Electrocatalysts For Oxygen Reduction Reaction Research Articles

Nitrogen, Fluorine, and Phosphorus Tri‐Doped Porous Carbon with High Electrical Conductivity as an Excellent Metal‐Free Electrocatalyst for Oxygen Reduction Reaction

AbstractToday's oxygen reduction reaction (ORR) depends on the precious metal Pt‐based catalysts, limiting the large commercialization of promising energy conversion technologies such as proton exchange membrane fuel cells (PEMFCs) and metal‐air batteries. Therefore, the rational design of low‐cost and highly efficient electrocatalysts for ORR is strongly desired. Herein, we report a porous carbon doped with nitrogen, fluorine, and phosphorus (N, F, P tri‐doped carbon) prepared via only a heating process using low‐cost glycine, ammonium fluoride, and phytic acid as precursors. X‐ray photoelectron spectroscopy (XPS) analysis revealed the existence of pyridinic‐N and the co‐existence of graphitic‐N and oxidized graphitic‐P, which can be active sites, with semi‐ionic C−F bonds highly boosting ORR activity. Remarkably, the resultant N, F, P tri‐doped carbon exhibited outstanding activity for the ORR with an onset potential comparable to that of commercial 20 wt % Pt/C catalyst, the half‐wave potential superior to that of the Pt/C catalyst, and the electron transfer number close to 4.

Molten Salt-Assisted Synthesis of Ferric Oxide/M-N-C Nanosheet Electrocatalysts for Efficient Oxygen Reduction Reaction.

Efficient, stable, and low-cost oxygen reduction catalysts are the key to the large-scale application of metal-air batteries. Herein, high-dispersive Fe2O3 nanoparticles (NPs) with abundant oxygen vacancies uniformly are anchored on lignin-derived metal-nitrogen-carbon (M-N-C) hierarchical porous nanosheets as efficient oxygen reduction reaction (ORR) catalysts (Fe2O3/M-N-C, M═Cu, Mn, W, Mo) based on a general and economical KCl molten salt-assisted method. The combination of Fe with the highly electronegative O induces charge redistribution through the Fe-O-M structure, thereby reducing the adsorption energy of oxygen-containing substances. The coupling effect of Fe2O3 NPs with M-N-C expedites the catalytic activity toward ORR by promoting proton generation on Fe2O3 and transfer to M-N-C. Experimental and theoretical calculation further revealed the remarkable electronic structure evolution of the metal site during the ORR process, where the emission density and local magnetic moment of the metal atoms change continuously throughout their reaction. The unique layered porous structure and highly active M-N4 sites resulted in the excellent ORR activity of Fe2O3/Cu-N-C with the onset potential of 0.977V, which is superior to Pt/C. This study offers a feasible strategy for the preparation of non-noble metal catalysts and provides a new comprehension of the catalytic mechanism of M-N-C catalysts.

Reaction-driven restructuring of defective PtSe2 into ultrastable catalyst for the oxygen reduction reaction.

PtM (M = S, Se, Te) dichalcogenides are promising two-dimensional materials for electronics, optoelectronics and gas sensors due to their high air stability, tunable bandgap and high carrier mobility. However, their potential as electrocatalysts for the oxygen reduction reaction (ORR) is often underestimated due to their semiconducting properties and limited surface area from van der Waals stacking. Here we show an approach for synthesizing a highly efficient and stable ORR catalyst by restructuring defective platinum diselenide (DEF-PtSe2) through electrochemical cycling in an O2-saturated electrolyte. After 42,000 cycles, DEF-PtSe2 exhibited 1.3 times higher specific activity and 2.6 times higher mass activity compared with a commercial Pt/C electrocatalyst. Even after 126,000 cycles, it maintained superior ORR performance with minimal decay. Quantum mechanical calculations using hybrid density functional theory reveal that the improved performance is due to the synergistic contributions from Pt nanoparticles and the apical active sites on the DEF-PtSe2 surface. This work highlights the potential of DEF-PtSe2 as a durable electrocatalyst for ORR, offering insights into PtM dichalcogenide electrochemistry and the design of advanced catalysts.

L10-PtCo and L12-Pt3Co Intermetallics for Oxygen Reduction Reaction: the Influence of Composition and Structure on Properties.

