Catalysts For Electrocatalysis Research Articles

Novel ZnSe@d-Ti3CNTx nanocomposite as efficient bifunctional electrocatalyst for water splitting system

Electrocatalytic water splitting is an environmentally friendly approach for producing hydrogen and oxygen from water. ZnSe@d-Ti3CNTx nanocomposite was synthesized by a hydrothermal approach. The ZnSe@d-Ti3CNTx nanocomposite was examined with several techniques, including Raman, p-XRD, microscopy, SEM/EDS, and XPS spectroscopy. Electrochemical properties were studied by CV, LSV, EIS, and chronoamperometry. As Ti3CN is a conductive material, to improve its electron transport efficiency, ZnSe was incorporated into it, which not only enhances its electrochemical behavior but also prevents it from restacking. By integrating the features of d-Ti3CNTX MXene and ZnSe nanoparticles, the HER and OER performance of the electrocatalyst is improved at low overpotentials of 270 mV and 232 mV, respectively. The ZnSe@d-Ti3CNTx nanocomposite.kept 84 % of its starting current after 50 h at an applied potential of 1.56 V, demonstrating excellent long-term stability. According to the results of this research, the ZnSe@d-Ti3CNTx nanocomposite has the potential to serve as a highly efficient and long-lasting electrocatalytic catalyst for water splitting.

Two-Dimensional Covalent Organic Frameworks with Pentagonal Pores.

The pore shapes of two-dimensional covalent organic frameworks (2D COFs) significantly limit their practical applications in separation and catalysis. Although various 2D COFs with polygonal pores have been well developed, constructing COFs with pentagonal pores remains an enormous challenge. In this work, we developed one kind of pentagonal COFs with the mcm topological structure for the first time, through the rational combination of C4 and C2 symmetric building blocks. The resulting pentagonal COFs exhibit high crystallinity, excellent porosity, and strong robustness. Moreover, the inbuilt porphyrin units render these COFs as efficient electrocatalytic catalysts toward oxygen reduction reaction with a half-wave potential of up to 0.81 V, which ranks as one of the highest values among COFs-based electrocatalysts. This work not only verified the possibility of constructing 2D COFs with pentagonal pores but also developed a strategy for the construction of functional 2D COFs for interesting applications.

Transformation of Bi4Cl2S5 into sub-10 nm Bi2O2CO3 nanowires for electrochemical reduction of CO2

The development of highly efficient catalysts for the selective electrochemical reduction reaction of CO2 (eCO2RR) to high-valued formate remains a challenge in achieving carbon neutrality and renewable energy conversion. In this study, ultrathin Bi4Cl2S5 nanowires, synthesized using different branched-chain thiols as sulfur sources, were reported for the first time as precatalysts for eCO2RR to formate. Systematic material characterization demonstrated that Bi4Cl2S5 can undergo in-situ evolution into Bi2O2CO3 nanowires, serving as the genuine electrocatalyst for eCO2RR. Through the fine-tuning of ligands during the synthesis of Bi4Cl2S5 nanowires, the optimized Bi4Cl2S5-derived Bi2O2CO3 nanowires exhibited a maximum formate Faradaic efficiency (FEformate) of 95.3 % in eCO2RR using a traditional H-cell, surpassing other prepared samples. Furthermore, an FEformate of over 92.9 % was achieved in a wide potential window of 500 mV, and high performance was maintained over 20 h. This outstanding performance is attributed to the high intrinsic activity, accelerated charge transfer, and the large electrochemical active surface area associated with the characteristic sub-10 nm diameter nanowire structure. Moreover, density function theory calculations further revealed that Bi2O2CO3 can reduce the energy barriers for the formation of *OCHO intermediate and bolster formate production. Our work provides a novel synthesis strategy for excellent Bi-based catalysts in electrocatalysis.

