Synergistic coupling of FeNi3 alloy with graphene carbon dots for advanced oxygen evolution reaction electrocatalysis

Carbon nanotube-encapsulated Co/Co3Fe7 heterojunctions as a highly-efficient bifunctional electrocatalyst for rechargeable zinc-air batteries

In oxygen electrocatalysis, how to rationally design low-cost catalysts with reasonable structure and long-term stability is a crucial issue. Here, an in-situ growth strategy is used to construct a shaped structure encapsulating a uniformly-dispersed Co/Co3Fe7 heterojunction in nitrogen-doped carbon nanotubes (Co/Co3Fe7@NCNTs). Hollow CoFe layered-double-hydroxide prisms act as sacrifices for in-situ growth of Co/Co3Fe7 nanoparticles, which also catalyze the growth of bamboo-like NCNTs. Tubular structure not only accelerates the charge transfer through the interactions between Co and Co3Fe7, but also limits the aggregation of the particles, thereby promoting the 4e- oxygen reduction/evolution reactions (ORR/OER) kinetics and stabilizing the bifunctional activity. Co/Co3Fe7@NCNTs-800 (pyrolyzed at 800 °C) shows exceptional ORR activity (half-wave potential of 0.89 V) and methanol tolerance. Meanwhile, Co/Co3Fe7@NCNTs-800 shows a small OER overpotential of 280 mV, which increases by only 9 mV after 1000 cyclic voltammetry (CV) cycles. The outstanding bifunctionality (potential gap of 0.62 V) is ascribed to the electronic structure modulation at the Co/Co3Fe7 heterointerface. Notably, it also has a high performance as an air-cathode for rechargeable zinc-air battery, showing high power density (165 mW cm-2) and specific capacity (770.5 m Ah kg-1). This work provides a new reference for promoting the development of alloy catalysts with heterogeneous interfaces.

Voltage activation induced MoO42- dissolution to enhance performance of iron doped nickel molybdate for oxygen evolution reaction

Transition metal-based precatalysts are typically voltage-activated before electrochemical testing in the condition of alkaline oxygen evolution reaction. Nevertheless, the impact of voltage on the catalyst and the anion dissolution is frequently disregarded. In this study, Fe-doped NiMoO4 (Fe-NiMoO4) was synthesized as a precursor through a straightforward hydrothermal method, and MoFe-modified Ni (oxygen) hydroxide (MoFe-NiOxHy) was obtained via cyclic voltammetry (CV) activation. The effects of voltage on Fe-NiMoO4 and the dissolved inactive MoO42- ions in the process were examined in relation to OER performance. It has demonstrated that the crystallinity of the catalyst is reduced by voltage, thereby enhancing its electrocatalytic activity. The electron distribution state can be adjusted during the application of voltage, leading to the generation of additional active sites and an acceleration in the reaction rate. Additionally, MoO42- exhibits potential dependence during its dissolution. In the OER process, the dissolution of MoO42- enhances the reconstruction degree of Fe-NiMoO4 into the active substance and expedites the formation of active Ni(Fe)OOH. Hence, the optimized MoFe-NiOxHy exhibited exceptional electrocatalytic performance, with a current density of 100 mA cm-2 achieved at an overpotential of only 256 mV. This discovery contributes to a more comprehensive understanding of alkaline OER performance under the influence of applied voltage and the presence of inactive oxygen ions, offering a promising avenue for the development of efficient electrocatalysts.

Recent Advances in Flexible Wearable Technology: From Textile Fibers to Devices

Smart textile fabrics have been widely investigated and used in flexible wearable electronics because of their unique structure, flexibility and breathability, which are highly desirable with integrated multifunctionality. Recent years have witnessed the rapid development of textile fiber-based flexible wearable devices. However, the pristine textile fibers still can't meet the high standards for practical flexible wearable devices, which calls for the development of some effective modification strategies. In this review, we summarize the recent advances in the flexible wearable devices based on the textile fibers, putting special emphasis on the design and modifications of textile fibers. In addition, the applications of textile fibers in various fields and the critical role of textile fibers are also systematically discussed, which include the supercapacitors, sensors, triboelectric nanogenerators, thermoelectrics, and other self-powered electronic devices. Finally, the main challenges that should be overcome and some effective solutions are also manifested, which will guide the future development of more effective textile fiber-based flexible wearable devices.

Modification of PAN electrospun nanofiber membranes with g-C3N4 nanotubes/carbon dots to enhance MBR performance

This study is dedicated to the enhancement of electrospun polyacrylonitrile (PAN) nanofiber membranes for their application in membrane bioreactor (MBR) processes. The improvement is achieved through the incorporation of graphitic carbon nitride nanotubes/carbon dots (g-C3N4 NT/CDs) and subsequent heat post-treatments at varying temperatures. Notably, the hot-pressing methodology effectively mitigates surface roughness and significantly reduces issues related to peeling during nanofiber experimentation. Our results demonstrate that the introduction of 0.5 wt% of g-C3N4 NT/CDs leads to a substantial enhancement in water flux. In particular, nanocomposite membranes subjected to hot-pressing at 90 °C for 10 min exhibited an impressive flux recovery ratio (FRR) of 70%. Furthermore, the heat-treated nanocomposite membranes exhibited remarkable antifouling properties and significantly reduced fouling rates when compared to their heat-treated bare counterparts. This study underscores the noteworthy potential of g-C3N4 NT/CDs-modified PAN nanofiber membranes to substantially elevate MBR performance, firmly positioning them as highly promising candidates for critical applications in the domains of water and wastewater treatment. However, it is imperative to underscore that the existing written material necessitates a comprehensive overhaul to align with the provided structural framework.