Pt-based intermetallics are regarded as highly efficient electrocatalysts for oxygen reduction reaction (ORR). However, Pt-based intermetallics with different Pt: M atomic ratios have different atomic arrangements and crystal structures, which will change the electronic structure and coordination environment of Pt, thus affecting the electrocatalytic activity. In this work, we prepared L12-Pt3Co and L10-PtCo intermetallic catalysts by modulating the molar ratio of Pt and Co precursors using a thermal annealing method. The mass activity (MA) of L10-PtCo is 0.52 A mg-1Pt at 0.9 V, which is 1.44 times larger than that of L12-Pt3Co (0.36 A mg-1Pt). In addition, the MA of L10-PtCo decreases by 17.31 % after 10,000 CV cycles, which is smaller than that of L12-Pt3Co (25.00 % loss in MA), showing excellent structural stability. Theoretical calculations reveal that compared to L12-Pt3Co, L10-PtCo has more electrons transferred to the Pt sites, which further optimizes the electronic structure of Pt and reduces the d-band center, leading to the increase of the electrocatalytic performance. This work provides new insights into the study of Pt-based intermetallics with different Pt: M ratios, which is helpful for the screening and preparation of high-performance Pt-based intermetallics.

Pt-decorated binary transition metal oxides (MnO-NiO, MnO-TiO2) for enhanced electrocatalysis of oxygen reduction and borohydride oxidation

Integrating transition metal oxides with precious metals is a strategic approach to designing cost-effective electrocatalysts with enhanced stability. Herein, platinum (Pt) nanoparticles (NPs) were prepared by microwave irradiation and anchored onto MnO and two binary metal oxides, MnO-NiO and MnO-TiO2, obtained by solid-state dispersion. Voltammetric and electrochemical impedance spectroscopy techniques evaluated their performance for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) in alkaline media. Tafel slope and the number of exchanged electrons, n, were determined to compare the three electrocatalysts’ performance for fuel cell applications. Pt/MnO-NiO revealed a Tafel slope of 177 mV dec–1 for ORR and an n value of ca. 4 and 3 e- for ORR and BOR, respectively. These findings demonstrate that Pt NPs supported on binary metal oxide supports, particularly Pt/MnO-NiO, are promising electrocatalysts for ORR and BOR in alkaline media, thus recommending their use in direct borohydride fuel cells.

Carbothermal Reduction-Assisted Synthesis of a Carbon-Supported Highly Dispersed PtSn Nanoalloy for the Oxygen Reduction Reaction.

Exploring high-performance and low-platinum-based electrocatalysts to accelerate the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries remains crucial. Herein, by combining electroless deposition and carbothermal reduction, a nitrogen-doped carbon-supported highly dispersed PtSn alloy nanocatalyst (PtSn/NC) was prepared for a high-efficiency ORR process. Electrochemical measurements show that PtSn/NC exhibits excellent electrocatalytic ORR activity with a half-wave potential of 0.850 V versus reversible hydrogen electrode (RHE), which is higher than that of commercial Pt/C (0.815 V). The PtSn/NC-based (20 μgPt cm-2) rechargeable Zn-air battery exhibited astonishing performance with a maximum power density of up to 150.1 mW cm-2, as well as excellent rate performance and charge/discharge stability. Physical characterization reveals that carbothermal reduction could compel the transformation of Sn oxide into metallic Sn, which then alloys with the deposited Pt atoms to form the PtSn nanoalloy, in which electrons are transferred from Sn atoms to neighboring Pt atoms, thereby improving the ability of Pt-based active sites to catalyze the ORR process in PtSn/NC by optimizing the unoccupied d-band of Pt atoms. This work provides a reliable and innovative route for the rational design of highly dispersed Pt-based alloy ORR electrocatalysts.

A Janus Platinum/Tin Oxide Heterostructure for Durable Oxygen Reduction Reaction.

