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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.

The development of oxygen reduction reaction (ORR) catalysts is critical for energy conversion technologies such as fuel cells. This paper proposes an approach to synthesize a hollow-sphere nitrogen-doped carbon shell loaded with cobalt nanoparticles derived from a polystyrene@bimetallic zeolitic imidazolate framework (PS@BMZIF) core@shell, which exhibits high activity as an ORR catalyst. The ORR activity can be enhanced by performing carbonization in the presence of hydrogen, resulting in the growth of additional carbon nanotubes on the hollow-sphere porous carbon shell (h_CoNC/CNT) derived from the PS@BMZIF. The electrocatalyst obtained exhibits excellent ORR activity with a half-wave potential of 0.894 V and long-term stability for 5000 cycles in alkaline media. The h_CoNC/CNT catalyst is applied to the membrane electrode assembly of an anion exchange membrane fuel cell, where it demonstrates a performance of 140 mA/cm2 at 0.6 V and 133 mW/cm2 at the maximum power density and improves mass transfer. The exceptional electrochemical properties of h_CoNC/CNT can be attributed to its desirable hollow-sphere structure with CNTs and the adjustment of efficient active sites of the nitrogen-doped porous material. These findings suggest a potential approach by which to select the structure of the ZIFs and control the pyrolysis condition for ZIF-derived ORR electrocatalysts.

Currently, efficient hydrogen production via water electrolysis is hindered by the insufficient performance, high cost, and complex fabrication procedure of the hydrogen evolution reaction (HER) electrode. Herein, a facile fabrication method consisting of electrodeposition and a subsequent electrochemical etching process is proposed for high-performance Mo oxide-decorated NiMo (MoO3–MoO2@NiMo) heterostructure catalysts supported by carbon paper. By controlling the conditions used in electrodeposition, the composition and morphology of NiMo deposits could be manipulated. The parameters in the following etching process could be further adjusted to tune the MoO3–MoO2@NiMo heterostructure catalysts, with a significant effect on the intrinsic HER activity. Owing to the synergetic effect of the interface with a roughened morphology, the optimized catalyst exhibited Pt-like activity in the universal pH range. In particular, the HER overpotentials at −10 mA cm−2 are 27.9, 82.6, and 33.4 mV in 0.5 M H2SO4, 1.0 M PBS, and 1.0 M NaOH electrolytes, respectively, which mostly exceed the results for state-of-the-art catalysts. The present strategy for preparing high-performance MoO3–MoO2@NiMo heterostructure electrodes at room temperature and ambient pressure could be expanded to explore elemental synergy in other metal oxide@metal heterostructure electrodes.

The development of non Pt-based catalysts (non-PBCs) that show excellent oxygen reduction reaction (ORR) activity for high-performance Zn–air battery (ZAB) and anion exchange membrane fuel cell (AEMFC) is highly necessitated. Here, the unprecedented single-atom ORR activity of Fe, Si, and N co-doped carbon (FeSiNC) supported on 3D interconnected mesoporous carbons (25 and 50 nm) derived from silica templates is reported. Si moieties connected to a carbon surface were involved in the formation of an atomically distributed FeSixN4−x site through substitution of Si at the N position in the Fe–N4 site, which is the ORR active site of the conventional FeNC. FeSiNC with its larger mesopore (50 nm) exhibits outstanding ORR activity comparable to the most efficient non-Pt-based catalysts and enhanced single-cell performances due to its enhanced mass-transport property. According to theoretical calculations, the ORR activity is originated from not only FeSixN4−x sites located at the basal plane and inter-edge sites, but also C sites adjacent to the Si dopant in both edge and basal regions. Therefore, this study provides a facile strategy toward the rational design of inexpensive and highly active ORR catalysts applicable to single-cell devices.

