Electrocatalysts For Oxygen Reduction Reaction Research Articles

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.

Boron-Doped Biomass Carbon Nanostructures as Electrocatalysts for the Two-Electron Oxygen Reduction Reaction

Boron-Doped Biomass Carbon Nanostructures as Electrocatalysts for the Two-Electron Oxygen Reduction Reaction

Designing Highly Efficient Electrocatalyst for ORR and OER Based on Nb2CO2 MXene: The Role of Transition Metals and N-Doping Content.

Finding efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative for advancing zinc-air batteries. Herein, the effect of transition metal anchored on Nb2CO2 with different N content to form TM-Nx-Nb2CO2 on the catalytic activity of ORR and OER is investigated by density functional theory. Among all the designed TM-Nx-Nb2CO2, Pt-N12.50%-Nb2CO2, Pt-N37.50%-Nb2CO2, Pt-N50.00%-Nb2CO2, Pd-N68.75%-Nb2CO2, and Pd-N100%-Nb2CO2 are excellent ORR electrocatalysts with ηORR values of 0.38, 0.36, 0.38, 0.38, and 0.34 V, respectively. Rh-Nb2CO2, Rh-N12.50%-Nb2CO2, Rh-N31.25%-Nb2CO2, Rh-N37.50%-Nb2CO2, Rh-N50.00%-Nb2CO2, Pt-N50.00%-Nb2CO2, Rh-N68.75%-Nb2CO2, and Rh-N81.25%-Nb2CO2 are excellent OER electrocatalysts with ηOER values of 0.33, 0.37, 0.34, 0.36, 0.37, 0.34, 0.38, and 0.33 V, respectively. Notably, Rh-Nb2CO2 and Pt-N50.00%-Nb2CO2 exhibit outstanding ORR and OER bifunctional catalytic activity with potential gap values of 0.80 and 0.72 V, respectively, which are higher than the activities of most reported bifunctional catalysts. Furthermore, electronic structure analysis indicates that the moderate adsorption strength of oxygen-containing intermediates on active centers is crucial for achieving highly active bifunctional catalysts for ORR and OER. This study provides a strategy for the design of novel ORR and OER catalysts using 2D MXene materials.

Direct Synthesis of Pd2+‐Rich Palladene Aerogels as Bifunctional Electrocatalysts for Formic Acid Oxidation Reaction and Oxygen Reduction Reaction

AbstractIn this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature‐dependent growth mechanism. Besides the typical three‐dimensional networks and wrinkled surface morphologies, the as‐prepared aerogel is endowed with abundant Pd2+. The as‐prepared aerogel exhibits an excellent mass activity in the formic acid oxidation reaction and a good half‐wave potential in the oxygen reduction reaction in comparison with Pd/C and a Pd aerogel. This work expands the range of metal aerogels from the perspective of the building block units and demonstrates a direct approach to fabricate highly promising bifunctional electrocatalysts for fuel cells.

Spinel oxide modified FeCoNi alloy composites prepared with one-step pyrolytic reduction as bifunctional catalyst for ORR/OER

The development of low-cost and highly efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) is a challenging topic in the fuel cells and metal-air batteries field. Herein, a noble metal-free composite consisting of nano-FeCoNi alloy and spinel oxide was successfully prepared through a simple one-step pyrolytic reduction strategy as identified by XRD, TEM, HRTEM, XPS, and other techniques. The effect of the reduction temperatures (700, 850, and 950 °C) on the composite structure as well as its OER/ORR performances was further investigated. It was observed that FeCoNi@Mn2AlO4 was harvested at the temperature of 700 °C, while FeCoNi@MnAl2O4 was finally formed when the reduction temperature was 850 °C and 950 °C. The composites showed comparable electrocatalytic performance to Pt/C in ORR as well as RuO2 in OER. Moreover, all three catalysts showed great potential for bifunctional catalysis while FeCoNi@MnAl2O4-850 with a ΔEgap of 0.75 V, FeCoNi@MnAl2O4-950 with a ΔEgap of 0.77 V, and FeCoNi@Mn2AlO4-700 with a ΔEgap of 0.83 V. Density functional theory (DFT) computations further confirmed the synergistic effect between FeCoNi and MnAl2O4. This work provides a facile approach to prepare an alternative bifunctional composite electrocatalyst for ORR/OER with deep understanding on the structure-performance relationship.

