Sub-2 nm PtBi alloy nanoparticles on Bi-N-C single-atom catalyst for selective oxidation of glycerol to 1,3-dihydroxyacetone
0 Abstract
Nanoscale metal particle-decorated single-atom catalysts (SACs) have been widely used in the fields of photocatalysis, electrocatalysis and thermal catalysis due to the combination of the advantages of nanoparticles and SACs. Herein, a strategy based on Pt-Bi atomic exchange is proposed for the formation of ultrafine (sub-2 nm) PtBi nanoclusters on single atomic Bi-N-C. The dynamic structural evolution between single atomic Bi-N-C on nitrogen-doped carbon nanosheets and Pt nanoclusters on the reconfiguration of stable PtBi alloy nanoparticles was demonstrated through a spherical aberration-corrected transmission electron microscope, X-ray absorption spectroscopy and density functional theory calculations. By our synthesis strategy, the Bi-N-C sites significantly improve the dispersion of PtBi alloy nanoparticles, resulting in a high turnover frequency of up to 224.4 h-1 and the 1,3-dihydroxyacetone selectivity of 77.4%, 3.5 times higher than that of commercial 5Pt/C. On the other hand, the strong interaction between SAC and nanoparticles enhanced the catalytic stability by preventing leaching of Bi. It opens new avenues toward the rational design of high-performance nanoparticle-SACs, enabled by the in-depth understanding of the interaction between nanoparticles and SACs, which determines the structure of real active sites.
Keywords
INTRODUCTION
As a by-product of the biodiesel production process[1], the high-value utilization of glycerol (less than €0.5 per kg) is essential to improve the yield and competitiveness of biodiesel. Glycerol selective oxidation can produce glyceraldehyde (GLYD), glyceric acid (GA), 1,3-dihydroxyacetone (DHA) and other products of C2 and C1[2]. Among them, DHA (~€132 per kg) can be used as a pharmaceutical intermediate and cosmetic addition[3], which has high economic value and market demand. Au[4,5], Pt[6,7], and Pd[8,9] are commonly used as heterogeneous catalysts for glycerol oxidation. Additionally, other non-noble metal catalysts, coupled with glycerol oxidation and CO2 electroreduction, promote the formation of C1 oxygenated products[10]. Au catalysts usually require strong alkaline conditions to display high catalytic activity for glycerol conversion[5,11]. Under base-free conditions, Pt has a high catalytic performance in the oxidation of glycerol to GA and GLYD[12]. However, improving the DHA selectivity of Pt catalyst in base-free oxidation of glycerol is still a great challenge.
Kimura et al. have modified Pt catalysts with Pb, Te, Se, Bi and Sb as additives, and found that doping Bi on Pt/C catalyst could increase the yield of DHA from 4% to 20%[13]. To date, the Bi-promoted catalysts have been regarded as one of the most effective ones for the selective oxidation of glycerol to produce DHA[7,14,15]. Several theories have been proposed to explain the promotion effect of Bi on secondary hydroxyl oxidation of noble metal nanoparticles (NPs), including inhibition of excessive oxidation of noble metals[9,13], and geometric blocking effect[9,13,16]. Bi is usually introduced into the catalyst in the form of alloys[17,18], NPs[19], or oxides[13,20]. Ning et al. synthesized Pt-Bi catalysts in situ by directly adding bismuth salt or bismuth oxide to the glycerol reaction solution[16]. It was revealed that the strong chelation of the reaction product GA with Bi3+ promoted the leaching of Bi from Pt-Bi catalysts, thus leading to unsatisfactory stability. Xiao et al. used density functional theory (DFT) to study the mechanism of Pt-Bi active sites in detail, and further confirmed that bismuth, as an ad-atom adjacent to Pt, rather than located in the interior of Pt, is the necessary condition for promoting DHA formation[21]. In order to reduce the coverage of Bi on Pt NPs, the adjacent Pt-Bi active sites are preferred.