Recent developments of single atom alloy catalysts for electrocatalytic hydrogenation reactions

This review discusses the recent developments of single-atom alloy (SAA) catalysts toward CO2, CO, N2, and NO3– hydrogenation reactions in the electrocatalysis context, a natural expansion from the thermal catalysis origin where the concept of SAA was born and validated. Electrocatalytic hydrogenations of CO2, CO, NO3–, and N2 into value-added chemicals offer an attractive general route to mitigate greenhouse gas emissions using renewable energy without H2 feed stream. These reactions typically involve multiple electron-transfer-coupled elementary reaction steps that are of broad relevance to many electrocatalytic applications, making them well-positioned for translational fundamental studies relevant to other emerging electrochemical reactions. While there has been exciting progress in SAA research for various thermal catalytic reactions in the last decade, the design, application, and characterization of SAA catalysts in electrocatalysis remain nascent with intriguing uncertainties and ample opportunities. We highlight the recent research findings in this growing area, where the SAAs, owing to their unique doped metal properties and atomically precise bimetallic synergies, promote selective reaction pathways by tuning binding energies and distributions of adsorbates/intermediates. We also provide our perspective on this growing research area's potential challenges and opportunities.

Dual-functional electrocatalyst of defective cobalt-nitrogen-doped porous carbon for enhanced in-situ hydrogen peroxide generation and electro-Fenton tetracycline degradation

Tetracycline hydrochloride (TC) is one of the organic pollutants that can be consistently monitored in the aquatic environment and pose a great threat to the environment. The development of a bifunctional electro-Fenton (EF) catalyst capable of in situ H2O2 production and decomposition to ·OH to degrade the pollutant is an efficient and green approach to deal with antibiotic pollution. The bifunctional catalysts Co, N double doped defective carbon materials were prepared by pyrolysis ball milling method using zeolite imidazolium ester skeleton structural materials (ZIFs) series materials as precursors, which showed more than 80% selectivity to H2O2 and could basically remove TC within 120 min in EF system. Carbon defects and graphitic nitrogen can effectively improve the selectivity and yield of H2O2, while graphitization degree improves the charge transfer rate, the doping of Co and pyridinic-N contribute to the decomposition of H2O2 into ·OH. The active species present in the Co1/Zn1-NPC/EF system is ·OH, and factors such as coexisting ions, humic acid and water quality have little effect on the efficiency of the degradation of TC in the Co1/Zn1-NPC/EF system, whereas Co1/Zn1-NPC electrocatalytic catalyst has excellent stability and stable treatment performance for a wide range of pollutants, as well as being an environmentally friendly green catalyst without metal leaching. Furthermore, the possible pathways and the toxicity hazard of TC degradation were proposed. The bifunctional electrocatalyst prepared in this research provides a novel strategy for the green and efficient treatment of pollutants in wastewater.

Core-shell-structured NiCo2O4 composite with GO/C to enhance its electrocatalytic performance as a cathode catalyst in zinc-air batteries

This study employed a simple and effective method to synthesize a composite material comprising core-shell NiCo2O4 and GO/C. The combination of core-shell NiCo2O4 and GO effectively improved the poor conductivity of NiCo2O4 and prevented the aggregation of NiCo2O4 microspheres. In electrochemical tests, compared to pure core-shell NiCo2O4, NiCo2O4@GO/C exhibits improved catalytic performance in both oxygen reduction (ORR) and oxygen evolution reactions (OER). Its OER catalytic performance is notably superior to that of noble metal catalysts. The NiCo2O4@GO/C-based liquid-state zinc-air battery exhibited a stable cycling efficiency of 51% over 200 h of charge-discharge cycles, significantly outperforming precious metal-based batteries. Additionally, a flexible quasi-solid-state zinc-air battery, assembled with the NiCo2O4@GO/C composite material as the cathode catalyst, exhibited an outstanding cycling efficiency of 58% in charge-discharge cycles. These results indicate that the NiCo2O4@GO/C composite material holds great potential as a bifunctional electrocatalytic catalyst for zinc-air batteries.

