Alternative Catalyst Research Articles

Material Engineering Strategies for Efficient Hydrogen Evolution Reaction Catalysts.

Water electrolysis, a key enabler of hydrogen energy production, presents significant potential as a strategy for achieving net-zero emissions. However, the widespread deployment of water electrolysis is currently limited by the high-cost and scarce noble metal electrocatalysts in hydrogen evolution reaction (HER). Given this challenge, design and synthesis of cost-effective and high-performance alternative catalysts have become a research focus, which necessitates insightful understandings of HER fundamentals and material engineering strategies. Distinct from typical reviews that concentrate only on the summary of recent catalyst materials, this review article shifts focus to material engineering strategies for developing efficient HER catalysts. In-depth analysis of key material design approaches for HER catalysts, such as doping, vacancy defect creation, phase engineering, and metal-support engineering, are illustrated along with typical research cases. A special emphasis is placed on designing noble metal-free catalysts with a brief discussion on recent advancements in electrocatalytic water-splitting technology. The article also delves into important descriptors, reliable evaluation parameters and characterization techniques, aiming to link the fundamental mechanisms of HER with its catalytic performance. In conclusion, it explores future trends in HER catalysts by integrating theoretical, experimental and industrial perspectives, while acknowledging the challenges that remain.

A Review of the Structure–Property Relationship of Nickel Phosphides in Hydrogen Production

Hydrogen, one of the most promising forms of new energy sources, due to its high energy density, low emissions, and potential to decarbonize various sectors, has attracted significant research attention. It is known that electrocatalytic hydrogen production is one of the most widely investigated research directions due to its high efficiency in the conversion of electricity to H2 gas. However, given the limited reserves and high cost of precious metals, the search for non-precious metal-based catalysts has been widely explored, for example, transition metal phosphides, oxides, and sulfides. Despite this interest, a detailed survey unveils that the surface and internal structures of the alternative catalysts, including their surface reconstruction, composition, and electronic structure, are poorly studied. As a result, a disconnection in the structure–property relationship severely hinders the rational design of efficient and reliable non-precious metal-based catalysts. In this review, by focusing on Ni5P4, a bifunctional catalyst for water splitting, we systematically summarize the material motifs pertaining to the different synthetic methods, surface characteristics, and hydrolysis properties. It is believed that a cascaded correlation may provide insights toward understanding the fundamental catalytic mechanism and design of robust alternative catalysts for hydrogen production.

Collective Synergistic Catalysis of Electrochemical CO2 Reduction on Nonstoichiometric Double Perovskites

AbstractPerovskite oxides show great promise as an alternative catalyst to the conventional nickel cermets for CO2 reduction reactions (CO2RR) in solid oxide electrolysis cells (SOECs) owing to their advantages of redox stability and coking resistance. Nevertheless, practical applications of these oxides are prevented largely by their poor CO2RR activities. Herein, a novel donor and acceptor co‐doped nonstoichiometric double perovskite, La0.3Sr1.55Fe1.5Ni0.1Mo0.4O6−δ (LSFNM), is developed with in situ exsolved FeNi3 nanoparticles to efficiently catalyze CO2RR in SOECs. Pure CO2 electrolysis over the impregnated FeNi3@LSFNM catalysts is evaluated on two types of SOECs—one with thin (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 (SSZ) electrolytes supported on 430L alloys and the other with thin La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolytes supported on impregnated SmBa0.5Sr0.5Co2O5+δ (SBSCO)@LSGM anodes, producing unprecedently high current densities of 2.84 A cm−2 for the former and 3.07 A cm−2 for the latter at 1.5 V and 800 °C. Experimental analysis and density‐functional theory (DFT) calculations reveal collective synergistic catalysis of oxygen vacancies (), the doping Ni2+ ions and FeNi3 nanoparticles via the cooperative ‐O(CO2), and Ni(II)–C(sp) and Ni(0)–O(CO2) interactions in LSFNM, not only facilitating CO2 chemisorption on oxygen vacancies but also destabilizing and dissociating surface carbonates in the vicinity of FeNi3 spontaneously into CO.