Metal NPs modified single-atom catalysts (SACs), named NP-SACs[22], combine the advantages of both to enhance catalytic performance through four pathways: (1) Synergistic enhancement. NPs may provide alternative active sites for the adsorption and activation of a substrate, which is difficult at the SA sites[23]; (2) Tandem enhancement. SA sites alone are active only for some reactions, while NPs provide sites for others[24]; (3) Reinforcing enhancement. NPs can help adjust the geometric and electronic structure of the SA sites to optimize substrate adsorption/activation, thereby improving catalytic performance[25]; (4) Parallel enhancement. NPs catalyze one or more reactions that SA sites cannot catalyze, meeting the requirements of multifunctional catalysis. He et al. studied the effect of Me-N-C SACs (Me=Co, Fe, Ni)-wrapped carbon nanotubes as support of Pt NPs on the base-free oxidation of glycerol[26]. Me-N-C not only enhanced the dispersion of Pt, but also promoted the activation of oxygen, which significantly increased the glycerol conversion and turnover frequency (TOF). However, the primary hydroxyl oxidation of glycerol was dominant, and the DHA selectivity was much lower than GLYD. Huang et al. used nitrogen-doped carbon to load Bi single atoms[27]. After loading Pt NPs, the adjacent Pt-Bi active sites can be generated, showing good glycerol oxidation activity and DHA selectivity. They suggested that the cooperation of Pt NPs with the adjacent Bi-N-C sites on the support promotes the oxidation of the secondary hydroxyl group. However, it is unclear if the coordination of single-atomic Bi with nitrogen may suppress the leaching of Bi. In addition, it is still understudied whether the interaction between SAs and NPs reconfigures the active sites due to the high activity of SAs and NPs in the heteronuclear NP-SACs. Liu et al. observed that, when applying reduction potential, the isolated Cu atoms migrated from the vertex position of the Au NP to the stable (100) plane of the first atomic layer of Au[28]. DFT calculations showed that surface atomic migration significantly regulated the electronic structure of Au, thereby improving the catalytic performance. Therefore, exploring the dynamic surface structure evolution between SA and NPs at the atomic level is important to identify the real active site that determines the catalytic performance.
In this work, we focus on the interaction between single atomic Bi-N-C sites and Pt clusters, which may play a role in reconfiguration of catalytic active sites. A synthesis strategy of PtBi alloy nanoclusters was proposed based on surface atomic exchange between single atomic Bi-N-C sites on nitrogen-doped carbon nanosheets and Pt NPs by impregnation-reduction[29,30]. It was uncovered that when reduced in H2, the Pt clusters underwent an atomic exchange with Bi-N-C sites to form stable Pt-Bi alloy NPs driven by thermodynamics. Thanks to the kinetic barrier caused by the strong Bi−N bonding, homogeneous and ultrafine (sub-2 nm) PtBi alloy NPs were generated, offering maximally exposed Pt atoms and stable Pt-Bi adjacency. The catalytic performance in the glycerol oxidation reaction was systematically studied to demonstrate the improved DHA yield and catalyst stability.
EXPERIMENTAL
Materials
Bismuth powder (99.99%), bismuth nitrate pentahydrate (99%), melamine (99%), ammonium chloride (GR, 99.8%), Pt/C catalyst and chloroplatinic acid (ACS, Pt 37.5% min) are purchased from Aladdin. Glycerin (AR) and glucose (99%) are purchased from Sinopharm Chemical Reagent Co., LTD. DHA (99%), GLYD (90%) and potassium hydroxide (90%) are purchased from McLean. GA (20% aqueous solution) is purchased from TCI Reagent Co., LTD. All the reagents were used as received.