Bifunctional electrocatalytic reduction performance of nitrogen containing biomass based nanoreactors loaded with Ni nanoparticles for oxygen and carbon dioxide

In the face of increasing energy demand, the approach of transformation that combines energy restructuring and environmental governance has become a popular research direction. As an important part of electrocatalytic reactions for gas molecules, reduction reactions of oxygen (ORR) and carbon dioxide (CO2RR) are very indispensable in the field of energy conversion and storage. However, the non-interchangeability and irreversibility of electrode materials have always been a challenge in electrocatalysis. Hereon, nickel and nitrogen decorated biomass carbon-based materials (Ni/N-BC) has been prepared by high temperature pyrolysis using agricultural waste straw as raw material. Surprisingly, it possesses abundant active sites and specific surface area as a bifunctional electrocatalyst for ORR and CO2RR. The three-dimensional porous cavity structure for the framework of biomass could not only provide a strong anchoring foundation for the active site, but also facilitate the transport and enrichment of reactants around the site. In addition, temperature modulation during the preparation process also optimizes the composition and structure of biomass carbon and nitrogen. Benefit from above structure and morphology advantages, Ni/N-BC-800 exhibits the superior electrocatalytic activity for both ORR and CO2RR simultaneously. More specifically, Ni/N-BC-800 exhibits satisfactory ORR activity in terms of initial potential and half wave potential, while also enables the production of CO under high selective. The research results provide ideas for the development and design of electrode materials and green electrocatalysts, and also expand new applications of agricultural waste in fields such as energy conversion, environmental protection, and resource utilization.

Bimetallic sulfide/N-doped carbon composite derived from Prussian blue analogues/cellulose nanofibers film toward enhanced oxygen evolution reaction.

Exploiting effective, stable, and cost-efficient electrocatalysts for the water oxidation reaction is highly desirable for renewable energy conversion techniques. Constructional design and compositional manipulation are widely used approaches to efficaciously boost the electrocatalytic performance. Herein, we designed a NiFe-bimetallic sulfide/N-doped carbon composite via a two-step thermal treatment of Prussian blue analogues/cellulose nanofibers (PBA/CNFs) film. The NiFe-bimetallic sulfide/N-doped carbon composite displayed enhanced OER performance in an alkaline environment, with an overpotential of 282 mV at 10 mA cm-2, a Tafel slope of 59.71 mV dec-1, and good stability, making the composite a candidate electrocatalyst for OER-related energy equipment. The introduction of CNFs in the precursor prevented the aggregation of PBA nanoparticles (NPs), exposed more active sites, and the resulting carbon substrate enhanced the electroconductivity of the composite. Moreover, the synergistic effect of Ni and Fe in the bimetallic sulfide could modulate the configuration of electrons, enrich the catalytically active sites, and augment the electric conductivity, thus ameliorating the OER performance. This study broadens the application of MOF-CNF composites to construct hierarchical structures of metal compounds and provides some thoughts for the development of cost-effective precious-metal-free catalysts for electrocatalysis.

Locally Ordered Single-Atom Catalysts for Electrocatalysis.

Single-atom catalysts manifest nearly 100 % atom utilization efficiency, well-defined active sites, and high selectivity. However, their practical applications are hindered by a low atom loading density, uncontrollable location, and ambiguous interaction with the support, thereby posing challenges to maximizing their electrocatalytic performance. To address these limitations, the ability to arrange randomly dispersed single atoms into locally ordered single-atom catalysts (LO-SACs) substantially influences the electronic effect between reactive sites and the support, the synergistic interaction among neighboring single atoms, the bonding energy of intermediates with reactive sites and the complexity of the mechanism. As such, it dramatically promotes reaction kinetics, reduces the energy barrier of the reaction, improves the performance of the catalyst and simplifies the reaction mechanism. In this review, firstly, we introduce a variety of compelling characteristics of LO-SACs as electrocatalysts. Subsequently, the synthetic strategies, characterization methods and applications of LO-SACs in electrocatalysis are discussed. Finally, the future opportunities and challenges are elaborated to encourage further exploration in this rapidly evolving field.

