Bifunctional Electrocatalysts Research Articles

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.

Microenvironment Tailoring of NiCo Alloys Coupled with FePc as Efficient Bifunctional Catalysts for High-Rate Zn-Air Batteries.

The practical application of Zn-air batteries require exploring cost-effective and durable bifunctional electrocatalysts. However, the simultaneous preparation of catalysts with bifunctional activities for oxygen reduction reaction (ORR) and oxygen precipitation reaction (OER) remains challenging. Herein, we synthesized a novel hybrid catalyst (FePc/NiCo/CNT), which couples NiCo alloy with FePc through electrostatic interaction. The interaction between FePc and NiCo alloy can enhance the intrinsic catalytic activity of the active site Fe-N4 and prevent the electrolyte corrosion of the metal alloy, ultimately improving the stability of the catalyst by the microenvironment-tailoring strategy. The resultant FePc/NiCo/CNT catalyst exhibits outstanding oxygen reduction reaction (ORR) activity with a half-wave potential of 0.88 V, which is attributed to the abundant Fe-Nx active sites. Furthermore, the electron interactions between NiCo/CNT and FePc accelerate electron transfer and enhance the activation of oxygen intermediates, consequently boosting the OER activity with an overpotential of 260 mV at 10 mA cm-2. The Zn-air batteries assembled with FePc/NiCo/CNT show a high power density of 175.1 mW cm-2 and excellent cycling stability for up to 430 h at 20 mA cm-2. The preparation of oxygen electrode catalysts for renewable clean energy devices can be made more convenient with this directly engineered strategy for ORR and OER active centers.

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.

Electronic modulation of MOF-derived CoxMnyB nanosheet arrays toward efficient bifunctional electrocatalysts for water splitting

The design of robust and efficient bifunctional electrocatalysts for total water splitting is of paramount importance for the advancement of sustainable energy conversion technologies. To fully exploit the electrocatalytic capabilities of transition metal borides, we integrate manganese-incorporated cobalt boride (CoxMnyB) nanoarrays derived from metal-organic frameworks (MOFs). CoxMnyB nanosheet arrays exhibit pronounced electronic modulation, indicating superior electrochemical behavior. CoxMnyB can served as a binder-free catalytic electrode, which exhibits bifunctional electrocatalytic activity of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). CoxMnyB demonstrates an overpotential ∼ 277 mV under 10 mA cm−2 and a Tafel slope of 71 mV dec-1 for HER. It also exhibits optimised OER characteristics, with a potential of 1.54 V at a current density of 10 mA cm−2 and the lowest Tafel slope of 62 mV dec-1. CoxMnyB catalysts emerge as promising candidates for bifunctional electrocatalysts in overall water splitting, delivering remarkable and enduring electrocatalytic functionalities. The intricate mechanisms governing the electrocatalytic performance of the CoxMnyB bifunctional catalyst are systematically discussed in relation to nanostructure, conductive behavior, and the covalent bonding nature of metal-metalloid borides. Density functional theory (DFT) calculations reveal a reduced hydrogen binding energy at the catalyst surface and a weakened energy barrier of OOH*. This study suggests a favourable and feasible pathway for deploying metal borides in high-efficiency electrocatalysis and energy storage applications.

Phytogenic Cu2OBi2O3ZrO2 nanomaterial for supercapacitor and water splitting: Synthesis, characterization, and energy applications