The development of Pt-based alloy nanoparticles has contributed to improving fuel cell performance. Nevertheless, the commercialization of the catalysts is limited due to structural stability issues. To enhance the durability of Pt-based alloy catalysts, carbon-encapsulated nanoparticles have been widely studied. However, fine-tuning the carbon shell structure at the atomic scale remains a challenge when adopting a typical top-down approach, which involves a high-temperature graphitization process after polymer coating. Here, we propose a bottom-up approach to carbon encapsulation of Pt3Fe1 nanoparticles. Using extremely small amounts of carbon sources produced by the decomposition of organic ligands in metal precursors, carbon-encapsulated Pt3Fe1 nanoparticles with ultrathin carbon shells are fabricated without additional polymer coating process. Furthermore, the pore structure of the carbon shells is rationally modulated at the sub-nm level without changing the particle size via carbon etching using H2 gas. In-depth studies prove that the fine-tuned carbon shell structure has a significant effect on the activity and durability of Pt3Fe1 nanoparticles. Using the testing protocol suggested by the US Department of Energy, a target-customized carbon shell structure has been discovered that satisfies the 2025 targets of “

Hollow Pt-based nanoparticles are known to possess the properties of high electrocatalytic activity and durability. Nonetheless, their practical applications as catalytic materials are limited because of the requirement for exhaustive preparation. In this study, we prepared carbon-supported hollow PtNix (x = the moles of the Ni precursor to the Pt precursor in the catalyst preparation step) catalysts using a one-step preparation method, which substantially reduced the complexity of the conventional method for preparing hollow Pt-based catalysts. In particular, this hollow structure formation mechanism was proposed based on extensive characterizations. The prepared catalysts were examined to determine if they could be used as electrocatalysts for the oxygen reduction reaction (ORR). Among the investigated catalysts, the acid-treated hollow PtNi3/C catalyst demonstrated the best ORR activity, which was 3 times higher and 2.3 times higher than those of the commercial Pt/C and acid-treated particulate PtNi3/C catalysts, respectively.

Electrochemical nitrogen reduction reaction (NRR) is a promising method for energy-efficient and low-emission NH3 production. Herein, we report electrochemical NH3 production using a copper sulfide...

The hydrogen economy expansion triggered studies on the durability of hydrogen-powered proton-exchange membrane fuel cells (PEMFCs), which revealed that their performance is largely hindered by the...

In many catalyst systems, including fuel cell applications, control of the catalyst surface composition is important for improving activity since catalytic reactions occur only at the surface. However, it is very difficult to modify the surface composition without changing the morphology of metal nanoparticles. Herein, carbon-supported Pd3Au1 nanoparticles with uniform size and distribution are fabricated by tert-butylamine reduction method. Pd or Au surface segregation is induced by simply heating as-prepared Pd3Au1 nanoparticles under CO or Ar atmosphere, respectively. Especially, CO-induced Pd surface segregation allows the alloy nanoparticles to have a Pd-rich surface, which is attributed to the strong CO binding energy of Pd. To demonstrate the change in surface composition of Pd3Au1 alloy catalyst with the annealing gas species, the oxygen reduction reaction performance is investigated and consequently, Pd3Au1 catalyst with the highest number of surface Pd atoms indicates excellent catalytic activity. Therefore, the present work provides insights into the development of metal-based alloys with optimum structures and surface compositions for various catalytic systems.

We demonstrate that control of the defect level on carbon materials is effective for enhancing the oxygen reduction reaction (ORR) performance of nonprecious-metal catalysts. Vapor-grown carbon nanofiber (VGCNF) with high crystallinity and high electronic conductivity was chosen as the substrate of our ORR catalysts. To induce defects on the VGCNF, it was subjected to ball-milling for various controlled times, yielding BMx-VGCNF (x represents the ball-milling time, 0-6 h). The defect level introduced on the VGCNF was effectively regulated by controlling the ball-milling time. Although the density of defect sites increased with increasing ball-milling time, the surface area was high-est in BM2-VGCNF. Nonprecious-metal ORR catalysts (BMx-Fe-VGCNF) were prepared by NH3 pyrolysis of Fe-ion-adsorbed BMx-VGCNF. The ball-milling of VGCNF was effective to introduce nitrogen onto the catalyst. In particular, the controlled ball-milling was important to generate highly active sites on the catalyst surface. Among the catalysts studied, BM2-Fe-VGCNF exhibited the best ORR performance, which was 2.5-times greater than that of BMx-Fe-VGCNF (x=4, 6).

In this paper, we report the preparation of highly active and durable ordered intermetallic PdFe catalyst supported on carbon black for formic acid oxidation reaction (FAOR) by high-temperature hea...

