To alleviate the pressure on the petrochemical industry and address environmental concerns, the utilization of polyurethane (PU) derived from castor oil (CO) (as an ester polyol replacement of petrochemicalbased materials) has garnered significant attention in recent decades. Extending the service life of materials requires imparting self-healing properties to vegetable oil-based polymers, an aspect that has received limited attention in current studies. However, low self-healing efficiency still poses a significant challenge, and non-conductivity also remains an obstacle in current research, crucial for their application in electronic devices. In this work, we present the first series of electrically self-healing biopolymer composites constructed by incorporating carbon nanotube (CNT) networks into crosslinked castor oil-based polyurethane (BPU) through a simple curing process. These materials address the challenges mentioned above and exhibit improved mechanical, electrical, and self-healing capabilities compared to other biobased self-healing materials. The resulting BPU/CNT composite demonstrated exceptional repeated selfhealing capacity, restoring both mechanical properties and electrical performance even after experiencing severe mechanical damage. Notably, this composite served as a conductive substrate in flexible solid-state supercapacitor (FSSC) devices. Consequently, the FSSC derived from the composite conductive substrate achieved an impressive 92.4 % self-healing efficiency even after undergoing 7 cutting/healing cycles. The device remained virtually unchanged even after being bent at a 180 degrees angle with a bending radius of 1.6 mm, indicating excellent repeatability and durability. The exceptional self-healing ability, with similar to 98 % electrical recovery at 100 degrees C for 70 s and 93 % at 80 degrees C after 6 min, of these composites was attributed to the synergistic interactions of the dynamic exchange reactions of disulfide bonds and dense hydrogen bonds within the BPU matrix, which provide a reversible dynamic polymer network. The healing efficiency of these dynamic bonds was evaluated by adjusting the composition ratio of the long linear chain of pTHF in hybrid polyols of the crosslinked polymer network. Overall, this work highlights a series of green, simple, and highly efficient self-healing polymer composites derived from renewable castor oil, and it establishes an essential framework for future sustainable polymer composite design. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Early integrated solar-rechargeable supercapacitor (ISRS) systems with four physically distinguishable electrodes are cumbersome and require multistep manufacturing process with application disadvantages. Therefore, a stacked ISRS with a three-electrode mode that uses a dual-functional-layered (shared) electrode, which is particularly important to integrate two main active components, is one of the target configurations for a compact, safe and efficient power supplier in advanced soft electronics. This work reports the effect of various fabrication methods on the surface morphology profile of a graphene oxide-incorporated poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (m-PHGO) as a shared electrode; this process exhibited a significant impact on the charge/ discharge rate and ISRS efficiency. By controlling the deposition method, the shared electrode fabricated by a modified spin/spray-coating technique using an m-PHGO dispersion features an interface that meets all of the requirements of a dual-functional layer. It is effective for hole charge filtration, transfer, and storage in the stacked ISRS. Under 1-sun illumination, the supercapacitor moiety is charged entirely by the organic solar cell unit within 5 s to build a fusion ISRS capable of approaching a high charging voltage of -0.6 V. The as-developed ISRS (with a thickness of -2.6 mu m and the substrate) shows an impressive energy-storage efficiency of -81%. This study provides insights about fabricating high-performance and easy-to-use compact electronic devices.

Incorporating conjugated small molecules comprising electron-withdrawing and -donating moieties as interfacial modifiers (IMs) between the electron transporting layer (ETL) and photoactive layer offers a promising strategy for fabrication of high-performance inverted organic solar cells (iOSCs). This approach effectively reduces charge trapping and recombination at the interface between the ETL and the photoactive layer, leading to improved device performance and stability. The introduction of IMs resulted in the transformation of the hydrophilic ZnO ETL surface to a hydrophobic state. When employed as the ETL in small-area iOSCs, IM/ZnO demonstrated a remarkable maximum power conversion efficiency (PCE) of 3.8% accompanied by enhanced open-circuit voltage (VOC) and fill factor (FF) values. The significant contribution of the IM was evident in achieving a uniform film deposition and complete coverage of the spray-coated photoactive P3HT:PCBM layer in large-area applications. Despite an observed decrease in average performance of iOSC devices as the photoactive area increased, inclusion of IM/ZnO ETL in these iOSCs led to average PCE values that were 1.3-2.9 times higher with reduced variability compared to iOSCs utilizing a pristine ZnO ETL. This highlighted the potential for conjugated smallmolecule IM-modified ZnO as a promising ETL candidate for achieving high-performance and scalable organic electronics.