Copper-based nanocomposites are regarded as sustainable energy materials having tremendous potential for energy storage supercapacitors and energy generation water splitting applications. Herein, a facile Cu-based ternary Cu2OBi2O3ZrO2 nanocomposite is prepared by a sustainable, lower-cost, and simple hydrothermal-based phyto-synthesis route by using Amaranthus Viridis L. amaranthaceae plant (abbreviated as AVL.A). The synthesized AVL.A-Cu2OBi2O3ZrO2 nanocomposite is characterized by powder-X-ray diffraction and FE-Scanning electron microscopy for its phase composition and surface morphology. The electrochemical efficiency of AVL.A-Cu2OBi2O3ZrO2 nanocomposite is investigated for supercapacitors and overall water splitting. The fabricated Cu2OBi2O3ZrO2 nanocomposite-based Nickel foam (NF) electrode shows superior performance with a specific capacitance of 524.5 F/g at 2 mV/s and 400 F/g at 1 A/g. The excellent rate capability is observed at scan rates from 2 mv/s to 300 mV/s and at current densities from 0.5 A/g to 30 A/g for AVL.A-Cu2OBi2O3ZrO2–NF. Furthermore, fabricated AVL.A-Cu2OBi2O3ZrO2–NF shows excellent electrochemical stability with 100% Coulombic efficiency till 5000 charge-discharge cycles. As bifunctional electrocatalyst AVL.A-Cu2OBi2O3ZrO2–NF electrode exhibits 117 mV overpotential at 10 mA/cm2 current density for HER kinetics along with 112 mV/dec Tafel slope values. The same Tafel slope value is also observed for OER measurements. These values of overpotential and Tafel slope for AVL.A-Cu2OBi2O3ZrO2–NF suggest a rapid and efficient electrochemical process of AVL.A-Cu2OBi2O3ZrO2–NF bifunctional electrocatalyst for energy generation. Overall study highly proposed AVL.A-Cu2OBi2O3ZrO2–NF as the potential electrode for energy storage supercapacitor and energy generation overall water splitting.

Record-breaking bifunctional oxygen electrocatalyst accomplished by a data-driven approach for zinc-air batteries

Record-breaking bifunctional oxygen electrocatalyst accomplished by a data-driven approach for zinc-air batteries

CoFe2O4 Nanoparticles on Bio-Based Polymer Derived Nitrogen Doped Carbon as Bifunctional Electrocatalyst for Li-Air Battery

Lithium-air batteries (LABs) are gaining attention as a promising energy storage solution. Their theoretical energy density of 3,505 Whkg−1 exceeds that of conventional lithium-ion batteries (500–800 Whkg−1). The commercial viability and widespread adoption of lithium-air batteries face challenges such as poor cycling stability, limited lifespan, and unresolved side reactions. In this study, we synthesized spinel CoFe2O4-decorated on bio-based poly(2,5-benzimidazole) derived N-doped carbon for electrocatalysts. Notably, strong metal-substrate interaction (SMSI) was observed through various characterizations. The bifunctional electrocatalytic activity and stability toward oxygen reduction reaction and oxygen evolution reaction were significantly enhanced by the SMSI, The LAB demonstrated a high discharge capacity of 18,356 mAhg−1 at a current density of 200 mAg−1, maintaining a remarkable discharge capacity of 1,000 mAhg−1 even at a high current density of 400 mAg−1 for 200 cycles. CoFe2O4-decorated on bio-derived ABPBI holds promise as a practical air-breathing electrode for high-capacity rechargeable LABs.

Structurally optimized rosette-like microspheres carbon with Fe-Ni single atom sites for bifunctional oxygen electrocatalysis in Zinc-Air batteries

Developing a secure and effective bifunctional oxygen catalyst for the ORR and OER is still a significant obstacle in the design of rechargeable zinc-air batteries. Here, a hollow rose-shaped bifunctional electrocatalyst is synthesized with an sacrificial template strategy (FeNi-NC). X-ray absorption fine structure analysis reveals the FeNi-NC catalyst contains FeN4 and NiN4 active sites as well as FeNi3 alloy. This hollow, flower-like structure performs low density, large specific surface area, and high permeability. Its inner cavities not only provide additional triple-phase interfaces to accelerate the reduction and oxidation of O2, but also enhance the diffusion of reactants on the catalyst. By controlling the input of Fe and nickel metal salts, the dispersion of active sites can be effectively tuned. Owing to the large number of exposed active sites on the carbon nanosheets, the synthesized FeNi-NC catalysts exhibit high electrocatalytic activity in both ORR (E1/2 = 0.852 V) and OER (ηj=10 = 359 mV). The construction of rechargeable zinc-air batteries resulted in a high power density of 135.78 mW cm−2, a better specific capacitance of 726.9 Wh kgZn−1 and 210 h enduring durability. More importantly, density functional theory (DFT) calculations indicate that the electronic interactions between Fe/Ni and nitrogen-doped carbon matrices play a pivotal role in enhancing the electrocatalytic performance of functional groups. These interactions effectively disrupt the electronic neutrality of carbon atoms, thereby accelerating the kinetics of the reaction. This research provides a new method for the preparation of single atom catalysts with bifunctional activities.