Designing a Pt-based catalyst with high oxygen reduction reaction (ORR) performance is very important for the improvement of the economic feasibility of polymer electrolyte fuel cells. Herein, we suggest a method to prepare a Pt-based core-shell catalyst with high ORR activity and durability by galvanic displacement between Cu on a thermally annealed sample of (PtxAuy)1Cu5/C-HT and Pt ions. The resultant catalysts ((PtxAuy)1Cu5@Pt/C) showed a porous core–shell structure with a Pt-enriched surface. The composition of (PtxAuy)1Cu5/C-HT influenced the physical properties of the resultant (PtxAuy)1Cu5@Pt/C catalysts. (PtxAuy)1Cu5@Pt/C catalysts exhibited better ORR performance than a commercial Pt/C one and their performance varied with the composition. Among the catalysts examined, (Pt1Au0.1)1Cu5@Pt/C showed the best ORR activity. Specifically, it delivered a mass and specific activity of 0.660 mA/mgPGM and 1506.2 mA/cm2Pt at 0.9 V (vs. RHE), respectively. These are 2.7 and 4.2 times higher than corresponding values obtained for Pt/C. In an accelerated degradation test, addition of Au proved beneficial for the design of a highly durable catalyst. The effect of the Au content on the physical properties and ORR performance of catalysts was interpreted in detail.

Platinum alloys with other transition metals are widely used as catalysts as a promising strategy to improve the activity. However, the vulnerability of transition metals to the liquid electrolyte and fuel gases present during the device operation results in degradation of the catalytic activity. Highly stable catalyst is achieved by encapsulating the carbon-supported PtCo intermetallic core nanoparticles in a robust Pt shell. The hydride from Hantzsch ester reduces the residual Cl on the surface of the Pt skeleton and slowly forms negatively charged defect sites without damaging the core structure. Then, a secondary Pt reduction reaction via the hydride is employed to cover the activated surfaces of the Pt skeleton to optimize the shell thickness without the formation of isolated Pt nanoparticles. The PtCo@Pt with the unique Pt shell shows higher catalytic activity and durability than commercial Pt/C for oxygen reduction reaction electrocatalysts in proton exchange membrane fuel cells.

Herein, we prepare various types of PtCo nanocatalysts with Pt skin structure for oxygen reduction reaction (ORR) in acidic electrolyte by utilizing post-treatments such as acid leaching, additional Pt reduction (PtCo–Pt (chem)), and thermal annealing (PtCo–Pt (annealed)). The physical and electrochemical properties of these catalyst were analyzed and compared to commercial Pt/C. The Pt skin structure nanocatalysts exhibited approximately improved catalytic activity by 2-fold compared with commercial Pt/C catalysts owing to the optimization of d-band center of Pt by alloying effect with Co. Furthermore, the accelerated degradation test (ADT) was conducted under harsh condition and the Pt skin structure nanocatalysts displayed the superior ORR activity to initial performance of commercial Pt/C in spite of low loading amount of Pt. The causes of enhancement in long-term durability were investigated through several analysis after ADT subsequently. In particular, it is confirmed that the Pt skin structure of PtCo–Pt (chem) has contributed to improvement of durability by hindering dissolution of Co like as “nano-shield”.

Performance degradation generated by reverse current flow during fuel cell shut-down/start-up is a big challenge for commercialization of polymer electrolyte membrane fuel cells in automobile applications. Under transient operating conditions, the formation of H2/O2 boundaries on Pt surfaces and the occurrence of undesired oxygen reduction reaction (ORR) in an anode cause severe degradation of carbon supports and Pt catalysts in a cathode because of an increase of the cathode potential up to ∼1.5 V. Herein, to directly prevent the formation of H2/O2 boundaries in the anode, we propose a unique metal-carbon hybrid core-shell anode catalyst having Pt nanoparticles encapsulated in nanoporous carbon shells for selective H2 permeation. This hybrid catalyst exhibits high hydrogen oxidation reaction (HOR) selectivity along with fully subdued ORR activity during long-term operation because of the excellent stability of the carbon molecular sieves. Furthermore, the HOR-selective catalyst effectively suppresses the reverse current flow in a single cell under shut-down/start-up conditions.

Here, we prepare a bimetallic CuFe–N–C catalyst for the oxygen reduction reaction (ORR) by annealing metal precursor-adsorbed polyaniline under an NH3 gas atmosphere at high temperature. The catalyst exhibits higher ORR activity and durability than Pt/C and other monometallic Cu (Fe)–N–C catalysts in 0.1 M KOH. The remarkable catalytic activity of the CuFe–N–C catalyst is due to the interaction between Cu and Fe, which facilitates ORR and also results in higher contents of total N and active N species. In the same vein, single cell using the CuFe–N–C catalyst exhibits greatly enhanced performance compared to those using other catalysts.

