.56 times greater than that of commercial Pt/C (1064 mA mgPt−1). Notably, the catalytic activity and resistance to CO poisoning of PtAuBi aerogels are improved by the addition of an efficient “active additive” Au. The results analysis reveals that the increased performance of PtAuBi aerogel is mostly attributable to the integrated function of the 3D porous network structure, the downward shift of the Pt d-band center, and the synergistic effect of the “Pt–Bi” and/or “Pt–Au” dual active sites.

Pt2CeO2 Heterojunction Supported on Multiwalled Carbon Nanotubes for Robust Electrocatalytic Oxidation of Methanol

Herein, we prepared Pt2CeO2 heterojunction nanocluster (HJNS) on multiwalled carbon nanotubes (MWCNTs) in deep eutectic solvents (DESs) which is a special class of ionic liquids. The catalyst was then heat-treated at 400 °C in N2 (refer to Pt2CeO2/CNTs-400). The Pt2CeO2/CNTs-400 catalyst showed remarkably improved electrocatalytic performance towards methanol oxidation reaction (MOR) (839.1 mA mgPt-1) compared to Pt2CeO2/CNTs-500 (620.3 mA mgPt-1), Pt2CeO2/CNTs-300 (459.2 mA mgPt-1), Pt2CeO2/CNTs (641.6 mAmg-1) (the catalyst which has not been heat-treated) and commercial Pt/C (229.9 mAmg-1). Additionally, the Pt2CeO2/CNTs-400 catalyst also showed better CO poisoning resistance (onset potential: 0.47 V) compared to Pt2CeO2/CNTs (0.56 V) and commercial Pt/C (0.58 V). The improved performance of Pt2CeO2/CNTs-400 catalyst is attributed to the addition of appropriate CeO2, which changed the electronic state around the Pt atoms, lowered the d-band of Pt atoms, formed more Ce-O-Pt bonds acting as new active sites, affected the adsorption of toxic intermediates and weakened the dissolution of Pt; on the other hand, with the assistance of thermal treatment at 400 °C, the obtained Pt2CeO2 HJNS expose more new active sites at the interface between Pt and CeO2 to enhance the electrochemical active surface area (ECSA) and the dehydrogenation process of MOR. Thirdly, DES is beneficial to the increase of the effective component Pt(0) in the carbonization process. The study shows a new way to construct high-performance Pt-CeO2 catalyst for the direct methanol fuel cell (DMFC).

Adjusting the Near-Surface Composition of Pt–Zn Intermetallic Nanoparticles to Enhance Methanol Oxidation Activity and Stability

Platinum-based materials are promising catalysts for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), but it is challenging to balance activity and stability in actual application. Thus, in our work, the graphitized porous carbon (PC) with a high specific surface area and hierarchical porous structure was successfully prepared as the supported material. Disordered A1-PtZn NPs supported on PC was synthesized via one-step coreduction method at 300 °C and H2 atmosphere. Afterward, an ordered PtZn intermetallic compound (L10-PtZn/PC) was acquired at a higher annealing treatment of 600 °C for 12 h, and L10-PtZn/PC-acid with Pt-skin was also obtained via acid etching. The smaller PtZn nanoparticles (ca. < 5 nm) can be synthesized and distributed on the PC homogeneously. The L10-PtZn/PC-acid catalysts display a high order degree and stronger electronic interaction between Pt and Zn atoms, which is favorable for withstanding CO poisoning in MOR. Thus, the L10-PtZn/PC-acid catalyst has a mass activity of 1130 mA mgPt–1 and a specific activity of 2.23 mA cm–2, which are 3.0 and 2.2 times higher than commercial Pt/C. Additionally, the Pt-skin of L10-PtZn/PC-acid can provide a protection for subsurface Zn and keep the structural stability effectively. Therefore, after 2000 cycles of cyclic voltammetry, the L10-PtZn/PC-acid sample remains 86.62% of the initial peak current density, while commercial Pt/C only retains 47.65%. In situ FTIR studies have demonstrated that the OHads species easily absorbed on the Zn atoms and facilitates a direct pathway without CO in the MOR on the intermetallic PtZn. This work provides a novel strategy to develop an ideal near-surface composition Pt-based nanocatalyst with high activity and stability for direct methanol fuel cells.

