Efficient Cathode Catalyst Research Articles

Partial‐Oxidation Enabling Homologous Ru/RuO2 Heterostructures With Proper d‐Dand Center as Efficient and Durable Cathode Catalysts for Ultralong Cycle Life in Li–O2 Batteries

AbstractThe sluggish cycle kinetics is one of the major obstacles to the commercial application of Li–O2 batteries (LOBs), despite their large theoretical energy density. Efficient and long‐term durable cathode catalysts are urgently desired to strengthen their cycle stability and rate performance. Density functional theory calculations reveal that Ru/RuO2 Mott–Schottky heterostructures can manipulate the adsorption capacities of intermediates by modulating the d‐band center and redistribute interfacial charges, enabling efficient redox kinetics, reducing overpotentials, and optimizing the growth pathway of discharge products. Herein, a wet impregnation approach followed by partial oxidization of Ru nanodots to construct homologous Ru/RuO2 heterostructures as advanced cathode catalysts for boosting the electrochemical activities of LOBs is employed. They exhibit superior electrochemical performance, including high discharge specific capacity (17 120 mAh g−1 at 200 mA g−1), small overpotential (0.96 V), and ultralong cycle lifetime of 1209 cycles (>2400 h) at 500 mA g−1. Over 1260‐h stable cycle in air atmosphere at 500 mA g−1 demonstrates the potential application prospects of the Ru/RuO2 heterostructures in Li‐air batteries. Multiple ex/in situ measurements and theoretical calculation are conducted to investigate the optimizing mechanism of electrochemical performances.

Mutually Activated 2D Ti0.87O2/MXene Monolayers Through Electronic Compensation Effect as Highly Efficient Cathode Catalysts of Li–O2 Batteries

Abstract2D materials exhibit remarkable electrochemical performance as the cathode catalyst in lithium–oxygen batteries (LOBs). Their catalytic capability mainly derives from their 2D surface with tunable surface chemistry and unique electronic states. Herein, Ti0.87O2 and Ti3C2 MXene monolayers are applied to construct a face/face 2D heterostructure to enhance the catalytic performance in LOBs. It is demonstrated that electronic compensation from the O‐terminated MXene to Ti0.87O2 side is achieved through the built‐in electric field and the overlap of Ti 3d and O 2p orbitals between Ti0.87O2 and MXene units. As a result, the ORR/OER catalytic activity is improved in Ti0.87O2/MXene heterojunction due to the modulated p‐band center that optimizes the s–p coupling with the key intermediate LiO2. The Ti0.87O2/MXene cathode presents a structural stability and long‐term cycling life of 425 cycles (2534 h) at 200 mA g−1 and 407 cycles at 1000 mA g−1 with a fixed capacity of 600 mAh g−1, being nearly five and three times higher than that of pure Ti0.87O2 and MXene cathodes, respectively.

Defect Engineering in CuS1- x Nanoflowers Enables Low-Overpotential and Long-Cycle-Life of Lithium-Oxygen Batteries.

The defect engineering is essential for the development of efficient cathode catalysts for lithium-oxygen batteries. Herein, CuS1 -x nanoflowers are fabricated by microwave hydrothermal method. Through theoretical and experimental analysis, the S vacancies are observed, which result in augmented charge around Cu, improved adsorption of LiO2, and reduced overpotential. On the one hand, the generated electronic defects cause the Fermi level to shift toward the conduction band, which enhances the electronic conductivity and ion transfer. On the other hand, the increased S vacancies provide a large number of Cu active sites, which increase the charge transfer from Cu to LiO2, which improves the stability of the intermediate adsorption. Interactively, CuS1- x catalyst obtains a capacity of 23,227 mAh g-1 and a cycle life of 225 at 500mA g-1. This work will be helpful for obtaining an efficient cathode catalyst by providing a deep understanding of vacancy modulation in advanced catalysts.