Coupling Ir single atom with NiFe LDH/NiMo heterointerface toward efficient and durable water splitting at large current density

Developing efficient and robust bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at large current density is important to facilitate the industrial water splitting. Herein, a promising strategy is presented to couple Ir single atom with NiFe LDH/NiMo heterointerface. IrSA-NiFe LDH/NiMo requires ultralow overpotentials of 139/236mV and 350/450mV to deliver large current densities of 500 and 1000mAcm−2 for HER/OER in 1M KOH. Moreover, the electrode shows remarkable durability of 10000 cycles and long-term durability at 500mAcm−2 over 500h for both HER and OER. The water electrolyzer exhibits a low cell voltage of 1.84V to attain 500mAcm−2. The theoretical calculations decipher that the Ir single atom modulates the electronic properties of the active sites, which tune the adsorption strength of the key reaction intermediates and boost the overall water splitting.

Cation-induced interface electric field redistribution and molecular orbital coupling in Co-FeS/MoS2 for boosting electrocatalytic overall water splitting

A green hydrogen economy requires efficient bifunctional electrocatalysts for simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this study, a mild sulfuration strategy was used to create a Co-FeS/MoS2 catalyst from metal-organic frameworks (MOFs) on foam nickel. This catalyst exhibits exceptional activity in 1 M KOH, only requiring ultralow overpotentials of 63 mV and 230 mV to achieve current densities of 10 mA cm−2 and 100 mA cm−2 for the HER and OER processes. Additionally, it achieves a low cell voltage of 1.45 V at 10 mA cm−2, surpassing reported catalysts. DFT calculations and XPS tests show that Co introduction induces high-valence Fe active sites and facilitates interface electric field redistribution. Crystal orbital Hamilton population (COHP) calculations reveal d-p orbital hybridization, enhancing conductivity and charge transfer kinetics. This research sheds light on the catalytic impacts of metal cations on transition metal sulfides to design high efficient electrocatalysts.

Assembly of low-voltage driven Co-production of hydrogen and sulfur via Ru nanoclusters on metal-sulfur coordination: Insights from DFT calculations

Herein, we propose a simple and rapid approach for synthesizing a CuS/Ru composite that serves as a bifunctional electrocatalyst to promote hydrogen production and concurrently convert sulfion into a value-added sulfur product. This composite comprises Ru nanoclusters supported on the CuS nanostructure, achieved through simple pulsed laser irradiation in liquid approach. The optimized CuS/Ru-30 electrocatalyst demonstrates remarkable bifunctional electrocatalytic activity, exhibiting a negligible working potential of 0.28 V (vs. RHE) for the anodic sulfion oxidation reaction (SOR) and a minimal overpotential of 182 mV for cathodic hydrogen evolution reaction (HER) to achieve 10 mA cm−2 of current density. Moreover, the CuS/Ru-30 electrocatalyst shows exceptional selectivity for converting sulfion into valuable sulfur during anodic oxidation reactions. Remarkably, in a two-electrode electrolyzer system utilizing CuS/Ru-30 as both the anode and cathode, the coupled water electrolysis system demands only 0.52 V to reach 10 mA cm−2, which is considerably lesser instead of the overall water electrolysis (1.85 V). The experimental results and density function theory (DFT) calculations reveal that the strong electron interaction between CuS and Ru nanoclusters generates a built-in electric field, greatly enhancing electron transfer efficiency. This significantly boosts the HER performance and facilitates the adsorption and production of sulfur intermediates. This study presents a rapid and simple strategy for synthesizing a dual-functional catalyst suitable for low-voltage hydrogen generation while facilitating the recovery of valuable sulfur sources.

