Inducing Covalent Atomic Interaction in Intermetallic Pt Alloy Nanocatalysts for High-Performance Fuel Cells

The harsh working environments of proton exchange membrane fuel cells (PEMFCs) pose huge challenges to the stability of Pt-based alloy catalysts. The widespread presence of metallic bonds with significantly delocalized electron distribution often lead to component segregation and rapid performance decay. Here we report L1₀−Pt₂CuGa intermetallic nanoparticles with a unique covalent atomic interaction between Pt−Ga as high-performance PEMFC cathode catalysts. The L1₀−Pt₂CuGa/C catalyst shows superb oxygen reduction reaction (ORR) activity and stability in fuel cell cathode (mass activity=0.57 A mg_Pt⁻¹ at 0.9 V, peak power density=2.60/1.24 W cm⁻² in H₂-O₂/air, 28 mV voltage loss at 0.8 A cm⁻² after 30 000 cycles). Theoretical calculations reveal the optimized adsorption of oxygen intermediates via the formed biaxial strain on L1₀−Pt₂CuGa surface, and the durability enhancement stems from the stronger Pt−M bonds than those in L1₁−PtCu resulted from Pt−Ga covalent interactions.     

One-Step Approach for Constructing High-Density Single-Atom Catalysts toward Overall Water Splitting at Industrial Current Densities

The construction of highly active, durable, and cost-effective catalysts is urgently needed for green hydrogen production. Herein, catalysts consisting of high-density Pt (24 atoms nm⁻²) and Ir (32 atoms nm⁻²) single atoms anchored on Co(OH)₂ were constructed by a facile one-step approach. Remarkably, Pt₁/Co(OH)₂ and Ir₁/Co(OH)₂ only required 4 and 178 mV at 10 mA cm⁻² for hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the assembled Pt₁/Co(OH)₂//Ir₁/Co(OH)₂ system showed mass activity of 4.9 A mg_{noble metal}⁻¹ at 2.0 V in an alkaline water electrolyzer, which is 316.1 times higher than that of Pt/C//IrO₂. Mechanistic studies revealed that reconstructed Ir−O₆ single atoms and remodeled Pt triple-atom sites enhanced the occupancy of Ir−O bonding orbitals and improved the occupation of Pt−H antibonding orbital, respectively, contributing to the formation of the O−O bond and the desorption of hydrogen. This one-step approach was also generalized to fabricate other 20 single-atom catalysts.     

One-Pot Synthesis of Pd@PtnL Core-Shell Icosahedral Nanocrystals in High Throughput through a Quantitative Analysis of the Reduction Kinetics

The rational design and implementation of a one-pot method is reported for the facile synthesis of Pd@Pt_nL (nL denotes the number of Pt atomic layers) core-shell icosahedral nanocrystals in a single step. The success of this method relies on the use of Na₂PdCl₄ and Pt(acac)₂ as the precursors to Pd and Pt atoms, respectively. Our quantitative analysis of the reduction kinetics indicates that the Pd^II and Pt^II precursors are sequentially reduced with a major gap between the two events. Specifically, the Pd^II precursor is reduced first, leading to the formation of Pd-based icosahedral seeds with a multiply-twinned structure. In contrast, the Pt^II precursor prefers to take a surface reduction pathway on the just-formed icosahedral seeds. As such, the otherwise extremely slow reduction of the Pt^II precursor can be dramatically accelerated through an autocatalytic process for the deposition of Pt atoms as a conformal shell on each Pd icosahedral core. Compared to the conventional approach of seed-mediated growth, the throughput for the one-pot synthesis of Pd@Pt_nL core-shell nanocrystals can be increased by more than 30-fold. When used as catalysts, the Pd@Pt_4.5L core-shell icosahedral nanocrystals show specific and mass activities of 0.83 mA cm⁻² and 0.39 A mg_Pt⁻¹, respectively, at 0.9 V toward oxygen reduction. The Pt-based nanocages derived from the core-shell nanocrystals also show enhanced specific (1.45 mA cm⁻²) and mass activities (0.75 A mg_Pt⁻¹) at 0.9 V, which are 3.8 and 3.3 times greater than those of the commercial Pt/C, respectively.     

