High-performance Bifunctional Electrocatalysts Research Articles

Structure-engineered bifunctional oxygen electrocatalysts with Ni3S2 quantum dot embedded S/N-doped carbon nanosheets for rechargeable Zn-air batteries

• Ni 3 S 2 -QDs/SNC nanocomposite was firstly designed and fabricated. • The authentic role of Ni 3 S 2 -QDs has been demonstrated by the various test. • The electrocatalyst shows excellent catalytic activity with ORR and OER. • The zinc-air battery shows a high power density and excellent rechargeability. The rational design of a high-efficiency and low-cost bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is significant but challenging for energy conversion devices such as Zn-air battery, fuel cell and water splitting. Herein, a two-dimensional heterostructure of S/N co-doped carbon nanosheets decorated with ultrafine Ni 3 S 2 quantum dots (Ni 3 S 2 -QDs/SNC) is designed and fabricated via a facile hydrothermal and high-temperature pyrolysis procedures. The heterostructure of Ni 3 S 2 -QDs/SNC is in situ formed from the Ni 3 S 2 QDs without sulfidation. Meanwhile, the S/N co-doped carbon carrier dramatically enhances the electrical conductivity and creates more effective active sites for ORR and OER. As a result, the Ni 3 S 2 -QDs/SNC affords a half-wave potential of 0.864 V for ORR and an overpotential of 0.310 V at 10 mA cm −2 for OER, outperforming the benchmark of Pt/C and RuO 2 . Moreover, the assembled Zn-air battery with Ni 3 S 2 -QDs/SNC air cathode exhibits a high power density (212 mW cm −2 ), energy density (962 Wh kg Zn − 1 ), and satisfactory stability (more than 200 h), which are superior than those of Pt/C-based Zn-air battery. Density functional theory calculations further illustrate that the interfacial Ni site of Ni 3 S 2 -QDs/SNC exhibits enhanced capacities for both the ORR and OER. This approach provides a novel strategy for the exploration of high-performance bifunctional oxygen electrocatalysts for energy-related applications.

Edge-segregated ternary Pd–Pt–Ni spiral nanosheets as high-performance bifunctional oxygen redox electrocatalysts for rechargeable zinc–air batteries

Ultrathin Pd45Pt44Ni11 spiral nanosheets with abundant Pt/Ni-segregated edges exhibit excellent ORR and OER dual-electrocatalysis in alkaline, showcasing a workable air cathode electrocatalyst for high-efficiency and rechargeable Zn–air batteries.

A hollow PdCuMoNiCo high-entropy alloy as an efficient bi-functional electrocatalyst for oxygen reduction and formic acid oxidation

A hollow PdCuMoNiCo high-entropy alloy on carbon hybrid was developed as a high-performance bi-functional electrocatalyst for the oxygen reduction reaction and formic acid oxidation reaction in an acidic medium.

Eutectic dual-phase microstructure modulated porous high-entropy alloys as high-performance bifunctional electrocatalysts for water splitting

High entropy alloys (HEAs) are promising as multifunctional electrocatalysts owing to their inherent compositional and structural complexity and thus the multiple active sites for different reactions.

Fe–Ni–Co trimetallic oxide hierarchical nanospheres as high-performance bifunctional electrocatalysts for water electrolysis

Fe–Ni–Co spheres were used as bifunctional catalysts exhibit high total water decomposition activity. Only a cell voltage of 1.61 V was required to attain a current density of 10 mA cm−2.

