Preparation Of Electrocatalysts Research Articles

Hybridization of bimetallic cobalt-molybdenum oxide multihole nanosheets with selenium adulteration as advanced bifunctional electrocatalysts for boosting overall water splitting

Electrocatalytic water splitting produces green and pollution-free hydrogen as a clean energy carrier, which can effectively alleviate energy crisis. In this paper, bimetallic and selenium doped cobalt molybdate (Se-CoMoO4) nanosheets with rough surface are resoundingly prepared. The multihole Se-CoMoO4 nanosheets display ultrathin and rectangular architecture with the dimensions of ∼ 3.5 μm and 700 nm for length and width, respectively. The Se-CoMoO4 electrocatalyst shows remarkable water electrolysis activity and stability. The overpotentials of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are 270 and 63.3 mV at 10 mA cm−2, along with low Tafel slopes of 51.6 and 62.0 mV dec-1. Furthermore, the Se-CoMoO4 couple electrolyzer merely requires a cell voltage of 1.48 V to achieve 10 mA cm−2 current density and presents no apparent attenuation for 30 h. This investigation declares that the hybridization of transition bimetallic oxide with nonmetallic adulteration can afford a tactic for the preparation of bifunctional non-precious metal-based electrocatalysts.

Bimetallic Fe/Ni-BTC MOF decorated MXene hybrid for improved oxidation of water

Electrochemical production of green hydrogen via water-splitting is an emerging technology to generate a substitute source of energy. However, due to the slow kinetics of oxygen evolution reaction (OER), high cost, lesser availability and easy oxidation of noble metal-based electrocatalysts led the explorers to find an efficient and low-cost electrocatalysts. In the current communication, we have developed a synthesis strategy for the preparation of hybrid electrocatalyst composed of bimetallic (iron, nickel) based metal organic framework (FeNiBTC MOF) and MXene (Ti3C2Tx) via solvothermal reaction. Thanks to the ultrathin heterostructure with high electrical conductivity of MXene, with abundant active sites of FeNiBTC MOF, the as-prepared hybrid electrocatalyst FeNiBTC@MXene, leads the high efficiency OER in an alkaline environment. FeNiBTC MOF was impeccably decorated on the surfaces of MXene nanosheets with different FeNiBTC to MXene ratios and was characterized via pXRD, FESEM/EDS, XPS and BET. The optimized hybrid structured catalyst (FeNiBTC@Mx-3) revealed the best performance for OER with a low overpotential of 210 mV vs. RHE at a current density of 10 mA/cm2 and a Tafel plot value of 38.4 mV/dec and stable up to 1000th CV cycles.

Application of molecularly imprinted polymers in the water environmental field: A review on the detection and efficient removal of emerging contaminants

The emerging contaminants in the environment pose a threat to ecological security and human health. At present, traditional technologies are difficult to detect and remove existing trace emerging contaminants in water bodies. Therefore, efficient removal of low concentration emerging contaminants is a key issue in ensuring water safety. As an emerging technology, molecular imprinting technology (MIT) can synthesize polymers with specific recognition ability for target pollutants, providing a new approach for efficient removal of emerging contaminants. It is worth noting that combining MIT with traditional catalysts is an effective method to improve detection limits and removal efficiency. This review mainly introduced the research progress of using MIT to detect pollutants in various sensors and using advanced oxidation technology to remove pollutants in recent years, focusing on the preparation and application of MIT-based photocatalysts, electrocatalysts, and Fenton-like catalysts. In addition, possible interactions between the target analyte and MIT were discussed, as well as the reusability and stability of imprinted catalysts in water treatment, and their potential ecological toxicity risks were analyzed. Finally, the challenges of MIT based pollutant mitigation and the application prospects of molecular imprinting technology in environmental analysis were elaborated from multiple perspectives.