Stabilizing Ni atoms on PtNi crystals by constructing PtNix-(CeO2)y heterostructures for improving durability of oxygen reduction reaction in acidic media

The oxygen reduction reaction (ORR) activity of PtNi alloys is easily decreased on account of the Ni leaching under the harsh acidic environment. Therefore, we prepared a PtNi1.5-(CeO2)0.8/C electrocatalyst with abundant PtNi1.5-(CeO2)0.8 interfaces by a wet-chemical synthesis strategy. Electrochemical tests revealed that PtNi1.5-(CeO2)0.8/C exhibits excellent ORR performance with mass activity (MA) of 551.1 mA mgPt−1 and specific activity (SA) of 1.3 mA cmPt−2 @ 0.9 V vs. RHE, respectively, which are better than commercial JM Pt/C (MA of 152.9 mA mgPt−1 and SA of 0.2 mA cmPt−2@ 0.9 V vs. RHE). More interestingly, it displays remarkable durability with 9.0% of its initial MA loss after 10,000 CV cycles, outperforming JM Pt/C (a 15.1% loss) and PtNi1.5/C counterparts (a 35.5% loss). The density functional theory (DFT) calculations explained that the electronic interaction at interfaces leads to a lower d-band center (εd) and weaker oxygen adsorption energy E(ads)(O) in Pt atoms of PtNi1.5-(CeO2)0.8 than that in Pt NPs, which is favorable for the desorption of O* and promotes the ORR process. Furthermore, the diffusion energy barrier E(FS-IS) of Ni atoms in PtNi1.5-(CeO2)0.8 from subsurface to surface is higher than that in PtNi1.5 counterparts, indicating the Ni leaching can be decelerated.

Small-size MOF derived highly active low-platinum catalysts for oxygen reduction reactions

Platinum catalysts derived from MOF have shown excellent potential in oxygen reduction reaction (ORR) of fuel cells. In this paper, we applied a simple and efficient synthesis method to prepare ZIF-67-Rx(x ​= ​0–4) with different sizes. Co@MOF-Rx(x ​= ​0–4) skeleton supports with carbon nanotube structure were obtained by further pyrolysis. Pt/Co@MOF-Rx(x ​= ​0–4) catalysts were synthesized by loading Co@MOF-Rx with 10% Pt. By changing the content of metal precursor, the nanometer size of ZIF-67-Rx was reduced from 722 ​nm to 93 ​nm. Pt/Co@MOF-Rx showed super high oxygen reduction activity and superior cycle stability. At 0.9 ​V, the mass activity(MA) and specific activity(SA) were 9.63 ​mA mgPt−1and 1.33 ​mA ​cm2, respectively, which were 1.54 and 1.23 times higher than those of Pt/C(20%). After 6000 cycles, it shows excellent stability than Pt/C(20%). This work brings new opportunities to design and prepare promising catalyst supports for proton exchange membrane fuel cells.

Understanding the key role of the surface structure of L11-ordered PtCu intermetallic electrocatalyst toward methanol oxidation reaction by dealloying methods

An accurate understanding of the surface structure–activity relationship is essential to rational designing highly efficient electrocatalysts for methanol oxidation reaction (MOR). Here, L11-ordered PtCu/C with rough and smooth Pt shells were obtained by electrochemically (ED) and chemically dealloying (CD) methods to investigate the difference in their MOR performances. The rough Pt shells (PtCu/C-700-ED) exhibited mass activity (MA) of 1625.2 mA mgPt−1 at peak potential, 2.19 and 2.74 times higher than smooth Pt shells (PtCu/C-700-CD) (743.1 mA mgPt−1) and commercial Pt/C (593.5 mA mgPt−1), respectively. DFT calculations indicate that PtCu with rough surfaces has a weaker CO binding energy than that with smooth surfaces, leading to better CO resistance and MOR activity. However, accelerated durability tests exhibit that the PtCu/C-700-CD catalysts obtained activity above the initial current density after 2000 cycles compared to PtCu/C-700-ED (36.48% loss) and commercial Pt/C (67.35% loss), indicating that smooth Pt shells have prominent structural stability. In addition, similar results were found simultaneously for other ordered Pt-based binary catalysts.