Preparation of BixNC-t
A certain amount of bismuth powder, 5 g melamine, 1 g glucose and 5 g ammonium chloride were mixed by ball milling, and then the mixture was put into a tubular furnace. It was heated at 10 °C/min ramp to
Preparation of 5Pt/BixNC-t(H2)
First, 300 mg BixNC-t and 300 mL deionized water were sonicated in a beaker for 20 min to obtain a homogeneous suspension. Then, 11 mL H2PtCl6 aqueous solution (1.45 mg/mL) was added dropwise to the suspension with stirring. After an additional 15 min sonication and continuous stirring for 30 min at room temperature, KOH aqueous solution (0.5 mol/L) was added to adjust pH to 9.5. The resulting homogeneous suspension was heated at 80 °C for 1.5 h. After filtering and drying in vacuum at
Preparation of 2Bi-5Pt/NC-900(H2)
First, 300 mg Bi0NC-900, 11mg Bi(NO3)3·5H2O, and 300 mL deionized water were sonicated for 20 min to obtain a homogeneous suspension. Then, 11 mL H2PtCl6 aqueous solution (1.45 mg/mL) was added dropwise to the suspension with stirring. After an additional 15 min sonication and continuous stirring for 30 min at room temperature, KOH aqueous solution (0.5 mol/L) was added to adjust pH to 9.5. The resulting homogeneous suspension was heated at 80 °C for 1.5 h. After filtering and drying in vacuum at
Catalyst characterizations
The Pt and Bi contents in the catalysts were measured by an Agilent 5110 inductively coupled plasma emission spectrometer (ICP-OES). PANalytical X’Pert Powder diffractometer (XRD), equipped with a Cu
The Pt dispersion of the catalysts was determined by CO stripping, conducted at room temperature in a cell connected to an electrochemical workstation (CHI 660D). A glass carbon electrode served as the working electrode, platinum wire acted as the counter electrode, and a Hg/Hg2SO4 electrode was used as the reference electrode. A volume of 10 μL catalyst ink (2 mg/mL) was coated on the glass carbon electrode and dried. The electrochemical test was performed in a 0.5 mol/L H2SO4 solution.
Catalytic tests
The thermo-catalytic oxidation reaction of glycerol was carried out in a 25 mL three-neck flask with a reflux, a bubbler and a thermometer. An aqueous solution of glycerol (5 g, 10 wt.%) and 40 mg catalyst were added to the flask, which was then heated to 60 °C at 1,200 rpm. The reaction was initiated by passing a flow of oxygen (150 Ncm3/min) as the ultimate oxidant. After reaction, the oxygen flowmeter and heating device were immediately turned off and the flask was cooled in an ice-water bath to stop the reaction. The products in the reactor were then weighed. After filtration through a polyether sulfone filter head, the products were analyzed using an Agilent high-performance liquid chromatograph (HPLC 1260 Infinity), equipped with a Refractive Index Detector (RID), an ultraviolet (UV) detector and Bio-Rad Aminex HPX-87H Column. A 0.005 mol/L H2SO4 solution was used as the mobile phase. The detection conditions are as follows: the flow rate of the mobile phase is 0.5 mL/min, the column temperature is 65 °C, the wavelength of the UV detector is 210 nm, and the analysis time is 20 min. Quantitative analysis was carried out by external standard method.
Density functional theory calculation method
The periodic DFT executed in the Vienna ab initio simulation package (VASP 6) is applied for all the calculations[31-34]. Exchange and correlation are treated within the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA)[35]. The valence electrons are described by a plane wave basis set with the kinetic cutoff energy of 400 eV, and the core electrons are replaced by the projector augmented wave (PAW) pseudopotentials[31,36]. To improve computational efficiency, a 3 × 3 × 1 Monkhorst-Pack
The adsorption energy (ΔE) is calculated using
in which Etotal is the total energy of the whole system upon adsorption, Ecluster is the energy of the metal cluster, and Eslab is the energy of the nitrogen-doped graphene.