Designing efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is essential for proton exchange membrane fuel cells (PEMFCs). Platinum-based catalysts are considered efficient ORR catalysts due to their high activity. However, the degradation of Pt species leads to poor durability of catalysts, limiting their applications in PEMFCs. Herein, a Janus heterostructure is designed for high durability ORR in acidic media. The Janus heterostructure composes of crystalline platinum and cassiterite tin oxide nanoparticles with carbon support (J-Pt@SnO2/C). Based on the synchrotron fine structure analysis and electrochemical investigation, the crystalline reconstruction and charge redistribution at the interface of Janus structure are revealed. The tightly coupled interface could optimize the valance states of Pt and the adsorption/desorption of oxygenated intermediates. As a result, the J-Pt@SnO2/C catalyst possesses distinguishing long-term stability during the accelerated durability test without obvious degradation after 40000 cycles and keeps the majority of activity after 70000 cycles. Meanwhile, the catalyst exhibits outstanding activity with half-wave potential at 0.905V and a mass activity of 0.355AmgPt -1 (2.7 times higher than Pt/C). The approach of the Janus catalyst paves an avenue for designing highly efficient and stable Pt-based ORR catalyst in the future implementation.

Lignin-derived Fe–N–C electrocatalyst with 3D porous structure for efficient oxygen reduction reaction

Developing low-cost, high-performance oxygen reduction reaction (ORR) catalysts is crucial for the commercialization of fuel cells and zinc-air batteries. Herein, we report a lignin-derived Fe/N co-doped 3D porous carbon electrocatalyst Fe-NLC-1 as an alternative to commercial Pt/C catalysts, which was synthesized by a green and facile in situ carbonization strategy. Fe-NLC-1 exhibits higher oxygen reduction activity with a half-wave potential (E1/2) of 0.90 V vs. RHE than commercial 20 wt% Pt/C (E1/2 = 0.85 V) in the alkaline conditions, as well as excellent methanol tolerance and stability. Furthermore, the Zn-air battery loaded with Fe-NLC-1 exhibits a maximum power density of 125 mW cm−2, an open circuit voltage of 1.477 V, and stable discharge performance, which are comparable or even better than the commercial Pt/C. This study highlights the potential of biomass-derived porous carbon materials for the development of high-performance ORR electrocatalysts.

Tuning d-band center of Pt via Pt-Pt5La heterostructure interface as efficient and stable electrocatalyst for oxygen reduction and methanol oxidation reactions in DMFCs

Developing Pt-based electrocatalysts with superior activity and durability is essential for direct methanol fuel cells (DMFCs), and regulating the interfacial electronic interaction for Pt-based composites can significantly modulate the electrocatalytic performances. Herein, the Pt-Pt5La/C heterostructure catalyst was developed to enhance the catalytic property towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Experimental analyses and theoretical calculations demonstrated the electron redistribution at the interface and reduction of the d-band center of Pt for this unique Pt-Pt5La/C heterostructure. As the results, Pt-Pt5La/C exhibited 5.0- and 6.4-times higher mass activity and specific activity towards alkaline ORR compared to Pt/C, and the excellent electrocatalytic MOR performance due to the interfacial interaction. These superior electrocatalytic property promoted Pt-Pt5La/C as the bifunctional catalyst for DMFC application with outstanding power density and durability. Consequently, this work proposed a novel interfacial regulation strategy for designing Pt-rare earth (RE) alloy heterostructures and their reliable operation of DMFCs.

Joule heating synthesis for single-atomic Fe sites on porous carbon spheres and armchair-type edge defect engineering dominated oxygen reduction reaction performance

Single-atom catalysts (SACs) embedded in heteroatom-doped carbon are the most promising oxygen reduction reaction (ORR) electrocatalysts. However, the expeditious and facile synthesis of high-performance SACs with Fe-Nx active sites and identifying the role of edge-type defect at the atomic level in carbon support are essential but remain challenging. Herein, joule heating is applied to anchor Fe single atoms on newly defect rich porous carbon spheres (Fe-N-DCSs) in milliseconds. Fe-N-DCSs achieves exceptional ORR performance, with a half-wave potential (E1/2) of 0.90V and E1/2 lost of only 20mV after 30,000 cycles in 0.1M KOH, and superior Zn-air batteries performances. Density functional theory calculations establish that armchair-type edge defects decorated Fe-N4 active sites boost the desorption of OH⁎ and diminish the ORR overpotential. This work not only provides a speedy route for the fabrication of SACs but also presents new insights into the excellent ORR activity.