Supercapacitors with multiple features, such as high capacitance, high-rate capability, high flexibility, and self-healing properties, are regarded as good candidates for powering portable and wearable electronics. Herein, a symmetric supercapacitor with multiple functions is fabricated by sandwiching a highly con-ductive self-healable composite current collector electrode with an active material, poly(3,4-ethylene-dioxythiophene):poly(styrene sulfonate)/multiwalled carbon nanotubes (PEDOT:PSS/MWNTs), and a poly (vinyl alcohol)/ phosphoric acid (PVA/H3PO4) electrolyte. The novelty of this work lies in the synergy arising from the combination of two conducting carbon nanofillers, referred to as hybrid carbon nanofiller (HCF), coupled with healable polymer matrices (HCF/HPU) to fabricate self-healing high-conductivity composite current collector electrodes. These can be used in flexible metal-free supercapacitors, which have not been specifically considered previously. The use of two geometrically varied nanofillers with proper selection of the nanofiller content ratio can induce the formation of an effectively conductive co-supporting network, which drastically enhances the electrical properties and mechanical strength of the composite current collector compared to that of single nanofillers. More importantly, the supercapacitor assembled by the HCF/HPU composite current collector delivers high specific capacitance and energy density. In addition, noticeable cycling stability with only similar to 10 % capacitance loss was observed after 20,000 consecutive charge/ discharge cycles at a high current density of 10 mA cm-2. Furthermore, at a medium temperature of 60 degrees C, supercapacitors with this HCF/HPU composite current collector restore at least 96.2 % of their capacitance properties even after 5 cycles of severing/healing. The capacitive retention rate after 2000 bending cycles was 97.4 % at a bending radius of 4.0 mm. These properties indicate this HCF/HPU composite current col-lector is a promising candidate for use in high-performance flexible energy storage devices.(c) 2022 Elsevier B.V. All rights reserved.

The problems posed by the presence of ionic defects on the surface and at the grain boundaries of perovskite films must be solved before the power conversion efficiency of organic-inorganic halide perovskite solar cells can be enhanced. While a number of strategies to address this problem have been developed, the challenge of achieving both effective passivation and charge transporting performance remains. In this paper, inorganic perovskite nanomaterials, shaped into nanowires (NWs), were introduced as a strategy to passivate defects at the grain boundaries and facilitate charge transport across the interfacial charge transport layer. The NW-modified perovskite film significantly reduced defect sites and extended carrier lifetime compared to quantum dot -modified and pristine perovskite films, reducing non-radiative recombination significantly. The perovskite solar cells passivated with NWs achieved a power conversion efficiency of 21.56% and improved device stability over a 3500-hour period.

Using an interfacial modifier (IM) agent to overcome interfacial problems of zinc oxide (ZnO), which is commonly used as an electron transport layer (ETL), is an effective interfacial engineering strategy that can be used to improve the performance and stability of optoelectronic devices, such as inverted organic solar cells (iOSCs). In this work, a conjugated polymer electrolyte (CPE) is employed as an IM agent to modify the surface morphology of ZnO ETL-based iOSC devices. Compared to a pristine ZnO ETL, the CPE-modified ZnO (CPE/ZnO) ETL is more hydrophobic with a smooth surface induced by an interfacial dipole, resulting in better energy alignment to the LUMO of the photoactive layer. The power conversion efficiency (PCE) of poly(3-hexylthiophene) (P3HT) and phenyl-C60-butyric acid methyl ester (PCBM) blend-based planar iOSCs with a CPE/ZnO ETL increases from 3.8% to 4.2% and from 1.8% to 2.2% for bottom and top transparent devices, respectively. The CPE/ZnO ETL is further employed to fabricate a fiber-shaped iOSC (FS-iOSC), which is a promising wearable optoelectronic device. In FS-iOSCs fabricated by a dip-coating method with a CPE/ZnO ETL, the PCE improves to 1.02%, which is a near 2-fold improvement over devices using a pristine ZnO ETL. Additionally, our concept has also been successfully applied to inverted polymer light-emitting diodes (iPLED) with planar and fiber-shaped configurations. These results suggest that the surface modification of metal oxide ETLs (e.g., ZnO) with organic interfacial modifiers (e.g., CPE) is a simple but effective approach to fabricating planar and fiber-shaped optoelectronic devices with high performance.

