Next Article in Journal
Green Aerogels for Atmospheric Water Harvesting: A PRISMA-Guided Systematic Review of Bio-Derived Materials and Pathways to 2035
Previous Article in Journal
Site-Specific Recruitment, Localization of Ionized Monomer to Macromolecular Crowded Droplet Compartments Can Lead to Catalytic Coacervates for Photo-RAFT in Dilution
Previous Article in Special Issue
Adsorption of Bisphenol A onto β-Cyclodextrin–Based Nanosponges and Innovative Supercritical Green Regeneration of the Sustainable Adsorbent
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Polymers
Volume 18
Issue 1
10.3390/polym18010105
polymers-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Recycling Waste Plastics from Urban Landscapes to Porous Carbon for Clean Energy Storage

by
Lin Ma
1,* and
Xuecheng Chen
2,*
1
Ningbo Tech University, No. 1, Xuefu Rd., Yinzhou District, Ningbo 315211, China
2
Department of Nanomaterials Physicochemistry, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology in Szczecin, Piastow 45, 70-310 Szczecin, Poland
*
Authors to whom correspondence should be addressed.
Polymers 2026, 18(1), 105; https://doi.org/10.3390/polym18010105 (registering DOI)
Submission received: 18 November 2025 / Revised: 14 December 2025 / Accepted: 23 December 2025 / Published: 30 December 2025
(This article belongs to the Collection Polymer Applications in Environmental Science)
Browse Figures
Versions Notes

Abstract

With the rapid increase in plastic consumption worldwide, the resulting plastic waste has had a significant negative impact on the environment. Converting waste plastics into carbon nanosheets (CNSs) has emerged as one of the most promising methods for both waste management and the synthesis of high-performance carbon materials. The incorporation of palladium (Pd) nanoparticles onto CNSs can notably enhance their hydrogen storage capacity. To address the environmental pressures posed by waste plastic, we propose a strategy for synthesizing CNSs from waste polypropylene (PP). Hydrogen uptake Meas. at room temperature show that Pd-supported CNSs exhibit the highest hydrogen adsorption capacity of 0.43 wt% at 298 K and 41 bar. These findings confirm the critical influence of Pd content, particle size, and carbon structure on hydrogen storage performance under varying pressures. This study provides a new pathway for the valuable reutilization of waste plastics through functional energy conversion. This strategy not only aims to reduce plastic pollution but also creates a sustainable method for green energy storage.

1. Introduction

The widespread use of plastic materials in urban landscape construction has become commonplace, yet it simultaneously poses severe challenges for municipal solid waste management. The environmental impact of plastic waste is profound: according to statistics, recycling one ton of plastic can save approximately one ton of petroleum, prevent the incineration of an equivalent amount of waste, and indirectly reduce carbon dioxide emissions by about five tons [1]. However, the global generation of municipal solid waste continues to rise and is projected to increase by 70% between 2020 and 2050, reaching around 3.4 billion tons annually [2]. This rapid growth underscores the urgent need for efficient waste management strategies, particularly for plastic materials that are ubiquitous in modern urban infrastructure. Driven by both the principles of the circular economy and sustainable urban planning, public demand for architectural landscapes is steadily increasing, and the application of landscape design in contemporary cities is becoming ever more extensive [3]. Beyond traditional decorative features and public amenities, plastics are increasingly being integrated into infrastructural elements such as roads, seating, fences, and modular educational or community buildings [4]. Notably, innovative applications of plastics are also opening new pathways for sustainable community development (Table 1), concretely illustrating how plastics can enhance community sustainability through innovative design. In light of the waste plastics produced from this polymer, treating this massive plastic waste is a great challenge. The present recycling methods, such as physical and chemical recycling methods, have some drawbacks. The drawbacks of physical recycling for waste plastics largely include susceptibility to contamination during processing and the low quality of recycled output, often resulting in downcycling, which hinders true closed-loop recycling. Furthermore, physical recycling requires rigorous sorting and cleaning of mixed or contaminated plastics, leading to significantly high costs. While chemical recycling has the potential to break plastics down into monomers or raw materials for high-quality regeneration, it currently faces challenges such as high energy consumption, underdeveloped technology, and poor economic viability. Many chemical recycling processes also produce harmful by-products, and large-scale industrial application remains problematic. Both methods struggle to completely replace virgin plastic production [5]. As shown in Table 1, plastics are categorized within urban landscapes to link their material properties with sustainable design principles [6,7,8]. Among various landscape plastics, polypropylene (PP) is the most commonly used due to its light weight, excellent mechanical properties, ease of processing, and cost-effectiveness [9]. Conversion of waste PP into carbon products is a promising endeavor due to the high carbon content of PP. Significant progress has been made in this field, with waste plastics selectively carbonized into carbon nanosheets, carbon spheres, and carbon nanotubes [10,11,12,13]. However, these methods often demonstrate poor catalytic kinetics, which significantly diminishes catalytic efficiency and carbon yield.
Hydrogen is a clean energy carrier, yet its storage remains a major challenge for commercialization. Porous carbons are promising materials due to their high surface area, stability, and low cost. Research shows that dispersing metal nanoparticles like platinum, nickel, and particularly palladium on carbon supports significantly enhances hydrogen uptake via the spillover effect, where hydrogen molecules dissociate on the metal and migrate to the carbon surface [14,15,16]. For example, Pd-loaded carbon nanomaterials have shown a fourfold increase in capacity compared to pure carbon [7,8,9,10,11,12,13,14,15,16]. Optimizing metal loading and nanoparticle size is critical for performance [17,18,19,20]. However, most carbon supports are derived from synthetic precursors, conflicting with sustainability goals. Notably, waste polymer-derived carbons remain under-explored for hydrogen storage, despite their potential for sustainable waste-to-energy applications. Based on the description above, combining hydrogen storage with waste plastic recycling would represent a significant step toward a greener environment and sustainable energy storage.
In this study, waste PP was catalytically carbonized into carbon nanosheets using ferrocene and sulfur as a combined catalyst. The subsequent activation process resulted in a high surface area of porous carbon nanosheets (PCNS). A Pd loading content of 57 wt% and a large Pd particle size of 17 nm were achieved during the Pd loading process. The investigation of H2 uptake demonstrated that the Pd-supported PCNSs exhibit a hydrogen adsorption capacity as high as 0.43 wt%, significantly exceeding that of PCNS, which is 0.14 wt%. These results confirm the critical roles of Pd content, Pd particle size, and carbon in enhancing hydrogen storage capacity under various pressures.