Mesoporous Palladium Catalyst for Efficient Electrochemical Semi‐Hydrogenation of Alkynes

AbstractDeveloping robust electrocatalysts for efficient semi‐hydrogenation of alkynes to markedly important alkenes is highly desirable in both research and industry areas. In this work, it is reported that robust palladium mesoporous nanospheres (Pd MSs) with electron‐rich active sites perform perfectly as cathode electrocatalyst for electrochemical semi‐hydrogenation of alkynes in water. In comparison to its counterparts, Pd MSs hold remarkable conversion (97%), superior selectivity (98%), good operation stability in selective semi‐hydrogenation of p‐aminophenylene. High performance is assigned to electron‐rich Pd sites within mesopores that not only favor the formation of active H* but also accelerate the desorption of p‐aminostyrene. Meanwhile, Pd MSs are also highly efficient in selective semi‐hydrogenation of various terminal alkynes with different substituents. It is thus expected that robust Pd MSs can be demonstrated as an alternative catalyst design paradigm for other electrochemical hydrogenation reactions.

Nanoarchitecture of 2D materials: Unveiling the power trio-Ni, Co, and GNF-in eco-friendly air breathing zinc air battery through layered double hydroxides

Zinc-air batteries emerge as sustainable and efficient energy storage device towing to its potential for high energy density and environmental friendliness. Layered double hydroxide (LDH) specifically, exhibit unique properties like high surface area, stability and ion-exchange capacity, making them attractive for various applications. In this work, a simple and scalable one-pot urea hydrolysis process is adopted to synthesize NiCo-LDH supported on graphene nanofiber (GNF) sheets as a good substitute as a non-precious bifunctional catalyst. Ammonium fluoride as a structural-mediating agent is employed which offers a unique homogeneous 3D micro-sized hierarchical petal-like morphology of NiCo-OH. Electrochemical analysis shows low over potential with high durable around 15,000 potential cycles in a 0.5 M KOH solution which confirms the structural integrity and superior activity of NiCo-LDH/GNF catalyst in oxygen reduction and evolution reactions. The resulting NiCo-LDH/GNF composites demonstrate outstanding specific capacitance of 806 mAh g−1 with stable cycling performance up to 950 cycles and rate capability, making it promising alternative bifunctional electro catalyst in Zinc-air batteries.

Production of green hydrogen through PEM water electrolysis

Abstract The need for abundant, sustainable, and clean energy is becoming increasingly important in the modern world due to continuous population growth and industrial expansion. Hydrogen (H2) has been identified as a potential energy carrier due to its high gravimetric energy density. Because H2 is not frequently found in its molecular form, it has to be obtained through various methods such as steam methane reforming, coal gasification, fossil fuels, and electrochemical techniques. H2 produced via PEMWE has proved to be an efficient method compared to other electrolysers. The limiting factor of a PEM electrolyser system is the OER catalyst. Commercially, IrO2 and RuO2 are used; however, both these metals are rare and expensive. Current research reports the use of binary metal oxides as an alternative OER catalyst to decrease the overall CAPEX costs. Various synthesis methods are available, with the Adams’ fusion method being the simplest. Characterisation techniques used to evaluate the performance of these catalysts include cyclic voltammetry (CV), linear scan voltammetry (LSV), XRD, XRF, SEM/EDS, and chronopotentiometry. Hydrogen as a clean fuel has a broad potential for use across all sectors, including transportation, residential, and industrial. In recent years, extensive research has been done on all aspects of hydrogen production, storage, and transportation. This review paper aims to study other bimetallic metals to reduce the Ir content used as an oxidative evolution reaction to reduce the capital cost of the PEM electrolyser. To produce green hydrogen that could reduce the carbon footprint in several industrial processes.