For the first time, highly efficient, corrosion resistant, and chemically stable rock barnacle carapace-derived chitosan (CH) supported non-noble nano aluminum-tungsten bimetallic-alloy based bifunctional electrocatalyst has been developed for waste pork lard-derived glycerol (WPLG) electrolysis in NaOH medium, ascertaining sustainability. An indirect bio-glycerol oxidation mechanism has been well executed to produce industrially important glyceric acid (6.65 mmol cm(-2) h(-1), 79.92% selectivity, similar to 90% FE%) and formic acid (1.67 mmol cm(-2) h(-1), 18.07% selectivity) at the anode at ambient temperature and pressure. However, among the various prepared unsupported and supported nanocomposite electrocatalysts, the optimal aluminumtungsten alloy anchored over chitosan renovated carbon nanotube (Al:W = 1:2 mole/mole) electrode rendered the lowest onset potential (0.95 V vs. RHE) and highest peak current density (119.61 mA cm(-2)) for the WPLG electrooxidation at the anode, coupled with H-2 generation (28.55 ml cm(-2) h(-1)) in the cathode in a membrane free electrochemical-cell by replacing sluggish oxygen evolution reaction. Comparing the electricity consumption for H-2 production from various prepared catalysts, the supported optimum catalyst consumed 9.3% less energy (only 2.9 kWh/m(3) H-2) and 67.91% less corrosion current density as compared to the unsupported Al/ W electrocatalyst, exhibiting excellent stability and durability (>200 cycles) due to good alloy-support interaction. Finally, a comprehensive life cycle impact assessment and life cycle costing of the overall WPLG electrolysis demonstrated 12.29% lower global warming potential (GWP100) while saving 11.03% of the cost compared to commercial glycerol electrolysis, which could procreate an effective approach toward inexpensive catalyst fabrication and its subsequent application for sustainable glycerol electrolysis.

Inverted organic solar cells (iOSCs) have attracted considerable attention because of their ease of fabrication and suitability for roll-to-roll processing. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), with multiple favorable properties, is the most actively studied hole-transporting layer (HTL) material. However, the pristine state of PEDOT:PSS is limited by its inefficient, poor, and inhomogeneous conductivity. Herein, we demonstrate strategies to enhance the performance of iOSC devices by introducing carbon quantum dots (CQDs), which have controllable conductivity and band edges, into the PEDOT:PSS HTL. This is considered to be an efficient route for modifying the intrinsic properties and electrical conductivity of PEDOT:PSS. The CQDs were first synthesized through a microwave-assisted process by employing eco-friendly and low-cost material sources. By optimizing the ratio of CQDs incorporated into PEDOT:PSS (PH-G0.05), an iOSC with a remarkable enhancement of 3.90% in power conversion efficiency, was obtained. Using PH-G0.05 HTL helped to improve the contact quality and assisted the hole extraction/transport ability at the photoactive/top Ag anode interface with high electrical conductivity (2.80 S cm(-1)), good surface morphology (RMS = 7.34 nm), and suitable work function (4.78 eV). Our efforts to develop a solution process for CQDs-incorporated PEDOT:PSS HTLs shows considerable promise for the potential replacement of vacuum-based methods in iOSC applications.

This work reports on the fabrication of a flexible and self-healing high-performance quasi-solid-state supercapacitor that uses a conductive composite electrode. The supercapacitor employs an active layer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS)-multiwalled carbon nanotube (MWNT)-coated polyurethane/carbon black composite electrode sandwiched with a poly(vinyl alcohol) (PVA)/H3PO4 gel electrolyte. The supercapacitor possesses the highest capacitance over 47 mF cm(-2) and a high energy density from 5.8 to 1.7 mu Wh cm(-2) with the corresponding power density changing from 0.13 to 0.61 W cm(-2) at a current density from 1 to 8 mA cm(-2). The supercapacitor can retain up to 94% of its electrochemical performance even after a fifth severing/healing cycle, and using capacitance retention, it maintains mechanical stability under various bending deformations. As a result, this self-healing supercapacitor features device-level toughness with more than 96% areal capacitance conserved, even under 180 degrees bending (1.6 mm of bending radius). With its high durability and longevity against dynamic deformation and damage, our study demonstrates the high application potential of this supercapacitor in portable/wearable electronics.

