Bifunctional Electrocatalysts Research Articles

Nickel molybdenum selenide on carbon cloth as an efficient bifunctional electrocatalyst for alkaline seawater splitting

Exploring cost-effective and highly efficient electrocatalysts is desirable for the overall water-splitting challenge. In this work, a promising bifunctional electrocatalyst for oxygen evolution and hydrogen evolution reactions (OER/HER) in an alkaline medium (1 M KOH) and simulated alkaline seawater (1 M KOH + 0.5 M NaCl) was rationally developed by a simple, one-step, inexpensive, and eco-friendly method. Mo-doped nickel selenide supported on activated carbon cloth (NiMoSe@CC) was successfully synthesized via a hydrothermal method. NiMoSe nanoparticles were observed to be densely grown with better uniformity on the carbon fibers, as confirmed by different characterization techniques. The NiMoSe@CC showed an enhanced OER activity with a low overpotential of 320 mV (alkaline medium) and 360 mV (alkaline seawater) at 10 mA cm−2. The HER performance of the NiMoSe@CC was also the highest amongst NiMoSe, NiSe@CC, and MoSe@CC in both the alkaline and seawater environments. In addition, NiMoSe@CC bears a high electrochemically active surface area, low charge transfer resistance of 1.77 Ω, and high stability for both OER and HER. The NiMoSe@CC//NiMoSe@CC system was stable for 5000 LSV cycles with η10 values of 1.63 V (1st LSV cycle) and 1.71 V (5000th LSV cycle).

Novel mixed heterovalent (Mo/Co)Ox-zerovalent Cu system as bi-functional electrocatalyst for overall water splitting

A novel hybrid ternary metallic electrocatalyst of amorphous Mo/Co oxides and crystallized Cu metal was deposited over Ni foam using a one-pot, simple, and scalable solvothermal technique. The chemical structure of the prepared ternary electrocatalyst was systematically characterized and confirmed via XRD, FTIR, EDS, and XPS analysis techniques. FESEM images of (Mo/Co)Ox–Cu@NF display the formation of 3D hierarchical structure with a particle size range of 3–5 µm. The developed (Mo/Co)Ox–Cu@NF ternary electrocatalyst exhibits the maximum activity with 188 mV and 410 mV overpotentials at 50 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Electrochemical impedance spectroscopy (EIS) results for the (Mo/Co)Ox–Cu@NF sample demonstrate the minimum charge transfer resistance (Rct) and maximum constant phase element (CPE) values. A two-electrode cell based on the ternary electrocatalyst just needs a voltage of about 1.86 V at 50 mA cm−2 for overall water splitting (OWS). The electrocatalyst shows satisfactory durability during the OWS for 24 h at 10 mA cm−2 with an increase of only 33 mV in the cell potential.

P-doped RuPd nanoparticles anchored on Y2Ru2-xPdxO7 pyrochlore oxide surface as oxygen evolution and reduction electrocatalysts for Zn-air battery

Metal-air battery technology is the most promising green technology. However, the sluggish kinetics of the oxygen evolution/reduction reaction (OER and ORR), which are key reactions in air cathode, must be improved. In this study, Pd substitution was introduced into Y2Ru2O7 pyrochlore oxides and the ratio of Pd was varied (YRPO-x). Then, P-doped RuPd nanoparticles were synthesized on Pd-substituted YRPO pyrochlore (YRPO/RuPd-P) by an in situ exsolution process to create bifunctional electrocatalysts facilitating both reactions. The uniquely designed YRPO/RuPd-P catalyst exhibited the OER overpotential and Tafel slope (Ej10 = 232 mV; Tafel slope = 37.1 mV/dec). Furthermore, YRPO/RuPd-P shows an E1/2 of 0.82 V, indicating superior ORR activity. This was further investigated by applying in a unit-cell battery system, which showed an outstanding power density (163 mW/cm2) and robust charge–discharge stability. This study proposes a novel design strategy for bifunctional electrocatalysts.