Ortho-parahydrogen catalyst test facility

With the growing interest in hydrogen as one pillar of the future energy economy, the relevance of hydrogen liquefaction for storage and transportation is increasing rapidly. However, the liquefaction process still offers much potential for improvement in terms of cost and efficiency. One problem faced with achieving more cost- and energy-efficient liquefiers is the uncertainty associated with the dimensioning of the ortho-para converters. Literature data on the existing ortho-para catalysts stem mainly from the 1950s and 1960s and are partly inconsistent. Therefore, a new facility for the comprehensive investigation of catalytic ortho-parahydrogen conversion was set up at the Dresden University of Technology (TU Dresden) as part of the government-funded HyCat (“Improvement of the Ortho-Para-Catalysts for Hydrogen Liquefaction”) project. It enables the testing of catalysts in the whole operational range of ortho-para converters in modern large-scale liquefaction plants by allowing the independent variation of temperature, pressure, flow rate, inlet ortho-para ratio, and sample reactor internal geometry. The setup has been tested and validated preliminarily. It can soon be used to produce new high-quality data sets on the performance of the commercial catalyst Ionex (hydrous ferric oxide), for the qualification of alternative catalysts, and for gaining a deeper understanding of the reaction kinetics involved.

Influence of the modification of chlorophyll-rich extracts on the hydrogen evolution reaction of rGO-based electrocatalysts

The great efforts to develop alternative electrocatalysts for efficient hydrogen evolution reaction (HER) applications through environmentally friendly synthesis still need to be completed. We explore a green route using spinach extract to simultaneously reduce and functionalize graphene oxide (GO). A spinach extract, rich in green reducing agents and chlorophyll, was obtained and modified by saponification and demetallation to yield Chln-H2 and further used to reduce and functionalize GO in a one-step procedure. The resulting RGO/Chln-H2 electrocatalyst was evaluated on the HER by Lineal Sweep Voltammetry (LSV), achieving a current density of −34.84 mA/cm2 starting its activation from an onset potential of −0.68 V vs reference hydrogen electrode (RHE). The effect of saponification and demetallation produces a new metal-free alternative catalyst with increased current density seven times, boosting hydrogen production performance.

Investigating the electrochemical performance of Mn3O4/MoMn2P12 mixed-phase catalyst on MWCNT for high specific energy supercapacitors and HER/OER reactions

A versatile Mn/MoMn hybrid oxide/phosphide composite (MnO/MoMnP) supported on MWCNT is synthesized using hydrothermal method and in-situ phosphorization methods. This composite serves as a catalyst for supercapacitors and oxygen and hydrogen evolution reactions (OER/HER) in electrochemical water splitting. XRD analysis confirmed the presence of mixed-phase of Mn3O4 and MoMn2P12. Electrochemical tests revealed exceptional charge storage performance for MnO/MoMnP/MWCNT, with a high specific capacitance(436 F g−1 at 1 A g−1) and impressive capacitance retention (96.51 % for 5000 cycles at 15 A g−1). This performance surpasses that of bare MnO/MoMnP by 50 %. Furthermore, we assembled a MnO/MoMnP/MWCNT//MWCNT device, that achieved a remarkable energy density of 128.11 W h kg−1 at an ultra-high-power density of 1920 W kg−1, along with excellent cycling stability (92.5 % for 5000 cycles). Moreover, the MnO/MoMnP/MWCNT composite exhibited a remarkable bifunctional electro catalytic activity for OER and HER, with low overpotentials of 335 and 430 mV at 10 mA cm−2 in 1 M KOH solution. These results highlight MnO/MoMnP/MWCNT as a promising and efficient alternative catalyst for future applications in supercapacitors and water electrolysis.

A heterostructured ternary transition metal oxide composite as an efficient electrocatalyst for the hydrogen evolution reaction

A key method for hydrogen production is water electrolysis involving the oxygen and hydrogen evolution reactions. The efficiency of these processes is largely dependent on the use of effective electrode catalysts. Despite the high water-splitting catalytic activity of noble metals such as Pt, Ru, and Ir, their scarcity and costliness pose significant challenges. Although Fe and Fe-based compounds have recently been identified as promising alternative catalysts due to their abundance, affordability, and low toxicity, particularly under the alkaline conditions required for the hydrogen evolution reaction, both can be reduced to unstable forms during the reaction. To address this, the focus of the present study is on developing a ternary transition metal oxide electrocatalyst comprising Ni, Fe, and Co oxides. Thereby, we leveraged the synergistic interactions among them to provide a heterogeneous electrocatalyst for the hydrogen evolution reaction with a sufficiently low overpotential of 45 mV and suitably high Tafel kinetics of 44.99 mV dec−1 and long-term stability. The ternary transition metal oxide electrode showcased superior performance compared to one comprising binary transition metal oxides by achieving a lower overpotential and a better Tafel slope while maintaining catalytic stability even for 100 h at a current density of 1000 mA cm−2. This innovative approach offers a highly efficient alternative catalyst to Fe, which is known to have stability issues for hydrogen production, especially at high current density.