The thin-film fabrication of PEDOT:PSS-based dispersions via solution-processing techniques is critical to developing a hole transporting layer (HTL) for inverted organic photovoltaic (iOPV) devices. However, the highly hydrophilic nature of PEDOT:PSS solutions is a drawback that strongly inhibits their usage as HTLs in iOPV devices. In this study, the hydrophilic nature of PEDOT:PSS solutions was tuned successfully using various solvents and surfactants. Additionally, the dispersion of graphene oxide (GO) colloidal suspensions within the PEDOT:PSS was used to enhance the electrical conductivity of the PEDOT:PSS. These modifications have the benefit of enabling effective coating of a PEDOT:PSS/GO blend as an HTL on top of a hydrophobic photoactive layer, resulting in a homogeneous, conductive thin film for iOPV devices. In order to further optimize the ratio of PEDOT:PSS to GO, the effect of the GO dosage is investigated systematically, which demonstrated the influence of this ratio on the overall power conversion efficiency of devices. The results demonstrate that the additive- and GO-modified PEDOT:PSS can lead to enhancement of device efficiency, mainly due to enhanced HTL film morphology, high electrical conductivity, high adhesiveness, and well-matched bandgap energy. We believe that the modified PEDOT:PSS/GO is a prospective candidate for utilization in the HTL for iOPV devices in next-generation energy conversion applications and other potential energy management devices.

The electrically conductive healing polymer composites, which have the ability to recover conductivity after damage, are promising candidates as electrodes for electrical devices. In this work, a solvent casting method was used to prepare a healing conductive polymer composite of polyurethane (PU) and carbon black (CB). PU contains dynamic disulfide bonds that can undergo metathesis inducing a fast healing property. The electrical conductivity of the PU/CB composite is recovered by heating at 70 degrees C for 1 min as a result of the synergistic effect of the hydrogen bond and disulfide metathesis. The tensile test shows complete recovery of stress but lower strain after cut and heals at 70 degrees C for 1 h. The fast healing electrical conductivity, excellent mechanical property recovery along with easy preparation offer this PU/CB composite as a prospective candidate for optoelectronic and energy-related devices.

Biomass derived carbon via hydrothermal carbonization are critically important for the catalysis research field requiring high activity with low cost. However, most of them present low activity due to low surface areas with large particle size originating from unnecessary compounds in raw status. Here, we report a porous carbon decorated with Fe3C/Fe3O4 nanoparticles via pretreatment of pig blood (PB) by employing solvent pretreatment and pyrolyzing in regulated environment using a Fe-porphyrin-type macrocycle as catalyst precursors. Importantly, the addition of toluene to the raw form of PB as pretreatment plays a significant role in not only producing the nanoparticles with porous carbon materials but also removing impurities that deteriorate the active sites of molecular nitrogen carbon (MNC) type catalysts during high-temperature activation. Furthermore, the temperature for hydrothermal treatment and pyrolysis influences oxygen reduction reaction (ORR) performances. The highest-performing PB-derived catalyst delivered its kinetic current and the degree of degradation (after 10,000 potential cycles) were 1.57 mA/cm(2) (at 0.9 V) and 19 mV (half-wave potential), and those of Pt/C were 1.26 mA/cm(2) and 43 mV, respectively. The catalysts were prepared by applying pretreatment to the PB and characterized systematically to investigate how such pretreatment influences the physical properties and ORR performances.

Biomass is a useful precursor for manufacturing electrocatalysts because it is highly abundant, eco-friendly, and is composed of organic materials that include Fe and nitrogen precursors. Among the numerous waste biomass types, slaughtered pig blood contains a high concentration of Fe-porphyrin inside the hemoglobin, and this characteristic makes it an ideal precursor for fabricating a bio-inspired Fe-N-C oxygen reduction reaction (ORR) catalyst. Here, Zinc (Zn)-hydrolysates are obtained from purified waste pig blood was used as a porous carbon source for two-dimensional (2D) sheet-like porous single-atom electrocatalysts. In addition, pig blood provides Fe single-atom catalytic sites derived from hemoglobin in (Zn)-hydrolysates and shows excellent ORR activity by retaining excellent mass transfer due to the presence of mesopores generated by Zn activation under NH3 pyrolysis Furthermore, one of the catalytic materials is a Zn-incorporated Fe single-atom porous carbon catalyst (designated Zn/FeSA-PC)/950/NH3, was successfully integrated as an Anion Exchange Membrane Fuel Cells (AEMFCs) and Zn-Air Batteries (ZABs) where it supported maximum power densities of 352 and 220 mW/cm2, respectively. This study demonstrates the new designs and preparation procedures for high-performance electrocatalysts that can be manufactured at low cost from abundant and renewable blood biomass.