Hollow RuV-Co(OH)2 arrays for efficiently electrocatalytic H2 production assisted by glucose oxidation

Electrochemical water splitting is a promising method for hydrogen production but is restricted by sluggish oxygen evolution reaction (OER), so we propose to replace OER with the thermodynamically preferred glucose oxidation reaction (GOR) to reduce the supply voltage. Herein, hollow RuV-Co(OH)2 arrays have been fabricated by the hydrothermal method of sacrificing ZIF-67 to codope vanadium (V) and ruthenium (Ru). Electrochemical studies show that RuV-Co(OH)2 has excellent hydrogen evolution reaction (HER) activity with a low overpotential of 77 mV at the current density of 10 mA cm−2 (η10 = 77 mV) and good GOR activity. Density functional theory (DFT) calculations indicate that V and Ru tune the electronic structure of RuV-Co(OH)2, greatly increasing the density of the active sites. Moreover, RuV-Co(OH)2 assembled glucose-assisted hydrogen evolution cell exhibits a battery voltage of 1.42 V for a current density of 10 mA cm−2, a significant reduction of 240 mV compared to overall water splitting along with higher-value glucose oxidation products. Furthermore, RuV-Co(OH)2 exhibits outstanding stability. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis demonstrate that RuV-Co(OH)2 has superior mechanical stability. This work opens up a new approach to designing novel bifunctional electrocatalysts for energy-saving H2 production and valuable coproductions.

Engineering the Electronic Interaction Between Single Au Atoms and CoN Through Nitrogen‐Coordination Bonding as an Efficient Bifunctional Electrocatalyst for Rechargeable Zn–Air Batteries

AbstractSingle‐atom catalysts hold significance in the field of electrocatalysis. In this study, cobalt nitride (CoN), known for its semiconductor characteristics, is selected as the substrate, on which single gold (Au) atoms are loaded, to synthesize the catalyst Au SAC CoN@NF with Au single atoms anchored on CoN catalysts and grown on nickel foam. The introduction of single Au atoms results in an exceptional double‐layer capacitance (1425.7 mF cm−2), which offers immense possibilities for the applications of zinc–air batteries based on Au SAC CoN@NF. The zinc–air batteries demonstrated remarkable performance metrics, including a power density of 161.94 mW cm−2, a specific capacity of 813.80 mAh g−1, and a cycling stability of more than 260 h at 10 mA cm−2. In addition, these batteries show an outstanding round‐trip efficiency of 65.1%. Density functional theory calculations reveal that Au SAC CoN@NF can optimize the adsorption energies of intermediates for oxygen evolution reaction and promote single Au atoms in transporting electrons to the OH− species at an Au–N active site for oxygen reduction reaction. The proposed electronic metal‐support interaction strategy offers fresh insights for designing single‐atom catalysts to enhance electrocatalysis efficiency, thereby expanding the practical application prospects of zinc–air batteries.

B doped cobalt-nickel bimetallic phosphide as bifunctional catalyst for ethanol oxidation reaction and hydrogen evolution reaction

The ethanol oxidation reaction (EOR) is an ideal alternative to the oxygen evolution reaction (OER) towards energy efficient hydrogen production. Here, the chrysanthemum-shaped B doped cobalt-nickel bimetallic phosphide with heterogeneous structure grown on nickel foam (B-Ni2P/CoP/NF) are synthesized and can act as a high activity bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and EOR. In 1.0 M KOH, the obtained catalyst shows good activity and excellent long-term stability (no decay after 108 h) for HER, with an overpotential of only 33 mV (vs. RHE) to reach a current density of 10 mA cm−2. The calculation of turnover frequency (TOF) and transfer coefficient (β) prove that the catalyst has good intrinsic catalytic activity, For EOR, in 1.0 M KOH+1.0 M C2H5OH solution, the B-Ni2P/CoP/NF catalyst requires only 1.45 V (vs. RHE) oxidation potential to reach the current density of 50 mA cm−2, which is 270 mV less than OER. Using B-Ni2P/CoP/NF as a bifunctional catalyst, the current density of 20 mA cm−2 can be achieved with only 1.48 V cell voltage in 1.0 M KOH+ 1.0 M C2H5OH solution, which is remarkably lower than the required cell voltage of water electrolysis (1.63 V) to achieve the same current density. This study demonstrates an efficient bimetallic phosphide as earth-abundant bifunctional electrocatalysts for green hydrogen production coupled with electrolysis of ethanol.