The Development of Uniform-Sized Pt-Based Binary Alloy Electrocatalysts for ORR in Polymer Electrolyte Fuel Cells

Developing a highly efficient and durable reduced platinum metal (PtM) alloy catalyst with high oxygen reduction reaction (ORR)activity for polymer electrolyte fuel cells (PEFCs) is of significant interest. In this study, platinum-iron (PtFe), platinum-nickel (PtNi), and platinum-cobalt (PtCo) alloys were prepared with an average diameter of ca. 3 nm, uniformly dispersed on a high surface area carbon. The ORR activity of the prepared PtM/C catalysts was investigated under both RDE and MEA conditions. The resulting PtM/C catalysts demonstrated improved I-V cell performance at low-current density (LCD) and high-current density (HCD) regions. These findings suggest that high ORR activity and enhanced durability can be achieved through the formation of uniform Pt skin with higher electrochemical surface area (ECSA).

Pyrolysis of Copper Phthalocyanine as Non-noble Metal Electrocatalysts for Oxygen Reduction Reaction

Pyrolysis of Copper Phthalocyanine as Non-noble Metal Electrocatalysts for Oxygen Reduction Reaction

Engineering peripheral S-doped atomic Fe-N4 in defect-rich porous carbon nanoshells for durable oxygen reduction reaction and Zn-air batteries

Iron-nitrogen-carbon (Fe-N-C) single-atom materials have emerged as the most promising catalysts for the oxygen reduction reaction (ORR), which yet suffers from inadequate stability arising from the attack of ·OH and HO2· radicals generated by H2O2. In this study, density functional theory (DFT) calculations reveal that the presence of peripheral S atoms can regulate the electronic structure of the Fe center and suppress the formation of H2O2 to enhance the catalyst's durability. Thereafter, atomic Fe-N4 with peripheral S doping is intricately engineered in defect-rich porous carbon nanoshells (Fe-NS-C) through an adsorption-pyrolysis method. The incorporation of S not only optimizes the coordination microenvironment of Fe-N4 but also induces a larger specific surface area and richer defects. The Fe-NS-C catalyst displays remarkable ORR performance, featuring a half-wave potential (E1/2) of 0.90 V. Its low H2O2 yield (below 1.1 %) and excellent stability (10 mV day in E1/2 after 10,000 cycles) further underscore the superiority of Fe-NS-C. When employed as the cathode for Zn-air battery, Fe-NS-C achieves an impressive peak power density of 230.1 mW cm−2 and stable charge/discharge potentials over an extended duration of 150 h. This study presents an effective strategy for engineering efficient and durable single-atom electrocatalysts for ORR and Zn-air batteries.

Spin Manipulation of Heterogeneous Molecular Electrocatalysts by an Integrated Magnetic Field for Efficient Oxygen Redox Reactions.

Understanding the spin-dependent activity of nitrogen-coordinated single metal atom (M-N-C) electrocatalysts for oxygen reduction and evolution reactions (ORR and OER) remains challenging due to the lack of structure-defined catalysts and effective spin manipulation tools. Herein, both challenges using a magnetic field integrated heterogeneous molecular electrocatalyst prepared by anchoring cobalt phthalocyanine (CoPc) deposited carbon black on polymer-protected magnet nanoparticles, are addressed. The built-in magnetic field can shift the Co center from low- to high-spin (HS) state without atomic structure modification, affording one-order higher turnover frequency, a 50% increased H2O2 selectivity for ORR, and a ≈4000% magnetocurrent enhancement for OER. This catalyst can significantly minimize magnet usage, enabling safe and continuous production of a pure H2O2 solution for 100 h from a 100 cm2 electrolyzer. The new strategy demonstrated here also applies to other metal phthalocyanine-based catalysts, offering a universal platform for studying spin-related electrochemical processes.

Ni-Phthalocyanine Derived Electrocatalysts for Oxygen Reduction Reaction and Hydrogen Evolution Reaction: Active Sites Formation and Electrocatalytic Activity

Ni-Phthalocyanine Derived Electrocatalysts for Oxygen Reduction Reaction and Hydrogen Evolution Reaction: Active Sites Formation and Electrocatalytic Activity

Aminotriazine derived N-doped mesoporous carbon with a tunable nitrogen content and their improved oxygen reduction reaction performance.