Interfacial carbon dots introduced distribution-structure modulation of Pt loading on graphene towards enhanced electrocatalytic hydrogen evolution reaction

To easily load Pt on smoothy graphene synthesized by cathodic exfoliation method and achieve adjacent plane distribution of Pt, carbon dots (CDs) are used to construct anchoring points to load highly dispersed Pt species due to strong interaction between CDs and Pt species. The composite of Pt-CDs/graphene is synthesized via a continuous process of cathodic exfoliation-hydrothermal-impregnation-reduction. Characterization results indicate the distribution configuration of Pt varies from coated structure of CDs@Pt to dispersed configuration of CDs&Pt or Pt&CDs, then to wrapping configuration of Pt@CDs with increased amount of CDs. It's found that suitable introduction of CDs promotes the adjacent plane distribution of Pt species. The obtained best Pt-4CDs/G shows the low overpotential of 36 mV (10 mA⋅cm-2) and high mass activity of 3747.8 mA mg-1 at -40 mV towards electrocatalytic hydrogen evolution reaction (HER), 9.2 times more active than that of Pt/C (406.2 mA mg-1). The superior HER performance of Pt-4CDs/G is attributed to its relatively adjacent plane distribution of Pt, which supports high electrochemically active surface area and more adjacent Pt sites for H* adsorption. Benefitting from that, the HER process for Pt-4CDs/G favorably follows the Tafel pathway, resulting in low hydrogen adsorption free energy and excellent HER activity.

Ligand leaching enabling improved electrocatalytic oxygen evolution performance

Design and fabrication of cost-effective (pre-)catalysts are important for water splitting and metal-air batteries. In this direction, various metal-organic frameworks (MOFs) have been investigated as pre-catalysts for oxygen evolution. However, the activation process and the complex reconstruction behaviour of these MOFs are not well understood. Herein, square-like MOF nanosheets in which carbon nanotubes were embedded were prepared by introducing an amine ligand to coordinate with Ni ions and then reacting with [Fe(CN)₆]^3-. The formed MOF nanosheets containing nickel and iron species were then activated by NaBH₄, inducing the leaching of ligands and the formation of tiny active species in situ loaded on carbon nanotubes. The prepared catalyst shows superior oxygen evolution performance with an ultralow overpotential of 231 mV for 10 mA cm^-2, a fast reaction kinetics with a small Tafel slope of 52.3 mV dec^-1, and outstanding catalysis stability. The excellent electrocatalytic performance for oxygen evolution can be attributed to the structural advantage of in situ derived small sized active species and one-dimensional conductive networks. This work provides a new thought for the enhancement of the electrocatalytic performance of MOF materials.

Duplex Interpenetrating-Phase FeNiZn and FeNi3 Heterostructure with Low-Gibbs Free Energy Interface Coupling for Highly Efficient Overall Water Splitting

The sluggish kinetics of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) generate the large overpotential in water electrolysis and thus high-cost hydrogen production. Here, multidimensional nanoporous interpenetrating-phase FeNiZn alloy and FeNi3 intermetallic heterostructure is in situ constructed on NiFe foam (FeNiZn/FeNi3@NiFe) by dealloying protocol. Coupling with the eminent synergism among specific constituents and the highly efficient mass transport from integrated porous backbone, FeNiZn/FeNi3@NiFe depicts exceptional bifunctional activities for water splitting with extremely low overpotentials toward OER and HER (η1000 = 367/245 mV) as well as the robust durability during the 400 h testing in alkaline solution. The as-built water electrolyzer with FeNiZn/FeNi3@NiFe as both anode and cathode exhibits record-high performances for sustainable hydrogen output in terms of much lower cell voltage of 1.759 and 1.919 V to deliver the current density of 500 and 1000 mA cm-2 as well long working lives. Density functional theory calculations disclose that the interface interaction between FeNiZn alloy and FeNi3 intermetallic generates the modulated electron structure state and optimized intermediate chemisorption, thus diminishing the energy barriers for hydrogen production in water splitting. With the merits of fine performances, scalable fabrication, and low cost, FeNiZn/FeNi3@NiFe holds prospective application potential as the bifunctional electrocatalyst for water splitting.