2. Experimental Section

2.1. Synthesis of PCNS from Waste PP

Waste PP was collected and purified using ethanol and distilled water multiple times. In a typical synthesis, 1.5 g of purified waste PP was introduced into an autoclave. Subsequently, 0.5 g of ferrocene and 0.5 g of sulfur (Sigma-aldrich) were added, followed by tightly sealing the autoclave. The autoclave was then placed in a muffle furnace at 700 °C for 1.5 h. Afterward, carbon nanosheets (CNS) were obtained through purification with 10 wt% hydrochloric acid (HCl, STANLAB, Lublin, Poland) and water [21]. To create a porous structure, the resulting CNS was impregnated with potassium hydroxide (KOH, Eurochem, Tarnow, Poland) at a mass ratio of mKOH/mCNS = 4 in an ethanol solution, followed by sonication for 20 min and evaporation at 75 °C. The mixture was then heated at 800 °C for 1 h in a tube furnace with a nitrogen (N2, SIAD, 41-700 Ruda Śląska, Poland) flow rate of 100 mL min−1. After refluxing with 10 wt% HCl and washing with distilled water, the resulting AC material was designated as PCNS.

2.2. Preparation of Pd-Supported Porous Carbon Nanosheets (PCNS@Pd)

To load Pd nanoparticles (NPs) onto the resulting PCNS, 30 mg of palladium nitrate (Pd(NO3)2·H2O) was dissolved in 100 mL of ethanol under sonication. Subsequently, 30 mg of PCNS was added to the solution. The mixture was then transferred to a flask and refluxed at 100 °C for 12 h. The resulting sample was purified with distilled water several times and then dried at 80 °C in a vacuum overnight, designated as Pd@PCNS-1. Next, 30 mg of palladium nitrate (Pd(NO3)2·H2O) was added to the ethanol solution (100 mL), followed by the addition of 30 mg of Pd@PCNS-1. After refluxing at 100 °C for 12 h, the resulting sample was designated as Pd@PCNS-2. Finally, 30 mg of palladium nitrate (Pd(NO3)2·H2O) was added to the ethanol solution (100 mL), followed by the addition of 30 mg of Pd@PCNS-2. After refluxing at 100 °C for 12 h, the resulting sample was designated as Pd@PCNS-3 [18].