To dramatically improve the performance of non-precious catalyst-based anion exchange membrane fuel cells (AEMFCs), a conceptual change in the structure of conventional electrocatalysts is needed. Here we report a novel work function tailoring of graphene via adopting a graphene shell-encapsulated Co nanoarchitecture to efficiently activate the graphitic carbon shell as an exclusive and main active site for the oxygen reduction reaction (ORR). Theoretical calculations and electrochemical analysis suggest that the charge transfer from core Co nanoparticles to the outer graphene shell results in a significant change in the electronic structure of the graphene shell and reduces its work function. The present catalyst shows high ORR catalytic activity but exceptionally enhanced durability compared to a Pt catalyst in alkaline media, which is attributed mainly to the reduced work function of the outer graphene shell and the 3D nanographene structure providing a large number of active carbon sites. The single cell using the graphene shell-encapsulated Co nanoparticles as a cathode catalyst produces a high maximum power density of 412 mW cm−2, making this among the best non-precious catalysts for the ORR reported so far. Therefore, our results demonstrate a promising strategy to rationally design inexpensive and durable oxygen reduction catalysts, and this hybrid concept will provide a new perspective for catalyst structures which can practically be used in AEMFCs.

Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell electrocatalysis. However, direct synthesis of homogeneous intermetallic alloy nanocatalysts on carbonaceous supports with high loading is still challenging. Herein, we report a novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading. Importantly, a unique bimetallic compound, composed of [M(bpy)

Despite recent efforts on replacing a noble Pt to less expensive catalysts (such as Pt-Ni and Pt-Co alloys) for improving oxygen reduction reaction (ORR) for PEMFC (polymer electrolyte membrane fuel cell) application, the performance and stability of a noble Pt catalyst still remains superior. In the present study, we have proposed the systematic procedure for designing the Ir3M (M = 3d, 4 d, 5 d transition metal) nanoalloy as Pt alternatives with enhanced ORR activity and stability using density functional theory (DFT) and experimental methods. First, we computationally optimized the surface occupied/unoccupied d states and lattice distance of the thermodynamically-stable Ir3M nanoalloy in order to achieve the wanted oxygen affinity for promoting ORR. In the next screening process, the nanoalloy prone to the segregation of inside M atom toward the surface layer was excluded, leading ultimately to the potential candidates such as the pure Ir monolayer on the top of Ir3Cr, Ir3V, Ir3Re, and Ir3Tc alloy cores. Finally, a pure Ir monolayer on the top of Ir3Cr core (which was expected to show the most enhanced ORR activity among the computationally-screened candidates) was experimentally prepared via physical vapor deposition method (PVD) and electrochemically evaluated for confirming our DFT prediction. Our synthesis successfully produced a 3 nm Ir-covered (so-called Ir skinlayer) Ir3Cr nanoparticle (Ir/Ir3Cr), which displayed the surface lattice contraction by 1.03% compared to the pure Ir case. The specific activity (at 0.7 V vs RHE) of a Ir/Ir3Cr catalyst with the very high durability (showing only 0.05% decrease from the initial activity after 3000 potential cycles) was 12.3 times higher than a Ir catalyst. The detail mechanism on the enhanced activity in Ir-M alloy was also examined. The design principle of alloy catalysts used in this study can be further extended to the screening of catalytic materials for the application to the next-level electrochemical reaction.

MoO2 microspheres doped with various metal species (Zr, Ti or Co) were simply prepared by means of a one-step ultrasonic spray pyrolysis. The dopant metal species were used as a reducing agent to promote the synthesis of MoO2, which is a metastable phase. The differences in electronegativity and radius between Mo and the dopant metal species influenced the structure and catalytic activity of the resulting MoO2 material. Partial oxidation of n-dodecane, a surrogate of Jet A fuel, was performed to evaluate the catalytic activity of MoO2 spheres doped with Zr, Ti, or Co. Among the produced samples, Co-doped MoO2 microspheres showed the highest H2 and CO yield as well as the highest C12 conversion. Various metal-doped MoO2 microspheres (with Ti, Zr, or Co dopants) were simply prepared by means of a one-step ultrasonic spray pyrolysis, where the dopant metal species were used as a reducing agent to promote the synthesis of MoO2. The differences in electronegativity and radius between Mo and the dopant metal species influenced the structure and catalytic activity for partial oxidation of n-dodecane.

