Platinum-Ruthenium Single Atom Alloy as a Bifunctional Electrocatalyst toward Methanol and Hydrogen Oxidation Reactions

Surface Engineering of PtSe2 Crystal for Highly Efficient Electrocatalytic Ethanol Oxidation

The development of efficient electrocatalysts for ethanol oxidation reaction (EOR) is crucial for the potential commercialization of direct ethanol fuel cells, yet it faces significant challenges between catalytic performance and cost-effectiveness. 2D materials have recently emerged as a promising group of electrocatalysts due to their large surface area, efficient charge transport, tunable band structures, and excellent catalytic activity. In this study, the novel 2D layered noble-metal dichalcogenide, PtSe2, is explored for efficient ethanol oxidation electrocatalysis from a microscopic perspective based on an on-chip microelectrochemical platform. While pristine PtSe2 demonstrates similar EOR activities to Pt, argon plasma treatment significantly enhances the performance on EOR activity, If/Ib ratio, onset and peak potentials, and durability. Detail investigations reveal that plasma treatment results in the exposure of PtSe2 surface, which is responsible for significantly enhanced EOR activity and poison-resistance as also confirmed by theoretical calculations. In situ electrical transport measurements for monitoring the catalyst surface intermediates, elucidate that both optimized OHads coverage and appropriate ethanol molecular adsorption on PtSe2 are the key for the high performance. This work demonstrates noble-metal dichalcogenides as promising EOR electrocatalysts, and establishes on-chip electrocatalytic microdevice as a promising probing platform for diverse electrocatalytic measurements.

Lattice-Confined Ru Electrocatalysts with Optimal Localized Interfacial Electrons for Efficient Alkaline Hydrogen Oxidation

The interfacial electronic structure has a significant influence on the electrocatalytic activity and durability of metal oxide-supported ruthenium (Ru) electrocatalysts for the alkaline hydrogen oxidation reaction (HOR). Herein, we optimize the interfacial electronic structure by tuning the Ru-O bonds within MnO lattice-confined Ru electrocatalysts, creating efficient and stable sites for alkaline HOR. The formed Ru-O bonds generate localized interfacial electrons and a downshifted d-band center of interfacial Ru atoms, which results in optimal adsorption ability of H* and OH* together with the reduced energy barrier of H2O formation. The mass activity achieves 1.26 mA μgRu-1 in 0.1 M KOH, which is 13.0-fold and 8.0-fold higher than that of the contrast Ru/C (0.097 mA μgRu-1) and commercial Pt/C (0.158 mA μgPt-1), respectively, while also exhibiting favorable durability and CO tolerance. This work highlights the rational design of Ru-O bonds in optimizing the interfacial electronic structure to enhance the alkaline HOR activity.

Advances in simulating dilute alloy nanoparticles for catalysis

Dilute alloy (DA) catalysts, including single-atom alloys (SAAs), which are comprised of trace amounts of an active promoter metal dispersed on the surface of a selective host metal, offer exceptional activity and selectivity while utilizing precious metals more efficiently. Although most SAA and DA applications have focused on partial hydrogenation and oxidation reactions, their use has steadily expanded into more complex thermo-, photo-, and electro-catalytic processes. This progress has been largely driven by mechanistic insights derived from computational chemistry and is expected to accelerate with the advancement of artificial intelligence. This minireview discusses novel advances in simulating SAAs and DAs for catalysis applications, including ab initio calculations, multiscale modeling, and machine learning. Emphasis is placed on the impact of reaction conditions, promoter ensembles, and nanoparticle morphology on the stability and catalytic performance of SAAs and DAs. Finally, a perspective is offered on potential future directions of SAA and DA simulations and their extension to other systems with distinct, well-defined active sites.