Copper nanoparticles anchored on nitrogen-doped carbon nanofibers derived from MOFs and bacterial cellulose: Advanced electrocatalysts for oxygen reduction in microbial fuel cells

The development of efficient and inexpensive cathode catalysts contributes to energy conservation. Herein, nitrogen-doped carbon nanofiber (CNF) composites (Cu@N-CNFs) loaded with copper nanoparticles were successfully synthesized as cathode electrocatalysts for microbial fuel cells (MFCs), utilizing metal-organic frameworks (MOFs) and bacterial cellulose (BC) as precursors. The characterization results show that Cu@N-CNFs has a large specific surface area and contains catalytic active substances such as pyridine nitrogen and graphite nitrogen, along with that the graphitization degree of carbon skeleton structure is high. Therefore, Cu@N-CNFs has outstanding catalytic performance in alkaline and neutral environments, with half-wave potentials of 0.83 V and 0.78 V, as well as limiting current densities of −5.70 mA cm−2 and −5.73 mA cm−2, respectively. Moreover, these performances are comparable to those of Pt/C. The composite material is coated on the surface of the carbon cloth and processed into MFC cathode, which has a good improvement in its power production performance.

Combining Solid FePc Immobilized on Py-Functionalized Carbon Matrix with Soluble Redox Mediator FePc As an Efficient Cathode Catalyst for Non-Aqueous Li-O2 Batteries

It is important to develop bifunctional catalysts with high activity and stability for reversible oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in lithium-oxygen (Li-O2) batteries. Recently, the iron phthalocyanine (FePc) complex has been considered a promising candidate for bifunctional (ORR/OER) O2 catalysts due to its low cost, high catalytic properties, and ease of preparation. In this work, two different structural types of FePc-based solution-phase catalysts as soluble redox mediators (SRMs) and solid FePc immobilized on pyridine-functional carbon supports (multi-walled carbon nanotube, MWCNT and graphene, GR) are investigated to evaluate the influence of FePc structural design on their catalytic activity and kinetics.Our work demonstrated that FePc(solid)/Py/MWCNT exhibited better bifunctional catalytic activity than FePc(solid)/Py/GR in the same electrolyte because of the stronger axial bonding between FePc(solid) and Py/MWCNT. The combination of FePc(solid)/Py/MWCNT and FePc(sol) displays the best cyclability, which can be attributed to the highly efficient solid-liquid interface. Moreover, FePc(solid)/Py/MWCNT without FePc(sol) shows the lowest overpotential owing to the surface-grown thin film Li2O2 is structurally less order than the solution-grown toroidal Li2O2.

Hydrangea Macrophylla-Like CeO2 Coated by Nitrogen-Doped Carbon as Highly Efficient ORR Cathode Catalyst in a Hybrid Proton Battery

Hydrangea Macrophylla-Like CeO2 Coated by Nitrogen-Doped Carbon as Highly Efficient ORR Cathode Catalyst in a Hybrid Proton Battery

Exfoliated 2D Nanosheet-Based Conjugated Polymer Composites with P-N Heterojunction Interfaces for Highly Efficient Electrocatalytic Hydrogen Evolution.

We have achieved a significant breakthrough in the preparation and development of two-dimensional nanocomposites with P-N heterojunction interfaces as efficient cathode catalysts for electrochemical hydrogen evolution reaction (HER) and iodide oxidation reaction (IOR). P-type acid-doped polyaniline (PANI) and N-type exfoliated molybdenum disulfide (MoS2) nanosheets can form structurally stable composites due to formation of P-N heterojunction structures at their interfaces. These P-N heterojunctions facilitate charge transfer from PANI to MoS2 structures and thus significantly enhance the catalytic efficiency of MoS2 in the HER and IOR. Herein, by combining efficient sodium-functionalized chitosan-assisted MoS2 exfoliation, electropolymerization of PANI on nickel foam (NF) substrate, and electrochemical activation, controllable and scalable Na-Chitosan/MoS2/PANI/NF electrodes are successfully constructed as non-noble metal-based electrochemical catalysts. Compared to a commercial platinum/carbon (Pt/C) catalyst, the Na-Chitosan/MoS2/PANI/NF electrode exhibits significantly lower resistance and overpotential, a similar Tafel slope, and excellent catalytic stability at high current densities, demonstrating excellent catalytic performance in the HER under acidic conditions. More importantly, results obtained from proton exchange membrane fuel cell devices confirm the Na-Chitosan/MoS2/PANI/NF electrode exhibits a low turn-on voltage, high current density, and stable operation at 2 V. Thus, this system holds potential as a replacement for Pt/C with feasibility for applications in energy-related fields.