Proton exchange membrane fuel cells (PEMFC) are regarded as a promising renewable energy source for a future hydrogen energy society. However, highly active and durable catalysts are required for the PEMFCs because of their intrinsic high overpotential at the cathode and operation under the acidic condition for oxygen reduction reaction (ORR). Since the discovery of the exceptionally high surface activity of Pt3Ni(111), the octahedral PtNi nanoparticles have been synthesized and tested. Nonetheless, their milligram-scale synthesis method and poor durability make them unsuitable for the commercialization of PEMFCs. In this study, we focus on gram-scale synthesis of octahedral PtNi nanoparticles with Pt overlayers (PtNi@Pt) supported on the carbon, resulting in enhanced catalytic activity and durability. Such PtNi@Pt catalysts show high mass activity (1.24 A mgPt−1) at 0.9 V (vs RHE) for the ORR, compared to commercial Pt/C (0.22 A mgPt−1). Single-cell performance and electrochemical impedance spectroscopy (EIS) were also tested. The PtNi@Pt catalysts showed enhanced current density of 3.1 A cm−2 at 0.6 V in O2 flow while the commercial Pt/C had the value of 2.5 A cm−2. After 30,000 cycles of the accelerated degradation test (ADT), the PtNi@Pt still showed better performance than the commercial Pt/C in a single-cell system. The Pt layers deposition could enhance the catalytic performance and durability of octahedral PtNi nanoparticles.

In this study, IrO2-coated Ti mesh (e-IrO2/Ti) is proposed to be an efficient and durable oxygen electrode for high-temperature polymer-membrane-electrolyte water electrolyzers (HT-PEMWEs). A thin IrO2 film of submicron thickness was uniformly coated onto a porous Ti mesh substrate by anodic electrodeposition. The electrodeposited IrO2 film plays the dual role of a catalyst layer for the oxygen evolution reaction (OER), and a corrosion-protection layer that prevents oxidation of the inner Ti. The e-IrO2/Ti exhibited high performance (0.97 A cm−2 at 1.6 V) despite a low IrO2 loading (0.4 mg cm−2) in single-cell tests conducted at 120 °C, which is comparable to that of conventional electrodes with greater catalyst loadings (0.8–5 mg cm−2). Furthermore, corrosion polarization tests reveal that the IrO2 coating physically blocks exposure of the Ti diffusion layer, thereby reducing Ti corrosion by 82% in 0.5 M H2SO4 at 25 °C. The low degradation rate (1.5 mA cm‐2 h−1 (0.11% h−1)) obtained in aging experiments at 120 °C and 1.72 V (voltage efficiency of 85%) confirms the excellent stability of this electrode.

Carbon-supported hollow PdCu2@Pt core@shell nanoparticles with ordered intermetallic cores were prepared as an efficient and durable oxygen reduction reaction (ORR) electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs). PdCu2 cores prepared using a chemical reduction method were thermally treated to produce ordered intermetallic structures. A Pt shell was then deposited via a galvanic displacement process. The effect of the galvanic displacement conditions on the properties and structure of the obtained core–shell nanoparticles was investigated by varying the solution pH and anion concentration. Acidic conditions and low Cl− concentrations were found to provide a uniform Pt layer with a hollow core, while maintaining the ordered intermetallic core structure. These hollow PdCu2@Pt core@shell nanoparticles showed high activity and stability for ORR electrocatalysis in PEMFCs.

The strategy of employing Pt alloys with other transition metals (TMs) is advantageous owing to the enhancement of the oxygen reduction reaction (ORR) activity and the reduction of Pt usage. The ternary alloy system with early TMs can overcome stability issues and even enhance the intrinsic activity of the catalysts owing to rearrangement of electronic structures between three metal elements. Herein, efficient catalysts with V—an early TM—were successfully obtained via a plasma-induced alloying strategy. The effect of V in the PtCoV/C catalyst, which exhibits the highest ORR activity among the synthesized Pt–TM–V (TM = Co, Ni, Cu) catalysts, was determined. The addition of V induces electron rearrangement in PtCoV, inhibiting the oxidation of Co and V and optimizing the oxygen-binding energy of Pt. Thus, incorporation of V into PtCoV nanoparticles enhances the electrochemical ORR activity and stability. The catalytic performance of PtCoV achieved 966 mV of half-wave potential, 3.05 A/ mg PGM of mass activity, and 8.58 mA/ cm Pt 2 of specific activity. This systemic strategy not only proposes a novel and facile approach for the synthesis of ternary alloy catalysts but also reveals the intricacies of the catalytic activity, allowing the application of ternary alloy electrocatalysts.