RESULTS AND DISCUSSION
DFT calculation for the PtBi alloy formation
DFT calculation was carried out to study the interaction between single atomic Bi-N4 modified nitrogen-doped carbon nanosheets and Pt clusters. The binding energies of Pt and Bi atoms with a N4 vacancy were compared. As shown in Figure 1A and B, the binding energy of a Pt atom with N4 is 2.6 times that of Bi, indicating that the formation of Pt-N4 is preferred over Bi-N4. The strong bonding was also observed for a Pt4 cluster on the N4 vacancy [Figure 1C]. It suggests that a reconfiguration may occur driven by thermodynamics when contacting Bi-N4 SACs with Pt. To verify this, the adsorption of a Pt4 cluster on
Figure 1. The optimized geometries and binding energies of (A) a single atomic Pt-N4 site, (B) a single atomic Bi-N4 site, and (C) a Pt4 cluster on N4 vacancy; (D-G) Four geometries and corresponding adsorption energies of a Pt4 cluster on a single atomic Bi-N4 site. The corresponding side views can be found in Supplementary Figure 2.
Formation of sub-2 nm PtBi NPs
The synthesis of PtBi alloy NPs on Bi-N-C is schematically shown in Figure 2. Firstly, single atomic Bi-N-C-modified nitrogen-doped carbon nanosheets are prepared by a one-step pyrolysis. Glucose, melamine, ammonium chloride and bismuth powder are mixed evenly by ball milling and calcined under inert atmosphere. Among them, glucose and melamine are carbon and nitrogen sources, respectively. Ammonium chloride assists the transportation of metal by converting Bi to bismuth chloride, whose diffusion contributes to the capture of Bi at the defects of nitrogen-doped carbon nanosheets[42]. After the impregnation of K2PtCl6, the reduction at 250 °C under H2 atmosphere enables the atomic exchange between Pt and single atomic Bi-N-C to generate the PtBi alloy NPs. Thanks to the strong binding between NPs and the N-containing vacant defects, the agglomeration among NPs is greatly suppressed, allowing for the formation of highly dispersed PtBi NPs.
Figure 2. Schematic diagram of the synthesis of PtBi alloy nanoclusters on Bi-N-C.
A series of nitrogen-doped carbon nanosheets with different Bi addition amounts were obtained by pyrolysis at 800, 900 and 1,000 °C [Supplementary Table 1]. With the same Bi dosage, the Bi content decreases with the increase of temperature because of the increasing bismuth chloride evaporation. The pyrolysis at 800 and 900 °C resulted in considerable Bi contents in the products, which are suitable for the further preparation of PtBi catalysts for glycerol oxidation. The Zeta potential measurements indicate that the points of zero charge are dependent on the pyrolysis temperature [Supplementary Figure 3]. BixNC-800 displays a point of zero charge between pH = 4.5~6.0, while BixNC-900 and BixNC-1000 demonstrate this characteristic between pH = 7.0~8.5. Since the subsequent deposition of Pt NPs requires a weakly alkaline condition for the adsorption of PtCl62-, 900 °C was selected as the optimal pyrolysis temperature for carbon nanosheet preparation. XRD analysis [Supplementary Figure 4] displayed that the condensed phases of Bi, such as Bi2O3 and Bi, are almost invisible in the XRD patterns of BixNC-900 and BixNC-1000, indicating the formation of highly dispersed/atomic Bi species. The N2 adsorption-desorption measurements
The TEM images of BixNC-900 show the morphology of thin-layer carbon nanosheets, with the absence of metal NPs, which is consistent with the XRD result [Supplementary Figure 7]. A large number of uniformly dispersed Bi single atoms can be seen in AC-TEM images [Figure 3A], demonstrating the generation of
Figure 3. (A) AC-TEM image; (B) AC-HAADF-STEM image and corresponding EDS element maps of Bi50NC-900; TEM images and histograms of NP diameters of (C) 5Pt/Bi0NC-900(H2), (D) 5Pt/Bi30NC-900(H2), (E) 5Pt/Bi40NC-900(H2), (F) 5Pt/Bi50NC-900(H2); (G) Cyclic voltammetry curves of CO electro-oxidation over 5Pt/BixNC-900(H2). AC-TEM: Aberration-corrected transmission electron microscope; AC-HAADF-STEM: aberration-corrected high-angle-annular-dark-field scanning transmission electron microscopy.