Pd3Pb1@Pt2 core–shell concave nanocubes to boost the ethanol oxidation reaction

The secret to raising catalyst selectivity and activity is to design nanocatalysts by regulating pore size and particle properties. Hence, it was effectively established that manipulating pore size and particle properties allowed for the manufacture of ternary Pd3Pb1@Pt2 concave nanocubes (Pd3Pb1@Pt2 CNCs). The synthesized Pd3Pb1@Pt2 CNCs/C shows superior electrocatalytic activity of 7500 mA mgPt+Pd−1 towards ethanol oxidation reaction (EOR) which is 7.08 times greater than the JM Pt/C (1060 mA mgPt−1). The catalyst has excellent stability, and the mass activity is still better than JM Pt/C after 3600 s stability test. The CO stripping measurements shows that the adsorption of CO is particularly weak, which proves that the catalyst has excellent resistance to medium toxicity. In situ attenuated total reflection infrared spectroscopy (ATR-IR) and external reflection-absorption infrared spectroscopy (IRRAS) have been employed to examine the molecular aspects of the EOR process. ATR-IR can monitor the production and removal of CO species in real time during EOR on Pd3Pb1@Pt2 CNCs/C. The band of CO2 is noticeably stronger on Pd3Pb1@Pt2 CNCs/C than it is on bare other catalysts, suggesting that the ethanol oxidation process may be promoted.

Anchoring a Pt-based alloy on oxygen-vacancy-defected MXene nanosheets for efficient hydrogen evolution reaction and oxygen reduction reaction.

Rational design and controllable synthesis of Pt-based materials with intimate interfacial contact open up the possibility for boosting the performance of the ORR (oxygen reduction reaction) and HER (hydrogen evolution reaction). However, it is still challenging to prevent the oxidation of Pt during the formation of alloys and to clarify the interfacial synergistic effects on the catalytic performance between Pt alloys and the dispersed substrate. Herein, the wet chemical stripping and intercalation methods were employed to synthesize a two-dimensional (2D) MXene with abundant defect sites, which can anchor Pt3Co/Pt3Ni nanoparticles and prevent the oxidation of Pt during the process of atomic rearrangement at high temperatures. The obtained Pt3Co/MXene and Pt3Ni/MXene displayed different phase compositions and alloying degrees on adjusting the annealing temperature. Electrochemical test results showed that the optimized HER and ORR electrocatalytic activities occurred at 700 °C. Compared with Pt3Ni/MXene-700, Pt3Co/MXene-700 exhibited an HER overpotential of 1.3 mV at a current density of 10 mA cm-2, and a Tafel slope of 27.11 mV dec-1 in 0.1 M HClO4 solution. Furthermore, Pt3Co/MXene-700 exhibited an ORR half-wave potential of 0.897 V, and a mass activity of 241.1 mA mg-1Pt in 0.1 M HClO4 solution. This can be attributed to the formation of intermetallic compounds in Pt3Co/MXene. The electronic structure analysis showed that the enhanced performance could be assigned to the electron-capturing capability of the MXene, less oxidation of Pt and synergistic interactions between the Pt alloy and the MXene substrate. These findings provide a new strategy for the synthesis of highly active HER/ORR catalysts and broaden the way for the design of MXene-based catalysts.

Nickel coating on carbon nanotubes and PProDOT-2CH2SH supported Pt nanoparticles as the electrocatalyst for methanol oxidation reaction

The electricity generated by direct methanol fuel cells (DMFCs) comes from methanol oxidation reaction (MOR), which is affected by electrocatalytic activity of anode materials. Herein, Pt nanoparticles supported by the composite of thiol group grafted poly(3,4-propylenedioxythiophene) (PProDOT-2CH2SH) and Ni–N co-doped bamboo-like carbon nanotubes (Ni-NCNT) are prepared and proposed as an anode material for DMFCs. The results from morphological analysis show that the Pt nanoparticles uniformly disperse on the surface of support (PProDOT-2CH2SH/Ni-NCNT) with bamboo-like structure, and there is an electronic effect between the Pt and Ni confirmed by X-ray photoelectron spectroscopy analysis. Electrochemical tests reveal that the PProDOT-2CH2SH/Ni-NCNT/Pt catalyst demonstrates good electrocatalytic activity for the MOR in acidic electrolyte, and the catalyst has higher resistance to CO poisoning than commercial Pt/C. The mass activity (MA) of catalyst is up to 1670.54 mA mgPt−1 with an electrochemical active surface area (ECSA) of 98.0 m2 g−1, and the catalyst maintains good performance after 800 cycles. This work provides a high-performance MOR catalyst in practical application for DMFCs.

