Bifunctional Catalysts Research Articles

Efficient Nitrate to Ammonia Conversion on Bifunctional IrCu4 Alloy Nanoparticles.

Electrochemical nitrate reduction (NO3RR) to ammonia presents a promising alternative strategy to the traditional Haber-Bosch process. However, the competitive hydrogen evolution reaction (HER) reduces the Faradaic efficiency toward ammonia, while the oxygen evolution reaction (OER) increases the energy consumption. This study designs IrCu4 alloy nanoparticles as a bifunctional catalyst to achieve efficient NO3RR and OER while suppressing the unwanted HER. This is achieved by operating the NO3RR at positive potentials using the IrCu4 catalyst, which allows a Faradaic efficiency of 93.6% for NO3RR. When applied to OER catalysis, the IrCu4 alloy also shows excellent results, with a relatively low overpotential of 260 mV at 10 mA cm-2. Stable ammonia production can be achieved for 50 h in a 16 cm2 flow electrolyzer in simulated working conditions. Our research provides a pathway for optimizing NO3RR through bifunctional catalysts in a tandem approach.

Bifunctional mixed-valence ruthenium heterostructure for robust electrocatalytic water splitting in acid media

The incorporation of non-metal dopants can significantly enhance catalytic activity and improve stability. Furthermore, the creation of heterostructures is particularly advantageous to facilitate charge transfer and optimize electronic properties. This study presents an effective bifunctional mixed-valence Ruthenium heterostructure synthesized through a cascading process involving grinding with carbon nitride and subsequent thermal treatment. The catalyst exhibits outstanding electrocatalytic performance with remarkably low overpotentials of 197 mV for the oxygen evolution reaction (OER) and 24.8 mV for the hydrogen evolution reaction (HER), respectively, with the stability exceeding 24 h at a current density of 10 mA cm⁻2 in acidic media. Additionally, when employed in an acidic oxygen water splitting (OWS) electrolyzer, the bifunctional catalyst demonstrates excellent activity, achieving an ultralow cell voltage of 1.53 V to sustain 10 mA cm⁻2. Enhanced performance is attributed to efficient charge transfer and increased exposure of active sites, providing valuable insights for the development of effective acidic water-electrolysis catalysts for sustainable hydrogen production.

NiCo2O4/P,N‐doped Carbon with Engineered Interface to Improve the Rechargeability of Zn‐Air Batteries at High Energy Demands

The search for cost‐effective, high‐performance bifunctional catalysts for Zn‐air batteries (ZABs) requires extensive research into precious‐metal‐free materials. This study provides insight into the synergy between nickel cobaltite and P,N‐doped carbon modified through interface engineering by inducing oxygen vacancies in the spinel and non‐metallic heteroatoms in the carbon material. NiCo2O4 with various oxygen vacancy levels was synthesized via an ethylene glycol‐assisted solvothermal route. This resulted in significant changes in the structural and morphological properties, such as reduced crystallite size, lattice distortion, and increased oxygen vacancies, as observed from the physicochemical results. This was further verified by X‐ray photoelectron spectroscopy (XPS) and high‐resolution transmission electron microscopy (HR‐TEM), which showed a homogeneous dispersion of nickel cobaltite nanorods on the carbonaceous matrix, along with an increased concentration of pyridinic nitrogen and the formation of P–N and P–C bonds, both of which enhance electrocatalytic activity. NiCo2O4DI/P,N‐C exhibited superior discharge polarization behavior, achieving power and current densities of 124.4 mW cm−2 and 215.8 mA cm−2. The catalyst presented excellent stability (up to 100 h), while Pt‐IrO2/C lasted near 21 h. These results demonstrate the great potential of tailoring surface defects and heteroatom doping via interface engineering, resulting in high‐performance precious‐metal‐free electrocatalysts for long‐lasting and high‐efficiency ZABs.

What Is the Mechanism by which the Introduction of Amorphous SeOx Effectively Promotes Urea-Assisted Water Electrolysis Performance of Ni(OH)2?