Single-atom nickel on defective g-C4N3 as a promising bifunctional electrocatalyst for the OER and ORR: a first-principles analysis

Searching for inexpensive and highly active materials to replace noble metals for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is an important challenge. The two-dimensional semi-metallic carbon nitride g-C4N3 is an excellent candidate for electrochemical reactions owing to its eminent conductivity and stability. Here, using density functional theory (DFT) a series of low-budget non-noble transition metal single-atom (SAC) loaded on the g-C4N3 (named as TM@C4N3, TM = Cr, Mn, Fe, Co, Ni, Cu) were investigated as electrocatalysts for OER and ORR. Ni@C4N3 shows an enormous application potential as electrode material, with OER and ORR overpotentials of 0.59 V and 0.23 V, respectively. The second lowest binding energy between Ni and support g-C4N3 indicates that Ni@C4N3 possesses good overall stability. The d-band center as well as metal valence as the descriptor exhibit good agreement with the adsorption energy of the intermediate. A linear relationship exists among the adsorption energies of the three intermediates O, OH, and OOH, given the similarity that they are all bonded to the metal through one oxygen atom. By adjusting the adsorption energy of these intermediates, the catalytic activity of electrocatalysts can be tuned for OER and ORR. This study confirmed that Ni@C4N3 is a good bifunctional catalyst and provides important guidance for the design of bifunctional electrocatalysts for OER and ORR.

Synthesis of polyhedral Pt-Pd-Ni nanobelts regulated by W(CO)6 and applied as a highly performing oxygen reduction reaction electrocatalyst

Pt-Pd-Ni polyhedral nanobelt (PNBs) composite catalysts are synthesized in presence of tungsten hexacarbonyl [W(CO)6] by a simple solvothermal method, combining both higher specific surface area and more index active site than the corresponding single-structure catalysts. The thermal decomposition of W(CO)6 plays a crucial role in the morphology formation. The tenuous composite with a moderate nanobelt width of 7.46 nm formed after heating for 6 h (Pt-Pd-Ni PNBs2) shows better ORR performance and durability than the ternary (Pt-Pd-Ni) and binary (Pt-Pd) single structures. It exhibits a mass activity of 1.49 (A mgPt−1), which only degrades by about 10.63 % after 50,000 durability cycles. The metal regulatory effects induced by the carbonyl compounds cause the contraction of the Pt-Pt bonds. Density functional theory calculations indicate that the compressive strain of Pt-Pd-Ni PNBs2 leads to a decrease in the d-band center and overpotential negatively shifted, thus provide a more sufficient and faster ORR proceeding process in thermodynamics, facilitating a higher energy conversion efficiency.

Nitrogen and sulfur incorporated chitosan-derived carbon sphere hybrid MXene as highly efficient electrocatalyst for oxygen reduction reaction

The quest for non-precious electrocatalysts through biomass for energy applications has attracted keen interest, but optimization for fuel cells remains challenging. Herein, we have developed a nitrogen and sulfur-anchored MXene hybrid chitosan-derived carbon sphere (N,S-MXC) reporting for the first time as a novel oxygen reduction reaction (ORR) electrocatalyst. Interestingly, as the mass ratio of MXene to Chitosan varied by (1:2, 1:1, and 2:1), the microstructures of the as-prepared catalysts changed, which drastically influenced the corresponding ORR performance. Notably, when the mass ratio was maintained to be 1:2, Ti3C2 nanoparticles were dispersed on the surface of the biomass carbon core shell. They created multimodal porous morphology that helps to facilitate faster electron transfer, resulting in a high onset-potential of 0.89 V and limiting current density of −4.2 mA/cm2 as well as excellent durability with minimum half-wave potential loss of 2.3 mV after 5000 cyclic voltammetry (CV) cycles than benchmark Pt/C. In addition, the corresponding catalyst also possessed robust stability of 87.47 % and an excellent methanal poisoning tolerance effect in an alkaline medium. In a nutshell, this work paves the pathway for converting sea animal waste to develop porous carbon as supporting material for fuel cells that directly or indirectly support achieving carbon neutrality.