2.3. Characterization

The microstructure of the samples was investigated using a transmission electron microscope (TEM, FEI Tecnai F30, Thermo Fisher Scientific, Waltham, MA, USA). X-ray diffraction (XRD) analysis was performed with a Philips diffractometer utilizing Cu Kα radiation. Nitrogen adsorption–desorption isotherms were obtained at 77 K using a Quantachrome Autosorb-1C-MS instrument. The specific surface area (SSA) and pore size distribution were calculated using the Brunauer–Emmett–Teller (BET) method and quenched solid density functional theory (QSDFT), respectively. Raman spectroscopy was conducted with a Renishaw InVia Raman microscope (excitation beam wavelength: 785 nm) to characterize the vibrational properties of the samples. The weight content of palladium (Pd) particles in the composites was analyzed using thermogravimetric analysis (TGA) in an air atmosphere with a heating rate of 10 °C min−1, employing a DTA-Q600 SDT TA instrument.

3. Results and Discussion

As depicted in the TEM image, PCNS exhibits a typical sheet-like morphology with a rough surface (Figure 1b1,b2). The Pd loading results in a homogeneous distribution of small Pd NPs with diameters ranging from 10 to 16 nm on the surface of the PCNS (Figure 1c1–e2). In Figure 1d1,d2, the PCNS@Pd-2 sample displays larger Pd NPs (17 nm) along with partially uncoated carbon surfaces, likely due to the growth of Pd particles during the second reflux. However, as shown in Figure 1e1,e2, the third reflux resulted in the PCNS@Pd-3 sample, which exhibits a distinct morphology with a network structure, indicating the cladding and overlap of loaded Pd NPs on the surface of the PCNS. No CNSs are visible. These results demonstrate that the coated area and particle size of Pd increase with the number of reflux cycles.
N2 adsorption–desorption isotherms of all samples were performed to characterize their textural properties (Figure 2a). The CNS exhibits a type II isotherm, indicating unrestricted monolayer-multilayer adsorption at high relative pressure (P/P0), which suggests a limited number of pores in the carbon matrix. In contrast, PCNS displays a typical I/IV isotherm with a hysteresis loop. An apparent micropore filling is observed at very low relative pressure (P/P0 < 0.01), attributed to the abundance of micropores. The steep uptake at moderate relative pressures (0.3 < P/P0 < 0.9) with a type-H4 hysteresis loop is indicative of adsorption metastability leading to capillary condensation, suggesting the presence of numerous mesopores [22]. At high relative pressures (P/P0 > 0.9), a significant increase in adsorption indicates unlimited multilayer adsorption in macropores. PCNS possess an ultrahigh surface area of 3200 m2 g−1 and a substantial pore volume of 3.7 cm3 g−1. Following Pd loading, the samples exhibit a decreased N2 adsorption value, indicating that most of the pores in the PCNS have been occupied by the Pd nanoparticles, which is consistent with TEM observations. As shown in Table 2, in comparison to the PCNS, the samples after Pd loading demonstrate a significantly reduced surface area (535~1083 m2 g−1) and a smaller pore volume (<1 cm3 g−1). The pore size distribution for the samples was estimated using a non-local density functional theory (NLDFT) method, which reveals the presence of micropores (1~2 nm) and mesopores (3~6 nm) in the PCNS (Figure 2b). In contrast, the Pd-loaded samples exhibit fewer micropores and mesopores. The significant difference in pore size distribution between the two can be attributed to the coverage of Pd NPs on the surface of the PCNS.
As shown in Figure 3a, the XRD pattern of CNSs exhibits two broad diffraction peaks at 25° and 45°, corresponding to the (002) and (101) planes of graphitic carbon, respectively. In contrast, the XRD pattern of PCNS shows that these two peaks become broader and weaker, indicating a lower degree of graphitization due to KOH activation. After Pd loading, five well-defined intense peaks at 40°, 46°, 68°, 82°, and 87° appear in the XRD patterns of the Pd-loaded samples, which can be indexed to the (111), (200), (220), (311), and (222) diffraction planes of the palladium phase (JCPDS card no. 50-0681), respectively. This confirms that the Pd nanoparticles were successfully loaded onto the PCNS. Meanwhile, the intensity at lower angles decreased with increasing reflux time due to the strong diffraction peak of Pd nanoparticles. This result is consistent with the findings from TEM and N2 adsorption–desorption isotherm analyses. The Scherrer equation was subsequently applied to calculate the Pd particle sizes (Table 2). The calculated average particle sizes are 13 nm for PCNS@Pd-1, 17 nm for PCNS@Pd-2, and 17 nm for PCNS@Pd-3, which aligns with the TEM analysis of the samples. Raman spectroscopy was conducted to analyze the phase structure of the samples. The D band at approximately 1350 cm−1 represents disordered carbon (sp3), while the G band at approximately 1580 cm−1 indicates ordered graphitic carbon (sp2). As shown in Figure 3b, the relative intensity ratios (IG/ID) for CNS, PCNS, PCNS@Pd-1, PCNS@Pd-2, and PCNS@Pd-3 are 1.31, 0.99, 0.97, 0.97, and 0.96, respectively. This result indicates that PCNS exhibits a significantly lower degree of graphitization compared to CNS, suggesting the introduction of abundant disordered carbon and defects during the activation process. The Pd-loaded samples demonstrate a slightly lower degree of graphitization than the PCNS, implying that the Pd loading process also introduces defects in the composites.