Nickel hydroxide (Ni(OH)2) is considered to be one of the most promising electrocatalysts for urea oxidation reaction (UOR) under alkaline conditions due to its flexible structure, wide composition and abundant 3D electrons. However, its slow electrochemical reaction rate, high affinity for the reaction intermediate *COOH, easy exposure to low exponential crystal faces and limited metal active sites that seriously hinder the further improvement of UOR activities. Herein it is reported electrocatalyst composed of rich oxygen-vacancy (Ov) defects with amorphous SeOx-covered Ni(OH)2 (Ov-SeOx/Ni(OH)2). Surprisingly, at 100 mA cm-2, compared with Ni(OH)2 (1.46 V (vs RHE)), Ov-SeOx/Ni(OH)2 has a potential of 1.35 V. Meanwhile, Ov-SeOx/Ni(OH)2 catalyst also showed good hydrogen evolution reaction (HER) performance, so it is used as the electrolytic cell assembled by UOR and HER bifunctional catalysts and only 1.57 V could reach 100 mA cm-2. Density functional theory (DFT) study revealed that introduce of amorphous SeOx optimizes the electronic structure of the central active metal, amorphous/crystalline interfaces promote charge-carrier transfer, shift d-band center and entail numerous spin-polarized electrons during the reaction, which speeds up the UOR reaction kinetics.

Mixed Metal Oxide Derived from Polyoxometalate-Based Metal–Organic Framework as a Bi-Functional Heterogeneous Catalyst for Wastewater Treatment

The efficient removal of dyes and Cr(VI) from wastewater is imperative. Therefore, a mixed metal oxide CuMoV(450) derived from a polyoxometalate-based metal–organic framework (POMOF) [Cu(2,2′-bipy)][Cu(2,2′-bipy)2]2[PMo8V6O42]•2H2O (CuMoV) was synthesized by calcination, fully characterized by XRD, XPS, FT-IR, and SEM methods, and explored for the heterogeneous catalytic degradation of methylene blue (MB) dye and the catalytic reduction of Cr(VI) in aqueous media over NaBH4 under mild conditions. The removal rates for MB and Cr(VI) were 95.9% (30 min) and 96.5% (2.0 min), respectively. The pseudo-first-order rate constants of MB degradation and Cr(VI) reduction were 0.093 min−1 and 1.536 min−1, respectively. The highly catalytic reusability of CuMoV(450) was confirmed by the recycling experiments. Moreover, the possible mechanisms of MB degradation and Cr(VI) reduction were proposed. The catalytic activities of CuMoV(450) were much better than those of its parent compound CuMoV, proving that POMOFs were good candidates for the preparation of mixed metal oxides with excellent catalytic performances. This work not only indicates that CuMoV(450) has the potential to be a satisfied catalyst for wastewater remediation via catalytic degradation and reduction, but also gives a clue to synthesize mixed metal oxides with excellent catalytic properties by the calcination of POMOFs.

Rapid Synthesis of Carbon-Supported Ru-RuO₂ Heterostructures for Efficient Electrochemical Water Splitting.

Development of high-performance electrocatalysts for water splitting is crucial for a sustainable hydrogen economy. In this study, rapid heating of ruthenium(III) acetylacetonate by magnetic induction heating (MIH) leads to the one-step production of Ru-RuO₂/C nanocomposites composed of closely integrated Ru and RuO₂ nanoparticles. The formation of Mott-Schottky heterojunctions significantly enhances charge transfer across the Ru-RuO2 interface leading to remarkable electrocatalytic activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1m KOH. Among the series, the sample prepares at 300 A for 10 s exhibits the best performance, with an overpotential of only -31mV for HER and +240mV for OER to reach the current density of 10mA cm⁻2. Additionally, the catalyst demonstrates excellent durability, with minimal impacts of electrolyte salinity. With the sample as the bifunctional catalysts for overall water splitting, an ultralow cell voltage of 1.43V is needed to reach 10mA cm⁻2, 160mV lower than that with a commercial 20% Pt/C and RuO₂/C mixture. These results highlight the significant potential of MIH in the ultrafast synthesis of high-performance catalysts for electrochemical water splitting and sustainable hydrogen production from seawater.

Biodiesel production using simultaneous esterification-transesterification method from waste cooking oil with CaO/Fe2O3 bifunctional catalyst

Biodiesel is one of the products resulting from the initiation of energy diversification which can overcome the energy crisis both in Indonesia and in the world. Biodiesel can reduce combustion emissions. The purpose of this study was to produce biodiesel from waste cooking oil (WCO). The study was conducted using the simultaneous esterification-transesterification method with the help of a catalyst. The catalyst used was a bifunctional catalyst, namely CaO/Fe2O3. Waste cooking oil raw materials and biodiesel products were analyzed by GC-MS, while the catalyst was analyzed by SEM-EDX and XRD. The catalyst calcination temperature was varied at 750-950°C and the esterification-transesterification reaction time was varied at 1-5 hours. The results of the study showed that the highest biodiesel yield was obtained at 82% at a catalyst calcination temperature of 800°C and a reaction time of 4 hours. The methyl ester composition formed was 97.61%. The research results show that the biodiesel products produced comply with SNI 7182-2015 standards. This finding proves that waste cooking oil can be used as a raw material for biodiesel so that it will reduce the impact of environmental pollution.