Metal contents, BET specific surface areas, average particle sizes and dispersions of Pt NPs in 5Pt/BixNC-900(H2)
| Catalysts | Bia (wt.%) | Ptb (wt.%) | SBET (m2/g) | dTEM (nm) | DTEMc (%) | DCOd (%) |
| 5Pt/Bi0NC-900(H2) | - | 3.73 | 160.3 | 1.7 ± 0.4 | 65.4 | 69.1 |
| 5Pt/Bi30NC-900(H2) | 1.32 | 4.43 | 149.5 | 1.8 ± 0.4 | 61.5 | 59.5 |
| 5Pt/Bi40NC-900(H2) | 1.57 | 4.08 | 130.8 | 1.6 ± 0.3 | 69.0 | 75.4 |
| 5Pt/Bi50NC-900(H2) | 1.98 | 3.91 | 161.3 | 1.3 ± 0.3 | 89.1 | 77.0 |
| 5Pt/Bi60NC-900(H2) | 1.81 | 3.99 | 175.9 | 1.9 ± 0.3 | 58.9 | 54.3 |
The composition of supported ultrafine particles was further explored by AC-TEM. Figure 4A shows the STEM image of 5Pt/Bi50NC-900(H2) in the dark field. The energy-dispersive X-ray spectroscopy (EDS) line scanning of one of the uniformly distributed Pt NPs shows strong elemental signals of Pt and Bi [Figure 4B]. Furthermore, the EDS mapping indicates the high overlap of the appearance of Pt and Bi, suggesting the enrichment of Bi from single atomic Bi-N-C support around Pt NPs. The reconstruction of single atomic Bi-N-C was further ascertained by the microscopical analysis on AC-HAADF-STEM. As shown in Figure 4C-E, NPs on graphene sheets decorated by single atomic Bi-N-C are observed. The EDS mapping of the particulates clearly shows that the individual particles are composed of Pt and Bi, which proves the formation of PtBi alloy nanoclusters. The lattice spacings in Figure 4D and E display the Pt (111) and Pt (200) planes as highlighted. It should be noted that the measured spacings slightly deviate from the standard values of Pt (111) (0.227 nm) and Pt (200) (0.196 nm) planes, probably due to the alloying of Bi. Those results are consistent with the aforementioned DFT calculations; namely, the formation of PtBi alloy is thermodynamically favorable when Pt is deposited on single atomic Bi-N-C.
Figure 4. (A) STEM image; (B) EDS line scanning of a single particle; (C) AC-HAADF-STEM image and corresponding EDS spectrum and EDS element maps; (D-E) AC-HAADF-STEM image and EDS element maps of 5Pt/Bi50NC-900(H2). STEM: Scanning transmission electron microscopy; EDS: energy-dispersive X-ray spectroscopy; AC-HAADF-STEM: aberration-corrected high-angle-annular-dark-field scanning transmission electron microscopy.
The chemical valences of Pt and Bi of BixNC-900 and 5Pt/BixNC-900(H2) were analyzed by XPS. As shown in Figure 5A, the Bi 4f binding energy of Bi50NC-900 is between those of elemental Bi (4f5/2: 162.9 eV, 4f7/2: 157.6 eV)[18,49] and Bi2O3(4f5/2: 164.7 eV, 4f7/2: 159.4 eV)[50], indicating the valence of Bi single atoms of between 0 and +3[51]. After loading Pt, in addition to the peaks of Bi single atoms, two peaks appear at 158.1 and 163.4 eV, slightly higher than the characteristic peaks of Bi(0), attributed to the formation of Pt−Bi bonds in the PtBi alloy. The Pt 4f XPS spectra are deconvoluted to Pt0, Pt2+ and Pt4+ [Figure 5B][52-55], with relative contents of 66.4%, 17.7%, 15.9% for 5Pt/Bi0NC-900(H2), and 59.7%, 29.2%, 11.1% for 5Pt/Bi50NC-900(H2), respectively. The Pt04f5/2 and Pt04f7/2 binding energies of 5Pt/Bi50NC-900(H2) are located at 75.2 and 71.9 eV, respectively, which have a negligible shift of 0.1 eV compared with the case in the absence of Bi in support [5Pt/Bi0NC-900(H2)], indicating the weak electronic interaction between Pt and Bi. It should be noted that the binding energy of Pt(0) of 5Pt/Bi50NC-900(H2) is considerably higher than that of elemental Pt (about 71.1eV[55]), which may originate from the size effect[56,57] or the incomplete oxidation state of Pt caused by the high activity of Pt on the surface of ultrafine particles.