Application of molecularly imprinted polymers in the water environmental field: A review on the detection and efficient removal of emerging contaminants

The emerging contaminants in the environment pose a threat to ecological security and human health. At present, traditional technologies are difficult to detect and remove existing trace emerging contaminants in water bodies. Therefore, efficient removal of low concentration emerging contaminants is a key issue in ensuring water safety. As an emerging technology, molecular imprinting technology (MIT) can synthesize polymers with specific recognition ability for target pollutants, providing a new approach for efficient removal of emerging contaminants. It is worth noting that combining MIT with traditional catalysts is an effective method to improve detection limits and removal efficiency. This review mainly introduced the research progress of using MIT to detect pollutants in various sensors and using advanced oxidation technology to remove pollutants in recent years, focusing on the preparation and application of MIT-based photocatalysts, electrocatalysts, and Fenton-like catalysts. In addition, possible interactions between the target analyte and MIT were discussed, as well as the reusability and stability of imprinted catalysts in water treatment, and their potential ecological toxicity risks were analyzed. Finally, the challenges of MIT based pollutant mitigation and the application prospects of molecular imprinting technology in environmental analysis were elaborated from multiple perspectives.

Preparation of Ni3S2 Electrocatalyst from Different Sulfur Sources and its Performance in Electrocatalytic Hydrogen Evolution Reaction

Preparation of Ni3S2 Electrocatalyst from Different Sulfur Sources and its Performance in Electrocatalytic Hydrogen Evolution Reaction

FeCo‐oxalate Organic Framework as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Developing nonprecious metallic electrocatalysts for water splitting is of vital importance for sustainable environment and energy technologies. As for oxygen evolution reaction (OER), FeCo‐based bimetallic catalysts have been found to act as promising candidates owing to their high intrinsic activity. Herein, a novel FeCo‐oxalate organic framework was grown on nickel foam (FeCo‐OA@NF) under mild conditions. The optimized electrocatalyst shows good OER performance with a low overpotential of 275 mV at the current density of 100 mA cm−2 in alkaline environment, comparable to that of commercial Ru‐based catalyst. Moreover, the quantification of produced oxygen by both gas chromatography and drainage method demonstrates nearly 100% Faradaic efficiency. Except for the contribution of Fe and Co species for the excellent OER catalytic activity, in‐situ Raman spectroscopy reveals that the positive effect of oxalate coordination also makes a difference, which can possibly reduce electron transport resistance and provide more active sites. This work provides a promising approach for the preparation of alkaline oxygen evolution electrocatalysts with low‐cost and high performance.

Synthesis of Metal-Nitrogen-Carbon Electrocatalysts with Atomically Regulated Nitrogen-Doped Polycyclic Aromatic Hydrocarbons.

Tuning the active site structure of metal-nitrogen-carbon electrocatalysts has recently attracted increasing interest. Herein, we report a bottom-up synthesis strategy in which atomically regulated N-doped polycyclic aromatic hydrocarbons (N-PAHs) of NxC42-x (x = 1, 2, 3, 4) were used as ligands to allow tuning of the active site's structures of M-Nx and establish correlations between the structures and electrocatalytic properties. Based on the synthesis process, detailed characterization, and DFT calculation results, active structures of Nx-Fe1-Nx in Fe1-Nx/RGO catalysts were constructed. The results demonstrated that the extra uncoordinated N atoms around the Fe1-N4 moieties disrupted the π-conjugated NxC42-x ligands, which led to more localized electronic state in the Fe1-N4 moieties and superior catalytic performance. Especially, the Fe1-N4/RGO exhibited optimized performance for ORR with E1/2 increasing by 80 mV and Jk at 0.85 V improved 18 times (compared with Fe1-N1/RGO). This synthesis strategy utilizing N-PAHs holds significant promise for enhancing the controllability of metal-nitrogen-carbon electrocatalyst preparation.