Elucidating and Controlling Reaction Pathways for 2-Methylfuran Aromatization Using Bifunctional Zeolite Catalysts

Elucidating and Controlling Reaction Pathways for 2-Methylfuran Aromatization Using Bifunctional Zeolite Catalysts

Platinum-Nickel@High-Entropy Alloy Core@Satellite Nanowires as Efficient Bifunctional Electrocatalysts for PEMFC.

The optimized composition and precisely tailored structure configuration play critical roles in enhancing the catalytic reaction kinetics. Here we report a distinctive core@satellite strategy for designing the advanced platinum-nickel@platinum-nickel-copper-cobalt-indium high-entropy alloy nanowires (Pt3Ni@HEA NWs) as efficient bifunctional catalysts in the proton exchange membrane fuel cell. Impressively, the Pt3Ni@HEA NWs/C shows 19.4/15.3 times higher mass/specific activity than that of commercial Pt/C for the oxygen reduction reaction. More importantly, synchronously as the cathodic and anodic catalysts, it can achieve a high membrane electrode assembly power density of 1653.5 mW cm-2 and long-term stability (only 3.9% voltage loss) for 280 h, largely outperforming those of commercial Pt/C. The weakened Pt-CO binding strength, quick removal of CO with linear adsorption, and favorable CO adsorption form contribute to the high performance of Pt3Ni@HEA NWs/C. This core@satellite strategy provides a new paradigm to develop the comprehensively efficient Pt-based functional catalysts for fuel cells and beyond.

Energy-Saving Electrochemical Hydrogen Production via Amorphous CoMoP/NF Bifunctional Catalyst Coupled with HMF Oxidation Reactions in Alkaline Electrolyte.

To improve water splitting efficiency and enhance energy utilization, it is crucial to develop catalysts with excellent activity, long-term stability, and low cost. In this study, we synthesized a three-dimensional nanostructured amorphous CoMoP/NF bifunctional catalyst for both the hydrogen evolution reaction (HER) and the 5-hydroxymethylfurfural oxidation reaction (HMFOR), using a sacrificial template method. Benefiting from element doping regulation and morphology control, CoMoP/NF exhibited outstanding catalytic activity. Notably, in an electrolytic water system coupled with HER and HMFOR, a cell voltage of only 1.5 V was required at a current density of 20 mA cm-2, approximately 189 mV lower than that of a traditional water electrolysis system. This study presents a novel energy-saving method for hydrogen production through the HER/HMFOR electrolysis system.

Tunable NiSe-Ni3Se2 Heterojunction for Energy-Efficient Hydrogen Production by Coupling Urea Degradation.

Urea-assisted water splitting is a promising energy-saving hydrogen (H2) production technology. However, its practical application is hindered by the lack of high-performance bifunctional catalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Herein, a heterostructured catalyst comprising highly active NiSe and Ni3Se2, along with a conductive graphene-coated nickel foam skeleton (NiSe-Ni3Se2/GNF) is reported. The heterostructured NiSe-Ni3Se2 originates from the in situ selenization of graphene-coated nickel foam, allowing for careful regulation of the NiSe to Ni3Se2 ratio by simply adjusting the calcination temperature. Theoretical calculations of the charge transfer between NiSe and Ni3Se2 components can optimize the reaction pathways and reduce the corresponding energy barriers. Accordingly, the designed catalyst exhibits excellent UOR and HER activity and stability. Furthermore, the NiSe-Ni3Se2/GNF-based UOR-HER electrolyzer requires only 1.54V to achieve a current density of 50mA cm-2, which is lower than many recent reports and much lower than 1.83V of NiSe-Ni3Se2/GNF-based OER-HER electrolyzers. Moreover, the UOR-HER electrolyzer exhibited negligible cell voltage variation during a 28-h stability test, indicating satisfactory stability, which provides a new viable paradigm for energy-saving H2 production.

Site-Selective Copper(I)-Catalyzed Hydrogenation of Amides.

We present a bifunctional catalyst consisting of a copper(I)/N-heterocyclic carbene and an organocatalytic guanidine moiety that enables, for the first time, a copper(I)-catalyzed reduction of amides with H2 as the terminal reducing agent. The guanidine allows for reactivity tuning of the originally weakly nucleophilic copper(I) hydrides - formed in situ - to be able to react with difficult-to-reduce amides. Additionally, the guanidine moiety is key for the selective recognition of "privileged" amides based on simple and readily available heterocycles in the presence of other amides within one molecule, giving rise to hitherto unknown site-selective catalytic amide hydrogenation. A substrate scope, mechanistic investigations, and a working hypothesis supported by computational analysis for site-selectivity are presented.