TGA was conducted to evaluate the thermal stability of all samples and to confirm the palladium content in the Pd-loaded PCNS (Figure 4). The first region of slight weight loss, occurring between 100 °C and 400 °C, is attributed to the release of chemisorbed water and oxygen-containing functional groups. The second region, characterized by significant weight loss from 400 °C to 600 °C, is associated with the oxidation of the carbon matrix. The PCNS exhibits noticeable weight loss starting at 300 °C, indicating the presence of numerous defects and functional groups. The residual weight of CNS and PCNS was nearly 0%, indicating the high purity of both CNSs and PCNSs. Notably, the Pd-loaded samples exhibit reduced thermal stability, likely due to the interaction between Pd and carbon, which introduces defects and accelerates the oxidation process of the carbon materials. The third region, above 800 °C for the Pd-loaded samples, is attributed to the decomposition of PdO to Pd. The data indicate that the palladium content in the composites is 49 wt% for PCNS@Pd-1, 57 wt% for PCNS@Pd-2, and 81 wt% for PCNS@Pd-3.
Finally, PCNS and the corresponding Pd-loaded carbon samples were used to evaluate their H2 storage capacities. The H2 adsorption isotherms were measured at 25 °C, under pressures ranging from 0 bar to 41 bar, and are presented in Figure 5a. Notably, the H2 adsorption isotherm for PCNS demonstrates an almost linear increase in H2 uptake with increasing pressure. This pressure-controlled adsorption is classified as physisorption due to the lower binding energy between H2 and carbon. After Pd loading, the isotherms of all Pd-loaded samples exhibit a steep uptake in the low-pressure range, mainly attributed to hydrogen chemisorption and the formation of palladium hydrides (PdHx) through the interaction between hydrogen and Pd NPs [23,24,25,26,27,28,29,30,31]. As the pressure increases, the H2 uptake isotherms for the Pd-loaded samples exhibit a similar linear increase compared to that of PCNS. Notably, as shown in Figure 5b, these Pd-loaded samples display different slopes for physisorption (slopes: PCNS@Pd-1 > PCNS@Pd-2 > PCNS@Pd-3), which suggests that the varying Pd-uncoated areas of these samples lead to different H2-carbon contact interfaces, resulting in diverse H2 uptake capacities at high pressures. The H2 uptake capacities are 0.14, 0.25, 0.43, and 0.40 wt% for PCNS, PCNS@Pd-1, PCNS@Pd-2, and PCNS@Pd-3, respectively. It is evident that the Pd-loaded PCNS samples demonstrate a significantly enhanced H2 uptake capacity compared to the PCNS, despite their lower surface area and reduced porosity following the Pd loading process. Interestingly, the second reflux cycle resulted in an increase in Pd content from 49 wt% in PCNS@Pd-1 to 57 wt% in PCNS@Pd-2, while the H2 uptake capacity increased by 72% from PCNS@Pd-1 to PCNS@Pd-2. This significant improvement is likely attributed to the larger Pd particles in PCNS@Pd-2, which exhibit a higher hydrogen sorption capacity per atom due to the abundant interstitial spaces in larger particles that promote hydride formation through an intense anti-bonding state. Additionally, the H2 uptake capacity shows an anomalous slight decrease for PCNS@Pd-3. This result is since, although PCNS@Pd-3 has the highest Pd content, the overlap of Pd NPs reduces the H2-accessible surface area and the active sites for hydrogen chemisorption, resulting in a comparable H2 uptake capacity at low pressure when compared to PCNS@Pd-2. At high pressure, the PCNS@Pd-2 exhibits a higher H2 uptake capacity due to its larger uncoated carbon surface, which facilitates enhanced physisorption. In summary, the elevated H2 uptake capacity of PCNS@Pd-2 is likely attributed to a combination of various hydrogen-binding mechanisms, including physisorption on PCNS, chemisorption on Pd particles, and hydrogen spillover from the Pd catalytic sites [32,33,34]. Table 2 summarizes the contributions of both PCNS and Pd NPs to hydrogen sorption at 10 and 40 bar. Regardless of the pressure, the Pd-loaded samples demonstrate enhanced hydrogen sorption, approximately three times higher than that of PCNS, highlighting the significant contribution of Pd particles. At high pressure, carbon physisorption plays a dominant role in hydrogen absorption due to the linear relationship between hydrogen uptake and applied pressure. Under ambient temperature and pressure, Pd can reversibly absorb and store hydrogen gas hundreds of times its own volume. This characteristic stems from the interstitial solid solution behavior of hydrogen atoms within its face-centered cubic lattice. After hydrogen molecules dissociate into hydrogen atoms on the Pd surface, they diffuse into the lattice interstices, forming a palladium-hydrogen solid solution (α-phase). As the hydrogen concentration increases, it further transforms into a hydride phase (β-phase), accompanied by significant lattice expansion and a phase transition plateau. The prominent advantages of Pd for H2 storage lie in its high H2 storage density under mild conditions, excellent kinetic performance, and its selectivity in purifying hydrogen [35].