Superhydrophilic Dendritic FeP/Cu3P Electrocatalyst for Urea Splitting via the Intramolecular Mechanism.

The electrocatalytic overall urea splitting can achieve the dual goals of urea treatment and hydrogen energy acquisition. Herein, we exploited the principle of precipitation dissolution equilibrium to obtain bimetallic phosphide FeP/Cu3P/CF for the simultaneous oxidation of urea and reduction of water and comprehensively reveal the inherent molecular thermodynamic mechanisms on the surface of catalysts. The excellent electrochemical performance can be derived from the super water affinity and synergistic effect. Especially, the theoretical calculation unveils that the synergistic effect between FeP and Cu3P can lower the activation energy required for urea electrooxidation, thereby promoting urea splitting. In situ differential electrochemical mass spectrometry (in situ DEMS) measurements further demonstrated that urea oxidation on FeP/Cu3P/CF proceeded according to the intramolecular mechanism. This work has laid the foundation for constructing highly efficient superhydrophilic bifunctional electrocatalysts.

Theoretical and experimental investigation on electrostatic field dynamics of Co3O4@NiPx electrocatalyst with core shell structure in overall water splitting reactions

Transition metal phosphides (TMPs) with platinum like electronic structures are becoming a potential choice to constructing bifunctional catalysts operated under alkaline conditions. Nevertheless, the instability of TMP prevents a further enhancement on its electrocatalytic activity. In this study, the Co3O4 core was first formed through thermal annealing in air, and then the outer NiPx layer was formed through the P-method, cleverly integrating the properties of the inner and outer materials and supplementing respective shortcomings, ultimately improving their water decomposition performance. When Co3O4@NiPx is used as a bifunctional electrocatalyst in 1 M KOH, the HER performance is determined to be 99 mV (η10). The electrocatalytic performance for oxygen evolution reaction (OER) is 249 mV (η50). For overall water decomposition, the bifunctional electrocatalysts Co3O4@NiPx coupled dual electrode alkaline battery only requires 1.51 V to obtain η50 and maintains its excellent electrocatalytic ability for 50 h. Finally, a combination of electrostatic field theory analysis and DFT calculations was used, the results indicated that the stability of core–shell materials can be significantly enhanced through Co3O4 core and internal electron redistribution by P atoms, thereby improving catalytic performance. The greatly improved electrochemical performance of Co3O4@NiPx indicates the rationality of the design and synthesis of the core–shell structure. The combination of electrostatic field theory analysis and DFT calculation also further reveals the rationality of its internal electrocatalytic mechanism.

MnFeNi‐Based Composite as a Case Study of a Bifunctional Oxygen Electrocatalyst under Dynamically Changing Electrode Potentials

AbstractHigh‐performance bifunctional electrocatalysts for the oxygen reduction (ORR) and oxygen evolution reaction (OER) are essential components in energy conversion and storage technologies. Yet, their poor reversibility hinders their applicability. A highly active ORR/OER catalyst, consisting of multiwalled carbon nanotubes‐supported MnFeNiOx nanoparticles, was subjected to sequences of chronoamperometric steps alternating between the ORR, the OER and highly cathodic potentials (Ec). Rotating ring disk electrode methods revealed that applying Ec leads to a small increase in the current and peroxide species yield during the ORR while enhancing substantially the OER. X‐ray absorption spectroscopy showed irreversible changes in the chemical state of MnFeNiOx correlating with its catalytic properties. The complexity of changes that a composite catalyst may undergo under varying potentials, the importance of monitoring product formation, and the convenience of using dynamic electrochemical sequences for the assessment of catalyst reversibility, as well as for the activation and/or restoration of their catalytic properties, are highlighted.