Locally Ordered Single‐Atom Catalysts for Electrocatalysis

AbstractSingle‐atom catalysts manifest nearly 100 % atom utilization efficiency, well‐defined active sites, and high selectivity. However, their practical applications are hindered by a low atom loading density, uncontrollable location, and ambiguous interaction with the support, thereby posing challenges to maximizing their electrocatalytic performance. To address these limitations, the ability to arrange randomly dispersed single atoms into locally ordered single‐atom catalysts (LO‐SACs) substantially influences the electronic effect between reactive sites and the support, the synergistic interaction among neighboring single atoms, the bonding energy of intermediates with reactive sites and the complexity of the mechanism. As such, it dramatically promotes reaction kinetics, reduces the energy barrier of the reaction, improves the performance of the catalyst and simplifies the reaction mechanism. In this review, firstly, we introduce a variety of compelling characteristics of LO‐SACs as electrocatalysts. Subsequently, the synthetic strategies, characterization methods and applications of LO‐SACs in electrocatalysis are discussed. Finally, the future opportunities and challenges are elaborated to encourage further exploration in this rapidly evolving field.

Morphological and microstructural engineering of Mn-N-C with strengthened Mn-N bond for efficient electrochemical oxygen reduction reaction

Revealing the correlation between the micro–macro structures and active sites of transition metal-nitrogen-carbon (M−N−C) for electrochemical oxygen reduction reaction (ORR) is essential to develop non-precious metal catalyzed fuel cells and metal-air batteries. Herein, Mn-N-C catalysts with various morphologies and microstructures were prepared using Mn2+ coordinated bis(imino)-pyridine-based polymer with N-rich content as a new platform of precursor, which was synthesized via a condensation reaction of 1H-1, 2, 4-Triazole-3, 5-Diamine and 2, 6-Diacetylpyridine. Results demonstrate that morphologies and fine structures (pore structure, N dopants, surface area, and atomic Mn-N bond length, etc.) of Mn-N-C catalysts are strongly dependent on the growth of the specific precursor with and without NaCl as a template and the secondary calcination temperature can further optimize the bond length of Mn-Nx moieties, resulting in significant activity differences between correspondingly derived Mn-N-C catalysts for ORR. Compared to Mn-N-C derived from the synthesized precursor without NaCl, Mn-N-C obtained by the precursor grown directly on NaCl features an ultra-thin nanosheet-like structure with a hierarchical pore distribution and a shorter Mn-N bond, presenting high ORR performance with a half-wave potential of 0.88 V in 0.1 M KOH and a tiny potential loss of 11 mV after 30 K cycles, which is also proved by high-performance practical single Zn-Air battery (139 mW·cm−2) and proton exchange membrane fuel cell (400 mW·cm−2). This work provides a new understanding of the critical role of morphology and Mn-N bonding length of M−N−C for enhancing ORR and a new route of developing non-Fe/Co-based M−N−C catalysts for electrocatalysis.

In-situ construction of water-soluble C60 derivative modified cobalt phosphides for efficient electrocatalytic hydrogen evolution in acidic and alkaline media

A zero-dimensional water-soluble ethylenediamine-functionalized C60 derivative (C60(en)n) was used to be in-situ supported on the surface of cobalt phosphides (CoP-Co2P), forming a highly efficient heterostructured electrocatalytic catalyst for the hydrogen evolution reaction (HER). Benefiting from the strong interfacial electronic interaction between C60(en)n and CoP-Co2P, the composite exhibits an exceptional catalytic performance with overpotentials of 129 and 117 mV to achieve a current density of 10 mA cm−2, and Tafel slopes of 59 and 72 mV dec−1 in acidic and alkaline conditions, respectively.

An efficient electrocatalytic catalyst for hydrogen production: MoS2/Cu2S/PANI with 'wheat ear' structure

An efficient electrocatalytic catalyst for hydrogen production: MoS2/Cu2S/PANI with 'wheat ear' structure

Metal-free Se-based tetra-doped carbon catalyst for high-selective electro-reduction of CO2 into CO

In electrocatalytic CO2 reduction reaction (CO2RR), metal-free Se-based multi-doping carbon has become a new focus. In this paper, a series of metal-free Se, B, P, N doped carbon-based catalysts (Se-BP-N-C) were prepared by a simple and scalable pyrolysis method. The electrocatalytic CO2 reduction results show that, the main product on Se-BP-N-C catalyst is CO, and there are no other by-products except H2. Specifically, the optimal one prepared at 1050 °C (named Se-BP-N-C (1050)), can selectively reduce CO2 into CO with Faradaic efficiency (FE) up to 96.2% (at − 0.5 V), and maintains long-term stability after continuous electrolysis for 10 h in a flow cell (current density remained 82.7%). This study would provide a good reference for designing advanced efficient metal-free catalysts in electrocatalysis.