UNLEASH: Ultralow Nanocluster Loading of Pt via Electro-Acoustic Seasoning of Heterocatalysts

The shift toward sustainable energy has fueled the development of advanced electrocatalysts to enable green fuel production and chemical synthesis. To date, no material outperforms Pt-group catalysts for key electrocatalytic reactions, necessitating advanced catalysts that minimize use of these rare and expensive constituents (i.e., Pt) to reduce cost without sacrificing activity. Whilst a myriad of routes involving co-synthesis of Pt with other elements have been reported, the Pt is often buried within the bulk of the composite, rendering a large proportion of it inaccessible to the interfacial electrocatalytic reaction. Surface decoration of Pt on arbitrary substrates is therefore desirable to maximize catalytic activity; nevertheless, Pt electrodeposition suffers from clustering and ripening effects that result in large (⌀ 0.1 - 1 μ m $\diameter \ \!0.1-1\ \umu{\rm m}$ ) aggregates that hinder electrocatalytic activity. Herein, an unconventional synthesis method is reported that utilizes high-frequency (10 MHz) acoustic waves to electrochemically 'season' a gold working electrode with an ultralow loading of Pt nanoclusters. The UNLEASH platform is shown to facilitate high-density dispersion of nanometer-order clusters at the bimetallic interface to enable superior atomic utilization of Pt. This is exemplified by its utility for methanol oxidation reaction (MOR), wherein a mass activity of 5.28 Amg Pt - 1 ${\rm mg}_{\rm Pt}^{-1}$ is obtained, outperforming all other Au/Pt bimetallic electrocatalysts reported to date.

Dilute Pd-Ni Alloy through Low-temperature Pyrolysis for Enhanced Electrocatalytic Hydrogen Oxidation

Designing highly active and cost-effective electrocatalysts for the alkaline hydrogen oxidation reaction (HOR) is critical for advancing anion-exchange membrane fuel cells (AEMFCs). While dilute metal alloys have demonstrated substantial potential in enhancing alkaline HOR performance, there has been limited exploration in terms of rational design, controllable synthesis, and mechanism study. Herein, we developed a series of dilute Pd-Ni alloys, denoted as x% Pd-Ni, based on a trace-Pd decorated Ni-based coordination polymer through a facile low-temperature pyrolysis approach. The x% Pd-Ni alloys exhibit efficient electrocatalytic activity for HOR in alkaline media. Notably, the optimal 0.5 % Pd-Ni catalyst demonstrates high intrinsic activity with an exchange current density of 0.055 mA cm-2, surpassing that of many other alkaline HOR catalysts. The mechanism study reveals that the strong synergy between Pd single atoms (SAs)/Pd dimer and Ni substrate can modulate the binding strength of proton (H)/hydroxyl (OH), thereby significantly reducing the activation energy barrier of a decisive reaction step. This work offers new insights into designing advanced dilute metal or single-atom-alloys (SAAs) for alkaline HOR and potentially other energy conversion processes.

Ultra-Low-Potential Methanol Oxidation on Single-Ir-Atom Catalyst

Methanol oxidation plays a central role to implement sustainable energy economy, which is restricted by the sluggish reaction kinetics due to the multi-electron transfer process accompanied by numerous sequential intermediate. In this study, an efficient cascade methanol oxidation reaction is catalyzed by single-Ir-atom catalyst at ultra-low potential (<0.1 V) with the promotion of the thermal and electrochemical integration in a high temperature polymer electrolyte membrane electrolyzer. At the elevated temperature, the electron deficient Ir site with higher methanol affinity could spontaneous catalyze the CH3OH dehydrogenation to CO under the voltage, then the generated CO and H2 was electrochemically oxidized to CO2 and proton. However, the methanol cannot thermally decompose with the voltage absence, which confirm the indispensable of the coupling of thermal and electrochemical integration for the methanol oxidation. By assembling the methanol oxidation reaction with hydrogen evolution reaction with single-Ir-atom catalysts in the anode chamber, a max hydrogen production rate reaches 18 mol gIr -1 h-1, which is much greater than that of Ir nanoparticles and commercial Pt/C. This study also demonstrated the electrochemical methanol oxidation activity of the single atom catalysts, which broadens the renewable energy devices and the catalyst design by an integration concept.

Atomic Distance Engineering in Metal Catalysts to Regulate Catalytic Performance

It is very important to understand the structure-performance relationship of metal catalysts by adjusting the microstructure of catalysts at the atomic scale. The atomic distance has an essential influence on the composition of the environment of active metal atom, which is a key factor for the design of targeted catalysts with desired function. In this review, we discuss and summarize strategies for changing the atomic distance from three aspects and relate their effects on the reactivity of catalysts. First, the effects of regulating bond length between metal and coordination atom at one single-atom site on the catalytic performance are introduced. The bond lengths are affected by the strain effect of the support and high-shell doping and can evolve during the reaction. Next, the influence of the distance between single-atom sites on the catalytic performance is discussed. Due to the space matching of adsorption and electron transport, the catalytic performance can be adjusted with the shortening of site distance. In addition, the effect of the arrangement spacing of the surface metal active atoms on the catalytic performance of metal nanocatalysts is studied. Finally, a comprehensive summary and outlook of the relationship between atomic distance and catalytic performance is given.

Thermally Methanol Oxidation via the Mn1@Co3O4(111) Facet: Non-CO Reaction Pathway

Co3O4, as the support of single-atom catalysts, is effective in electron-structure modulation to get distinct methanol adsorption behaviors and adjustable reaction pathways for the methanol oxidation reaction. Herein, we considered the facets that constitute a Co vacancy of the Co3O4(111) facet and a foreign metal atom M (M = Fe, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, Mn) leading to single-atom catalysts. The Mn1@Co3O4(111) facet is the facet considered the most favorable among all of the possible terminations. Oxygen adsorption, decomposition, and its co-adsorption with methanol are the vital steps of methanol oxidation at the exposed Mn1@Co3O4(111) facet, giving rise to the stable configuration: two O* and one CH3OH* adsorbates. Then, the Mn1@Co3O4(111) facet activates the O-H and C-H bonds within CH3OH*, advances CH3O* → H2CO* → HCOO* → COO*, and releases the products H2, H2O, and CO2 consecutively.

Toward Electrocatalytic Methanol Oxidation Reaction: Longstanding Debates and Emerging Catalysts

The study of direct methanol fuel cells (DMFCs) has lasted around 70 years, since the first investigation in the early 1950s. Though enormous effort has been devoted in this field, it is still far from commercialization. The methanol oxidation reaction (MOR), as a semi-reaction of DMFCs, is the bottleneck reaction that restricts the overall performance of DMFCs. To date, there has been intense debate on the complex six-electron reaction, but barely any reviews have systematically discussed this topic. To this end, the controversies and progress regarding the electrocatalytic mechanisms, performance evaluations as well as the design science toward MOR electrocatalysts are summarized. This review also provides a comprehensive introduction on the recent development of emerging MOR electrocatalysts with a focus on the innovation of the alloy, core-shell structure, heterostructure, and single-atom catalysts. Finally, perspectives on the future outlook toward study of the mechanisms and design of electrocatalysts are provided.

The Development of High-Performance Platinum-Ruthenium Catalysts for the Methanol Oxidation Reaction: Gram-Scale Synthesis, Composition, Morphology, and Functional Characteristics

To obtain the PtRu/C electrocatalysts, the surfactant-free (wet) synthesis methods have been used. The structural-morphological characteristics and electrochemical behavior of the catalysts have been studied. The possibility of ranging the crystallite size from 1.2 to 4.5 nm using different reducing agents (ethylene glycol, ethanol, and isopropanol) has been shown. The effect of both the particles’ size and the mass fraction of the metal component on the electrochemical surface area (ESA), activity in the methanol electrooxidation reaction (MOR), and tolerance to its intermediate products has been studied. The simple and scalable surfactant-free synthesis method of the highly active PtRu/C electrocatalysts with a different mass fraction of metals, with their tolerance to intermediate products of the oxidation being 2.3 times higher than the commercial analogue, has been first proposed. The authors have succeeded in obtaining the PtRu/C catalysts with the nanoparticles’ size of less than 2 nm, characterized by the ultranarrow size and uniform spatial distributions over the support surface, thus having the ESA of more than 90 m2gPtRu−1.