Constructed Mott–Schottky Heterostructure Catalyst to Trigger Interface Disturbance and Manipulate Redox Kinetics in Li-O2 Battery

HighlightsA carbon free self supported Mott-Schottky heterostructure was constructed as an efficient cathode catalyst for lithium oxygen batteries, achieving homogeneous contact between the two materials for strong interfacial interactions.The heterostructure triggered interfacial perturbations and band structure changes, which accelerated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, resulting in an extremely long cycle life of 800 cycles and an extremely low overpotential of 0.73 V.Combined with advanced characterization techniques and density functional theory calculations, the underlying mechanism behind the boosted ORR/OER activities and the electrocatalytic mechanism were revealed.

Steering the Orbital Hybridization to Boost the Redox Kinetics for Efficient Li-CO2 Batteries.

The sluggish CO2 reduction and evolution reaction kinetics are thorny problems for developing high-performance Li-CO2 batteries. For the complicated multiphase reactions and multielectron transfer processes in Li-CO2 batteries, exploring efficient cathode catalysts and understanding the interplay between structure and activity are crucial to couple with these pendent challenges. In this work, we applied the CoS as a model catalyst and adjusted its electronic structure by introducing sulfur vacancies to optimize the d-band and p-band centers, which steer the orbital hybridization and boost the redox kinetics between Li and CO2, thus improving the discharge platform of Li-CO2 batteries and altering the deposition behavior of discharge products. As a result, a highly efficient bidirectional catalyst exhibits an ultrasmall overpotential of 0.62 V and a high energy efficiency of 82.8% and circulates stably for nearly 600 h. Meanwhile, density functional theory calculations and multiphysics simulations further elucidate the mechanism of bidirectional activity. This work not only provides a proof of concept to design a remarkably efficient catalyst but also sheds light on promoting the reversible Li-CO2 reaction by tailoring the electronic structure.

Optimized electrochemical ammonia production: From metal-N2/NOx batteries to aqueous metal-NOx– batteries

Ammonia plays a crucial role in contemporary society, impacting medicine, agriculture, and the chemical industry. The conventional industrial synthesis of NH3 through the Haber-Bosch technique, carried out under severe reaction conditions, leads to substantial energy consumption and environmental pollution. It is thus imperative for NH3 synthesis methods to be investigated under more favorable conditions. Synthesis of ammonia by electrocatalysis can effectively reduce the environmental damage and other urgent problems, which is a promising solution. Metal-nitrogen series batteries (M−N batteries), such as metal-nitrogen gas batteries, metal-nitrogen oxide batteries and metal-oxynitride batteries have been regarded recently as an exemplar of concurrent NH3 synthesis and energy production.Nonetheless, the large-scale application of these batteries is still limited by numerous challenges are currently existing in building high-efficiency M−N batteries, including poor Faradic efficiency and low NH3 yield. Therefore, a comprehensive overview of M−N batteries is offered, specifically focusing on advanced strategies for designing highly efficient cathode catalysts in anticipation of future developments. The metal anodes, cathodic electro-reduction reactions, and design principles are encompassed in the discussion, offering detailed insights to enhance understanding. Mechanisms, feasibility analyses, technoeconomic assessments, device combinations, and comparative evaluations are delved into in the review, contributing to a thorough comprehension of diverse systems and their application potential. Perspectives and opportunities for future research directions are also delineated.

Bifunctional Catalysts for CO2 Reduction and O2 Evolution: A Pivotal for Aqueous Rechargeable Zn-CO2 Batteries.

The quest for the advancement of green energy storage technologies and reduction of carbon footprint is determinedly rising toward carbon neutrality. Aqueous rechargeable Zn-CO2 batteries (ARZCBs) hold the great potential to encounter both the targets simultaneously, i.e., green energy storage and CO2 conversion to value-added chemicals/fuels. The major descriptor of ARZCBs efficiency is allied with the reactions occurring at cathode during discharging (CO2 reduction) and charging (O2 evolution) which own different fundamental mechanisms and hence mandate the employment of two different catalysts. This presents an overall complex and expensive battery system which requires a concrete solution, while the development and application of a bifunctional cathode catalyst toward both reactions could reduce the complexity and cost and thus can be a pivotal for ARZCBs. However, despite the increasing research interest and ongoing research, a systematic evaluation of bifunctional catalysts is rarely reported. In this review, the need of bifunctional cathode catalysts for ARZCBs and associated challenges with strategies have been critically assessed. A detailed progress examination and understanding toward designing of bifunctional catalyst for ARZCBs have been provided. This review will enlighten the future research approaching boosted performance of ARZCBs through the development of efficient bifunctional cathode catalysts.