Interfacial Interaction in NiFe LDH/NiS2/VS2 for Enhanced Electrocatalytic Water Splitting.

A bifunctional electrocatalyst with high efficiency and low costs for overall water splitting is critical to achieving a green hydrogen economy and coping with the energy crisis. However, developing robust electrocatalysts still faces huge challenges, owing to unsatisfactory electron transfer and inherent activity. Herein, NiFe LDH/NiS2/VS2 heterojunctions have been designed as freestanding bifunctional electrocatalysts to split water, exhibiting enhanced electron transfer and abundant catalytic sites. The optimum NiFe LDH/NiS2/VS2 electrocatalyst exhibits a small overpotential of 380 mV at 10 mA cm-2 for overall water splitting and superior electrocatalytic performance in both hydrogen and oxygen evolution reactions (HER/OER). Specifically, the electrocatalyst requires overpotentials of 76 and 286 mV at 10 mA cm-2 for HER and OER, respectively, in alkaline electrolytes, which originate from the synergistic interaction among the facilitated electron transfer and increasingly exposed active sites due to the modulation of interfaces and construction of heterojunctions.

Self-supporting multi-channel Janus carbon fibers: A new strategy to achieve an efficient bifunctional electrocatalyst for overall water splitting

A new type of self-supporting multi-channel Janus carbon fibers with efficient water splitting has been successfully manufactured using a specially designed parallel spinneret through electrospinning technology and subsequent carbonization technique. Every single Janus fiber composes of a half side of Mo2C and the other half side of Ni components as Mo2C, Ni embedded in N-doped multi-channel Janus carbon fibers ([Mo2C/C]//[Ni/C]-NMCFs) for overall water splitting. Under optimized condition, the hydrogen evolution reaction overpotential of [Mo2C/C]//[Ni/C]-NMCFs (62 mV) is just 24 mV higher than 20 wt% Pt/C (38 mV) at a current density of 10 mA cm−2. Furthermore, it achieves current density of 10 mA cm−2 to require an overpotential of 324 mV for oxygen evolution reaction. Additionally, the cell assembled by the identical [Mo2C/C]//[Ni/C]-NMCFs catalyst as both the cathode and anode needs only 1.607 V at a current density of 10 mA cm−2, which is only 0.022 V higher than that of Pt/C-IrO2 electrodes. Moreover, [Mo2C/C]//[Ni/C]-NMCFs catalyst also exhibits a long-term stability. The synergistic effect and unique heterostructure of Mo2C and Ni enhance the catalytic activity.

NiCo2O4/MXene Hybrid as an Efficient Bifunctional Electrocatalyst for Oxygen Evolution and Reduction Reaction

AbstractFor the advancement of electrochemical energy conversion and storage technologies, bifunctional electrocatalysts are crucial for efficiently driving both the oxygen evolution (OER) and reduction reactions (ORR). Cobalt‐based spinel oxides are a class of promising bifunctional electrocatalysts. However their low electrical conductivity and stability may hinder further improvement. A novel composite material composed of NiCo2O4 nanoparticles integrated with emerging two dimensional MXene nanosheets (NiCo2O4/MXene) was developed. The successful integration of NiCo2O4 with MXene brings about a number of attractive structural features. This includes synergistic effects between NiCo2O4 and MXene, highly accessible surface areas, complete exposure of numerous active sites, and excellent electronic conductivity, all of which collectively contribute to the desirability of composite material for OER and ORR. The synthesized NiCo2O4/MXene composite showed extraordinary OER electrocatalytic activity with a lower overpotential of 360 mV at a current density of 10 mA/cm2, and a small Tafel slope of 64 mV/dec compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed). Additionally, NiCo2O4/MXene displays an ORR limiting current density of −4 mA/cm2 and exhibited highest onset potential and half wave potential of 0.92 V and 0.72 V vs. RHE, respectively, for the ORR in alkaline media compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed).