4. Conclusions

In summary, this article presents a method for recycling waste plastics into porous carbon nanosheets, where waste polypropylene (PP) is used as a carbon source and then infused with palladium (Pd) nanoparticles of controlled size for hydrogen storage applications. The results indicate that Pd-loaded PCNS samples exhibit significantly higher hydrogen uptake capacities compared to neat PCNS. Several factors influence hydrogen storage capacity, including the size and content of Pd nanoparticles as well as the properties of carbon support. At low pressure, larger Pd particles and higher Pd content enhance hydrogen chemisorption, while at high pressure, the carbon support facilitates hydrogen physisorption. The PCNS@Pd-2 sample, featuring 16 nm Pd particles and a Pd content of 57 wt%, achieves a maximum hydrogen uptake of 0.43 wt%. The synergistic interaction between the carbon support and Pd nanoparticles further enhances hydrogen storage capacity compared to using Pd nanoparticles alone. This research offers a sustainable approach to recycling plastic waste and provides a cost-effective method for hydrogen storage.

Author Contributions

Conceptualization, L.M.; Validation, X.C.; Data curation, X.C.; Writing—Original draft, L.M.; Writing, Review and Editing, X.C.; Supervision, X.C. All authors have read and agreed to the published version of the manuscript.

Funding

Financial support was from the National Science Centre, Poland, under Grant UMO-2020/39/B/ST8/02937 and The Fifth Batch of Cultural Research Engineering Projects in 2023, Project Number WH23-5-2, Ningbo, Zhejiang Province, China.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed at the corresponding author.