Carbon black supported PtCu nanoparticles derived from mix-phased Cu precursor for high-performanced oxygen reduction reaction in acid medium

Alloying high-cost Pt with transition metals has been considered as an effective route to synthesize the electrocatalysts with low Pt loading and excellent activity towards oxygen reduction reaction (ORR) under acid solution. The galvanic replacement method, as featured with efficiency and simplicity, is widely reported to produce Pt-based bimetallic alloys and thereby declare the significance of reductive transition metal precursor on the enhancement of ORR performance. Herein, mix-phased Cu−Cu₂O precursor was applied to prepare carbon black supported highly dispersed PtCu alloy nanoparticles (PtCu/C). The proper Cu−Cu₂O ratios can exactly facilitate the generation of small sized PtCu alloy nanoparticles with regulated bimetallic content. Meanwhile, the Cu₂O phase is revealed to benefit the electron transfer from Pt to Cu and thus improve the intrinsic activity of Pt active sites. And the metallic Cu can favor the promotion of electrochemical active surface area. Consequently, the as-prepared PtCu/C behaves impressive ORR activity with half-wave potential of 0.88 V (vs. RHE) and mass activity of 0.49 A cm⁻² mg_Pt⁻¹ at 0.8 V, which is 9.8 times of commercial Pt/C catalysts. Our work will offer helpful advices for the development and regulation of novel Pt-based alloy materials towards diverse electrocatalysis.     

Precisely Controlled Synthesis of Pt-Pd Octahedral Nanoframes as a Superior Catalyst towards Oxygen Reduction Reaction

Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in thickness. The Pt-Pd octahedral nanoframes were obtained through site-selected deposition of Pt atoms onto the edge sites of Pd octahedral seeds, followed by selective removal of the Pd octahedral cores via chemical etching. Due to that a combination of three-dimensional opens geometrical structure and Pt-skin surface compositional structure, the Pt-Pd octahedral nanoframes/C catalyst shows a mass activity of 1.15 A/mg_Pt towards oxygen reduction reaction, 5.8 times enhancement in mass activity relative to commercial Pt/C catalyst (0.20 A/mg_Pt). Moreover, even after 8000 cycles of accelerated durability test, the Pt-Pd octahedral nanoframes/C catalyst still exhibits a mass activity which is more than three times higher than that of pristine Pt/C catalyst.     

Study of anion adsorption on polycrystalline Pt by electrochemical quartz crystal microbalance

The changes observed on Pt surfaces during a potential incursion into the underpotentially deposited (UPD) hydrogen and double layer ranges (0.05 to 0.8 V versus HESS) were analyzed in perchloric, sulfuric, phosphoric and hydrochloric acid media. Surface occupation after hydrogen desorption was verified in terms of both mass variations and voltammetric charges measured by EQCM and cyclic voltammetry. Firstly, mass incorporation due to the adsorption of water molecules (approximately 39 ng cm⁻², corresponding to a full monolayer of adsorbed water) replacing the UPD H atoms was observed in every case. The potential range associated with water adsorption varied from 0.05 V to a final value that depended on the strength of anion adsorption on Pt (0.4 V for ClO₄⁻ and 0.3 V for Cl⁻). Secondly, the mass incorporations in the potential region between 0.4 and 0.8 V were associated to adsorption of the corresponding hydrated anions, i.e., ClO₄⁻·2H₂O, HSO₄⁻·2H₂O, HPO₄²⁻ and Cl⁻·6H₂O. Calculated anion coverage values varied from 7 (perchlorate) to 19% (phosphate) on the Pt surface.     

Carbon-supported ultrafine Pt nanoparticles modified with trace amounts of cobalt as enhanced oxygen reduction reaction catalysts for proton exchange membrane fuel cells

To accelerate the kinetics of the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells, ultrafine Pt nanoparticles modified with trace amounts of cobalt were fabricated and decorated on carbon black through a strategy involving modified glycol reduction and chemical etching. The obtained Pt₃₆Co/C catalyst exhibits a much larger electrochemical surface area (ECSA) and an improved ORR electrocatalytic activity compared to commercial Pt/C. Moreover, an electrode prepared with Pt₃₆Co/C was further evaluated under H₂-air single cell test conditions, and exhibited a maximum specific power density of 10.27 W mg_Pt^?1, which is 1.61 times higher than that of a conventional Pt/C electrode and also competitive with most state-of-the-art Pt-based architectures. In addition, the changes in ECSA, power density, and reacting resistance during the accelerated degradation process further demonstrate the enhanced durability of the Pt₃₆Co/C electrode. The superior performance observed in this work can be attributed to the synergy between the ultrasmall size and homogeneous distribution of catalyst nanoparticles, bimetallic ligand and electronic effects, and the dissolution of unstable Co with the rearrangement of surface structure brought about by acid etching. Furthermore, the accessible raw materials and simplified operating procedures involved in the fabrication process would result in great cost-effectiveness for practical applications of PEMFCs.     