Synthesis and Electrochemical Performances of a Versatile Nitrogen-Doped Carbon Skeleton Material Derived from a Humate-CoFe-ZIF/Melamine Precursor

Humic acid (HA), melamine, and ZIFs are superior precursors for preparing carbon materials. Especially, metal ions in ZIFs are excellent nanocatalysts for synthesizing CNTs or graphene, while melamine and ZIFs are good dopants for fabricating nitrogen-doped carbon materials. Here, nitrogen-doped carbon skeletal materials (NCS) assembled by a large number of bamboo-like CNTs and a small number of graphene layers were elaborately synthesized by a two-step pyrolysis process using a humate-CoFe-ZIF (HA-CoFe-ZIF) composite material as the template and melamine as the carbon and nitrogen source. NCS-II exhibits desirable supercapacitive characteristics and superior support performance due to a harmoniously assembled graphitic structure, favorite nitrogen incorporation mainly including pyridinic N and pyrrolic N at a high dosage of 5.24 wt %, abundant mesoporous structure, and large specific surface. As a supercapacitor electrode material, NCS-II demonstrates a high electrochemical capacitance (324 F g–1 at 1 A g–1), wide operating current density range (1–50 A g–1), and rate capability (64% from 5 A g–1 to 50 A g–1). And the prepared NCS-II//AC asymmetric supercapacitor also displays a large specific capacitance (129 F g–1 at 1 A g–1), good cycling stability (96% at 5 A g–1 for 10 000 cycles), and high energy density (25.6 Wh kg–1 at 600 W kg–1). As a catalyst support, the NCS-II provides plentiful active sites and a large specific surface area for the highly dispersed loading of PtCo nanoparticles. The prepared 1:1-PtCo/NCS-II catalyst exhibits high catalytic activity, good cycling stability, and strong CO tolerance ability for methanol oxidation reaction (MOR). Its ECSA value, CV peak current density, and peak current retention after 500 CV turns are high, up to 265.7 m2 gpt–1, 850 mA mgPt–1, and 79%, respectively.

Glycerol electrooxidation on carbon-supported Pt-CuO and PtCu-CuO catalysts

Herein, Pt and Pt0.85Cu0.15 nanoparticles were deposited over hybrid CuO/C supports (1.5, 3 and 5 wt.% on carbon) by a pulsed microwave-assisted reduction method and the as-prepared materials were evaluated as electrocatalysts toward the electrooxidation of glycerol in alkaline medium. The structural and morphological analysis showed that the platinum particles decrease from 4.2 nm to around 3.0 nm in size when the CuO crystallites are present on the surface of the carbonaceous material. The electrochemical experiments indicated that the nanoparticles deposited over the hybrid support present significantly improved electrocatalytic properties compared to Pt/C. Among them, Pt0.85Cu0.15CuO(3)/C catalyst exhibited the best performance for the GOR, delivering a mass activity of around 270 mA mgPt−1 at a fixed potential of 0.7 V, which is 5.4 times higher than that of Pt/C (∼50 mA mgPt−1). The results showed that the addition of very small amounts of copper oxide on the surface of the carbonaceous support and the addition of a small amount of Cu to Pt boost the activity of the active sites via the bifunctional mechanism, geometric strain and ligand effects.

N-Doped Carbon Nanotube Shell Encapsulating the NiFe Metal Core for Enhanced Catalytic Stability in Methanol Oxidation Reaction by the Structural Cooperation Mechanism.

Exploitation of high-efficiency catalysts toward methanol oxidation is a pivotal step to promote the commercialization of direct methanol fuel cells. Herein, a strategy is demonstrated to prepare nitrogen-doped carbon nanotubes with NiFe metal particles (NiFe@N-CNT) as the carrier material of Pt nanoparticles. Combining SEM and TEM, NiFe metal particles are fully encapsulated in N-CNTs, and they form the metal core and carbon nanotube shell structure based on the structural cooperation mechanism. Surprisingly, the as-prepared Pt/NiFe@N-CNT catalyst shows superior catalytic activity (1023 mA mg-1Pt) compared to commercial Pt/C (392 mA mg-1Pt), Pt/Ni@N-CNT (331 mA mg-1Pt), and Pt/Fe@N-CNT (592 mA mg-1Pt). After 1000 cycles, Pt/NiFe@N-CNT maintains the optimal catalytic activity (588 mA mg-1Pt), and its mass activity loss is 42.5%, which is better than those of commercial Pt/C (64.0%), Pt/Ni@N-CNT (67.7%), and Pt/Fe@N-CNT (59.6%) catalysts, indicating that the Pt/NiFe@N-CNT catalyst achieves excellent catalytic activity and stability, which stems chiefly from the homodispersed Pt nanoparticles and the generation of the metal core-carbon nanotube shell based on the structural cooperation mechanism. This study reports the facile construction of a metal core-carbon nanotube shell structure, which intrinsically ameliorates structural collapse of carrier material, thereby improving the catalytic stability of the Pt-based catalyst and broadening the view for design of other desire catalysts in methanol oxidation.