The electrocatalytic activity of carbon materials is highly dependent on the controlled modulation of their composition and porosity. Herein, mesoporous N-doped carbon with different amounts of nitrogen was synthesized through a unique strategy of using a high nitrogen containing CN precursor, 3-amino 1,2,4 triazine (3-ATZ) which is generally used for the preparation of carbon nitrides, integrated with the combination of a templating method and high temperature treatment. The nitrogen content and the graphitisation of the prepared materials were finely tuned with the simple adjustment of the carbonisation temperature (800-1100 °C). The optimised sample as an electrocatalyst for oxygen reduction reaction (ORR) exhibited an onset potential of 0.87 V vs. RHE with a current density of 5.1 mA cm-2 and a high kinetic current density (Jk) of 33.1 mA cm-2 at 0.55 V vs. RHE. The characterisation results of the prepared materials indicated that pyridinic and graphitic nitrogen in the carbon framework promoted ORR activity with improved four-electron selectivity and excellent methanol tolerance and stability. DFT calculations demonstrated that the structural and planar defects in the N-doped carbon regulated the surface electronic properties of the electrocatalyst, leading to a reduction in the energy barrier for the ORR activity. This strategy has the potential to unlock a platform for designing a series of catalysts for electrochemical applications.

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

Earth-Abundant Divalent Cation High-Entropy Spinel Ferrites as Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions

N, S Co-Doped Carbon Nanotubes Loaded With Cu Nanoclusters For Efficient Oxygen Reduction Reaction.

Developing highly superior precious-metal-free electrocatalysts for oxygen reduction reaction (ORR) are challenging and great significance. In this study, it is reported that an efficient ORR catalysts with N and S co-doped carbon nanotubes anchored to copper (Cu) nanoclusters by mechanical grinding and high temperature heat treatment. The obtained Cu-S1-N-C electrocatalysts exhibited a high ORR performance with an onset potential (Eonest) of 0.989 V and a half-wave potential (E1/2) of 0.905 V (vs. RHE) in alkaline electrolyte, which was superior to that of commercial Pt/C catalyst. In contrast to N doping alone, the defect structures and active species of the catalysts were optimized by precise modulation of S-atom doping, and moreover, the introduction of S-atoms provided more thiophene-sulfur active sites. This study provides an innovative idea for designing excellent ORR catalysts.

Modulating Spin of Atomic Manganese Center for High-Performance Oxygen Reduction Reaction.

Single atom catalysts (SACs) are promising non-precious catalysts for oxygen reduction reaction (ORR). Unfortunately, the ORR SACs usually suffer from unsatisfactory activity and in particular poor stability. Herein, we report atomically dispersed manganese (Mn) embedded on nitrogen and sulfur co-doped graphene as an efficient and robust electrocatalyst for ORR in alkaline electrolyte, realizing a half-wave potential (E1/2) of 0.883 V vs. reversible hydrogen electrode (RHE) with negligible activity degradation after 40,000 cyclic voltammetry (CV) cycles in 0.1 M KOH. Introducing sulfur (S) to form Mn-S coordination changes the spin state of single Mn atom from high-spin to low-spin, which effectively optimizes the oxygen intermediates adsorption over the single Mn atomic sites and thus greatly improves the ORR activity.

Inclusion Strategy for Constructing S/N Orbital Hybridization-Regulated sp3/sp2 Carbon toward Boost Electrocatalysis.

Metal-free carbon-based electrocatalysts have gained significant attention in the field of zinc-air batteries (ZABs) due to their affordability, good conductivity and chemical stability. However, unmodified carbon materials typically fall short in adsorbing and activating the substrates and intermediates involved in oxygen reduction reactions (ORR). Here, a metal-free carbon-based electrocatalyst with S atom p orbital hybrid modified N-sp3/sp2 carbon structure (C/NS) were prepared by cyclodextrins inclusion. The catalyst demonstrates impressive ORR activity (E1/2=0.885 V vs. RHE) and robust ZABs performance with a power density of 171.3 mW cm-2 and a specific capacity of 781.2 mAh g-1. Density functional theory (DFT) calculation reveals that S atom effectively regulates the charge distribution and p-band center of active site carbon atom in the N-sp3/sp2 carbon structure. This modification prompts the adsorption and dissociation of O2 and intermediates, resulting in higher reactive activity. This work provides a valuable and practical strategy for preparing cost-effective metal-free carbon-based electrocatalysts for ORR with high performance.