Ar/NH3 Plasma Etching of Cobalt-Nickel Selenide Microspheres Rich in Selenium Vacancies Wrapped with Nitrogen Doped Carbon Nanotubes as Highly Efficient Air Cathode Catalysts for Zinc-Air Batteries.

This work utilizes defect engineering, heterostructure, pyridine N-doping, and carbon supporting to enhance cobalt-nickel selenide microspheres' performance in the oxygen electrode reaction. Specifically, microspheres mainly composed of CoNiSe2 and Co9Se8 heterojunction rich in selenium vacancies (VSe·) wrapped with nitrogen-doped carbon nanotubes (p-CoNiSe/NCNT@CC) are prepared by Ar/NH3 radio frequency plasma etching technique. The synthesized p-CoNiSe/NCNT@CC shows high oxygen reduction reaction (ORR) performance (half-wave potential (E1/2) = 0.878V and limiting current density (JL) = 21.88mA cm-2). The JL exceeds the 20wt% Pt/C (19.34mA cm-2) and the E1/2 is close to the 20wt% Pt/C (0.881V). It also possesses excellent oxygen evolution reaction (OER) performance (overpotential of 324 mV@10mA cm-2), which even exceeds that of the commercial RuO2 (427 mV@10mA cm-2). The density functional theorycalculation indicates that the enhancement of ORR performance is attributed to the synergistic effect of plasma-induced VSe· and the CoNiSe2-Co9Se8 heterojunction. The p-CoNiSe/NCNT@CC electrode assembled Zinc-air batteries (ZABs) show a peak power density of 138.29mW cm-2, outperforming the 20wt% Pt/C+RuO2 (73.9mW cm-2) and other recently reported catalysts. Furthermore, all-solid-state ZAB delivers a high peak power density of 64.83mW cm-2 and ultra-robust cycling stability even under bending.

Anodic degradation of salicylic acid and simultaneous bio-electricity recovery in microbial fuel cell using waste-banana-peels derived biochar-supported MIL-53(Fe)-metal-organic framework as cathode catalyst

This research was aimed to synthesize waste banana peel biochar (BC) supported MIL-53(Fe) metal–organic framework (MOF) (MIL-53(Fe)/BC) as an efficient cathode catalyst for application in a microbial fuel cell (MFC) for the treatment of salicylic acid (SA)-laden wastewater. This investigation marks the first application of such a catalyst in a MFC for SA degradation. The results revealed an increment in power density of MFC-MIL-53(Fe)/BC by 2.34-folds (142.2 ± 1.5 mW/m2) as compared to MFC-MIL-53(Fe) (60.6 ± 1.8 mW/m2). Removal of chemical oxygen demand in MFC-MIL-53(Fe)/BC (93.8 ± 2.2 %) was found to be comparable to MFC-Pt/C (94.6 ± 1.5 %). The MFC-MIL-53(Fe)/BC demonstrated a 91.5 ± 2.0 % biodegradation of SA. The power recovery per unit cost by MFC-MIL-53(Fe)/BC was found to be 380.21 mW/US$, which is significantly higher than MFC-Pt/C (6.08 mW/US$), indicating that MIL-53(Fe)/BC could be an affordable replacement to pricey Pt as cathode catalyst for efficient oxygen reduction reaction.