Figure 5. (A) Bi 4f XPS spectra of Bi50NC-900 and 5Pt/Bi50NC-900(H2); (B) Pt 4f XPS spectra of 5Pt/Bi0NC-900(H2) and 5Pt/Bi50NC-900(H2); (C) Bi L3-edge XANES; (D) Fourier-transformed EXAFS in the R-space of Bi; (E) Pt L3-edge XANES; and (F) Fourier-transformed EXAFS in the R-space of Pt of Bi50NC-900, 5Pt/Bi50NC-900(H2) and the reference sample. XPS: X-ray photoelectron spectroscopy; XANES: X-ray absorption near edge structure; EXAFS: extended X-ray absorption fine structure.
The electron structure and coordination environment of Pt and Bi in Bi50NC-900 and 5Pt/Bi50NC-900(H2) were further analyzed by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). As shown in the Bi-L3 XANES spectrum [Figure 5C], the near-side absorption energy and white line peak of Bi50NC-900 are between Bi foil and Bi2O3, revealing its typical electronic structure as Bi (0 < δ < 3)[50,51], which is consistent with the results of XPS. The R-space EXAFS spectra of
Catalytic oxidation of glycerol
The synthesis temperature of BixNC-t has a great impact on the activity of glycerol oxidation on 5Pt/BixNC-t(H2) [Supplementary Figure 11]. Notably, 5Pt/BixNC-900(H2) shows significantly higher activity and the DHA selectivity than the catalysts synthesized at 800 and 1,000 °C, indicating the importance of achieving highly dispersive PtBi NPs. It should be noted that the activity of 5Pt/BixNC-900(H2) is considerably higher than that of commercial 5Pt/C with a Pt NP diameter of about 3 nm [Supplementary Figure 11]. As shown in the time course in Figure 6A, all the 5Pt/BixNC-900(H2) catalysts display higher conversion of glycerol at 10 h even without Bi on support, indicating the high activity of ultrasmall Pt NPs (1.7 nm)[7,59]. The highest pseudo-first-order reaction rate constant is achieved on 5Pt/Bi40NC-900(H2) and 5Pt/Bi50NC-900(H2), evidencing the importance of Bi incorporation with Pt NPs [Supplementary Figure 12]. The TOF of
Figure 6. (A) Time courses and (B) selectivity-conversion relationships of glycerol oxidation over 5Pt/BixNC-900(H2) and commercial 5Pt/C catalysts. (Reaction conditions: 5 g 10 wt.% glycerol solution, 40 mg catalyst, glycerol/Pt molar ratio = 670, O2 flow at 150
The incorporation of Bi significantly elevated the selectivity of DHA. As shown in Figure 6B, despite the higher activity of 5Pt/Bi0NC-900(H2) than commercial Pt/C, their dependences of DHA selectivity on glycerol conversion are similar. However, all the Bi-containing catalysts display high DHA selectivity at least three times and correspondingly reduced selectivity toward GLYD and GA. The DHA selectivity of
To evaluate the stability, 5Pt/Bi50NC-900(H2) was reused for five cycles. After the reaction for 6h, the catalyst is filtered and separated from the reaction liquid, and then, the recovered catalyst is washed and dried in vacuum. To remove GA adsorbed on the catalyst surface[60-62], the recovered catalyst was annealed at 250 °C in Ar atmosphere for 3h before the next glycerol oxidation reaction. As shown in Figure 7, in the second cycle reaction, the glycerol conversion increases by 4.6%, and the DHA selectivity decreases slightly by 5.0%. The glycerol conversion was almost unchanged after five cycles and a slight decrease of 4.8% was observed in the DHA selectivity, which may be due to the weak agglomeration of PtBi NPs caused by repeated annealing at 250 °C[63,64]. The TEM observation demonstrates that the average particle size increased to