Self-reconstructed ZIF-L/Co(OH)2 heterointerface modulates electronic structure of Ru and boosts electrocatalytic hydrogen evolution

Understanding the self-reconstruction behavior and activity modulation mechanism of MOFs in alkaline electrocatalysis is important for developing efficient Ru-based catalysts. As Co-based MOFs, leaf-shaped zeolitic imidazolate framework (ZIF-L) crystals can be partially self-reconstructed to Co(OH)2 by in situ alkaline electrochemical methods. In this regard, two models of ZIF@Ru/NF and Co(OH)2-ZIF@Ru/NF were fabricated, and calculated by DFT. The results showed that the Co(OH)2-ZIF heterointerface generated by self-reconstruction effectively modulated the chemical and electronic environment of Ru, leading to enhanced HER performance. Therefore, Co(OH)2-ZIF@Ru/NF was in situ grown on nickel foam (NF), using ZIF@Ru/NF as a precursor. After LSV activation, the leaf-shaped ZIF-L transformed into finely fragmented nanosheets of Co(OH)2. As anticipated, the Co(OH)2-ZIF@Ru/NF catalyst demonstrated superior electrocatalytic performance compared to numerous reported counterparts, exhibiting an overpotential of 22 mV at a current density of 10 mA cm−2 and a Tafel slope of 16.9 mV dec−1. This study presents a viable method for the preparation of HER electrocatalysts using electrochemical in situ self-reconstruction.

Laser Irradiation Synthesis of AuPd Alloy with Decreased Alloying Degree for Efficient Ethanol Oxidation Reaction.

The preparation of electrocatalysts with high performance for the ethanol oxidation reaction is vital for the large-scale commercialization of direct ethanol fuel cells. Here, we successfully synthesized a high-performance electrocatalyst of a AuPd alloy with a decreased alloying degree via pulsed laser irradiation in liquids. As indicated by the experimental results, the photochemical effect-induced surficial deposition of Pd atoms, combined with the photothermal effect-induced interdiffusion of Au and Pd atoms, resulted in the formation of AuPd alloys with a decreased alloying degree. Structural characterization reveals that L-AuPd exhibits a lower degree of alloying compared to C-AuPd prepared via the conventional co-reduction method. This distinct structure endows L-AuPd with outstanding catalytic activity and stability in EOR, achieving mass and specific activities as high as 16.01 A mgPd-1 and 20.69 mA cm-2, 9.1 and 5.2 times than that of the commercial Pd/C respectively. Furthermore, L-AuPd retains 90.1% of its initial mass activity after 300 cycles. This work offers guidance for laser-assisted fabrication of efficient Pd-based catalysts in EOR.

Dual-confinement regulating ternary metal-oxide activity sites derived from Co-MOF for enhanced electrocatalytic activity for glucose oxidation

Based on a dual-confinement strategy on a cobalt-metal-organic framework (Co-MOF), a series of trimetallic-oxide catalysts of Cux-O-Niy-O-Co3-x-y (x/y = 1/1, 1/3, 1/5 and 1/7) were developed for glucose oxidation. By chemical confinement regulation of ion exchange, diverse metal catalytic sites of Cu2+ and Ni2+ were introduced into Co-MOF, respectively; Then by spatial confinement synthesis of pyrolysis, trimetallic MOF of CuxNiyCo3-x-y-MOF was transformed into trimetallic-oxide of Cux-O-Niy-O-Co3-x-y, which maintained the regular morphology and highly ordered lattice structure of Co-MOF. The Cux-O-Niy-O-Co3-x-y composite modified glassy carbon electrode (Cux-O-Niy-O-Co3-x-y/GCE) exhibited enhanced electrocatalytic activity towards glucose oxidation when compared with Co-MOF/GCE, bimetallic MOFs of CuCo-MOF/GCE and NiCo-MOF/GCE, trimetallic MOF of CuxNiyCo3-x-y-MOF/GCE, as well as monometallic oxide Co3O4/GCE and bimetallic oxides of CuCo2O4/GCE and NiCo2O4/GCE, which was mainly due to the synergistic catalysis of electrocatalytically active Co-O-Cu-O-Ni bridges. With Cu2+/Ni2+ molar ratio of 1/3, Cux-O-Niy-O-Co3-x-y/GCE (x/y = 1/3) displayed excellent sensing behaviours on glucose detection. This work not only designed well-performed electrocatalysts for enhancing catalytic activity towards glucose oxidation, but also provided a new perspective to realize the controlled preparation of high-performance electrocatalysts.