Direct ammonia fuel cells (DAFCs), wherein the ammonia oxidation reaction (AOR) occurs at the anode and oxygen reduction at the cathode, are a promising clean energy production system using easily liquefied ammonia because they exhibit high energy density. However, only a few catalysts are, thus far, available for the AOR because of its sluggish six-electron-based reaction kinetics. Pt (100) is considered an optimal catalyst for the AOR; however, the synthesis of pristine Pt (100) is difficult because it requires the use of strong capping agents for faceting particles. Moreover, the capping agents block surface active sites, thereby deaccelerating electrochemical reactions. Herein, we report a novel synthetic method (hot separation) to achieve pristine Pt (100) by precisely controlling the formation kinetics of Pt nanocubes, wherein the further treatment for surface capping agent removal is not required. Hot separation prevents particle aggregation and overgrowth through the rapid separation of the Pt nanocubes and reaction solution and preserves the Pt (100) surface. Furthermore, the characterization of the pristine surface of Pt nanocubes was conducted to compare the properties of the Pt nanocubes with those of the particles prepared from conventional methods. The Pt nanocubes showed better mass activity toward the AOR and 2.3 times higher DAFC performance than those of commercial Pt.

A solar-powered integrated supercapacitor (SPIS) with an inverted organic solar cell (iOSC) as the energy conversion unit and a supercapacitor (SC) as the energy-storage unit is a workable combination that yields a highly effective self-powered pack. However, the current designs of these elements are cumbersome and entail multistep fabrication-two major application disadvantages. Herein, we report on a compact SPIS in series with a three-electrode configuration that uses modified graphene oxide-incorporated poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) as the common electrode, which is particularly important to integrate the iOSC with the SC and simultaneously play a role in the charge collection, transfer, and storage. The SPIS is successfully constructed through a solution process under mild conditions. Under 1-sun illumination, the iOSC features a weight-specific power density as high as 6.46 W g(-1), enabling the SC to be fully charged by the iOSC within 33 s to create a fusion SPIS able to reach similar to 0.6 V. The as-developed SPIS has a thickness of only similar to 2.6 mu m, and the substrate is a high-performance candidate for portable and wearable electronic devices in the future.

Herein, we report integrated photo-rechargeable supercapacitors (IPSs) composed of the inverted organic solar cell (iOSC) and solid-state supercapacitor (SC), enabling a high-performance self-power pack. The iOSC serves as a self-power source while the SC functions as energy storage, and both share an indium-tin-oxide (ITO) electrode that affords improved charge propagation across the devices. Combining the energy harvesting and storage devices in this way significantly alleviates the limitations of each device. The power fluctuation of the iOSC can be reimbursed by the SC, thus allowing for a stable energy output. Moreover, the SC is frequently charged by the iOSC during the daytime, thereby greatly reducing the charging time and avoiding a complete discharge as well. When the SC of the IPS is charged by the iOSC under AM 1.5 G of illumination, the overall energy conversion storage efficiency is ca. 2.27%. Our work provides an effective strategy for further study to fabricate a small, lightweight, portable/wearable self-power pack by integrating energy harvesting and energy storage devices into a single structure.