Optimization of SnPd Shell Configuration to Boost ORR Performance of Pt-Clusters Decorated CoOx@SnPd Core-Shell Nanocatalyst

Fuel cells are expected to bring change to the whole human race when commercialized, however, the sluggish kinetics of oxygen reduction reaction (ORR) severely hampers their commercial viability. Thus far, platinum (Pt) based catalysts are nearly inevitable due to the harsh redox environment of fuel cells. Thus, minimizing Pt metal loading and increasing Pt utilization is a paramount factor for realizing fuel cell technologies. In this context, herein, we developed a multi-metallic nanocatalyst (NC) comprising Pt-clusters (1 wt.%) decorated SnPd composite shell over cobalt-oxide core crystal underneath (denoted as CSPP). For optimizing the ORR performance of the as-prepared NC, we further modulated the configuration of the SnPd shell. In the optimum case, when the Sn/Pd ratio is 0.5 (denoted as CSPP 1005), the ORR mass activity (MA) is 3034.7 mA mgPt−1 at 0.85 V vs. RHE in 0.1 M KOH electrolyte, which is 45-times higher than the commercial Johnson Matthey-Pt/C (J.M.-Pt/C; 20 wt.% Pt) catalyst (67 mA mgPt−1). The results of physical inspections along with electrochemical analysis suggest that such high performance of CSPP 1005 NC can be attributed to the synergistic collaboration between Pt-clusters, PtPd nanoalloys, and adjacent SnPd domains, where Pt-clusters and PtPd nanoalloys promote the O2 adsorption and subsequent splitting, while the SnPd shell favours the OH− relocation step. We believe that the obtained results will open a new avenue for further exploring the high-performance Pt-based catalysts with low Pt-loading and high utilization.

Gas-Phase Synthesis of PtMo Alloy Electrocatalysts with Enhanced Activity and Durability for Oxygen Reduction Reaction

The proton-exchange membrane fuel cell is a promising technology to effectively utilize hydrogen energy, which is the ideal alternative to fossil fuels. However, the high dependency on scarce Pt as an oxygen reduction reaction (ORR) electrocatalyst is still a severe barrier that hinders widespread commercialization. Herein, we propose a facile synthetic strategy facilitating mass production of Pt–Mo solid-solution alloy nanoparticles on a carbon support (PtMo/C) as a highly active ORR electrocatalyst. Without using organic surfactants or reducing agents, our synthesis process based on the gas-phase method in an inert atmosphere is cost-effective and does not require any post-treatment, unlike most reported solution-based reduction processes. Both molybdenum metal and carbon monoxide decomposed from molybdenum hexacarbonyl contribute to the reduction of the PtMo alloy during the annealing process. By elucidating the growth and synthesis mechanisms, we optimized the particle size of PtMo/C to approximately 3.1 nm, annealed at 800 °C (PtMo/C-800). Consequently, PtMo/C-800 shows high mass activity (146 mA mgPt–1), which is superior to that of commercial Pt/C, and excellent durability after accelerated degradation tests.

Designing fuel cell catalyst support for superior catalytic activity and low mass-transport resistance

The development of low-Platinum content polymer electrolyte fuel cells (PEFCs) has been hindered by inexplicable reduction of oxygen reduction reaction (ORR) activity and unexpected O2 mass transport resistance when catalysts have been interfaced with ionomer in a cathode catalyst layer. In this study, we introduce a bottom-up designed spherical carbon support with intrinsic Nitrogen-doping that permits uniform dispersion of Pt catalyst, which reproducibly exhibits high ORR mass activity of 638 ± 68 mA mgPt−1 at 0.9 V and 100% relative humidity (RH) in a membrane electrode assembly. The uniformly distributed Nitrogen-functional surface groups on the carbon support surface promote high ionomer coverage directly evidenced by high-resolution electron microscopy and nearly humidity-independent double layer capacitance. The hydrophilic nature of the carbon surface appears to ensure high activity and performance for operation over a broad range of RH. The paradigm challenging large carbon support (~135 nm) combined with favourable ionomer film structure, hypothesized recently to arise from the interactions of an ionic moiety of the ionomer and Nitrogen-functional group of the catalyst support, results in an unprecedented low local oxygen transport resistance (5.0 s cm−1) for ultra-low Pt loading (34 ± 2 μgPt cm−2) catalyst layer.