Architecting N-doped Carbon Nanotube-Rich Carbon Nanofibers with Biomimetic Vine-Leaf-Whisker Structure as Robust Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries.

Efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are urgently desirable but challenging for rechargeable Zn-air batteries (ZABs), especially flexible wearable ZABs. Inspired by the vine-leaf-whisker structure in nature, we proposed a three-dimensional (3D) hierarchical bifunctional catalyst (denoted as Co-Fe-Zn@N-CNT/CNF) consisting of N-doped carbon nanotubes embedded with abundant CoFe alloy nanoparticles, leaf-shaped N-doped carbon nanoflakes, and porous carbon fibers for rechargeable ZABs. The special biomimetic structure provides a large specific surface area, allowing for high exposure of the active site and ensuring fast mass transport/charge transfer. The close combination of CoFe bimetallic alloys and N-doped carbon nanotubes delivers high electrocatalytic activity, while the coexistence of various active sites such as metal nanoparticles (NPs), metal-Nx, doped N species, and their synergistic interactions endows the catalysts with more active sites. As such, the Co-Fe-Zn@N-CNT/CNF catalyst achieves superior bifunctional catalytic activities for the ORR (a half-wave potential of 0.84 V) and the OER (an overpotential of 326 mV at 10 mA cm-2) in alkaline media, comparable to commercial Pt/C and RuO2. Remarkably, both aqueous and solid-state ZABs assembled with Co-Fe-Zn@N-CNT/CNF catalysts as air electrodes demonstrate excellent charging/discharging performance, high peak power density, and robust long-term cycling stability. More interestingly, the flexible ZAB performs well even under bending conditions, displaying satisfactory device stability and mechanical flexibility. This study presents a new collective morphological-composition-structural engineering strategy for exploiting the efficient bifunctional oxygen electrocatalysts, which is of great significance for high-performance rechargeable ZABs and wearable energy storage devices.

Highly Porous Metal-Organic Framework Entrapped by Cobalt Telluride-Manganese Telluride as an Efficient Bifunctional Electrocatalyst.

The electrochemical conversion of oxygen holds great promise in the development of sustainable energy for various applications, such as water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. Oxygen electrocatalysts are needed that are both highly efficient and affordable, since they can serve as alternatives to costly precious-metal-based catalysts. This aspect is particularly significant for their practical implementation on a large scale in the future. Herein, highly porous polyhedron-entrapped metal-organic framework (MOF)-assisted CoTe2/MnTe2 heterostructure one-dimensional nanorods were initially synthesized using a simple hydrothermal strategy and then transformed into ZIF-67 followed by tellurization which was used as a bifunctional electrocatalyst for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The designed MOF CoTe2/MnTe2 nanorod electrocatalyst exhibited superior activity for both OER (η = 220 mV@ 10 mA cm-2) and ORR (E1/2 = 0.81 V vs RHE) and outstanding stability. The exceptional achievement could be primarily credited to the porous structure, interconnected designs, and deliberately created deficiencies that enhanced the electrocatalytic activity for the OER/ORR. This improvement was predominantly due to the enhanced electrochemical surface area and charge transfer inherent in the materials. Therefore, this simple and cost-effective method can be used to produce highly active bifunctional oxygen electrocatalysts.

An ultrathin flocculent Co9S8/Ni3S2 hybrid as high-performance bifunctional catalyst for overall water splitting