Phosphorous and cations boost the electrocatalytic performances of Cu-based compounds for hydrogen/oxygen evolution reactions and overall water-splitting

Developing durable, effective and inexpensive electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are crucial for the advancement of water splitting as a solution to the energy shortage. In this study, nanospheres stacked into nanochains are successfully prepared by oxidative corrosive engineering, solvothermal, and following calcination process (Co-Cu3P/CF). The unique nanochain structure facilitates growing the specific surface area, thereby exposing plenitude active sites. The introduced phosphorus (P) and Co ions can alter the electronic characteristics of metal phosphides, not only can accelerate the electron transport of the catalysts, but speed up the reaction kinetics. Thus, the prepared Co-Cu3P/CF exhibits low overpotentials, with 240/84 mV, in alkaline media for OER/HER to attain 10 mA cm−2. In alkaline freshwater/seawater, the self-assembled electrolyzer needs only 1.51/1.58 V to achieve 10 mA cm−2. This work provides an approach for the preparation of high-performing and economical electrocatalysts.

Rational fabrication of metal phosphide nanoparticles immobilized in electrospun carbon nanofibers for efficient pH-universal hydrogen evolution and overall water splitting

Design and preparation of bifunctional electrocatalysts with optimized structures and abundant electrocatalytic active sites are significant for hydrogen generation in electrocatalytic water splitting. Herein, we have elaborately prepared Fe-doped CoP nanoparticles encapsulated in porous electrospun carbon nanofibers for bifunctional electrocatalysis on both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The morphologies, components, and properties of the prepared electrocatalysts are influenced by the introduction of a facile air calcination treatment. Porous nanostructure as well as the full conversion of metal active sites are simultaneously achieved. Owing to the protective electrospun carbon nanofibers as well as the abundant exposed active sites, the optimized electrocatalyst exhibits excellent pH-universal HER activities with small overpotentials (99 mV, 159 mV, and 185 mV) at 10 mA cm−2 in acidic, alkaline, and neutral electrolytes, and also presents remarkable OER performance. Moreover, a water electrolyzer cell, using the optimized electrocatalyst as the electrodes, manifests both a high efficiency (1.63 V@10 mA cm−2) and robust stability. This work provides a convenient route for the controllable fabrication of transition metal-based electrocatalysts toward energy conversion.

Valorising lignocellulosic biomass to high-performance electrocatalysts via anaerobic digestion pretreatment

AbstractAnaerobic digestion (AD) was initially evaluated as a potential preprocessing method for preparing biomass-based carbon electrocatalysts in this study. The AD pretreatment succeeded in the structural depolymerization and nitrogen enrichment of Hybrid Pennisetum, which provided favorable conditions to achieve efficient and homogeneous nitrogen introduction due to microorganism community enrichment and provided a porous structure by degradation of the biodegradable components. The resulted biochar exhibited improved physiochemical properties including higher specific surface areas, nitrogen content and graphitization degree than that obtained from pyrolyzing raw biomass. These improvements were positively correlated with the AD time and showed to have enhanced the performance in oxygen reduction reaction and practical microbial fuel cell applications. Amongst the investigated samples, the obtained biochar pretreated by AD for 15 days exhibited the most excellent performance with an onset potential of 0.17 V (VS. saturated calomel electrode) and the maximal power density of 543.2 mW cm−2 assembled in microbial fuel cells. This study suggested applying AD as a new biological pretreatment in the preparation of biomass-based electrocatalysts, and provided a unique pathway for fabricating high-performance biochar-based catalysts by structure optimization and N-containing active sites construction via gentle biological method, thereby providing a cost-effective method to fabricate metal-free catalysts for oxygen reduction reaction. Graphical Abstract

