High-efficiency methanol oxidation electrocatalysts realized by ultrathin PtRuM-O (M = Ni, Fe, Co) nanosheets

CuNi sulphidation maximizes MOR activity by expanding the accessibility of active sites!

Sulphidation of a CuNi alloy of Cu : Ni ratio 81 : 19 led to an exponential activity enhancement in the alkaline methanol oxidation reaction (MOR) by four fold due to an order of magnitude increase in the number of active Cu and Ni sites and improved charge transfer properties.

Lattice Strain and Composition Effects on the Methanol Oxidation Performance of Platinum-Ruthenium-Nickel Ternary Nanocatalysts

Ternary Pt-based structures are a positive progress in addressing the disadvantages of monometallic and bimetallic Pt-based alloys for the electrochemical oxidation process of simple alcohols, which is a vital half-reaction in fuel cell technologies. We herein report a facile NaBH4-assisted ethylene glycol reduction process for fabricating a series of nanosized PtRuNi ternary alloys to explore the relationship between physicochemical properties and electrocatalytic behaviors for the acidic methanol oxidation reaction (MOR). Owing to a balance between lattice strain and synergistic effects, the Pt60Ru20Ni20/C electrocatalyst shows the highest MOR efficiency with the mass activity/specific activity of 844.48 mA mgMetal-1/1.93 mA cm-2, being a 1.94 and 2.38 times increase compared to those of the PtRu catalyst, respectively. Also, the Pt60Ru20Ni20/C catalyst possesses superior CO-tolerance and durability in strongly acidic electrolytes. This work suggests that optimizing the surface strain and electronic effects can boost the overall MOR efficiency of multicomponent Pt-based materials, which can help to further develop next-generation catalysts for energy conversion-related technologies.

Controlled Synthesis of Carbon-Supported Pt-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans. However, their performance, cost, and durability are significantly related to Pt-based electrocatalysts, hampering their large-scale commercial application. Hence, considerable efforts have been devoted to improving the activity and durability of Pt-based electrocatalysts by controlled synthesis in recent years as an effective method for decreasing Pt use, and consequently, the cost. Therefore, this review article focuses on the synthesis processes of carbon-supported Pt-based electrocatalysts, which significantly affect the nanoparticle size, shape, and dispersion on supports and thus the activity and durability of the prepared electrocatalysts. The reviewed processes include (i) the functionalization of a commercial carbon support for enhanced catalyst–support interaction and additional catalytic effects, (ii) the methods for loading Pt-based electrocatalysts onto a carbon support that impact the manufacturing costs of electrocatalysts, (iii) the preparation of spherical and nonspherical Pt-based electrocatalysts (polyhedrons, nanocages, nanoframes, one- and two-dimensional nanostructures), and (iv) the postsynthesis treatments of supported electrocatalysts. The influences of the supports, key experimental parameters, and postsynthesis treatments on Pt-based electrocatalysts are scrutinized in detail. Future research directions are outlined, including (i) the full exploitation of the potential functionalization of commercial carbon supports, (ii) scaled-up one-pot synthesis of carbon-supported Pt-based electrocatalysts, and (iii) simplification of postsynthesis treatments. One-pot synthesis in aqueous instead of organic reaction systems and the minimal use of organic ligands are preferred to simplify the synthesis and postsynthesis treatment processes and to promote the mass production of commercial carbon-supported Pt-based electrocatalysts.

Graphical Abstract

This review focuses on the synthesis process of Pt-based electrocatalysts/C to develop aqueous one-pot synthesis at large-scale production for PEMFC stack application.

Ultrahigh Stable Methanol Oxidation Enabled by a High Hydroxyl Concentration on Pt Clusters/MXene Interfaces

Anchoring platinum catalysts on appropriate supports, e.g., MXenes, is a feasible pathway to achieve a desirable anode for direct methanol fuel cells. The authentic performance of Pt is often hindered by the occupancy and poisoning of active sites, weak interaction between Pt and supports, and the dissolution of Pt. Herein, we construct three-dimensional (3D) crumpled Ti₃C₂T_x MXene balls with abundant Ti vacancies for Pt confinement via a spray-drying process. The as-prepared Pt clusters/Ti₃C₂T_x (Ptc/Ti₃C₂T_x) show enhanced electrocatalytic methanol oxidation reaction (MOR) activity, including a relatively low overpotential, high tolerance to CO poisoning, and ultrahigh stability. Specifically, it achieves a high mass activity of up to 7.32 A mg_Pt^-1, which is the highest value reported to date in Pt-based electrocatalysts, and 42% of the current density is retained on Ptc/Ti₃C₂T_x even after the 3000 min operative time. In situ spectroscopy and theoretical calculations reveal that an electric field-induced repulsion on the Ptc/Ti₃C₂T_x interface accelerates the combination of OH^- and CO adsorption intermediates (CO_ads) in kinetics and thermodynamics. Besides, this Ptc/Ti₃C₂T_x also efficiently electrocatalyze ethanol, ethylene glycol, and glycerol oxidation reactions with comparable activity and stability to commercial Pt/C.