Modern industrial hydrogen production is a crucial solution to address the energy crisis. Therefore, the development of a cost-effective and highly efficient hydrolytic hydrogen production catalyst holds significant practical importance. In this study, we propose to synthesize an efficient bifunctional electrocatalyst of Co9S8/Ni3S2 grown on nickel foam (NF) by a one-step hydrothermal method, which has a large specific surface area due to its flocculated structure. Through electrochemical testing, the Co9S8/Ni3S2/NF electrode exhibits remarkable performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, low overpotentials of 53.6, 90.2, and 209.2 mV are required to achieve current densities of 10, 20, and 100 mA/cm2 during HER, respectively. Similarly, for OER, the overpotentials are only 107.6, 150.6, and 350.4 mV. Additionally, the Co9S8/Ni3S2/NF electrode demonstrates a small Tafel slope of 68.7 mV/dec for HER and 91.8 mV/dec for OER, indicating efficient reaction kinetics. Notably, the electrode exhibits exceptional long-term stability. Moreover, in a self-assembled monolithic water splitting device with Co9S8/Ni3S2/NF electrodes as cathode and anode, a cell potential of 1.55 V is required to drive the overall water splitting process at a current density of 10 mA/cm2, and the reaction shows excellent stability with a loss of voltage of only 16.5 mV over a 10-hour period. This paper presents a simple and innovative approach for constructing bimetallic sulfides electrocatalysts.

Electrocatalytic and structural investigation of trimetallic NiFeMo bifunctional electrocatalyst for industrial alkaline water electrolysis

In pursuit of sustainable hydrogen production, alkaline water electrolysis offers fossil-free technology for generating hydrogen. Exploring new non-precious metal electrocatalysts plays a crucial role in this endeavor. Herein, we investigate a trimetallic NiFeMo material on a nickel foam support, serving as a bifunctional electrocatalyst for catalyzing both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Scanning electron microscopy reveals a nanosheet array structure with a uniform distribution of Ni, Fe, and Mo compounds on the electrode surface. Furthermore, the chemical surface composition of the pristine and spent electrodes is elucidated via x-ray photoelectron spectroscopy, displaying primarily oxidized species on the electrocatalyst surface. Bifunctional performance is assessed in a three-electrode setup, unveiling overpotentials of 70 mV for the HER and 140 mV for the OER, in a 30 wt% KOH electrolyte at 90 °C. Additionally, in an industrial electrolysis cell, the activated electrode is evaluated as cathode and anode for 28 days, which decreased the overpotential of 330–350 mV at 200 mA cmgeo−2 compared with pristine nickel foam. The performance increase of the electroplated coating is attributed to the increased surface area and enhanced intrinsic activity. The electrolysis cell experiences a ∼6 % voltage loss during the experiment, indicating its robustness and suitability for industrial alkaline electrolysis applications.

Rational Construction of 3D Self-Supported MOF-Derived Cobalt Phosphide-Based Hollow Nanowall Arrays for Efficient Overall Water Splitting At large Current Density.

Developing efficient nonprecious bifunctional electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) in the same electrolyte with a low overpotential and large current density presents an appealing yet challenging goal for large-scale water electrolysis. Herein, a unique 3D self-branched hierarchical nanostructure composed of ultra-small cobalt phosphide (CoP) nanoparticles embedded into N, P-codoped carbon nanotubes knitted hollow nanowall arrays (CoPʘNPCNTs HNWAs) on carbon textiles (CTs) through a carbonization-phosphatization process is presented. Benefiting from the uniform protrusion distributions of CoP nanoparticles, the optimum CoPʘNPCNTs HNWAs composites with high abundant porosity exhibit superior electrocatalytic activity and excellent stability for OER in alkaline conditions, as well as for HER in both acidic and alkaline electrolytes, even under large current densities. Furthermore, the assembled CoPʘNPCNTs/CTs||CoPʘNPCNTs/CTs electrolyzer demonstrates exceptional performance, requiring an ultralow cell voltage of 1.50V to deliver the current density of 10mAcm-2 for overall water splitting (OWS) with favorable stability, even achieving a large current density of 200mAcm-2 at a low cell voltage of 1.78V. Density functional theory (DFT) calculation further reveals that all the C atoms between N and P atoms in CoPʘNPCNTs/CTs act as the most efficient active sites, significantly enhancing the electrocatalytic properties. This strategy, utilizing 2D MOF arrays as a structural and compositional material to create multifunctional composites/hybrids, opens new avenues for the exploration of highly efficient and robust non-noble-metal catalysts for energy-conversion reactions.