Acknowledgments

The authors are grateful for financial support from the National Science Centre, Poland, under Grant UMO-2020/39/B/ST8/02937 and The Fifth Batch of Cultural Research Engineering Projects in 2023, Project Number WH23-5-2, Ningbo, Zhejiang Province, China.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Kaza, S.; Yao, L.; Bhada-Tata, P.; Van Woerden, F. What Waste 2.0: A Global Snapshot of Solid Waste Management to 2050; World Bank: Washington, DC, USA, 2018. [Google Scholar]
  2. Cao, S.Y.; Chen, B.S.; Guo, H.; Sun, J.L. Environmental Footprint Assessment of Plastics in China; Beijing Institute of Petrochemical Technology: Beijing, China, 2020. [Google Scholar]
  3. Lv, J. Application of recyclable materials in the field of architectural landscape design materials under urban construction. Int. J. Mater. Prod. Technol. 2024, 69, 307–322. [Google Scholar] [CrossRef]
  4. Martins, A.J.G.; Sá, A.V. Sustainable construction solutions for outdoor public spaces: Modernity and tradition in optimising urban quality. U. Porto J. Eng. 2025, 11, 66–88. [Google Scholar] [CrossRef]
  5. Geyer, R.; Jambeck, J.R.; Law, K.L. Production, Use, and Fate of All Plastics Ever Made. Sci. Adv. 2017, 3, e1700782. [Google Scholar] [CrossRef] [PubMed]
  6. Pickett, J.E. Weathering of Plastics. In Handbook of Environmental Degradation of Materials, 3rd ed.; Kutz, M., Ed.; William Andrew Publishing: Norwich, NY, USA, 2018; pp. 163–184. [Google Scholar]
  7. Cohen, Q.M.; Glaese, M.; Meng, K.; Geissen, V.; Huerta-Lwanga, E. Parks and recreational areas as sinks of plastic debris in urban sites: The case of light-density microplastics in the city of Amsterdam, The Netherlands. Environments 2021, 9, 5. [Google Scholar] [CrossRef]
  8. Al-Salem, S.M.; Abraham, G.; Al-Qabandi, O.A.; Dashti, A.M. Investigating the effect of accelerated weathering on the mechanical and physical properties of high content plastic solid waste (PSW) blends with virgin linear low-density polyethylene (LLDPE). Polym. Test. 2015, 46, 116–121. [Google Scholar] [CrossRef]
  9. Alsabri, A.; Tahir, F.; Al-Ghamdi, S.G. Environmental impacts of polypropylene (PP) production and prospects of its recycling in the GCC region. Mater. Today Proc. 2022, 56, 2245–2251. [Google Scholar] [CrossRef]
  10. Ma, C.D.; Liu, X.G.; Min, J.K.; Li, J.X.; Gong, J.; Wen, X.; Chen, X.C.; Tang, T.; Mijowska, E. Sustainable recycling of waste polystyrene into hierarchical porous carbon nanosheets with potential applications in supercapacitors. Nanotechnology 2020, 31, 035402. [Google Scholar] [CrossRef]
  11. Chen, X.C.; Wang, H.; He, J.H. Synthesis of carbon nanotubes and nanospheres with controlled morphology using different catalyst precursors. Nanotechnology 2008, 19, 325607. [Google Scholar] [CrossRef]
  12. Gong, J.; Liu, J.; Chen, X.C.; Jiang, Z.W.; Wen, X.; Mijowska, E.; Tang, T. Converting real-world mixed waste plastics into porous carbon nanosheets with excellent performance in the adsorption of an organic dye from wastewater. J. Mater. Chem. A 2015, 3, 341–351. [Google Scholar] [CrossRef]
  13. Min, J.K.; Zhang, S.; Li, J.X.; Klingeler, R.; Wen, X.; Chen, X.C.; Zhao, X.; Tang, T.; Mijowska, E. From polystyrene waste to porous carbon flake and potential applications in supercapacitors. Waste Manag. 2019, 85, 333–340. [Google Scholar] [CrossRef]
  14. Li, Y.; Yang, R.T.; Liu, C.J.; Wang, Z. Hydrogen storage on carbon doped with platinum nanoparticles using plasma reduction. Ind. Eng. Chem. Res. 2007, 46, 8277–8281. [Google Scholar] [CrossRef]
  15. Yang, X.Q.; Liu, S.Y.; Li, W.B. Microporous carbon supported PdNi nanoalloys with adjustable alloying degree for hydrogen storage at room temperature. Colloids Surf. A Physicochem. Eng. Asp. 2025, 713, 136473. [Google Scholar] [CrossRef]
  16. Yang, X.Q.; Li, W.B. Pd Nanoparticle-Loaded Polyacrylonitrile-Based Microporous Carbon for Hydrogen Storage. Energy Fuels 2025, 39, 11689. [Google Scholar] [CrossRef]
  17. Xia, Y.D.; Yang, Z.X.; Zhu, Y.Q. Porous carbon-based materials for hydrogen storage: Advancement and challenges. J. Mater. Chem. A 2013, 1, 9365–9381. [Google Scholar] [CrossRef]