Strong metal-support interaction facilitated the formation of ternary alloy and interfacial oxygen vacancies for enhanced overall water splitting

The NiCoFe-based alloys are potential high-performing bifunctional electrocatalysts towards overall alkaline water splitting, though it is still challenging to achieve this goal. Herein, the NiCoFe/CeO2-x heterostructure with abundant interfacial oxygen vacancies is constructed through in-situ hydrogenation. The strong metal-support interaction favors the formation of the medium-entropy NiCoFe ternary alloy and the interfacial oxygen vacancies, while the introduction of the cobalt highly increases the electrochemically active surface area (ECSA). The ECSA of the NiCoFe/CeO2-x is more than 3 times those of the NiCoFe, NiFe/CeO2-x, NiCo/CeO2-x and CoFe/CeO2-x. Therefore, the NiCoFe/CeO2-x shows high catalytic performance towards both hydrogen evolution reaction and oxygen evolution reaction with a small overpotential of 42 and 238 mV at 10 mA cm−2 in 1 M KOH, respectively. More importantly, the NiCoFe/CeO2-x heterostructure with optimal elemental composition demonstrates excellent catalytic performance towards overall water splitting, exhibiting a small cell voltage of 1.52 V at 10 mA cm−2 without iR compensation. In addition, it shows good working stability in the overall water splitting at 100 mA cm−2 during a period of >10 h.

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.

Co-N-C/C Bifunctional Electrocatalyst for Dual Applications in Seawater Electrolysis and Catalyst in Hydrazine Fuel Cells.

The convergence of water electrolysis and alkaline fuel cells offers captivating solutions for sustainably harvesting energy. The research explores both hydrazine-assisted seawater electrolysis (hydrazine oxidation reaction (HzOR) and hydrogen production reaction (HER)), as well as alkaline hydrazine fuel cell reactions (HzOR and Oxygen reduction reaction (ORR)) by using a bifunctional cobalt polyaniline derived (Co PANI/C) catalyst. The catalyst shows excellent performance for hydrazine-assisted seawater electrolysis in harsh seawater environments to produce H2 as fuel with nearly 85% Faradaic efficiency and during alkaline HzOR, the bifunctional catalyst generates H2 with 95% Faradaic efficiency by acting as both anode and cathode side catalyst. Also, the same catalyst requires only a potential of 0.34V versus RHE and 0.906V versus RHE for HzOR and ORR, respectively, in 1m KOH, which makes this overall process useful for a Hz/O2 fuel cell.

CeVO4 Nanosheets as Bifunctional Electrocatalysts for Glycerol Oxidation and Hydrogen Peroxide Sensing

CeVO₄ Nanosheets as Bifunctional Electrocatalysts for Glycerol Oxidation and Hydrogen Peroxide Sensing

The CoFe-LDH/CuCo2O4 composite as an efficient bifunctional electrocatalyst under alkaline conditions for overall water splitting

To reduce energy crises and environmental pollution, it is imperative to logically create affordable, stable, efficient, and environmentally friendly bifunctional electrocatalysts based on non-precious metals for total water splitting. In this study, we designed and synthesized sea urchin-like structured CoFe/CuCo2O4 bifunctional electrocatalysts on nickel foam. Benefiting from the high conductivity of nickel foam and the positive synergistic effect between different component materials, this catalyst exhibited high activity in both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Specifically, the CoFe/CuCo2O4/NF-5 material required only 257 mV of OER overpotential and 178 mV of HER overpotential at a current density of 50 mA cm[Formula: see text]. It is worth noting that the alkaline electrolyzer prepared using CoFe/CuCo2O4/NF-5 material achieves a low cell voltage of 1.544 V to achieve a current density of 10 mA cm[Formula: see text] in overall water splitting and can operate stably for a prolonged period. This work also provides a feasible strategy for green and low-cost electrocatalyst synthesis.