Insights into Electrocatalytic Nitrate Reduction to Ammonia via Cu-Based Bimetallic Catalysts

Cu-based bimetallic catalysts have been studied in the electrocatalytic nitrate (NO3–) reduction reaction (NO3–RR) for a long time. However, few studies have focused on horizontal comparison of CuNi, CuCo, and CuFe (abbreviated as CuM) bimetallic catalysts in electrocatalytic NO3–RR for ammonia synthesis. Herein, we prepare the three series of Cu-based bimetallic catalysts, with different atom ratios of Cu/M (Cu/M = 7/3, 5/5, or 3/7) and ordered mesoporous carbon (OMC) as support (denoted as CuM/OMC). The characterization results reveal that the metallic particles of Cu and M components possess an intimate relationship on the CuM/OMC catalysts. The electrocatalytic NO3–RR performance uncovers that the optimal NH3 yield rates of CuM/OMC catalysts at −0.8 V (vs reversible hydrogen electrode (RHE)) follow this order: Cu5Fe5/OMC > Cu5Co5/OMC > Cu7Ni3/OMC > Cu/OMC > Fe/OMC > Co/OMC > Ni/OMC > OMC. The bimetallic CuM/OMC catalysts exhibit higher NH3 yield rates than the monometallic catalysts. This is attributed to strong synergistic effects between the Cu and M components. We expect that these insights can stimulate new developments of bimetallic catalysts in electrocatalysis.

TaIrTe4 Monolayer with Topological Insulator Characteristic: A New and Highly Efficient Electrocatalyst toward Oxygen Reduction Reaction

Topological materials with robust topological surface states can be a class of very promising catalysts in electrocatalysis. In this study, a freestanding 2D topological insulator (TI) nanomaterial, namely, TaIrTe4 monolayer with low Ir-loading, which can be exfoliated from the bulk phase with the layered structure, is demonstrated to be dynamically, mechanically, and thermodynamically stable under the first-principles calculations. More intriguingly, coupled with good conductivity, a 2D TaIrTe4 monolayer can be considered as an alternative to noble metal Pt-based electrocatalyst for the oxygen reduction reaction (ORR). Our calculations revealed that on the surface of the TaIrTe4 monolayer, the adsorbed O2 molecules can be effectively activated and dissociated into two separated O* species through a very small energy barrier (0.28 eV, even lower than that of Pt(111)). When the four-electron (4e) dissociation path of ORR occurs on the TaIrTe4 monolayer, a very small overpotential of 0.47 V can be observed, which can be even comparable to the Pt(111) surface. In addition, the 2D TaIrTe4 monolayer can also exhibit high selectivity, effectively inhibiting the formation of byproduct H2O2. It can be revealed that the TI topological states can have an important effect on the excellent ORR catalytic activity of the 2D TaIrTe4 monolayer. Undoubtedly, the design of ORR electrocatalysts based on the fascinating topological materials can be a new and effective way to replace the precious metal Pt-based ORR electrocatalysts.