Integrating ceria with cobalt sulfide as high-performance electrocatalysts for overall water splitting

The development of bifunctional electrocatalysts for overall water splitting is highly desired for converting electricity into chemical energy. However, the synthesis of high-performance bifunctional electrocatalysts remains a pressing challenge. Here, we found that both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of the Co3S4 electrode can be significantly improved by integration with CeO2. Specifically, as-prepared 5% Ce-Co3S4 and 1% Ce-Co3S4 delivered low overpotentials of 290 and 257 mV to achieve 10 mA cm−2 for the OER and HER in 1.0 M KOH, respectively. The crucial role of CeO2 originated from its unique surface with abundant oxygen vacancies, which were beneficial for the stabilization of Co2+ sites with high OER activity and both the adsorption and dissociation of water molecules in the HER process. This work is expected to provide a general approach to prepare a wide range of high-performance electrode materials for energy-related applications.

In-Situ derived Co1-xS@nitrogen-doped carbon nanoneedle array as a bifunctional electrocatalyst for flexible Zinc-air battery

• Co 1-x S@NC is prepared via a facile “CBD deposition-PDA coating-sulfurization” method. • The excellent OER and ORR electrocatalytic activities both mainly derive from Co 1-x S. • The 3D array structure of Co 1-x S@NC facilitates OER/ORR-related charge-and-mass transport. • There is wrapping-protection of NC on Co 1-x S and strong electron coupling between them. • Promising quasi-solid-state rechargeable Zn-air battery based on Co 1-x S@NC is achieved. It is of great significance to develop high-performance bifunctional electrocatalysts for catalyzing two vital reactions in rechargeable zinc-air battery (ZAB). Transitional metal sulfides and N-doped carbon materials are widely reported as effective electrocatalysts of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. Herein, an 3D-array-structured catalyst composed of Co 1-x S nanoneedles enwrapped by nitrogen-doped carbon (NC) is in-situ grown on carbon fibre paper substrate. It is revealed that the metastable hexagonal Co 1-x S itself possesses attractive electrocatalytic activities toward both OER and ORR. Additionally, owing to the wrapping-protection effect of polydopamine-derived NC on Co 1-x S, the strong electron coupling between Co 1-x S and NC, and the 3D array structure, Co 1-x S@NC presents excellent OER/ORR catalytic activities and long-term stabilities, superior to Co@NC, Co 1-x S, and NC, and comparable to noble metals and other reported state-of-the-art bifunctional oxygen electrocatalysts. A small energy gap (Δ E ) of 0.66 V between the ORR half-wave potential (0.86 V vs RHE) and OER potential (1.52 V vs RHE) at a current density of 10 mA cm −2 , and a diffusion-limit ORR current density of 11.37 mA cm −2 are achieved. Notably, the flexible ZAB using the catalyst exhibits a markedly higher peak power density of 242 mW cm 2 , and a small charge/discharge voltage gap of ∼ 0.68 V with a high round-trip efficiency of ∼ 64% when cycling at 5 mA/cm 2 .

Mott-Schottky heterojunction of Co/Co2P with built-in electric fields for bifunctional oxygen electrocatalysis and zinc-air battery

In this contribution, a high-performance bifunctional electrocatalyst composed of Co/Co2P nanoparticles encapsulated in nitrogen and phosphorus co-doped carbon nanotubes (NPCNTs) has been synthesized via a mechanochemistry-pyrolysis approach. The Schottky effect of metal-semiconductor heterojunction affords a built-in electric field at the interfaces to enhance electron transport, whereas the intertwined structure of one-dimensional (1D) NPCNTs facilitates the mass transfer of reactants and intermediates. Therefore, the as-prepared Co/Co2P@NPCNTs catalyst exhibits outstanding bifunctional ORR/OER activities, which are superior to those of commercial Pt/C and RuO2. It can also deliver a high power density and cycling life when used as the cathode for rechargeable ZABs. Theoretical calculation confirms that the spontaneous electron transport from Co to Co2P enables an up-shifted d-band center of Co/Co2P heterojunctions, which is beneficial for the intermediate adsorption in electrocatalytic process.