Homogeneous In‐Plane Lattice Strain Enabling d‐Band Center Modulation and Efficient d–π Interaction for an Ag2Mo2O7 Cathode Catalyst With Ultralong Cycle Life in Li‐O2 Batteries

AbstractAlthough lithium–oxygen batteries (LOBs) hold great promise as future energy storage systems, they are impeded by insulated discharge product Li2O2 and sluggish oxygen reduction reaction/oxygen evolution revolution (ORR/OER) kinetics. The application of a highly efficient cathode catalyst determines the LOBs performance. The d‐band modulation and catalytic kinetics promotion are important concept guidelines for the performance enhancement of cathode catalysts. In this work, the homogeneous in‐plane distortion‐derived synergistic catalytic capability of an Ag2Mo2O7 catalyst with modulated d‐band centers and promoted ORR/OER kinetics is demontrated. The uniform elongation of Ag─O bonds and compression of Mo─O bonds in (020) plane leads to d‐band splitting and d‐band center optimization and delivers improved adsorption behavior for high ORR/OER capability. Furthermore, the spatial and energy overlap of Ag dxz and O2 anti‐bonding π* orbitals facilitate electron injection during ORR process and reduce the energy barrier for charge transfer and O2 desorption during OER process, accelerating the ORR/OER kinetics. As a result, the (020) plane‐exposed Ag2Mo2O7 cathode exhibits ultralong cycle stability of 817 cycles at 500 mA g−1 and large specific discharge/charge capacities of 15898/15180 mAh g−1. This work provides facile concept guidance for optimizing catalytic capability through controlled lattice distortion in cathode catalysts for LOBs.

NiP2 as an efficient non-noble metal cathode catalyst for enhanced hydrogen isotope separation in proton exchange membrane water electrolysis

Proton exchange membrane (PEM) water electrolysis is crucial for efficient hydrogen isotope separation (HIS) in liquid water. However, current cathode catalysts like platinum (Pt) suffer from scarcity and limited HIS performance. To overcome this challenge, we propose a simple and effective approach involving the synthesis of highly dispersed NiP2 nanoparticles supported on carbon (NiP2/C) through a solid-phase phosphidation reaction, and for the first time report its enhanced HIS performance as the cathode catalyst in PEM electrolyzer. The NiP2/C catalyst demonstrates excellent catalytic properties as a cathode catalyst for hydrogen evolution reaction (HER) in an acidic electrolyte, achieving low overpotential of only 157 mV at 10 mA/cm2 and Tafel slope of 95.6 mV/dec. Meticulous investigations and density functional theory (DFT) calculations reveal the intrinsic factors behind its performance. Furthermore, DFT calculations predict the HIS performance of both NiP2/C and Ni/C catalysts, revealing the advantages of NiP2/C over Ni/C. Experimental results obtained in practical PEM water electrolysis validate these predictions, as NiP2/C exhibits an impressive separation factor α of 6.36, nearly twice that of the Pt/C catalyst. Moreover, NiP2/C demonstrates reliable and consistent HIS performance during a 100-hour PEM electrolysis process. Importantly, our calculation model for deuterium enrichment in liquid water reveals that catalysts with higher separation factors α show faster deuterium enrichment and higher deuterium recovery rates. The utilization of NiP2/C as a non-noble metal cathode catalyst holds great promise for efficient and sustainable hydrogen isotope separation, addressing the limitations of precious metal catalysts and advancing clean energy technologies.

Reducing Overpotential of Lithium-Oxygen Batteries by Diatomic Metal Catalyst Orbital Matching Strategy.

Aprotic Li-O2 batteries have sparked attention in recent years due to their ultrahigh theoretical energy density. Nevertheless, their practical implementation is impeded by the sluggish reaction kinetics at the cathode. Comprehending the catalytic mechanisms is pivotal to developing efficient cathode catalysts for high-performance Li-O2 batteries. Herein, the intrinsic activity map of Li-O2 batteries is established based on the specific adsorption mode of O2 induced by diatomic catalyst orbital matching and the transfer-acceptance-backdonation mechanism, and the four-step screening strategy based on the intrinsic activity map is proposed. Guided by the strategy, FeNi@NC and FeCu@NC promising durable stability with a low overpotential are screened out from 27 Fe-Metal diatomic catalysts. Our research not only provides insights into the fundamental understanding of the reaction mechanism of Li-O2 batteries but also accelerates the rational design of efficient Li-O2 batteries based on the structure-activity relationship.