Phosphorus Modification of Iron: Mechanistic Insights into Ammonia Synthesis on Fe2P Catalyst.

Ammonia (NH3) is a critical chemical for fertilizer production and a potential future energy carrier within a sustainable hydrogen economy. The industrial Haber-Bosch process, though effective, operates under harsh conditions due to the high thermodynamic stability of the nitrogen molecule (N2). This motivates the search for alternative catalysts that facilitate ammonia synthesis at milder temperatures and pressures. Theoretical and experimental studies suggest that circumventing the trade-off between N-N activation and subsequent NHx hydrogenation, governed by the Brønsted-Evans-Polanyi (BEP) relationship, is key to achieving this goal. Recent studies indicate metal phosphides as promising catalyst materials. In this work, a comprehensive density functional theory (DFT) study comparing the mechanisms and potential reaction pathways for ammonia synthesis on Fe(110) and Fe2P(001) is presented. The results reveal substantial differences in the adsorption strengths of NHx intermediates, with Fe2P(001) exhibiting weaker binding compared to Fe(110). For N-N bond cleavage, multiple competing pathways become viable on Fe2P(001), including routes involving the pre-hydrogenation of adsorbed N2 (e.g., through *NNH*). Analysis of DFT-derived turnover rates as a function of hydrogen pressure (H2) highlights the increased importance of these hydrogenated intermediates on Fe2P(001) compared to Fe(110) where direct N2 dissociation dominates. These findings suggest that phosphorus incorporation modifies the ammonia synthesis mechanism, offering alternative pathways that may circumvent the limitations of traditional transition metal catalysts. This work provides theoretical insights for the rational design of Fe-based catalysts and motivates further exploration of phosphide-based materials for sustainable ammonia production.

Periodic open cellular structures (POCS) as catalyst support for intensified heat transport in the partial oxidation of methanol to formaldehyde

Heat transport in catalytic reactors is one of the most important factors in reactor design, especially for highly endo- or exothermic reactions. The limited thermal conductivity of randomly packed beds can be significantly improved when alternative catalyst supports are used. A new generation thereof are periodic open cellular structures (POCS), which are used in this study as catalyst support for the partial oxidation of methanol to formaldehyde, an exothermic gas phase reaction. A comparison to traditional packed bed reactors revealed that a POCS made of the highly conductive alloy AlSi10Mg can significantly reduce the hot-spot temperature, allowing almost isothermal operation at optimal reaction conditions. The improved temperature control allows for operation with higher methanol inlet concentrations and wall temperatures as compared to the commercial process. The beneficial heat transport properties of POCS were used to conduct isothermal kinetic measurements at elevated temperature. Based on these findings and the design freedom of additive manufacturing, an optimized cellular structure was designed and fabricated, which improved the heat transport especially in the critical inlet section of the reactor.

Research on Alternative Pt-based or Non-Pt catalysts for Solid Oxide Fuel Cells

Nowadays, heavy environmental and economic pressure from energy consumption is increasingly evident, and the research and application of new batteries is an effective strategy to solve above problems. Fuel cell is a chemical device that produces electricity directly from chemical energy. It has attracted much attention due to its lightweight device, simple mechanism, and clean energy. In the operation of fuel cells, the efficiency and stability of cells are determined by the ability of catalyst in redox reactions. However, pure platinum or platinum-based catalysts commonly applicated in solid oxide fuel cells are normally expensive and not renewable. Therefore, it is particularly important to develop alternative Pt-based catalysts or non-Pt catalysts. In this paper, several alternative low-platinum or non-platinum catalysts are systematically investigated, and novel platinum-based and non-platinum multi-metal composite oxide catalysts are found to have higher catalytic activity and economic feasibility compared with pure platinum catalysts. The popularity of these new catalysts can effectively address the scarcity of resources and energy.