Unitized regenerative fuel cells (URFCs) are electrochemical devices operating as both fuel cells (FCs) or water electrolysis (WE). For practical efficiency in both FC and WE operations, a substantial amount of platinum and iridium, up to 3 mg cm−2, is often employed in URFCs. The main obstacle in catalysis of the URFC is oxygen reduction or water oxidation reactions for FC or WE operation, respectively. The electrode also requires different affinities for water, that is, hydrophobicity and hydrophilicity for gas and water transport, respectively. In this study, the water flux of the anode and cathode electrodes is systematically controlled by manipulating the relative humidity of the supplied gas and altering the selection of the electrode in amphiphilic membrane electrode assembly. By investigating the operation factors of URFC, 51 % of high round trip efficiency (@ 0.4 A cm−2) was achieved with only 0.65 mg(Pt+Ir) cm−2 of the noble catalyst.

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.

Pt-based multistructured nanocatalysts such as alloy, core–shell, and surface Pt-rich nanoparticles have been extensively studied for hydrogen fuel cell applications, and their catalytic performances for oxygen reduction reactions have been significantly upgraded for decades. Due to these technical enhancements, Pt-based nanoarchitectures have turned out to be compatible with commercially accessible fuel cell systems. In addition, based on physical and electrochemical backgrounds for the basic catalyst nanoarchitectures, novel catalyst designs with organic–inorganic hybrid concepts have been recently developed to more effectively improve the electrochemical reaction activities and durabilities. In this review, the typical class of Pt-based nanocatalysts are systematically explained according to their compositions and structures, and the emerging class of organic–inorganic hybrid catalyst designs are then thoroughly introduced. It is expected that the most recent improvements of Pt-based nanoarchitectures ...

A Rh–Sn nanoparticle is achieved by combinatorial approaches for application as an active and stable electrocatalyst in the oxygen reduction reaction. Both metallic Rh and metallic Sn exhibit activities too low to be utilized for electrocatalytic reduction of oxygen. However, a clean and active Rh surface can be activated by incorporation of Sn into a Rh nanoparticle through the combined effects of lateral repulsion, bifunctional mechanism, and electronic modification. The corrosion-resistant property of Rh contributes to the construction of a stable catalyst that can be used under harsh fuel cell conditions. Based on both theoretical and experimental research, Rh–Sn nanoparticle designs with inexpensive materials can be a potential alternative catalyst in terms of the economic feasibility of commercialization and its facile and simple surfactant-free microwave-assisted synthesis.

In this study, Cu–N–C catalysts were prepared by annealing metal-adsorbed polyaniline (PANI) or Vulcan carbon (VC), and their electrocatalytic properties were investigated. The results showed that Cu is used for the generation of active sites as well as utilized as the active component for oxygen reduction reaction (ORR). The catalysts prepared using PANI delivered higher ORR activity than those prepared with VC. Furthermore, the ORR activities of the prepared catalysts can be tuned by the heat-treatment conditions. The PANI-derived catalyst obtained under an NH 3 atmosphere showed the highest ORR performance among the prepared catalysts.

Electrochemical water splitting is one of the most promising systems by which to store energy produced from sustainable sources, such as solar and wind energy. Designing robust and stable electrocatalysts is urgently needed because of the relatively sluggish kinetics of the anodic reaction, i.e. the oxygen evolution reaction (OER). In this study, we investigate the anomalous in situ activation behaviour of carbon-supported Ni2P nanoparticles (Ni2P/C) during OER catalysis in alkaline media. The activated Ni2P/C shows an exceptionally high activity and stability under OER conditions in which the overpotential needed to achieve 10 mA cm−2 was reduced from approximately 350 mV to approximately 300 mV after 8,000 cyclic voltammetric scans. In situ and ex situ characterizations indicate that the activity enhancement of Ni2P catalysts is due to a favourable phase transformation of the Ni centre to β-NiOOH, including increases in the active area induced by structural deformation under the OER conditions. These findings provide new insights towards designing transition metal/phosphide-based materials for an efficient water splitting catalyst.