  18. Węńska, K.; Michalkiewicz, B.; Gong, J.; Tang, T.; Kalenczuk, R.J.; Chen, X.C.; Mijowska, E. In situ deposition of Pd nanoparticles with controllable diameters in hollow carbon spheres for hydrogen storage. Int. J. Hydrogen Energy 2013, 38, 16179–16184. [Google Scholar] [CrossRef]
  19. Baca, M.; Cendrowski, K.; Banach, P.; Michalkiewicz, B.; Mijowska, E.; Kalenczuk, R.J.; Zielińska, B. Hydrogen storage on carbon-based materials decorated with Pd nanoparticles. Int. J. Hydrogen Energy 2017, 42, 30461–30469. [Google Scholar] [CrossRef]
  20. Zielińska, B.; Michalkiewicz, B.; Mijowska, E.; Kalenczuk, R.J. Advances in Pd nanoparticle size decoration of mesoporous carbon spheres for energy application. Nanoscale Res. Lett. 2015, 10, 430. [Google Scholar] [CrossRef]
  21. Liu, X.; Ma, C.; Wen, Y.; Chen, X.; Zhao, X.; Tang, T.; Holze, R.; Mijowska, E. Highly Efficient Conversion of Waste Plastic into Thin Carbon Nanosheets for Superior Capacitive Energy Storage. Carbon 2021, 171, 819–828. [Google Scholar] [CrossRef]
  22. Donohue, M.D.; Aranovich, G.L. Adsorption Hysteresis in Porous Solids. J. Colloid Interface Sci. 1998, 205, 121–130. [Google Scholar] [CrossRef]
  23. Wang, J.C.; Luo, J.H.; Yao, Y.; Song, J.F.; Shi, Y. Room-temperature hydrogen adsorption in Pd nanoparticle decorated UiO-66-NH2 via spillover. Particuology 2024, 93, 309–315. [Google Scholar] [CrossRef]
  24. Heravi, M.; Farhadian, N. Improvement of Hydrogen Adsorption on the Simultaneously Decorated Graphene Sheet with Titanium and Palladium Atoms. Langmuir 2024, 40, 13879–13891. [Google Scholar] [CrossRef]
  25. Kohzadi, K.; Mehrabi, M.; Shirkani, H.; Karimi, S. Laser radiation, CDs and Pd-NPs: Three influential factors to enhance the hydrogen storage capacity of porous silicon. Int. J. Hydrogen Energy 2024, 50, 464–474. [Google Scholar] [CrossRef]
  26. Wang, L.; Guo, Y.; Xu, Q.; Xiong, J.; Chen, Y.; Nie, Z. Research progress of hydrogen storage based on carbon–based materials with the spillover method at room temperature. Int. J. Green Energy 2023, 21, 1969–1985. [Google Scholar] [CrossRef]
  27. Singh, P.; Kulkarni, M.V.; Gokhale, S.P.; Chikkali, S.H.; Kulkarni, C.V. Enhancing the hydrogen storage capacity of Pd-functionalized multi-walled carbon nanotubes. Appl. Surf. Sci. 2021, 258, 3405–3409. [Google Scholar] [CrossRef]
  28. Chen, B.W.J.; Mavrikakis, M. Effects of composition and morphology on the hydrogen storage properties of transition metal hydrides: Insights from PtPd nanoclusters. Nano Energy 2019, 63, 103858. [Google Scholar] [CrossRef]
  29. Rather, S.; Zacharia, R.; Hwang, S.W.; Naik, M.; Nahm, K.S. Hydrogen uptake of palladium embedded MWCNTs produced by impregnation and condensed phase reduction method. Chem. Phys. Lett. 2007, 441, 261–267. [Google Scholar] [CrossRef]
  30. Li, Y.W.; Yang, R.T. Hydrogen Storage in Metal-Organic Frameworks by Bridged Hydrogen Spillover. J. Am. Chem. Soc. 2006, 128, 8136–8137. [Google Scholar] [CrossRef]
  31. Li, Y.W.; Yang, R.T. Significantly Enhanced Hydrogen Storage in Metal-Organic Frameworks via Spillover. J. Am. Chem. Soc. 2005, 128, 726–727. [Google Scholar] [CrossRef]
  32. Mori, K.; Hashimoto, N.; Kamiuchi, N.; Yoshida, H.; Kobayashi, H.; Yamashita, H. Hydrogen spillover-driven synthesis of high-entropy nanoparticles as a robust catalyst for CO2 hydrogenation. Nat. Commun. 2021, 12, 3884. [Google Scholar] [CrossRef]
  33. Peng, Z.Z.; Li, Z.Y.; Liu, Y.Q.; Shuai, Y.; Tong, J.N.; Wang, D.; Ye, Y.Y.; Li, S.R. Supported Pd nanoclusters with enhanced hydrogen spillover for NOx removal via H2-SCR: The elimination of “volcano-type” behavior. Chem. Commun. 2017, 53, 5958–5961. [Google Scholar] [CrossRef]
  34. Adams, B.D.; Ostrom, C.K.; Chen, S.; Chen, A.C. High-Performance Pd-Based Hydrogen Spillover Catalysts for Hydrogen Storage. J. Phys. Chem. C 2010, 114, 19875–19882. [Google Scholar] [CrossRef]