Bifunctional Pd-Pt Supported Nanoparticles for the Mild Hydrodeoxygenation and Oxidation of Biomass-Derived Compounds.

The conversion of bio-based molecules into valuable chemicals is essential for advancing sustainable processes and addressing global resource challenges. However, conventional catalytic methods often demand harsh conditions and suffer from low product selectivity. This study introduces a series of bifunctional PdxPty catalysts supported on TiO2, designed for achieving selective and mild-temperature catalysis in biomass conversion. Synthesized via a sol immobilization method and characterized by XRF, N2 physisorption, HRTEM, HAADF-STEM, and XPS, these catalysts demonstrate superior selectivity and activity over monometallic counterparts. In fact, at 20 bar H2, Pt/TiO2 show a low selectivity in benzophenone hydrodeoxygenation, favoring the benzhydrol hydrogenation product; similarly, Pd/TiO2 preferentially form the diphenylmethane hydrodeoxygenation (HDO) product, but with slow conversion rates. The synergistic combination of the two metals in Pd4Pt1/TiO2 drastically improve performance, with 100 % benzophenone conversion and 73 % diphenylmethane selectivity. DFT calculations confirm the synergy between Pd and Pt as the key to drive the activity and selectivity. Additionally, the catalysts also demonstrate high recyclability with minimal performance loss, and have been generalized for the HDO of vanillin and furfural, and in HMF oxidation. Overall, this work highlights the potential of bimetallic catalysts in enabling efficient and selective bio-based molecule conversion under mild conditions.

Controllable loading of an Fe/Co alloy on heteroatom-doped hollow graphene spheres realized via regulation of small molecules for rechargeable zinc–air batteries

The controllable loading of an Fe/Co alloy on heteroatom-doped hollow graphene spheres (FeCo@NGHS) is realized via the regulation of small molecules for ORR/OER bifunctional catalysts.

Enhancing Activity and Stability of RuO2 as Bifunctional Catalyst Using Thermally Tuned α-MnO2 Interlayer for Hydrogen Production

Hydrogen is a vital and significant alternative fuel that can play a major role in reducing the impact of climate change. Developing robust and highly active bifunctional catalysts is essential...

Low-Pt coupled with atomic Ni-N5 doped carbon dots as efficient ORR/HER bifunctional catalyst

Low-Pt coupled with atomic Ni-N5 doped carbon dots as efficient ORR/HER bifunctional catalyst

Single-atom Pd directly anchored on biphenylene: a promising bifunctional electrocatalyst for overall water splitting.

The development of bifunctional single-atom catalysts (SACs) for overall water splitting is crucial for clean energy production in the context of sustainable development. Using first-principles calculations, the catalytic capability of different transition metal (TM) atoms supported on biphenylene (Bip) monolayers (TM@Bip, TM = V-Cu, Ru-Ag, and Ir-Au) is comprehensively investigated. Bip can directly anchor TM atoms without engineered vacancies or nitrogen defects. Among the screened SACs, Pd@Bip is found to be an excellent bifunctional catalyst for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The overpotentials for the HER and the OER were calculated to be 0.05 and 0.50 V, respectively, which are even superior to the commercialized catalysts like Pt and IrO2. Furthermore, adjusting the d-band center of TM atoms effectively modulates the catalytic activity, and the optimal OER performance of TM-Bip can be achieved with a d-band center of -2.32 eV, which can serve as a principle to design Bip-based SACs. Our findings may serve as a practical theoretical guide for the exploration of effective bifunctional SACs for overall water splitting.

Core-shell bifunctional catalysts: Controllable intimacy between metals and acids within nanometer-scale for n-alkane conversion

Core-shell bifunctional catalysts: Controllable intimacy between metals and acids within nanometer-scale for n-alkane conversion

Direct conversion of syngas to aromatics via a two-stage C–C coupling over MnZr/HZSM-5 bifunctional catalysts employing OX-ZEO strategy

The surface C–C coupling between the adsorbed alkyl groups and surface formate group shortens the CO activation pathway and triggers an oxygenated cycle in the OX-ZEO strategy.

Bifunctional catalysts for the coupling processes of CO2 capture and conversion: a minireview

A bifunctional catalyst for integrated CO2 capture and utilization (ICCU).