A novel exsolution technique—twice lasers: rapidly aroused explosive exsolution of nanoparticles to boost electrochemical performance

Abstract

The exsolution of nanoparticles (NPs) on material surfaces exhibits good performance with great potential in the field of catalysis. In this study, a method with twice lasers treatment (TLT) is proposed for the first time to rapidly promote the exsolution of Co NPs to the surface of (La0.7Sr0.3)0.93Ti0.93Co0.07O3 (LSTC) by laser rapid heating (LRH) to enhance the electrochemical performance of the LSTC. The entire process from precursor powder - stable perovskite crystal structure - Co NPs exsolution on the LSTC surface takes only ≈ 36 s by TLT. The Co NPs exsolution was confirmed by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). After TLT, a large number of Co NPs reached 75 particles μm-2 appeared on the surface of LSTC with the onset potential of 1.38 V, the overpotential of 214 mV, and the Tafel slope of 81.14 mV dec-1, showing good catalytic activity and long-term stability. The novel process of using TLT to rapidly induce exsolution of NPs enables the rapid preparation of nanoparticle-decorated perovskite materials with better electrochemical properties, thus enriching exsolution technology and opening a new avenue for surface science research.

Femtosecond laser ultrafast photothermal exsolution

“…Table 1 compares the conventional/emerging exsolution methods and their corresponding advantages and disadvantages with inclusion of some examples. Generally, triggering exsolution needs an external stimulus by either nitrogen quenching [9], microwave irradiation [43], thermal reduction (most conventionally adopted) [44], topotactic ion exchange [45][46][47], topochemical anion exchange [48], water-mediated exsolution [49], thermal shocking [10], plasma/IPL/laser irradiation [11,15,21], electrochemical poling/switching [8,50] or compressive/tensile strains [7], with host matrix dominant by perovskite oxides [44]. Each exsolution technique has its own advantages and disadvantages, while in comparison, many properties of fs laser ablation enable unique exsolution (figure 6) including the whole surface coverage of exsolved materials rather than induce the formation of exsolved nanoparticles, benefiting from ultrafast process; the material-deficiency layer reaches as deep as 10 µm, highly possible to become much deeper by further exploration.…”

“…Jeong et al summarized diverse energy applications of emerging exsolution materials, including solid oxide fuel cells, oxygen reduction/evolution reaction (ORR/OER) catalysts for metal-air batteries and water splitting, gas sensor and reforming catalysts [51]. Such applications should be also suitable for our method in light of the feasibility of fiber laser induced exsolution of perovskite oxides [11]. In comparison, fiber laser needs twice treatment with the 1st round to create defects for triggering exsolution upon the 2nd laser irradiation, whereas our method can realize iron-oxide exsolution in one step and the scan speed is fast (200 mm•s −1 ) enough to ensure large-scale (cm 2 order) interfacial exsolution for practical applications.…”

“…ion diffusion, reduction, particle growth [1]), potentially to be used as functional interfaces for catalytic and energy applications [2]. Exsolution is often triggered by furnace annealing/sintering in a reductive gas [3][4][5], also available by other methods such as ionic liquid-assisted voltage-driven [6], straindriven [7], electrical-potential-driven [8], quenching treatment [9], thermal shock [10], twice fiber laser treatment [11]), ion irradiation [12], plasma [13] irradiation, and intense pulsed light (IPL) momentary photothermal (>1800 • C within 20 ms [14,15]) treatment. New pathways for exsolution have been opened by non-contact high-energy light/beam irradiation.…”

New trends in nanoparticle exsolution

“…The perovskite with laserinduced Co exsolution exhibited stable electrocatalytic activity for the oxygen evolution reaction (OER), highlighting the potential benefits of this treatment in the functionalization of perovskite oxide electrocatalysts. 112 f. Ion irradiation alloy exsolution. One of the latest breakthroughs in the field of exsolution has been the work by Wang et al on the fabrication of exsolved alloy nanoparticles using ion irradiation.…”

“…Laser-induced exsolution was demonstrated on (La 0.7 Sr 0.3 ) 0.93 Ti 0.93 Co 0.07 O 3 to obtain metallic Co nanocatalysts. 112 This method applied a two-laser (200 W power) treatment to exsolve nanoparticles in a fast manner, achieving nanoparticle dispersions of about 75 particles per μm 2 after just 36 s of treatment. The perovskite with laser-induced Co exsolution exhibited stable electrocatalytic activity for the oxygen evolution reaction (OER), highlighting the potential benefits of this treatment in the functionalization of perovskite oxide electrocatalysts.…”