Sandwich structured Fe3O4/NiFe LDH/Fe3O4 as a bifunctional electrocatalyst with superior stability for highly sustained overall water splitting

Modifying electrocatalysts' structures and regulating their reaction kinetics is essential to improve the performance of electrocatalysts. Here, we report the Fe3O4/NiFe layered double hydroxides/Fe3O4 (Fe3O4/NiFe LDH/Fe3O4) with a sandwich structure by a one-step hydrothermal process. The interface synergistic effect between Fe3O4 and NiFe LDH together with abundant electroactive sites encapsulated inside the Fe3O4 oxide layer can stabilize important charge transfer intermediates and promote the reaction kinetics, which could result in remarkable electrochemical performance. As a result, the resulting Fe3O4/NiFe LDH/Fe3O4 exhibits the lowest overpotential requirements of η10 = 134 mV and η50 = 267 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, respectively. A two-electrode electrolyzer assembled with Fe3O4/NiFe LDH/Fe3O4 as both cathode and anode require a low cell voltage of 1.648 V to achieve the current density response of 10 mA cm−2 toward overall water splitting. Furthermore, the Fe3O4/NiFe LDH/Fe3O4 also displays excellent industrial catalytic performance by simulating the industrial electrolysis for OER, requiring only 353 mV at the large current density of 1000 mA cm−2. This work puts a deep insight into the role of the confined space of transition metal-based catalysts in electrocatalysis.

Recent Progress of Diatomic Catalysts: General Design Fundamentals and Diversified Catalytic Applications.

In recent years, some experiments and theoretical work have pointed out that diatomic catalysts not only retain the advantages of monoatomic catalysts, but also introduce a variety of interactions, which exceed the theoretical limit of catalytic performance and can be applied to many catalytic fields. Here, the interaction between adjacent metal atoms in diatomic catalysts is elaborated: synergistic effect, spacing enhancement effect (geometric effect), and electronic effect. With regard to the classification and characterization of various new diatomic catalysts, diatomic catalysts are classified into four categories: heteronuclear/homonuclear, with/without carbon carriers, and their characterization measures are introduced and explained in detail. In the aspect of preparation of diatomic catalysts, the widely used atomic layer deposition method, metal-organic framework derivative method, and simple ball milling method are introduced, with emphasis on the formation mechanism of diatomic catalysts. Finally, the effective control strategies of four diatomic catalysts and the key applications of diatomic catalysts in electrocatalysis, photocatalysis, thermal catalysis, and other catalytic fields are given.

Pt-Co Electrocatalysts: Syntheses, Morphologies, and Applications.

Pt-Co electrocatalysts have attracted significant attention because of their excellent performance in many electrochemical reactions. This review focuses on Pt-Co electrocatalysts designed and prepared for electrocatalytic applications. First, the various synthetic methods and synthesis mechanisms are systematically summarized; typical examples and core synthesis parameters are discussed for regulating the morphology and structure. Then, starting with the design and structure-activity relationship of catalysts, the research progress of the morphologies and structures of Pt-Co electrocatalysts obtained based on various strategies, the structure-activity relationship between them, and their properties are summarized. In addition, the important electrocatalytic applications and mechanisms of Pt-Co catalysts, including electrocatalytic oxidation/reduction and bifunctional catalytic reactions, are described and summarized, and their high catalytic activities are discussed on the basis of their mechanism and active sites. Moreover, the advanced electrochemical in situ characterization techniques are summarized, and the challenges and direction concerning the development of high-performance Pt-Co catalysts in electrocatalysis are discussed.

Cu cluster embedded porous nanofibers for high-performance CO2 electroreduction

Metal-doped carbon materials, as one of the most important electrocatalytic catalysts for CO2 reduction reaction (CO2RR), have attracted increasing attention. Herein, a series of Cu cluster embedded highly porous nanofibers have been prepared through the carbonization of electro-spun MOF/PAN nanofibers. The obtained Cu cluster doped porous nanofibers possessed fibrous morphology, high porosity, conductivity, and uniformly dispersed Cu clusters, which could be applied as promising CO2RR catalysts. Specifically, best of them, MCP-500 exhibited high catalytic performance for CO2RR, in which the Faradaic efficiency of CO (FECO) was as high as 98% at −0.8 V and maintained above 95% after 10 h continuous electrocatalysis. The high performance might be attributed to the synergistic effect of tremendously layered graphene skeleton and uniformly dispersed Cu clusters that could largely promote the electron conductivity, mass transfer and catalytic activity during the electrocatalytic CO2RR process. This attempt will provide a new idea to design highly active CO2RR electrocatalyst.