Modulating electronic structure of cobalt phosphide porous nanofiber by ruthenium and nickel dual doping for highly-efficiency overall water splitting at high current density

The rational design and construction of high-efficiency bifunctional electrocatalysts are the central challenges for improving the overall water splitting efficiency. In this paper, Ru and Ni dual-metal doped CoP (Ru, Ni–CoP) porous nanofibers were fabricated. Dual-metal doping can be more efficiently used to modulate the electronic structure than single-metal doping, thereby, achieving decreased water dissociation energy and optimized adsorption energy for different reaction intermediates. Consequently, Ru, Ni–CoP porous nanofibers exhibit highly enhanced bifunctional activities. The electrolytic cell based on Ru, Ni–CoP porous nanofibers, which is significantly superior to Pt/C‖IrO2 pairs, requires a low voltage of 1.448 and 1.757 V at 10 and 500 mA cm−2, respectively. The electrolytic cell exhibits excellent long-term stability at 400 mA cm−2. This excellent activity and stability at high-current density provides the considerable potential for the practical applications of Ru, Ni-CoP porous nanofibers as high-performance bifunctional electrocatalysts.

Metal-substituted zirconium diboride (Zr1-xTMxB2; TM = Ni, Co, and Fe) as low-cost and high-performance bifunctional electrocatalyst for water splitting

Recent years have witnessed an unprecedented surge in research on earth-abundant and efficient electrocatalysts for the water splitting process. Among those, the development of boron-based advanced catalysts is subject to designing the active and durable compounds, working as bifunctional materials under alkaline medium. In this study, a series of ZrB2-based catalysts with a general formula of Zr(1-x)TMxB2 (x = 0.05, 0.1, and 0.2) (TM = Fe, Co, and Ni) were prepared through a straightforward route and employed as bifunctional electrocatalysts in hydrogen and oxygen evolution reactions (HER and OER). The electrochemical measurements confirmed that the incorporation of Ni into the crystal structure of ZrB2 in the Zr0.8Ni0.2B2 sample led to an onset potential of 1.58 V in OER at a current density of 10 mA cm–2, indicating a remarkable performance with a very low overpotential of 350 mV. Besides, Zr0.8Ni0.2B2 displayed an infinitesimal value of 56.6 mV dec–1 regarding the Tafel slope, which was lesser as compared to the commercial RuO2 (66.2 mV dec–1). For the case of HER, Zr0.8Co0.2B2 showed the best performance compared to other samples with an overpotential of 420 mV and a Tafel slope of 101.6 mV dec–1, following the Volmer mechanism. Both catalysts were examined for their long-term stability, manifesting excellent catalytic durability even after 12 h. Surprisingly, Zr0.8Co0.2B2 exhibited a drop from 420 to 380 mV in the overpotential value after 1000 CV sweeps, providing a promising performance in terms of HER. As-prepared metal-substituted ZrB2 electrocatalysts have great potential to be implemented in various green energy system applications.

Co-doped Ni3S2 porous nanocones as high-performance bifunctional electrocatalysts in water splitting

Developing non-precious nickel-based catalysts with high activity and low cost is a big challenge for industrial alkaline water splitting. Herein, Co-doped Ni3S2 nanocones (Co12@Ni3S2/NF) are prepared by vulcanizing a cobalt oxide nanofilm on the porous nickel foam (NF) by atomic layer deposition (ALD). The electrocatalysts boast a large specific surface area, abundant active sites for rapid diffusion of electrolyte ions, fast electron transportation, and high electrochemical activity. Especially, the Co12@Ni3S2/NF electrode exhibits excellent catalytic reactivity such as a small overpotential of 62 mV to attain a current density of 10 mA cm−2 and Tafel slope of 49 mV dec−1 for HER as well as 297 mV versus RHE at 20 mA cm−2 and Tafel slope of 50.3 mV dec−1 for OER. First-principles calculations show that the proper Co dopant concentration in Ni3S2 causes large surface lattice distortion resulting in high effective ionic charge of Co atoms to greatly enhance water splitting. The strategy and materials provide insights into the design and preparation of efficient, low-cost, and durable electrodes in water splitting applications.