Pt shells were synthesized on Pd-based alloy-cores via the chemical reduction method. Pt shells containing 1, 2, or 3 layers were prepared by controlling the amounts of Pt precursor used during synthesis. The thicknesses of Pt shell layers were calculated using the difference in the particle size between core and core-shell nanocatalysts, as determined from Cs-corrected scanning transmission electron microscopy (Cs-STEM) data. The shape and elemental distribution in the core-shell structured nanoparticles were analyzed using line profiles and elemental mapping from Cs-STEM. High-resolution X-ray diffraction and X-ray photoelectron spectroscopy analyses suggested that the structural and electronic properties of core-shell nanocatalysts were dependent on the number of shell layers. The activity and durability of the core-shell nanocatalysts were analyzed by the electrochemical method. Accelerated durability tests (ADT) were conducted in the potential range of 0.6–1 V for 10000 cycles, and the mass and specific activities of ADT were shown to be stable for the carbon-supported core-shell nanocatalyst with two Pt shell layers (core@Pt[2](*)/C). In addition, excellent electrochemical performance was observed for the core@Pt[2]/C sample before and after the ADT compared to the commercial samples as well as other samples prepared in this study. Importantly, the optimized Pt usage demonstrated in this study would significantly contribute to the commercialization of proton exchange membrane fuel cells.

Carbon-based nanomaterials are frequently used as a support for proton exchange membrane fuel cell (PEMFC) catalysts, due to their high electrical conductivity and large surface area; however, the limited long-term stability of carbon-based catalysts under PEMFC operation causes huge problems in practical applications. Here we report the use of vanadium nitride (VN) nanofiber membrane as a highly durable catalyst support for oxygen reduction reaction (ORR). Nanofibrous VN was prepared using a simple electrospinning process, followed by sequential heat treatments in air and NH 3 . The NH 3 treatment temperature affected the crystallinity as well as the crystal size of VN, which ultimately affected the catalytic ORR activity of Pt-decorated catalysts. The optimized Pt/VN catalysts exhibited excellent ORR activity and durability in acid electrolyte. Much higher durability of Pt/VN than Pt/C was verified by chrono-amperometry analysis. Density functional theory (DFT) calculations provided further evidence of the strong interaction of Pt and VN, which contributed to the high stability of the catalyst.

The microporous structure of Fe–N-doped carbon (Fe–N–C) catalysts plays a pivotal role in the oxygen reduction reaction (ORR) because the catalytically active N-coordinated Fe ion sites are located within accessible micropores (

Efficient water management is considered a prerequisite to advance the commercialization of anion exchange membrane fuel cells because water imbalance not only results in flooding and drying issues in the electrodes, but also leads to performance degradation. Herein, strategic electrode structures to achieve desirable water behavior during operation are reported. Carbon supports are employed as reservoirs to store the produced water and as carbon-supported catalysts with poly(N-isopropylacrylamide), possessing hydrophobic characteristics at the operating temperatures, as the polymer entangles by itself. This polymer is preferentially functionalized on the carbon surface before the reduction of the precursors to minimize the blocking of the catalyst active sites. X-ray photoelectron spectroscopy and electrochemical analyses support that the electronic structures of the catalysts are not significantly affected even when the polymer is functionalized. Furthermore, the synergistic effect of the reservoir and thermo-responsive polymer is demonstrated in a real device exhibiting performance enhancement. The resulting electrode shows 11.9% increase in the current density at 0.6 V and 21.3% increase in the maximum power density compared to those observed with the conventional electrodes. This phenomenon is attributed to favorable water distribution, as confirmed by in-situ visualization via synchrotron X-ray imaging.

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/cm2 (at 0.9 V) and 19 mV (half-wave potential), and those of Pt/C were 1.26 mA/cm2 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.

Although the electrochemical hydrogen evolution reaction (HER) has been intensively investigated for decades as a promising hydrogen production source, its economic feasibility is still questionable because of the high cost of Pt-based electrocatalysts. Transition metal phosphides are potential replacements for Pt; however, a fundamental understanding of the active catalyst site chemistry is still lacking. Such an understanding is crucial to design robust catalytic materials. The aim of this study is to rationalize the HER on the active sites of nickel phosphide (Ni2P) nanowires. Using experimental and theoretical analyses, it can be concluded that the active site of Ni2P nanowires is an exposed Ni3P2 surface generated by the oxygenated Ni3P_P surface created during the HER. This work is a breakthrough in the efficient design of phosphide-based non-Pt catalysts for electrochemical hydrogen production.