Elucidating the effects of nitrogen and phosphorus co-doped carbon on complex spinel NiFe2O4 towards oxygen reduction reaction in alkaline media

The study presents for the first time complex spinel NiFe2O4 nanoparticles supported on nitrogen and phosphorus co-doped carbon nanosheets (NPCNS) prepared using sol gel and the carbonization of graphitic carbon nitride with lecithin as a highly active and durable electrocatalyst for oxygen reduction reaction. The physicochemical properties of complex spinel NiFe2O4 on NPCNS and subsequent nanomaterials were investigated using techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrochemical activity of the electrocatalysts was evaluated using hydrodynamic linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. The electrocatalytic performance of the NiFe2O4/NPCNS nanohybrid electrocatalyst is dominated by the 4e− transfer mechanism, with an onset potential of 0.92 V vs. RHE, which is closer to that of the Pt/C, and a current density of 7.81 mA/cm2 that far exceeds that of the Pt/C. The nanohybrid demonstrated the best stability after 14 400 s, outstanding durability after 521 cycles, and the best ability to oxidize methanol and remove CO from its active sites during CO tolerance studies. This improved catalytic activity can be attributed to small nanoparticle sizes of the unique complex spinel nickel ferrite structure, N-Fe/Ni coordination of nanocomposite, high dispersion, substantial ECSA of 47.03 mF/cm2, and synergy caused by strong metal-support and electronic coupling interactions.

Structure adjustment on Fe-based electrocatalyst to regulate oxygen reduction reaction selectivity for Zn-air battery and H2O2 production

Fe-based materials are famous electrocatalysts in oxygen reduction reaction (ORR), but their selectivity towards four- or two-electron ORR still requires further research in detail. Herein, two Fe-based ORR electrocatalysts are synthesized from MIL-101, a metal–organic framework (MOF). After calcined with dicyandiamide (DCDA) under N2 protection, Fe3O4@NCNTs (NCNTs = N-doped carbon nanotubes) is synthesized, in which small Fe3O4 particles reside in NCNTs homogeneously. It is a typical four-electron electrocatalyst in both alkaline and neutral electrolyte. Without DCDA, Fe2O3 forms and it acts as two-electron electrocatalyst in ORR. Theoretical calculation suggests the discrepancy in ORR selectivity between Fe3O4@NCNTs and Fe2O3 roots from their different interactions with OOH*. If Fe3O4@NCNTs serves as cathode material, peak power density of Zn-air battery reaches 125.1 mW·cm−2 in alkaline electrolyte. When discharge at 10 mA·cm−2, the specific capacitance and energy density reach 799.7 mAh·g−1 and 839.7 Wh·kg−1. The performance of Fe3O4@NCNTs is also well kept in neutral Zn-air battery. We expect this work elucidates the effect of structure on ORR selectivity for Fe-based electrocatalysts.

Single atom catalyst induced by redox reaction between iron ion and aniline monomer

The effective design of a low-cost, efficient, and stable non-noble metal electrocatalyst to substitute the noble metal electrocatalyst for oxygen reduction reaction is highly significant. Even though atomically dispersed metal catalyst shows excellent catalytic activity with maximized atom efficiency, the challenge often lies in achieving uniform distribution for single-atom catalysts owing to their tendency to aggregate. In this work, we present a sequential method that involves the reduction of iron (Fe) mediated by aniline (anchored on support), followed by pyrolysis to fabricate the Fe-Nx moieties and achieve the high density of single atom active sites. The resulting Fe SA 900 catalyst exhibited a half-wave potential of 0.84 V vs. reversible hydrogen electrode (RHE) for oxygen reduction reaction and outstanding stability in alkaline condition. Using various analysis techniques and electrochemical analysis, we demonstrated that the electrocatalytic activity of the catalyst arises from Fe single atom. To validate the practical applicability of Fe-N-C catalysts, we conducted an anion exchange membrane fuel cell (AEMFC) test, which demonstrated a high performance of 212 mW cm−2 at maximum power density. This study proves that the effectiveness of a sequential strategy adopting redox reaction and following pyrolysis for precise synthesis of a single atom Fe catalyst.

Boosting the Electrocatalytic Oxygen Reduction Activity of MnN4-Doped Graphene by Axial Halogen Ligand Modification

Exploring highly active electrocatalysts as platinum (Pt) substitutes for the oxygen reduction reaction (ORR) remains a significant challenge. In this work, single Mn embedded nitrogen-doped graphene (MnN4) with and without halogen ligands (F, Cl, Br, and I) modifying were systematically investigated by density functional theory (DFT) calculations. The calculated results indicated that these ligands can transform the dyz and dxz orbitals of Mn atom in MnN4 near the Fermi-level into dz2 orbital, and shift the d-band center away from the Fermi-level to reduce the adsorption capacity for reaction intermediates, thus enhancing the ORR catalytic activity of MnN4. Notably, Br and I modified MnN4 respectively with the lowest overpotentials of 0.41 and 0.39 V, possess superior ORR catalytic activity. This work is helpful for comprehensively understanding the ligand modification mechanism of single-atom catalysts and develops highly active ORR electrocatalysts.