Ultra-low platinum loading high-performance PEMFCs using buckypaper-supported electrodes

The microstructure of the catalyst layer in proton exchange membrane fuel cells (PEMFCs) greatly influences catalyst (Pt) utilization and cell performance. We demonstrated a functionally graded catalyst layer based on a double-layered carbon nanotube/nanofiber film- (buckypaper) supported Pt composite catalyst to approach an idealized microstructure. The gradient distribution of Pt, electrolyte and porosity along the thickness effectively depresses the transport resistance of proton and gas. A rated power of 0.88 W/cm² at 0.65 V was achieved at 80 °C with a low Pt loading of 0.11 mg/cm² resulting in a relatively high Pt utilization of 0.18g_Pt/kW. The accelerated degradation test of catalyst support showed a good durability of buckypaper support because of the high graphitization degree of carbon nanofibers.     

Doping Platinum with Germanium: An Effective Way to Mitigate the CO Poisoning

The vulnerability towards CO poisoning is a major drawback affecting the efficiency and long-term performance of platinum catalysts in fuel cells. In the present work, by a combination of density functional theory calculations and mass spectrometry experiments, we test and explain the promotional effect of Ge on Pt catalysts with higher resistance to deactivation via CO poisoning. A thorough exploration of the configurational space of gas-phase Pt_n⁺ and GePt_n−1⁺ (n=5–9) clusters using global minima search techniques and the subsequent electronic structure analysis reveals that germanium doping reduces the binding strength between Pt and CO by hindering the 2π-back-donation. Importantly, the clusters remain catalytically active towards H₂ dissociation. The ability of Ge to weaken the Pt−CO interaction was confirmed by mass spectrometry experiments. Ge can be a promising alloying agent to tune the selectivity and improve the durability of Pt particles, thus opening the way to novel catalytic alternatives for fuel cells.     

Preparation of Surfactant-Free Pt and PtRu Nanoparticles with High Activity for Methanol Oxidation

A simple and green approach to synthesize highly active electro-catalysts for methanol oxi- dation reaction （MOR） without using any organic agents is described. Pt nanoparticles are directly deposited on the pre-cleaned and pre-oxidized multiwall carbon nanotubes （MWC- NTs） from Pt salt by using CO as the reductant. MOR activity has been characterized by both cyclic voltammetry and chronoamperometry, the current density and mass specific current at the peak potential （ca. 0.9 V vs. RHE） reaches 11.6 mA/cm^2 and 860 mA/mgpt, respectively. After electro-deposition of Ru onto the Pt/MWCNTs surface, the catalysts show steady state mass specific current of 20 and 80 mA/mgpt at 0.5 and 0.6 V, respectively.     

Modulating Electronic Metal-Support Interactions to Boost Visible-Light-Driven Hydrolysis of Ammonia Borane: Nickel-Platinum Nanoparticles Supported on Phosphorus-Doped Titania

Ammonia borane (AB) is a promising material for chemical H₂ storage owing to its high H₂ density (up to 19.6 wt %). However, the development of an efficient catalyst for driving H₂ evolution through AB hydrolysis remains challenging. Therefore, a visible-light-driven strategy for generating H₂ through AB hydrolysis was implemented in this study using Ni−Pt nanoparticles supported on phosphorus-doped TiO₂ (Ni-Pt/P-TiO₂) as photocatalysts. Through surface engineering, P-TiO₂ was prepared by phytic-acid-assisted phosphorization and then employed as an ideal support for immobilizing Ni−Pt nanoparticles via a facile co-reduction strategy. Under visible-light irradiation at 283 K, Ni₄₀Pt₆₀/P-TiO₂ exhibited improved recyclability and a high turnover frequency of 967.8 mol mol_Pt⁻¹ min⁻¹. Characterization experiments and density functional theory calculations indicated that the enhanced performance of Ni₄₀Pt₆₀/P-TiO₂ originated from a combination of the Ni−Pt alloying effect, the Mott–Schottky junction at the metal-semiconductor interface, and strong metal-support interactions. These findings not only underscore the benefits of utilizing multipronged effects to construct highly active AB-hydrolyzing catalysts, but also pave a path toward designing high-performance catalysts by surface engineering to modulate the electronic metal-support interactions for other visible-light-induced reactions.     