Mesoporous LiTiPO4F nanoparticles: A new stable and high performance bifunctional electrocatalyst for electrochemical water splitting

Design of efficient and stable bifunctional electro-catalysts made of non-precious metals is a field of intense research in order to bring hydrogen production from laboratory to industrial scale. TiO2 is considered as electrochemically inactive may be due to the poor surface reactivity. Manipulating the electronic structure and stability of TiO2 to work under realistic conditions is crucial for the optimal production of hydrogen and oxygen. Herein, new class of titanium compound, LiTiPO4F, has been identified as a water splitting electrocatalyst. The resulted new mesoporous LiTiPO4F has been used as an efficient bifunctional electro-catalyst, to catalyse HER and OER, in alkaline medium, for the first time. The proposed LiTiPO4F catalyst demonstrated an ultrahigh electrocatalytic activity and stability towards HER and OER. The proposed mesoporous LiTiPO4F delivers ηOER, 100 mA cm−2 = 310 mV with Tafel slope of 93 mV dec−1 and ηHER, -100 mA cm−2 = -290 mV with small Tafel slope of 48 mV dec−1, revealing good OER/HER activity.

Complementary performance improved crystalline N-doped carbon encapsulated CoFe/mesoporous N-doped graphene foam as bifunctional catalyst

Future energy conversion that will replace fossil energy can be expected from oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) among high-performance bi-functional electrocatalysts. Herein, a hybrid material, CoFe@N-C/MNGF containing an N-doped carbon shell on the surface of CoFe alloy nanoparticles and three-dimensional (3D) mesoporous N-doped graphene foam with exposed active sites as an electron transfer substrate has been successfully synthesized to replace noble-metal catalysts. The electrocatalytic performance of CoFe@N-C/MNGF demonstrates better OER activity in 0.1 M KOH alkaline electrolyte with a remarkably low overpotential of 330 mV and low Tafel plot 130.6 mV⋅dec-1 at a current density of 10 mA⋅cm−2. And CoFe@N-C/MNGF has considerable ORR performance in terms of catalyst activity, electron transfer number and stability, which suggests its usefulness as a suitable replacement for ORR catalysts based on noble-metal used for cathode electrode of alkaline fuel cells. In particular, it showed a potential of 0.87 V in 0.1 M KOH alkaline electrolyte and low Tafel plot 71.7 mV⋅dec-1 at 5 mA⋅cm−2 and the number of electrons (n) transferred was estimated to be 2.1–3.61 at 0.15 to 0.35 V. Based on these results, this study provides new insights into a cost-efficient non-noble metal bi-functional electrocatalyst.

Constructing N, P-dually doped biochar materials from biomass wastes for high-performance bifunctional oxygen electrocatalysts

The large scale lignocellulosic biomass wastes could also be regarded as abundantly-available renewable resources, and how to convert them into value-added products via sustainable approaches is still a big challenge. In this work, we demonstrated a facile pyrolysis method to construct N, P-dually doped biochar materials from the lignocellulosic biomass wastes. The as-synthesized N, P-dually doped biochar samples could act as electrocatalysts for oxygen reduction and evolution reactions (ORR/OER), showing excellent catalytic performance and long-term durability, as well as robust tolerance to CO and methanol. The unique hierarchical porous structure, favorable electronic structure modified by the N and P doping, as well as a variety of defect sites induced by the N and P doping into the carbon framework were identified as the main contributions to the prominent catalytic activity of the as-synthesized N, P-dually doped biochar materials. We expect this work would spur more efforts into developing advanced materials from the large scale lignocellulosic biomass wastes.