The recent development of β‐cyclodextrin‐based catalysts system in Suzuki coupling reactions

β‐Cyclodextrin has drawn significant attention as a special class of cyclic oligomers over the past few decades. They have been employed in many organic conversions as green alternative catalysts to perform satisfactorily in catalytic activity and modify the efficiency of organic reactions. Its availability, nontoxicity, low cost, renewability, and high performance in organic transformations are several benefits of cyclodextrins that have captured the interest of many research groups worldwide. In recent decades, great progress has been made in developing metal‐catalyzed coupling reactions to create carbon–carbon bonds. For the transition‐metal‐catalyzed cross‐coupling, using modified β‐cyclodextrin derivatives as catalysts is much more pleasant due to the obvious advantages such as valuable catalytic properties and the capability to create an inclusion complex with different metals. The particular purpose of this review is to summarize the application of β‐cyclodextrin‐based catalyst systems in Suzuki coupling reaction for the synthesis of biaryl compounds covering the years 2019–2023.

Biodiesel production with DES (deep eutectic solvent) catalyst using used cooking oil feedstock through two-stage transesterification process

Most of biodiesel in Indonesia is still produced by costly processed utilizing pricey catalysts and high grade fatty acid methyl esther (FAME). Low cost catalysts need to be invented in order to make biodiesel more affordable, while raw material also need to be obtained from low cost alternatives. such as broadly available waste cooking oil.This research used waste cooking oil as raw material in biodiesel transesterification process, utilizing DES (Deep Eutectic Solvent) K2CO3-gliserol, as alternative catalyst. The output was biodiesel with near SNI 7182:2015 criteria. Optimum biodiesel production was achieved in low 65 oC temperature while utilizing two step transesterification process using DES K2CO3-gliserol 5.5 % and 35 % methanol, whereas glycerol total was 0.32 % and methyl esther contain was 96.89 %.

Highly efficient metal free aldehyde-functionalized indoles for direct glucose fuel cell anode catalyst

In this study, alternative organic catalysts to metal-containing catalysts for glucose electrooxidation were prepared by the Suzuki Miyaura coupling reaction method and characterized by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FT-IR), and liquid chromatography with tandem mass spectrometry (LC-MS-MS). InTA-1, InPA-1, InFA-1, InTA-2, InPA-2, InFA-2, InTA-3, InFA-3, and InPA-3 were obtained with the yield of 74%, 82%, 72%, 70%, 75%, 68%, 60%, 71%, and 85%. Among the synthesized catalysts, the InTA-3 catalyst possesses the highest electrocatalytic activity (3.17 mA cm−2) and long-term stability compared to other organic catalysts. InTA-3 catalyst has the lowest charge transfer resistance toward glucose electrooxidation. It was concluded that as a metal-free catalyst, InTA-3 is a cheap and promising electrocatalyst for direct glucose fuel cell anode.

PtZn/ZnO intermetallic catalyst prepared by reactive metal-support interaction for the semi-hydrogenation of 1,4-butynediol

The continuous flow selective hydrogenation of 1,4-butynediol to 2-butene-1,4-diol places high demands on the activity and stability of the catalyst. Herein, an intermetallic PtZn/ZnO catalyst is designed by using the coupling strategy of strong electrostatic adsorption and subsequent reactive metal-support interaction. The TOF value of the Pt/ZnO-H500 catalyst, including PtZn intermetallic compound with electron-rich Ptδ- active sites, reaches 1421.6 h−1, which is almost 8 times higher than that of Pt/ZnO-H200 catalyst with monometallic Pt as active sites. The activation energy of Pt/ZnO-H500 catalyst (35.5 kJ mol−1) is significantly lower than that of Pt/ZnO-H200 catalyst with 49.9 kJ mol−1. In addition, the Pt/ZnO-H500 presents high stability in the continuous flow selective hydrogenation of 1,4-butynediol to 2-butene-1,4-diol for 75 h. These results suggest the intermetallic PtZn/ZnO presents as an alternative Pt-based catalyst without modification by toxic metals or organic matter and is a promising catalyst for directional hydrogenation in fine chemical synthesis.

Cu-OFF/ERI Zeolite: Intergrowth Structure Synergistically Boosting Selective Catalytic Reduction of NOx with NH3.