Accelerating Ethanol Complete Electrooxidation via Introducing Ethylene as the Precursor for the C−C Bond Splitting

The crucial issue restricting the application of direct ethanol fuel cells (DEFCs) is the incomplete and sluggish electrooxidation of ethanol due to the chemically stable C−C bond thereof. Herein, a unique ethylene-mediated pathway with a 100 % C1-selectivity for ethanol oxidation reaction (EOR) is proposed for the first time based on a well-structured Pt/Al₂O₃@TiAl catalyst with cascade active sites. The electrochemical in situ Fourier transform infrared spectroscopy (FTIR) and differential electrochemical mass spectrometry (DEMS) analysis disclose that ethanol is primarily dehydrated on the surface of Al₂O₃@TiAl and the derived ethylene is further oxidized completely on nanostructured Pt. X-ray absorption and density functional theory (DFT) studies disclose the Al component doped in Pt nanocrystals can promote the EOR kinetics by lowering the reaction energy barriers and eliminating the poisonous species. Strikingly, Pt/Al₂O₃@TiAl exhibits a specific activity of 3.83 mA cm⁻²_Pt, 7.4 times higher than that of commercial Pt/C and superior long-term durability.     

Optimizing the Size of Platinum Nanoparticles for Enhanced Mass Activity in the Electrochemical Oxygen Reduction Reaction

High oxygen reduction (ORR) activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we prepare Pt nanoparticles with optimal size for the efficient ORR in proton‐exchange‐membrane fuel cells. Optimal nanoparticle sizes are predicted near 1, 2, and 3 nm by computational screening. To corroborate our computational results, we have addressed the challenge of approximately 1 nm sized Pt nanoparticle synthesis with a metal–organic framework (MOF) template approach. The electrocatalyst was characterized by HR‐TEM, XPS, and its ORR activity was measured using a rotating disk electrode setup. The observed mass activities (0.87±0.14 A mg_Pt^?1) are close to the computational prediction (0.99 A mg_Pt^?1). We report the highest to date mass activity among pure Pt catalysts for the ORR within similar size range. The specific and mass activities are twice as high as the Tanaka commercial Pt/C catalysis.     

Engineering Platinum–Oxygen Dual Catalytic Sites via Charge Transfer towards Highly Efficient Hydrogen Evolution

A dual-site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual-site interfaces in single-atom system to maximize the effect. Herein, we report a cation-deficient electrostatic anchorage route to fabricate an atomically dispersed platinum–titania catalyst (Pt₁^O1/Ti_1−xO₂), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional calculations reveal that Pt₁^O1/Ti_1−xO₂ experiences a Pt−O dual-site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the key role during the Volmer–Tafel process. There is almost no decay in the activity of Pt₁^O1/Ti_1−xO₂ over 300 000 cycles, meaning 30 times of enhancement in stability compared to the commercial Pt/C catalysts (10 000 cycles).     

Medium/High-Entropy Amalgamated Core/Shell Nanoplate Achieves Efficient Formic Acid Catalysis for Direct Formic Acid Fuel Cell

High-entropy alloys (HEAs) have been attracting extensive research interests in designing advanced nanomaterials, while their precise control is still in the infancy stage. Herein, we have reported a well-defined PtBiPbNiCo hexagonal nanoplates (HEA HPs) as high-performance electrocatalysts. Structure analysis decodes that the HEA HP is constructed with PtBiPb medium-entropy core and PtBiNiCo high-entropy shell. Significantly, the HEA HPs can reach the specific and mass activities of 27.2 mA cm⁻² and 7.1 A mg_Pt⁻¹ for formic acid oxidation reaction (FAOR), being the record catalyst ever achieved in Pt-based catalysts, and can realize the membrane electrode assembly (MEA) power density (321.2 mW cm⁻²) in fuel cell. Further experimental and theoretical analyses collectively evidence that the hexagonal intermetallic core/atomic layer shell structure and multi-element synergy greatly promote the direct dehydrogenation pathway of formic acid molecule and suppress the formation of CO*.     

Activated Single-Phase Ti4O7 Nanosheets with Efficient Use of Precious Metal for Inspired Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is central to modern energy storage and conversion technologies for grids such as fuel cells and electrolyzers, but challenges remain due to the lack of reliable, economic, and durable electrocatalysts. Here, we develop single-crystal conductive black titanium (Ti₄O₇) nanosheets (NSs) as a new precious metal carrier based on sacrificial hard templates and ultrasonic-assisted peeling, and deposit Pt clusters on Ti₄O₇ NSs induced by wetness impregnation under the irradiation of visible light (VI; 650 nm). Pt/Ti₄O₇ NSs provide Ti³⁺, Pt²⁺, and Pt⁰⁺ continuous active sites for the ORR multielectron process, achieving synergy among them. The assistance of visible light not only makes a more uniform and smaller distribution of Pt nanoclusters, but also strengthens the charge transfer, thereby constructing a strong metal-support interaction interface. VI−Pt/Ti₄O₇ NSs show superior initial oxidation potential and a mass activity of 1.61 A mg⁻¹_Pt at a E_1/2=0.91 V, which is nine times higher than that of commercial Pt/C. This work provides an effective strategy for achieving high-value applications of titanium sub-oxides and further explores the enhanced interface in metals Ti_nO_2n-1 by light radiation.     