Construction of unique ternary composite MCNTs@CoSx@MoS2 with three-dimensional lamellar heterostructure as high-performance bifunctional electrocatalysts for hydrogen evolution and oxygen evolution reactions

Developing non-noble and high activity electrocatalysts is the key to electrocatalytic water-splitting. Recently, MoS2 shows vast perspectives due to its excellent catalytic performance and chemical stability in acid condition. Herein, to expand its application in different environment, a unique ternary composite [email protected]x@MoS2 comprising three-dimensional lamellar heterostructure supported by multiwalled carbon nanotubes was successfully prepared by a two-step solvothermal strategy and used in electrocatalytic field. As a bifunctional electrocatalyst, heterostructure [email protected]x@MoS2 could catalyst HER with a small overpotential of 196 mV and low Tafel slope of 65 mV dec−1 in acid condition and exhibit outstanding OER performance with a low overpotential of 285 mV and small Tafel slope of 76 mV dec−1 in alkaline solution. Meanwhile, it displayed excellent durability both in an acid and alkaline solution. The remarkable electrochemical performance of [email protected]x@MoS2 can be attributed to novel construction advantages and synergy of MCNTs, small CoSx nanoparticles and lamellar MoS2. This work can be extended to the design and preparation of a series of composite materials with the advantage of structural diversity.

FeNi-functionalized 3D N, P doped graphene foam as a noble metal-free bifunctional electrocatalyst for direct methanol fuel cells

Designing high-performance bifunctional electrocatalysts for oxygen reduction (ORR) and methanol oxidation (MOR) reaction is essential for the wide application of direct methanol fuel cells. Here, we have prepared a novel three-dimensional (3D) FeNi-functionalized N, P doped graphene foam (FeNi@NP-GF) by a simple and cost-effective one-step pyrolysis method, as excellent bifunctional electrocatalyst for direct methanol fuel cells. Compared with metal-free and transition metal single-doped graphene foam catalysts (NP-GF, Fe@NP-GF and Ni@NP-GF), the resulting FeNi@NP-GF catalyst showed more positive half-wave potential and higher limiting current density in ORR reaction. Furthermore, it manifests a four-electron transfer process and strong methanol crossover resistance in the alkaline medium. The above results ascribed to the synergistic effect of Fe/Ni-Nx species formed with Fe/Ni and N species and multiple active sites in the 3D porous graphene material. Moreover, FeNi@NP-GF acted as good support for Pt nanoparticles (NPs). Pt/FeNi@NP-GF catalyst displayed remarkable catalytic performance and high stability for methanol electrooxidation reaction in acid medium.

Theoretical and experimental investigations of Co-Cu bimetallic alloys-incorporated carbon nanowires as an efficient bi-functional electrocatalyst for water splitting

Application of noble metal-free electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) during electrocatalytic water splitting is crucial for clean energy conversion and has drawn extensive attention. However, the development of highly active and low cost electrocatalysts is a considerable challenge. Herein, Co-Cu alloy nanoparticles-incorporated carbon nanowires electrocatalyst was synthesized and evaluated for both OER and HER. The nanomaterials were fabricated by facile electrospinning of sol-gel composed of cobalt acetate, copper acetate, and poly(vinyl alcohol) followed by calcination in an inert environment. Adjusting the composition of the metallic counterpart was found to significantly enhance electrochemical properties of the catalyst. Furthermore, the unique nanowire morphology and structural properties of incorporated Co-Cu alloy, the (Co0.95Cu0.05@CNWs) composition exhibits good electrocatalytic performance for both OER and HER in the alkaline medium. Physicochemical characterizations using X-ray diffraction, X-ray photoelectron spectroscope, scanning electron microscopy, and transmission electron microscopy have confirmed the formation of alloy structure and nanowire morphology. The optimum composition (Co0.95Cu0.05@CNWs) requires small overpotential, ɳ10 of ∼285 mV for oxygen evolution reaction (OER) and ∼160 mV for hydrogen evolution reaction (HER) with the corresponding Tafel slope of 92 mV dec−1 and 172 mV dec−1 versus the reversible hydrogen electrode, respectively. In addition, only negligible loss in activity was observed after 1000 cycles and prodeces cell voltage of 1.58 V at current of 10 mA/cm2 and 1.72 V at current density of 50 mA/cm2 in two electrode system. Density Functional Theory (DFT) calculations were employed to verify experimental results. Electronic density of states (DOS) results reveal an increase in electronic states near the Fermi level upon Co-Cu heterojunctioning with CNWs. This is indicative of improved catalytic activity and more favorable binding energies of HER and OER intermediates. Reaction coordinate diagrams for HER and OER were developed, which aided in identifying thermodynamically limiting steps. This work may provide a feasible approach for incorporating other transition metals to design low-cost and high-performance bifunctional electrocatalysts for overall water splitting.