Cu-SSZ-13 has been commercialized for selective catalytic reduction with ammonia (NH3-SCR) to remove NOx from diesel exhaust. As its synthesis usually requires toxic and costly organic templates, the discovery of alternative Cu-based zeolite catalysts with organotemplate-free synthesis and comparable or even superior NH3-SCR activity to that of Cu-SSZ-13 is of great academic and industrial significance. Herein, we demonstrated that Cu-T with an intergrowth structure of offretite (OFF) and erionite (ERI) synthesized by an organotemplate-free method showed better catalytic performance than Cu-ERI and Cu-OFF as well as Cu-SSZ-13. Structure characterizations and density functional theory calculations indicated that the intergrowth structure promoted more isolated Cu2+ located at the 6MR of the intergrowth interface, resulting in a better hydrothermal stability of Cu-T than Cu-ERI and Cu-OFF. Strikingly, the low-temperature activity of Cu-T significantly increased after hydrothermal aging, while that of Cu-ERI and Cu-OFF substantially decreased. Based on in situ diffuse reflectance infrared Fourier transform spectra analysis and density functional theory calculations, the reason can be attributed to the fact that NH4NO3 formed on the CuxOy species within ERI polymorph of Cu-T underwent a fast SCR reaction pathway with the assistance of Brønsted acid sites at the intergrowth interfaces under standard SCR reaction conditions. Significantly, Cu-T exhibited a wider temperature window at a catalytic activity of over 90% than Cu-SSZ-13 (175-550 vs 175-500 °C for fresh and 225-500 vs 250-400 °C for hydrothermal treatment). This work provides a new direction for the design of high-performance NH3-SCR catalysts in terms of the interplay of the intergrowth structure of zeolites.

Natural pyrite-stimulative periodate activation: efficiency and mechanism study.

Natural pyrite (NP) is an alternative catalyst for wastewater purification via advanced oxidation processes (AOPs). However, the activation performance and mechanism of periodate (PI) by NP have not yet been revealed. Herein, this work examines the activation performance of NP towards PI and its application in the degradation of antibiotic wastewater. Interestingly, 95.69% of chlortetracycline (CTC) was degraded by NP within 20min via PI activation. Besides, NP shows effective degradation of various pollutants such as rhodamine B (65.81%), sulfamethoxazole (89.04%), and sodium butylxanthate (99.77%) within 20min. The active species quenching experiment suggested that the active species , , 1O2 and the active complex of PI bonded with NP surface participated in CTC degradation. In addition, Fe(II) on NP surface is the main active site for PI activation, while Sn2- species accelerates the reduction of Fe(III) to Fe(II) and promotes sustained PI activation. This work provides new ideas for the application of NP in environmental pollution control.

Electrodeposition of PdPt Nanoparticles on Edges and S-Vacancies in Exfoliated MoS2 Nanosheets for Enhanced Hydrogen Evolution Activity.

Deposition of metal nanoparticles onto the molybdenum disulfide (MoS2) nanosheets is an efficient method to tune the electronic structure of the MoS2 and maximize its catalytic performance towards the hydrogen evolution reaction (HER). Herein, we report the electrodeposition of Pd and Pt nanoparticles onto desulfurized MoS2 nanosheets (MoS2-x) to achieve an improved HER activity in an acidic electrolyte. The initial MoS2 powder was exfoliated and isolated through centrifugation, followed by electrochemical desulfurization to create defect sites. Subsequently, Pt and Pd nanoparticles were electrodeposited onto the S-vacancies of MoS2-x nanosheets. The resulting PdPt nanoparticles, with a diameter of 3.3 ±1.7 nm, were distributed across the surfaces of the nanosheets. A preferential deposition was evident at the edges of the nanosheets, particularly when Pd was deposited first followed by Pt. Owing to this preferential deposition of Pd and Pt and the synergistic interaction of MoS2-x with Pd and Pt, the prepared catalyst exhibited a low overpotential of 30 mV at 10 mA cm-2, which is 2.7× lower than the MoS2-x alone. The prepared catalyst exhibited a 1.7× increase in the mass activity at 20 mV overpotential, relative to that of a commercial Pt/C nanocatalyst, showcasing its promising potential as an alternative catalyst.