Figure 7. Recycling experiments of glycerol oxidation over 5Pt/Bi50NC-900(H2) and 2Bi-5Pt/NC-900(H2). (Reaction conditions: 5 g
The composition, Pt dispersion of 5Pt/Bi50NC-900(H2) and 2Bi-5Pt/NC-900(H2) and the contents of Bi in reaction liquid measured by ICP-OES
| Catalysts | Bia (wt.%) | Ptb (wt.%) | dTEM (nm) | DTEMc (%) | DCOd (%) | Bi content in the reaction liquid after 6 h (mg/L) |
| 5Pt/Bi50NC-900(H2) | 1.98 | 3.91 | 1.3 ± 0.3 | 89.1 | 77.0 | 0.0017 |
| 2Bi-5Pt/NC-900(H2) | 2.28 | 3.53 | 2.0 ± 0.4 | 57.8 | 56.1 | 0.0359 |
CONCLUSIONS
We revealed the surface reconstruction phenomenon between single atomic Bi-N-C and Pt nanoclusters through spherical aberration transmission electron microscopy, X-ray absorption spectroscopy and DFT theoretical calculations. Pt-Bi atomic exchange can easily occur when the Bi-N-C single atomic sites interact with Pt driven by thermodynamics due to the stronger binding between Pt and N. Therefore, the original adjacent Pt/Bi-N-C will be transformed into more stable Pt-Bi alloy NPs. At the same time, the kinetic barrier caused by the strong Bi−N bonding which is undestroyed during Pt-Bi atomic exchange is conducive to the uniform dispersion of PtBi alloy nanoclusters. Ultrafine (sub-2 nm) PtBi alloy nanoclusters significantly improve the secondary hydroxyl oxidation of glycerol with TOF of 224.4 h-1 and 3.5 times higher DHA selectivity than commercial 5Pt/C. It should be noted that the strong interaction between PtBi alloy nanoclusters and Bi-N-C significantly suppresses the leaching of Bi, offering improved recyclability. By comparing with the counterpart catalyst synthesized by co-reduction of Pt and Bi on Bi0NC-900 carbon nanosheets, it is confirmed that the two-step synthesis strategy plays an important role in the synthesis of ultrafine sub-2 nm, high-performance and stable NP-SACs.
DECLARATIONS
Authors’ contributions
Writing - original draft, visualization, investigation, formal analysis, data curation: Tang, T.
Methodology, visualization, validation: Zhang, H.
Writing - review and editing, supervision: Wang, H. F.; Wang, H.; Cao, Y.
Software, visualization, data curation, funding acquisition: Zhou, L.
Conceptualization, writing - review and editing, supervision, resources, funding acquisition: Yu, H.
Availability of data and materials
The data can be found in the Supplementary Materials. More details are available from the corresponding author upon reasonable request.
Financial support and sponsorship
This work was supported by the National Natural Science Foundation of China (Nos. 22272056, 22078106, 22202048), Natural Science Foundation of Guangdong Province (2024B1515040016), and Guizhou Provincial Science and Technology Plan Project Natural Science Key Project (ZK[2022] 028).
Conflicts of interest
All authors declared that there are no conflicts of interest.
Ethical approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Copyright
© The Author(s) 2025.
Supplementary Materials
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Tang, T.; Zhang, H.; Wang, H. F.; Wang, H.; Cao, Y.; Zhou, L.; Yu, H. Sub-2 nm PtBi alloy nanoparticles on Bi-N-C single-atom catalyst for selective oxidation of glycerol to 1,3-dihydroxyacetone. Chem. Synth. 2025, 5, 28. http://dx.doi.org/10.20517/cs.2024.84
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