Among the Pt group metals, Pd has been considered the most efficient for application in electrocatalysts as an alternative to Pt. Despite the comparable electrochemical activities of Pd and Pd‐metal alloys, they are vulnerable to liquid acidic electrolytes, leading to degradation of catalytic activity. Pd–Ni alloys have been used to enhance catalytic activity because the electronic structure of Pd can be easily changed by adding Ni. In other studies, N atoms have been introduced for more stable M–Ni catalysts by inducing the formation of Ni4N species; however, the structural analysis and the role of nitrogen have not been fully understood yet. Herein, the Pd–Ni alloy nitride with a unique crystal structure shows a promising catalytic activity for oxygen reduction reaction (ORR). The nitride PdNi nanoparticles have a novel monolithic antiperovskite structure of chemical formula (PdxNi1−x)NNi3. The unique antiperovskite crystal (PdxNi1−x)NNi3 possesses superior ORR activity and stability, originating from the downshifted d‐band center of the monolayer Pd/antiperovskite surface and the lower formation energy of the antiperovskite core nanocrystal. Consequently, (PdxNi1−x)NNi3, as a Pt‐free Pd‐based electrocatalyst, overcomes the stability issue of Pd under acidic conditions by achieving 99‐times higher mass activity than commercial Pd/C, as shown by the durability test.

A simple wet-chemical route for the preparation of core-shell-structured catalysts was developed to achieve high oxygen reduction reaction (ORR) activity with a low Pt loading amount. Nickel nitride (Ni3N) nanoparticles were used as earth-abundant metal-based cores to support thin Pt layers. To realize the site-selective formation of Pt layers on the Ni3N core, hydrogen molecules (H2) were used as a mild reducing agent. As H2 oxidation is catalyzed by the surface of Ni3N, the redox reaction between H2 and Pt(IV) in solution was facilitated on the Ni3N surface, which resulted in the selective deposition of Pt on Ni3N. The controlled Pt formation led to a subnanometer (0.5-1 nm)-thick Pt shell on the Ni3N core. By adopting the core-shell structure, higher ORR activity than the commercial Pt/C was achieved. Electrochemical measurements showed that the thin Pt layer on Ni3N nanoparticle exhibits 5 times higher mass activity and specific activity than that of commercial Pt/C. Furthermore, it is expected that the proposed simple wet-chemical method can be utilized to prepare various transition-metal-based core-shell nanocatalysts for a wide range of energy conversion reactions.

Inorganic perovskite nanocrystals (NCs) have shown good potential as an emerging semiconducting building block owing to their excellent optoelectronic properties. However, despite extensive studies on their structure-dependent optical properties, they still suffer severely from chemical and phase instabilities in ambient conditions. Here, we report a facile method for the synthesis of mixed halide inorganic perovskite NCs based on recrystallization in an antisolvent mixture in an ambient atmosphere, at room temperature. We introduced an alcohol-derivative solvent, as a secondary antisolvent in the solvent mixture, which crystallizes at room temperature. This mediates and facilitates the perovskite crystallization, leading to a high chemical yield and stability. We demonstrate that this secondary antisolvent establishes intermolecular interactions with lead halide salt, which successfully stabilizes the gamma-dark phase of perovskite by encapsulating NCs in a solution and thin film. This allows us to produce concentrated NC solutions with a photoluminescence quantum yield of 70%. Finally, we fabricate CsPbI2Br NCs (optical bandgap 1.88 eV) solar cells, which showed a stabilized photovoltaic performance in ambient conditions, without encapsulation, showing a V-oc of 1.32 V.

Galvanic displacement reaction has been considered a simple method for fabricating hollow nanoparticles. However, the formation of hollow interiors in nanoparticles is not easily achieved owing to the easy oxidization of transition metals, which results in mixed morphologies, and the presence of surfactants on the nanoparticle surface, which severely deteriorates the catalytic activity. In this study, we developed a facile gram-scale methodology for the one-pot preparation of carbon-supported PtNi hollow nanoparticles as an efficient and durable oxygen reduction electrocatalyst without using stabilizing agents or additional processes. The hollow structures were evolved from sacrificial Ni nanoparticles via an in situ galvanic displacement reaction with a Pt precursor, directly following a preannealing process. By sampling the PtNi/C hollow nanoparticles at various reaction times, the structural formation mechanism was investigated using transmission electron microscopy with energy-dispersive X-ray spectroscopy mapping/line-scan profiling. We found out that the structure and morphology of the PtNi hollow nanoparticles were controlled by the acidity of the metal precursor solution and the nanoparticle core size. The synthesized PtNi hollow nanoparticles acted as an oxygen reduction electrocatalyst, with a catalytic activity superior to that of a commercial Pt catalyst. Even after 10 000 cycles of harsh accelerated durability testing, the PtNi/C hollow electrocatalyst showed high performance and durability. We concluded that the Pt-rich layers on the PtNi hollow nanoparticles improved the catalytic activity and durability considerably