Triggering efficient Mn active centers by tuning the localized Sr2+ sites in high-entropy ABO3 oxygen electrocatalysis

Understanding the function of individual elements in high-entropy perovskites is one of the critical issues for the design of inexpensive and efficient bifunctional electrocatalysts. Here, we report our findings in boosting the electrochemical activity and durability of a high-entropy perovskite catalyst via sequential substitution of Sr2+ for the A-site elements. According to the Sr2+ localized tuned, the catalyst of (LaSmGdSrPr)0.2MnO3 has a half-wave potential of 0.786 V vs. RHE and an overpotential of 0.378 V and has better ORR and OER electrocatalytic activity than the Sr-free high-entropy perovskite catalyst (LaSmGdYPr)0.2MnO3.This is attributed to the local doping of Sr2+ activating the active center of the high-entropy perovskite catalyst (LaSmGdSrPr)0.2MnO3, modulating the adsorption energy of the oxygen-containing intermediates and the electronic structure of the transition metal at the B-site, which results in efficient oxygen electrocatalytic activity. On the other hand, the introduction of Sr2+ enhances the hybridization between Mn 2p and O 1 s and accelerates the adsorption and desorption kinetics of the intermediates, leading to both enhanced activity and durability of (LaSmGdSrPr)0.2MnO3. DFT theoretical calculations also demonstrate the key role played by Sr2+ in the high-entropy perovskite structure for the improvement of the electrocatalytic activity. This study provides new insights for designing high-entropy electrocatalysts for various potential applications.

Single Transition-Metal Atom Anchored on a Rhenium Disulfide Monolayer: An Efficient Bifunctional Electrocatalyst for the Oxygen Evolution and Oxygen Reduction Reactions.

Developing efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts is attractive for rechargeable metal-air batteries. Meanwhile, single metal atoms embedded in 2D layered transition metal chalcogenides (TMDs) have become a very promising catalyst. Recently, many attentions have been paid to the 2D ReS2 electrocatalyst due to its unique distorted octahedral 1T' crystal structure and thickness-independent electronic properties. Here, the catalytic activity of different transition metal (TM) atoms embedded in ReS2 using the density functional theory is investigated. The results indicate that TM@ReS2 exhibits outstanding thermal stability, good electrical conductivity, and electron transfer for electrochemical reactions. And the Ir@ReS2 and Pd@ReS2 can be used as OER/ORR bifunctional electrocatalysts with a lower overpotential for OER (ηOER ) of 0.44 V and overpotentials for ORR (ηORR ) of 0.26 V and 0.27 V, respectively. The excellent catalytic activity is attributed to the optimal adsorption strength for oxygen intermediates coming from the effective modulation of the electronic structure of ReS2 after Ir/Pd doping. The results can help to deeply understand the catalytic activity of TM@ReS2 and develop novel and highly efficient OER/ORR electrocatalysts.

Three-dimensional heterostructured MnNiCoP/FeOOH cross-linked nano-flake supported by Ni Foam as a bifunctional electrocatalysts for overall water splitting

The production of three-dimensional heterogeneous structures is a vital approach for the creation of high-performance bifunctional electrocatalysts. Herein, three-dimensional heterostructure MnNiCoP/FeOOH (MNC-P/FeOOH) supported by Ni foam was prepared by simple electrodeposition and phosphorylation as a bifunctional electrocatalyst. The results showed that the required overpotential for MNC-P/FeOOH catalyst to reach 100 mA cm−2 current density was 124 mV and 251 mV in 1.0 M KOH solution, respectively. Construction of heterojunction not only improves the OER performance of MnNiCoP, but also reduces the potential required to drive the integral water splitting at 100 mA cm−2 current density. The electrocatalytic activity of MNC-P/FeOOH is greatly increased due to a distinctive interface synergy and strong electronic contacts in the MNC-P/FeOOH heterojunction. This design approach of bifunctional transition metal phosphides provides a potential route to achieve total water splitting.