Upgraded recycling of biodegradable PBAT plastic: Efficient hydrolysis and electrocatalytic conversion

Biodegradable plastics such as Poly (butylene adipate-co-terephthalate) (PBAT) have been extensively utilized in numerous fields. However, post-consumption, PBAT tends to pollute the environment and waste resources. Herein, a novel approach employing a 1,4-butanediol-alkali combined method for the hydrolysis of PBAT is introduced. At 130 °C, with a reaction time of 60 min, the hydrolysis rate of PBAT exceeds 99 %. Subsequently, a two-step synthesis rapidly produces a foam nickel-supported NiOOH catalyst for the electrocatalytic reformation of the PBAT hydrolysate into higher-value chemicals (succinate salts) at an impressive current density of 100 mA cm−2 at 1.43 V (vs. RHE) and a Faradaic efficiency of 97.6 %. Experimental results and density functional theory calculations have elucidated the active state changes of the foam nickel-supported NiOOH catalyst and the intermediates in the oxidation of 1,4-butanediol to succinate, alongside the reaction mechanism. This study offers a viable approach for the degradation of PBAT plastic through a 1,4-butanediol-alkali method and the rapid preparation of a foam nickel-supported NiOOH electrocatalyst, achieving the upgraded recycling of post-consumer biodegradable PBAT plastic.

Highly dispersed palladium nanoparticles decorated on nitrogen doped graphene for enhanced photoelectrochemical water splitting

Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE.

Co, N, and P co-doped few-layer graphene derived from cobalt phthalocyanine-based covalent organic polymers as bifunctional electrocatalysts for overall water splitting

Water electrolysis is considered to be one of the most promising approaches for developing sustainable energy technologies, however, the high cost and lack of stability of traditional precious metal electrocatalysts have hindered the development of the field of water electrolysis. Covalent organic polymers have greater potential for the preparation of low-cost electrocatalysts with high efficiency and long-term stability due to their low cost, controllable chemical composition, and rich pore structure. Cobalt phthalocyanine-based covalent organic polymers were loaded onto few-layer graphene by a hydrothermal method and then pyrolyzed to produce Co, N, and P co-doped few-layer graphene (Co–N/P-FG-700). Co–N/P-FG-700 demonstrates superior performance for oxygen evolution reaction (OER) due to the synergistic effect of abundant active sites and conductive carriers, with an overpotential of 358 mV at a current density of 10 mA cm−2 and 90% of the current density after 50,000 s of stability testing. Co–N/P-FG-700 exhibits excellent results for hydrogen evolution reaction (HER) with an overpotential of −275 mV at a current density of −10 mA cm−2 and a current density retention of 93% after a 50,000 s stability test. This study provides a rational pathway for the design of low-cost, high-performance, stable bifunctional OER/HER electrocatalysts.

The emerging Sr2FeMoO6-based electrocatalysts for solid oxide electrochemical cell: synthesis, modulation and applications

Solid oxide cells (SOCs) are regarded as a promising energy technology due to their large current density, diverse range of fuels, and high energy conversion efficiency. The double perovskite Sr2FeMoO6 (SFM) has attracted considerable attention for SOCs due to its tunable structure with superior performance of high conductivity, excellent thermal stability, and remarkable carbon deposition resistance in a reducing atmosphere. However, the electrocatalytic activity of SFM is considerably lower than that of commercial Ni-based SOC electrodes. A timely summary of the synthesis, modulation, and application of SFM perovskites is of great significance for its further development for SOCs. In this review, the methods employed in the preparation of SFM electrocatalysts are introduced first. Then, the advancements in the application of different SFM-based electrocatalysts in the field of SOCs are reviewed, and the research progress in the in situ exsolution of SFM-based electrocatalysts through ion regulation is assessed. Finally, the future issues associated with SFM-based electrocatalysts are addressed in the realm of electrocatalysis, to advance their application.