Effect of load-cycling amplitude on performance degradation for proton exchange membrane fuel cell

Durability is one of the critical issues to restrict the commercialization of proton exchange membrane fuel cells (PEMFCs) for the vehicle application. The practical dynamic operation significantly affects the PEMFCs durability by corroding its key components. In this work, the degradation behavior of a single PEMFC has been investigated under a simulated automotive load-cycling operation, with the aim of revealing the effect of load amplitude (0.8 and 0.2 A/cm² amplitude for the current density range of 0.1−0.9 and 0.1−0.3 A/cm², respectively) on its performance degradation. A more severe degradation on the fuel cell performance is observed under a higher load amplitude of 0.8 A/cm² cycling operation, with ∼10.5% decrease of cell voltage at a current density of 1.0 A/cm². The larger loss of fuel cell performance under the higher load amplitude test is mainly due to the frequent fluctuation of a wider potential cycling. Physicochemical characterizations analyses indicate that the Pt nanoparticles in cathodic catalyst layer grow faster with a higher increase extent of particle size under this circumstance because of their repeated oxidation/reduction and subsequent dissolution/agglomeration process, resulting in the degradation of platinum catalyst and thus the cell performance. Additionally, the detected microstructure change of the cathodic catalyst layer also contributes to the performance failure that causes a distinct increase in mass transfer resistance.     

New Ni–Pt Carbonyl Clusters with a Tetrahedron of Platinum Atoms Encapsulated in an Incomplete Tetrahedron of Nickel Atoms: [Ni36Pt4(CO)45]6− and [Ni37Pt4(CO)46]6−

A fully encapsulated Pt ₄ tetrahedron in an incomplete tetrahedron of 36 nickel atoms is present in [Ni₃₆Pt₄(CO)₄₅]⁶⁻ ( 1 ; see picture for the metal framework), which is obtained as an inseparable mixture with [Ni₃₇Pt₄(CO)₄₆]⁶⁻ ( 2 ) by reaction of [Ni₆(CO)₁₂]²⁻ with K₂[PtCl₄]. The trimethylbenzylammonium salts of 1 and 2 cocrystallize in a 1:1 ratio. The additional Ni atom of 2 caps the truncated vertex of 1 .     

Ultrafine PtRu Dilute Alloy Nanodendrites for Enhanced Electrocatalytic Methanol Oxidation

Dilute alloy nanostructures have been demonstrated to possess distinct catalytic properties. Noble-metal-induced reduction is one effective synthesis strategy to construct dilute alloys and modify the catalytic performance of the host metal. Herein, we report the synthesis of ultrafine PtRu dilute alloy nanodendrites (PtRu NDs, molar ratio Ru/Pt is 1:199) by the reduction of Ru^III ions induced by Pt metal. For the methanol oxidation reaction, PtRu NDs showed the highest forward peak current density (2.66 mA cm⁻², 1.14 A/mg_Pt) and the best stability compared to those of pure-Pt nanodendrites (pure-Pt NDs), commercial PtRu/C and commercial Pt/C catalysts.     

Platinum Oxide Nanoparticles for Electrochemical Hydrogen Evolution: Influence of Platinum Valence State

Electrochemical hydrogen generation is a rising prospect for future renewable energy storage and conversion. Platinum remains a leading choice of catalyst, but because of its high cost and low natural abundance, it is critical to optimize its use. In the present study, platinum oxide nanoparticles of approximately 2 nm in diameter are deposited on carbon nitride (C3N4) nanosheets by thermal refluxing of C3N4 and PtCl₂ or PtCl₄ in water. These nanoparticles exhibit apparent electrocatalytic activity toward the hydrogen evolution reaction (HER) in acid. Interestingly, the HER activity increases with increasing Pt⁴⁺ concentration in the nanoparticles, and the optimized catalyst even outperforms commercial Pt/C, exhibiting an overpotential of only −7.7 mV to reach the current density of 10 mA cm⁻² and a Tafel slope of −26.3 mV dec⁻¹. The results from this study suggest that the future design of platinum oxide catalysts should strive to maximize the Pt⁴⁺ sites and minimize the formation of the less active Pt²⁺ species.