Ultrathin and Porous 2D PtPdCu Nanoalloys as High-Performance Multifunctional Electrocatalysts for Various Alcohol Oxidation Reactions

We precisely synthesized two-dimensional (2D) PtPdCu nanostructures with the morphology varying from porous circular nanodisks (CNDs) and triangular nanoplates (TNPs) to triangular nanoboomerangs (TNBs) by tuning the molar ratios of metal precursors. The PtPdCu trimetallic nanoalloys exhibit superior electrocatalytic performances to alcohol oxidation reactions due to their unique structural features and the synergistic effect. Impressively, PtPdCu TNBs exhibit a high mass activity of 3.42 mg_Pt+Pd^-1 and 1.06 A·mg_Pt^-1 for ethanol and methanol oxidation compared to PtPd, PtCu, and pure Pt, which is 3.93 and 4.07 times that of commercial Pt/C catalysts, respectively. Moreover, 2D PtPdCu TNPs and PtPdCu CNDs also show a highly improved electrocatalytic activity. Furthermore, as all-in-one electrocatalysts, PtPdCu nanoalloys display excellent electrocatalytic activity and stability toward the oxidation of other alcohol molecules, such as isopropyl alcohol, glycerol, and ethylene glycol. The enhanced mechanism was well proposed to be the abundant active sites and upshifted d-band center based on density functional theory calculations.

NiCoPd Inlaid NiCo-Bimetallene for Efficient Electrocatalytic Methanol Oxidation

Pd-based metallenes have attracted great attention recently as newly burgeoning two-dimensional (2D) materials, attributed to their significantly increased active surface areas and intrinsic electrocatalytic activities. Therefore, they could be used as a potential candidate as the high-performance electrocatalyst for methanol oxidation reactions (MORs) in the direct methanol fuel cell. Herein, a new strategy is proposed to fabricate NiCoPd inlaid NiCo-bimetallene (NiCoPd/NiCo-bimetallene) by the structure directing effect of 18-crown-6 ether under an ultrasonic-pulse interface together with the HCHO reduction and atom-diffusion-aging process. NiCoPd ternary-alloys with uniformly dispersed Pd active sites are decorated onto NiCo-bimetallenes, achieving remarkably enhancing the effective utilization of Pd atoms. What is more, the intrinsic activity is enhanced by the "bifunctional mechanism" of NiCo-bimetallene adsorption of intermediate species and increased Pd-active sites. Moreover, the anti-CO poisoning ability is optimized through the "alloying ligand effect" of NiCoPd. Therefore, the NiCoPd/NiCo-bimetallene exhibits excellent mass activity for MOR, which is higher than commercial Pd/C. This work suggests a new way of the Pd-based metallenes catalyst approach to the efficient electrocatalytic MOR.

PdPtRu nanocages with tunable compositions for boosting the methanol oxidation reaction

PtRu/C is a well-known commercial electrocatalyst with promising performance for the methanol oxidation reaction (MOR). Further improving the MOR properties of PtRu-based electrocatalysts is highly desirable, especially through structure design. Here we report a facile approach for the synthesis of PdPtRu nanocages with different components through a seed-mediated approach followed by chemical etching. The Pd@PtRu nanocubes were first generated using Pd nanocubes as the seeds and some Pd atoms were subsequently etched away, leading to the nanocages. When evaluated as electrocatalysts for the MOR in acidic media, the PdPtRu nanocages exhibited substantially enhanced catalytic activity and stability relative to commercial Pt/C and PtRu/C. Specifically, PdPt_2.5Ru_2.4 achieved the highest specific (8.2 mA cm^-2) and mass (0.75 mA mg_Pt ^-1) activities for the MOR, which are 2.2 and 4.2 times higher than those of commercial Pt/C. Such an enhancement can be attributed to the highly open structure of the nanocages, and the possible synergistic effect between the three components.

Noble Metal (Pt, Rh, Pd, Ir) Doped Ru/CNT Ultra-Small Alloy for Acidic Hydrogen Evolution at High Current Density

There are still great challenges to prepare high-efficiency Ru-based catalysts that are superior to Pt/C under acidic conditions, especially under high current conditions. In this work, a series of surfactant-free noble metal doped Ru/CNT (M-Ru/CNT, M = Pt, Rh, Pd, Ir, CNT stands for carbon nanotube) are prepared by microwave reduction method in 1 minute with ≈3-3.5 nm in size for the first time. In 0.5 m H₂ SO₄ , the overpotential of Pt-Ru/CNT (Pt: 4.94 at %) is only 12 mV. What's more, it also has much larger electrochemical surface area and intrinsic activity than Pt/C. Pt-Ru/CNT still has an ultra-small overpotential under high current density (113 mV at 500 mA cm^-2 , 155 mV at 1000 mA cm^-2 ). At the same time, it possesses excellent stability regardless of high current or low current after the durability test of 100 h. Theoretical calculation also deeply reveals that Ru is the main adsorption site of H⁺ . The comparison of the electronic structure of a series of noble metals adjusted by Ru shows that Pt has the most excellent Gibbs free energy of the adsorbed hydrogen and promotes the desorption of the product.