Synergistically S/N self-doped biochar as a green bifunctional cathode catalyst in electrochemical degradation of organic pollutant

Biomass-derived heteroatom self-doped cathode catalysts has attracted considerable interest for electrochemical advanced oxidation processes (EAOPs) due to its high performance and sustainable synthesis. Herein, we illustrated the morphological fates of waste leaf-derived graphitic carbon (WLGC) produced from waste ginkgo leaves via pyrolysis temperature regulation and used as bifunctional cathode catalyst for simultaneous H2O2 electrochemical generation and organic pollutant degradation, discovering S/N-self-doping shown to facilitate a synergistic effect on reactive oxygen species (ROS) generation. Under the optimum temperature of 800 °C, the WLGC exhibited a H2O2 selectivity of 94.2% and tetracycline removal of 99.3% within 60 min. Density functional theory calculations and in-situ Fourier transformed infrared spectroscopy verified that graphitic N was the critical site for H2O2 generation. While pyridinic N and thiophene S were the main active sites responsible for •OH generation, N vacancies were the active sites to produce 1O2 from O2. The performance of the novel cathode for tetracycline degradation remains well under a wide pH range (3–11), maintaining excellent stability in 10 cycles. It is also industrially applicable, achieving satisfactory performance treating in real water matrices. This system facilitates both radical and non-radical degradation, offering valuable advances in the preparation of cost-effective and sustainable electrocatalysts and hold strong potentials in metal-free EAOPs for organic pollutant degradation.

Advanced Microwave Strategies Facilitate Structural Engineering for Efficient Electrocatalysis.

In the dynamic realm of energy conversion, the demand for efficient electrocatalysis has surged due to the urgent need to seamlessly integrate renewable energy. Traditional electrocatalyst preparation faces challenges like poor controllability, elevated costs, and stringent operational conditions. The introduction of microwave strategies represents a transformative shift, offering rapid response, high-temperature energy, and superior controllability. Notably, non-liquid-phase advanced microwave technology holds promise for introducing novel models and discoveries compared to traditional liquid-phase microwave methods. This review examines the nuanced applications of microwave technology in electrocatalyst structural engineering, emphasizing its pivotal role in the energy paradigm and addressing challenges in conventional methods. The ensuing discussion explores the profound impact of advanced microwave strategies on electrocatalyst structural engineering, highlighting discernible advantages in optimizing performance. Various applications of advanced microwave techniques in electrocatalysis are comprehensively discussed, providing a forward-looking perspective on their untapped potential to propel transformative strides in renewable energy research. It provides a forward-looking perspective, delving into the untapped potential of microwaves to propel transformative strides in renewable energy research.

NiCoP fibers as novel catalysts for hydrogen evolution in alkali and acidic environment

NiCoP transition metal phosphide has been recognized as a most promising candidate to alternate the noble metals in hydrogen evolution reaction. Herein, it is first time presented the facile preparation of NiCoP electrocatalyst in form of fibers with dominant 1D structure formed by needle-less electrospinning technology and finalized by defined heat treatment process. The study provides a precise method for the preparation of NiCoP or similar phosphide fibers, together with an experimental proof of their excellent electrocatalytic performance in alkali and acidic environments. The as-prepared fibrous NiCoP electrocatalyst sintered in air at 900 °C followed by sintering at 700 °C in Ar/H2 exhibits low hydrogen evolution reaction overpotential (η10) of 141 mV in alkali and 146 mV in acidic environment corresponding with low Tafel slopes of 53 and 97.8 mV/dec, respectively. The bimetallic phosphide also shows superior oxygen evolution reaction activity in alkaline medium 1 M KOH with satisfying durability in long-term stability tests. The highly innovative fibrous form of the material not only plays a significant role in regulation of the electronic structure and boosting the electrochemical active sites and thus the electrocatalytic performance in water splitting technology, but also allows tuning of the electrode electric conductivity, occurrence of the active sites probability and thus utilisation of the electrode, together with its permeability and mechanical stability.