Hierarchically designed CoMo marigold flower-like 3D nano-heterostructure as an efficient electrocatalyst for oxygen and hydrogen evolution reactions

Rational design of high performance bifunctional non-precious electrocatalysts is essential for the development of renewable energy conversion and storage technologies. Herein, we report a simple and effective hydrothermal method to synthesize a three-dimensional (3D) marigold-like cobalt-molybdenum layered double hydroxide (CoMo-LDH) flowers assembled by two-dimensional (2D) ultrathin nanosheets. Especially, the main difference with the previous reports of 2D CoMo-LDH nanosheets is the fact that the present 3D CoMo-LDH catalyst with high dense feature provide abundant active sites for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solution. Among the synthesized various Co/Mo ratios of LDHs (Co1Mo4, Co2Mo3, Co3Mo2, and Co4Mo1), the Co3Mo2-LDH exhibits the superior OER activity, delivering small overpotential of 266 mV at 10 mA cm−2 with low Tafel slope of 49 mV dec−1. Furthermore, Co3Mo2-LDH also show remarkable HER activity offering low overpotential of 325 mV at 100 mA cm−2, which outperforms the commercial Pt/C. Co3Mo2-LDH catalyst also demonstrates the excellent stability over 12 h. The enhanced OER and HER activity of Co3Mo2-LDH can be attributed to its high electrochemical surface area, inherent layered 2D structure, synergistic effects of Co and Mo metal atoms, and compositional merits.

Organically Capped Iridium Nanoparticles as High-Performance Bifunctional Electrocatalysts for Full Water Splitting in Both Acidic and Alkaline Media: Impacts of Metal–Ligand Interfacial Interactions

Design and engineering of bifunctional catalysts are critical in the development of electrochemical full water splitting. In this study, 4-ethylphenylacetylene-functionalized iridium (Ir–C≡, 1.7 ± ...

Bimetallic Co-Mo nitride nanosheet arrays as high-performance bifunctional electrocatalysts for overall water splitting

Developing non-precious metal electrocatalysts with high activity and stability are of great significance to achieve overall water splitting. In this work, cobalt-molybdenum nitride nanosheet arrays grown on Ni foam (CoMoNx NSAs/NF) were prepared via a facile hydrothermal and nitridation process. The resulting CoMoNx NSAs/NF not only has a specific large surface area and provides more active sites but also possesses good electrical conductivity, contributing to the fast reaction kinetics. Furthermore, the synergistic effect between Co2N and Mo2N cooperatively enhance the charge transfer, thus further improving the electrocatalytic activity. Benefiting from these merits, the optimal CoMoNx-500 NSAs/NF exhibits excellent activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with overpotentials of 91 and 231 mV at the current density of 10 mA cm−2, respectively. Moreover, the CoMoNx-500 NSAs/NF||CoMoNx-500 NSAs/NF couple requires a low cell voltage of 1.55 V at the current density of 10 mA cm−2, which is much superior to many other reported transition metal nitrides catalysts. This present work provides a reference for the design of bimetallic nitrides with superior electrocatalytic performance foroverall water splitting.