Designing highly efficient electrocatalyst for ORR and OER of transition metals doped g-C9N7: A density functional theory study

The application of fuel cells and metal-air batteries is limited by the rate of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Thus, the aim of this study is to find an efficient electrocatalyst to accelerate the reaction rate by DFT method. The structures of VIIB, VIII, IB, and IIB groups transition metals doped g-C9N7 as superb bifunctional electrocatalysts for ORR and OER are probed. The results show that Fe-, Pd-, and Au–C9N7 possess the superb ORR performance with the ORR overpotentials values of 0.35, 0.40, and 0.39 V, which gives them better performance than Pt(111). Moreover, Rh-, Pd-, and Pt–C9N7 have better OER performance with the OER overpotentials values of 0.30, 0.57, and 0.43 V, which makes them comparable to RuO2(110) and IrO2(110). Finally, the calculated bifunctional index (BI) results show that Pd–C9N7 can be used as an excellent bifunctional electrocatalyst because it has a minimum BI value of 0.97 V. This research has the potential to provide valuable theoretical direction into the use of M − C9N7 as electrocatalysts for both the ORR and OER.

Long‐Durability, Surfactant‐Free, and Bifunctional Ir‐Doped Pt3Co/MWCNTs Electrocatalysts towards ORR and OER in Acidic Media

AbstractDeveloping cost‐effective, high‐performance, and durable electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is pivotal for advancing hydrogen energy conversion and storage technologies. Simultaneously, establishing scalable methods for their production is essential for the widespread adoption of these renewable energy solutions. In this study, we present a successful large‐scale synthesis of surfactant‐free iridium‐doped Pt−cobalt nanoparticles supported on multiwalled carbon nanotubes (Ir−Pt3Co/MWCNTs). This composite demonstrates significantly enhanced ORR and OER activity compared to commercial Pt/C and IrO2 in acidic environments. The Ir−Pt3Co/MWCNTs catalyst composite exhibits a low overpotential of 357 mV at 10 mA cm−2 and a remarkable mass activity of 0.594 A/mgPt. Investigating the influence of Ir doping content on ORR and OER, we found that Pt3Co0.6Ir0.4/MWCNTs showcased the most superior activity in both reactions. We present a reproducible protocol for the synthesis of surfactant‐free Ir−Pt3Co nanoparticles supported on MWCNTs, yielding a bifunctional catalyst capable of efficiently catalyzing both ORR and OER with outstanding efficiency and stability in acidic media. Detailed X‐ray photoelectron spectroscopy (XPS) analysis elucidates the electron transfer between atoms, optimizing the electronic structure and adjusting the position of the d‐band. This optimization enhances the electrocatalytic activity and structural stability of the catalysts, contributing to their superior performance in ORR and OER.

In-situ construction of ionic liquid salt-derived graphene-like dual-heteroatoms doping engineering as efficient metal-free electrocatalyst for oxygen reduction reaction

Metal-free heteroatom-doped carbon catalysts can effectively eliminate the degradation and pollution problems caused by metal dissolution. However, single heteroatom doping often restricts the regulation of geometric and electronic structures for oxygen reduction reaction (ORR) electrocatalysts. Herein, a dual atomic doping engineering to optimize the electronic structure and local coordination environment of ionic liquid salt-derived graphene-like host material as an efficient metal-free electrocatalyst for ORR. The resultant PNG catalyst with a typical nanosheets morphology with a high specific surface area and unique hierarchical porous structure. Benefiting from the uniform doping of P, N heteroatoms, graphene-like structure, optimized electronic structure and coordination environment, thus-prepared PNG-2 exhibits outstanding ORR activity, which the onset potential and half-potential are negatively shifted by around 70 mV and 46 mV, respectively, as compared to the commercial Pt/C (20 wt.%) for ORR. Furthermore, the PNG-2 exhibits the higher diffusion limiting current density, superior long-term stability as well as excellent resistance to methanol oxidation than Pt/C. Experimental studies and density functional theory (DFT) calculations reveal that the enhanced chemisorption of oxygen species (*OOH, *O and *OH) onto the P and N sites of the PNG catalysts can effectively accelerate the charge transfer kinetics and promote a favorable ORR performance.