Nickel adsorbed algae biochar based oxygen reduction reaction catalyst

Lately, the bio electrochemical systems are emerging as an efficient wastewater treatment and energy conversion technology. However, their scaling-up is considerably restrained by slow-rate of cathodic oxygen reduction reaction (ORR) or otherwise by the high cost associated with the available efficient ORR catalysts. In this investigation, a cost-effective and eco-friendly approach for synthesizing Ni based ORR catalyst utilizing biosorption property of microalgae is accomplished. The synthesised Ni adsorbed algal biochar (NAB) served as an efficient cathode catalyst for enhancing ORR in a microbial carbon-capture cell (MCC). On increasing the initial concentration of Ni2+ in the aqueous medium from 100 mgL−1 to 500 mgL−1, the biosorption capacity was found to increase from 3 mgg−1 to 32 mgg−1 of algae cell. The MCC operated with NAB based cathode catalyst loading of 2 mgcm-2 exhibited 3.5 times higher power density (4.69 Wm−3) as compared to the one with commercial activated carbon. A significant organic matter removal (82 %) in the anodic chamber with simultaneous algal biomass productivity in the cathodic chamber was attained by MCC with cathode loaded with 2 mgcm−2 of NAB. Hence, this easily synthesised low-cost catalyst, out of waste stream, proved its ability to improve the performance of MCC.

Unique Hierarchically Structured High-Entropy Alloys with Multiple Adsorption Sites for Rechargeable Li-CO2 Batteries with High Capacity.

Lithium-carbon dioxide (Li-CO2) batteries offer the possibility of synchronous implementation of carbon neutrality and the development of advanced energy storage devices. The exploration of low-cost and efficient cathode catalysts is key to the improvement of Li-CO2 batteries. Herein, high-entropy alloys (HEAs)@C hierarchical nanosheet is synthesized from the simulation of the recycling solution of waste batteries to construct a cathode for the first time. Owing to the excellent electrical conductivity of the carbon material, the unique high-entropy effect of the HEAs, and the large number of catalytically active sites exposed by the hierarchical structure, the FeCoNiMnCuAl@C-based battery exhibits a superior discharge capability of 27664 mAh g-1 and outstanding durability of 134 cycles as well as low overpotential with 1.05V at a discharge/recharge rate of 100mA g-1. The adsorption capacity of different sites on the HEAs is deeply understood through density functional theory calculations combined with experiments. This work opens up the application of HEAs in Li-CO2 batteries catalytic cathodes and provides unique insights into the study of adsorption active sites in HEAs.

Modulating the d-Band Center of RuO2 via Ni Incorporation for Efficient and Durable Li-O2 batteries.

Rechargeable Li-O2 batteries (LOBs) are considered as one of the most promising candidates for new-generation energy storage devices. One of major impediments is the poor cycle stability derived from the sluggish reaction kinetics of unreliable cathode catalysts, hindering the commercial application of LOBs. Therefore, the rational design of efficient and durable catalysts is critical for LOBs. Optimizing surface electron structure via the negative shift of the d-band center offers a reasonable descriptor for enhancing the electrocatalytic activity. In this study, the construction of Ni-incorporating RuO2 porous nanospheres is proposed as the cathode catalyst to demonstrate the hypothesis. Density functional theory calculations reveal that the introduction of Ni atoms can effectively modulate the surface electron structure of RuO2 and the adsorption capacities of oxygen-containing intermediates, accelerating charge transfer between them and optimizing the growth pathway of discharge products. Resultantly, the LOBs exhibit a large discharge specific capacity of 19658mA h g-1 at 200mA g-1 and extraordinary cycle life of 791 cycles. This study confers the concept of d-band center modulation for efficient and durable cathode catalysts of LOBs.

Modulation Strategies and Activity Descriptors of Spinel Electrocatalysts for Lithium−Oxygen Batteries

AbstractThe exploitation of high energy density lithium−oxygen batteries (LOBs) holds significant importance for energy storage and applications. An efficient cathode catalyst can effectively prevent the accumulation of the insulating insoluble discharge product Li2O2, thereby enhancing the electrochemical performance. Spinel materials, widely available and cost‐effective, exhibit superior catalytic activity, making them ideal candidates for LOBs cathode catalysts. This review aims to offer a comprehensive and insightful overview of the recent progress in the design of spinel‐type electrocatalysts for LOBs. This review exhaustively summarizes various modification strategies applied to spinel materials and emphasizes the influential role of catalytic descriptors in designing highly active spinel‐type catalysts. This review provides guidance for the design and utilization of high‐performance spinel‐type catalysts, thereby contributing to the dynamic development of LOBs.