  35. Ferrin, P.; Kandoi, S.; Nilekar, A.U.; Mavrikakis, M. Hydrogen Adsorption, Absorption and Diffusion on and in Transition Metal Surfaces: A DFT Study. Surf. Sci. 2012, 606, 679–689. [Google Scholar] [CrossRef]
Polymers 18 00105 g001
Figure 1. (a) Synthesis of PCNS from Waste PP and Preparation of Pd-Supported Porous Carbon Nanosheets (PCNS@Pd). TEM and High-resolution TEM images of PCNS (b1,b2), PCNS@Pd-1 (c1,c2), PCNS@Pd-2 (d1,d2) and PCNS@Pd-3 (e1,e2).
Figure 1. (a) Synthesis of PCNS from Waste PP and Preparation of Pd-Supported Porous Carbon Nanosheets (PCNS@Pd). TEM and High-resolution TEM images of PCNS (b1,b2), PCNS@Pd-1 (c1,c2), PCNS@Pd-2 (d1,d2) and PCNS@Pd-3 (e1,e2).
Polymers 18 00105 g001
Polymers 18 00105 g002
Figure 2. N2 adsorption/desorption isotherms (a) and pore size distribution (b) of all CNS, PCNS and PCNS@Pd-x samples.
Figure 2. N2 adsorption/desorption isotherms (a) and pore size distribution (b) of all CNS, PCNS and PCNS@Pd-x samples.
Polymers 18 00105 g002
Polymers 18 00105 g003
Figure 3. XRD patterns (a) and Raman spectra (b) of CNS, PCNS and PCNS@Pd-x samples.
Figure 3. XRD patterns (a) and Raman spectra (b) of CNS, PCNS and PCNS@Pd-x samples.
Polymers 18 00105 g003
Polymers 18 00105 g004
Figure 4. TGA curves of CNS, PCNS and PCNS@Pd samples.
Figure 4. TGA curves of CNS, PCNS and PCNS@Pd samples.
Polymers 18 00105 g004
Polymers 18 00105 g005
Figure 5. (a) H2 uptake performance at 25 °C for the PCNS and Pd-supported PCNS. (b) The relationship between PCN@Pd-X and H2 storage capacities.
Figure 5. (a) H2 uptake performance at 25 °C for the PCNS and Pd-supported PCNS. (b) The relationship between PCN@Pd-X and H2 storage capacities.
Polymers 18 00105 g005
Table 1. Degradation Challenges of Plastics in Landscape Applications.
Table 1. Degradation Challenges of Plastics in Landscape Applications.
Plastic TypeRepresentative CasesHazards (Highlighting Non-Degradability)
PP (Polypropylene)People’s Pavilion (The Netherlands), Print Your City (Greece, partial)Poor durability and limited recyclability after decommissioning; emits toxic gases when incinerated; remains undegraded for a long time in landfills.
HDPE (High-Density Polyethylene)Tulum Plastic School (Mexico), People’s Pavilion (The Netherlands)Highly corrosion-resistant, virtually non-degradable in natural environments; easily brittle under UV radiation, generating microplastics.
Mixed Plastics/CompositesRecycling Loop Proposal (France), Print Your City (Greece, partial), Toy Story Residence (India), Urban Magnetic Field (China)Most difficult to treat mixed and inseparable composition → almost impossible to recycle again; typically disposed of via landfilling or incineration, forming long-term pollution sources.
Table 2. Physical parameters for CNS, PCNS and PCNS@Pd-x samples.
Table 2. Physical parameters for CNS, PCNS and PCNS@Pd-x samples.
Samples S B E T
( m 2 / g ) a		 Vt
( c m 3 / g ) b		 PSAV
(nm) c		 PSDFT
(nm) d
CNS3591.842.052.61
PCNS32003.74.60.93
PCNS@pd-110830.933.420.524
PCNS@pd-25760.553.790.524
PCNS@pd-35350.554.160.484
a: the Brunauer–Emmett–Teller (BET) method was used to calculate the surface area; b: the pore volume (Vt) was determined at a relative pressure of 0.98; c: the average pore size (PSAV); d: the average pore size was obtained by DFT analysis.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Ma, L.; Chen, X. Recycling Waste Plastics from Urban Landscapes to Porous Carbon for Clean Energy Storage. Polymers 2026, 18, 105. https://doi.org/10.3390/polym18010105

AMA Style

Ma L, Chen X. Recycling Waste Plastics from Urban Landscapes to Porous Carbon for Clean Energy Storage. Polymers. 2026; 18(1):105. https://doi.org/10.3390/polym18010105

Chicago/Turabian Style

Ma, Lin, and Xuecheng Chen. 2026. "Recycling Waste Plastics from Urban Landscapes to Porous Carbon for Clean Energy Storage" Polymers 18, no. 1: 105. https://doi.org/10.3390/polym18010105

APA Style

Ma, L., & Chen, X. (2026). Recycling Waste Plastics from Urban Landscapes to Porous Carbon for Clean Energy Storage. Polymers, 18(1), 105. https://doi.org/10.3390/polym18010105

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop