A single-Pt-atom-on-Ru-nanoparticle electrocatalyst for CO-resilient methanol oxidation

Abstract

Single Pt atom catalysts on non-active carbon supports have been key targets for electrochemical reactions because the high exposure of active Pt leads to record-high activities. PtRu alloy catalysts are the most active for the methanol oxidation reaction (MOR) as the Ru atoms decrease CO poisoning of the active Pt. To combine the exceptional activity of single atom Pt catalysts with the bene ts of an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. We have developed a concept to grow and spreads Pt islands on faceted Ru branched nanoparticles to make single Pt atom on Ru catalysts. By following the spreading process with in situ TEM, we show that the formation of single atoms is thermodynamically driven by the formation of strong Pt-Ru bonds and a lowering of surface area. The single Pt atom on Ru catalysts successfully limit CO poisoning during MOR to produce record current density and mass activity over time. MainThe methanol oxidation reaction (MOR) is the limiting reaction for the direct methanol fuel cell because CO-poisoning prevents high current densities over time 1 . CO poisoning is one of the most signi cant issues limiting the long-term use of catalysts for reactions such as MOR, ethanol oxidation and formic acid oxidation, where CO intermediates form 2,3 . Pt is the most active MOR catalyst, however CO ads intermediates bind strongly to poison the Pt sites, thus preventing access of methanol to these active sites 4 . CO poisoning occurs by the formation of CO ads bound on top of three Pt atoms in a triangular arrangement 5,6 . As a consequence, single atom catalysts are a promising target to overcome CO poisoning if Pt atoms can be dispersed on a support without formation of these triangular arrangements of Pt atoms.

Synthetic Strategies to Enhance the Electrocatalytic Properties of Branched Metal Nanoparticles

“…The use of single Pt atoms to decorate branched Ru nanoparticles created resilience to CO poisoning, which led to highly active and stable MOR performance. 4 The single Pt atoms on the Ru nanoparticle structure accelerate a bifunctional mechanism in which any CO ads intermediate that forms on Pt can be stripped by recombination with OH groups adsorbed on adjacent Ru atoms via the Langmuir−Hinshelwood mechanism (Pt−CO−OH−Ru), thus leaving Pt active sites free for further methanol adsorption. The use of single Pt atoms to decorate branched Ru nanoparticles ensures that all Pt atoms are surrounded by Ru (Figure 2e,f), leading to a high steady current density of 2.74 mA cm −2 even after 4 h at 0.6 V (Figure 2g).…”

“…48,49 The slow growth process can also be achieved by slowly injecting the second metal precursor into the solution containing preformed branched nanoparticles. 4,26 With care, the concentration of the second metal precursor can be kept low enough to avoid homogeneous nucleation, for example, by the use of Pt islands to decorate branched Ru nanoparticles by our group, by the slow injection of a Pt precursor using an automatic syringe pump at a rate of 0.2 mL min −1 to form a 2.5 nm Pt island.…”

“…These reactions include the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), methanol oxidation reaction (MOR), and biomass oxidation reaction. 2,4,13,14,16 By critically assessing the latest synthetic innovations and the resultant advances in catalytic perform- ance, this Account illustrates the state-of-the-art branched nanoparticle catalyst design and reveals opportunities for future development.…”

l-Lysine derived fabrication of Cu@Ni core–satellite nanoassemblies as efficient non-Pt catalysts for the methanol oxidation reaction

“…Pt, Pd, Rh) and their alloys primarily exhibit superior intrinsic activity. [5][6][7][8][9] However, the high cost, CO self-poisoning effect, and slow MOR kinetics of PGMs still remain as unsolved dilemmas, hindering their practical applications. 10,11 Great efforts have been devoted to seeking substitutable non-PGM electrocatalysts as efficient anode materials for the MOR.…”

Flow‐Based Synthesis of Gold‐Coated Magnetic Nanoparticles for Magnetoplasmonic Sensing Applications

“…Stepwise colloidal synthesis over hours or days has been the most effective method to achieve gold-coated magnetic nanoparticles, as this approach enables control over nucleation and growth stages separately to achieve coating across the entire sample. [11][12][13][14][15][16] A robust, scalable, and automated method is needed to rapidly coat larger sample sizes. Flow-based synthesis is promising method to achieve scalable and precise nanomaterial production.…”