Recent Advances in Confined Pt‐based Electrocatalysts for Oxygen Reduction Reaction

Recent Advances in Confined Pt‐based Electrocatalysts for Oxygen Reduction Reaction

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 the Bader Charge Transfer in Single p‐Block Atoms Doped Pd Metallene for Enhanced Oxygen Reduction Electrocatalysis

Metallene is considered as an emerging family of electrocatalysts due to its atomically layered structure and unique surface stress. Here we propose a strategy to modulate the Bader charge transfer (BCT) between Pd surface and oxygenated intermediates via p‐d electronic interaction by introducing single‐atomp‐block metal (M = In, Sn, Pb, Bi) into Pd metallene nanosheets towards efficient oxygen reduction reaction (ORR). X‐ray absorption and photoelectron spectroscopy suggests that doping p‐block metals could facilitate electron transfer to Pd sites and thus downshift the d‐band center of Pd and weaken the adsorption energy of O intermediates. Among them, the developed Bi‐Pd metallene shows extraordinarily high ORR mass activity of 11.34 A mgPd‐1 and 0.86 A mgPd‐1 at 0.9 V and 0.95 V in alkaline solution, respectively, representing the best Pd‐based ORR electrocatalysts ever reported. In the cathode of a Zinc‐air battery, Bi‐Pd metallene could achieve an open‐circuit voltage of 1.546 V and keep stable for 760 h at 10 mA cm‐2. Theoretical calculations suggest that the BCT between Pd surface and *OO intermediates greatly affects the bond length between them (dPd‐*OO) and Bi doping could appropriately reduce the amount of BCT and stretch the dPd‐*OO, thus enhancing the ORR activity.

Modulating the Bader Charge Transfer in Single p-Block Atoms Doped Pd Metallene for Enhanced Oxygen Reduction Electrocatalysis.

Metallene is considered as an emerging family of electrocatalysts due to its atomically layered structure and unique surface stress. Here we propose a strategy to modulate the Bader charge transfer (BCT) between Pd surface and oxygenated intermediates via p-d electronic interaction by introducing single-atomp-block metal (M = In, Sn, Pb, Bi) into Pd metallene nanosheets towards efficient oxygen reduction reaction (ORR). X-ray absorption and photoelectron spectroscopy suggests that doping p-block metals could facilitate electron transfer to Pd sites and thus downshift the d-band center of Pd and weaken the adsorption energy of O intermediates. Among them, the developed Bi-Pd metallene shows extraordinarily high ORR mass activity of 11.34 A mgPd-1 and 0.86 A mgPd-1 at 0.9 V and 0.95 V in alkaline solution, respectively, representing the best Pd-based ORR electrocatalysts ever reported. In the cathode of a Zinc-air battery, Bi-Pd metallene could achieve an open-circuit voltage of 1.546 V and keep stable for 760 h at 10 mA cm-2. Theoretical calculations suggest that the BCT between Pd surface and *OO intermediates greatly affects the bond length between them (dPd-*OO) and Bi doping could appropriately reduce the amount of BCT and stretch the dPd-*OO, thus enhancing the ORR activity.

Modulating the Bader Charge Transfer in Single p-Block Atoms Doped Pd Metallene for Enhanced Oxygen Reduction Electrocatalysis.

Metallene is considered as an emerging family of electrocatalysts due to its atomically layered structure and unique surface stress. Here we propose a strategy to modulate the Bader charge transfer (BCT) between Pd surface and oxygenated intermediates via p-d electronic interaction by introducing single-atomp-block metal (M = In, Sn, Pb, Bi) into Pd metallene nanosheets towards efficient oxygen reduction reaction (ORR). X-ray absorption and photoelectron spectroscopy suggests that doping p-block metals could facilitate electron transfer to Pd sites and thus downshift the d-band center of Pd and weaken the adsorption energy of O intermediates. Among them, the developed Bi-Pd metallene shows extraordinarily high ORR mass activity of 11.34 A mgPd-1 and 0.86 A mgPd-1 at 0.9 V and 0.95 V in alkaline solution, respectively, representing the best Pd-based ORR electrocatalysts ever reported. In the cathode of a Zinc-air battery, Bi-Pd metallene could achieve an open-circuit voltage of 1.546 V and keep stable for 760 h at 10 mA cm-2. Theoretical calculations suggest that the BCT between Pd surface and *OO intermediates greatly affects the bond length between them (dPd-*OO) and Bi doping could appropriately reduce the amount of BCT and stretch the dPd-*OO, thus enhancing the ORR activity.