Effect of Different N/C Coordination Electronic Structures on the Activity of Bifunctional Rare-Earth Ytterbium Electrocatalysts for Oxygen Electrodes.

The research and development of bifunctional electrocatalysts for the oxygen electrode is of great significance to solve the problem of electrochemical energy. Herein, the effect of different structure-activity relationships on the performance of YbNxCy-gra catalysts was explored. The bifunctional activity of graphene with a vacancy defect supported by single-atom rare-earth ytterbium was studied by density functional theory (DFT) calculations. We systematically analyzed the stability, electronic properties, and catalytic performance of potential bifunctional catalysts. The results showed that all catalysts were thermodynamically and kinetically stable. Under acidic conditions, YbN2C2-oppo-gra and YbN2C2-pen-gra showed good ORR activity, and their overpotentials were 0.53 and 0.65 V, respectively. In an alkaline environment, most of the Yb(OH)NxCy-gra catalysts showed excellent ORR and OER bifunctional catalytic activity. Their overpotentials were all below 0.6 V. In particular, the ηORR and ηOER of the Yb(OH)N4C0-gra electrocatalyst were as low as 0.33 and 0.42 V. This verified the practicability and feasibility of hydroxyl-modified catalysts to enhance activity. This research provides theoretical insights into the further design and development of high-efficiency rare-earth-supported bifunctional catalysts.

Co/CoP@NC heterostructures as bifunctional catalysts to enhance the alkaline water splitting

The development of efficient and stable non-precious bifunctional electrocatalysts is of great significance, but it remains a great challenge. Herein, we have constructed Co/CoP@NC heterojunction catalyst loaded with Co and CoP particles on a nitrogen-doped carbon (NC) substrate using the pyrolysis-oxidation-phosphating strategy. The synergistic effect of Co and CoP particles on the NC substrate increases the active specific surface area, accelerates the charge transfer rate, and improves the intrinsic activities of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The Co/CoP@NC catalyst exhibits superior HER and OER performance. Specifically, the overpotentials required for Co/CoP@NC to reach the current density of 10 mA cm−2 are 142 and 186 mV for HER and OER, respectively. This study provides new insights into the design and synthesis of efficient and stable Co-based heterostructure catalysts.

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.

Structural investigation of Cr2CTx/NiFe2O4 MXene composite as a bifunctional electrocatalyst for water splitting

The electrocatalytic water splitting offers great potential as an environmentally friendly and sustainable method to produce hydrogen and oxygen, the former serving as a renewable alternative to traditional fossil fuels. MXene, a novel two-dimensional (2D) layered class of materials, has gained enormous attention as an electrocatalyst for water splitting. This versatile material can be tailored to enhance its electroactive surface sites and stability toward electrocatalytic performance. Herein, we have designed a 2D hybrid material, Cr2CTx/NiFe2O4, via an in-situ hydrothermal approach. NiFe2O4 spheres decorated on layered-Cr2CTx are subjected to analysis using XRD, FTIR, TGA, XPS, FESEM, HRTEM-SAED, and optical profilometry. The synthesized hybrid MXene material shows outstanding activity for overall water splitting compared to Cr2CTx and NiFe2O4. Cr2CTx/NiFe2O4 exhibits an overpotential of 144 mV and 159 mV at a current density of 10 mA cm−2 for hydrogen evolution and oxygen evolution reactions, respectively, and achieves a cell potential of 1.69 V for overall water splitting. This study reveals valuable insights on bi-functional 2D hybrid MXene materials for electrocatalytic water splitting.