Interface engineering of Mo-doped Ni9S8/Ni3S2 multiphase heterostructure nanoflowers by one step synthesis for efficient overall water splitting

Accelerating charge transfer efficiency by constructing heterogeneous interfaces on metal-based substrates is an effective way to improve the electrocatalytic performance of materials. However, minimizing the substrate-catalyst interfacial resistance to maximize catalytic activity remains a challenge. This study reports a simple interface engineering strategy for constructing Mo-Ni₉S₈/Ni₃S₂ heterostructured nanoflowers. Experimental and theoretical investigations reveal that the primary role assumed by Ni₃S₂ in Mo-Ni₉S₈/Ni₃S₂ heterostructure is to replace nickel foam (NF) substrate for electron conduction, and Ni₃S₂ has a lower potential energy barrier (0.76 to 1.11 eV) than NF (1.87 eV), resulting in a more effortless electron transfer. The interface between Ni₃S₂ and Mo-Ni₉S₈ effectively regulates electron redistribution, and when the electrons from Ni₃S₂ are transferred to Mo-Ni₉S₈, the potential energy barriers at the heterogeneous interface are 1.06 eV, lower than that between NF and Ni₃S₂ (1.53 eV). Mo-Ni₉S₈/Ni₃S₂-0.1 exhibited excellent oxygen evolution reaction (OER)/hydrogen evolution reaction (HER) bifunctional catalytic activity in 1 M KOH, with overpotentials of only 223 mV@100 mA cm^-2 for OER and 116 mV@10 mA cm^-2 for HER. Moreover, when combined with an alkaline electrolytic cell, it required only an ultra-low cell voltage of 1.51 V to drive a current density of 10 mA cm^-2. This work provides new inspirations for rationally designing interface engineering for advanced catalytic materials.

Dimension Engineering in Noble-Metal-Based Electrocatalysts for Water Splitting

Dimension engineering plays a critical role in determining the electrocatalytic performance of catalysts towards water electrolysis since it is highly sensitive to the surface and interface properties. Bearing these considerations into mind, intensive efforts have been devoted to the rational dimension design and engineering, and many advanced nanocatalysts with multidimensions have been successfully fabricated. Aiming to provide more guidance for the fabrication of highly efficient noble-metal-based electrocatalysts, this review has focused on the recent progress in dimension engineering of noble-metal-based electrocatalysts towards water splitting, including the advanced engineering strategies, the application of noble-metal-based electrocatalysts with distinctive geometric structure from 0D to 1D, 2D, 3D, and multidimensions. In addition, the perspective insights and challenges of the dimension engineering in the noble-metal-based electrocatalysts is also systematically discussed.

Hollow Heterostructured Nanocatalysts for Boosting Electrocatalytic Water Splitting

The implementation of electrochemical water splitting demands the development and application of electrocatalysts to overcome sluggish reaction kinetics of hydrogen/oxygen evolution reaction (HER/OER). Hollow nanostructures, particularly for hollow heterostructured nanomaterials can provide multiple solutions to accelerate the HER/OER kinetics owing to their advantageous merit. Herein, the recent advances of hollow heterostructured nanocatalysts and their excellent performance for water splitting are systematically summarized. Starting by illustrating the intrinsically advantageous features of hollow heterostructures, achievements in engineering hollow heterostructured electrocatalysts are also highlighted with the focus on structural design, interfacial engineering, composition regulation, and catalytic evaluation. Finally, some perspective insights and future challenges of hollow heterostructured nanocatalysts for electrocatalytic water splitting are also discussed.

Pd-Based Metallenes for Fuel Cell Reactions

Pd-based metallenes, atomically thin layers composed primarily of under-coordinated Pd atoms, have emerged as the newest members in the family of two-dimensional (2D) nanomaterials. Moreover, the unique physiochemical properties, high intrinsic activity associated with metallenes coupled with the ease of applying chemical modifications result in great potential in catalyst engineering for fuel cell reactions. Especially in recent years, interest in Pd-based metallenes is growing, as evidenced by surge in available literatures. Herein, we have reviewed the recent findings achieved in Pd-based metallenes in fuel cells by highlighting the technologies available for deriving metallenes and manifesting the modification strategies for designing them to better suit the application demand. Moreover, we also discuss the perspective insights of Pd-based metallenes for fuel cells regarding the surfactant-free synthesis method, strain engineering, constructing high-entropy alloy, and so on.

Different Growth Behavior of MOF-on-MOF Heterostructures to Enhance Oxygen Evolution

The exploration of non-noble metal electrocatalysts with high catalytic activity and stability for oxygen evolution reaction (OER) has become particularly urgent. Here, FeNi-based Prussian blue analogues (PBAs) were obtained by adding different solvents, where PBA particles preferentially grew on the surface plane/edge of coordination polymer precursor (Ni-ABDC) with various polarities. This resulted in the formation of FeNi-PBA-plane/edge morphologies, respectively. Notably, on account of more exposed PBAs, FeNi nanoparticles were uniformly supported on the porous N-doped carbon nanomaterials. Among them, the calcined FeNi-NC-800 underwent an interesting pre-activation process and exhibited a low overpotential of 281 mV at 10 mA cm^-2 and a small Tafel slope of 82 mV dec^-1 in 1.0 m KOH. This bimetallic sample showed superior OER activity and stability in comparison with control materials, which could be attributed to its abundant FeNi nanoparticles, high nitrogen content, large specific surface area, and synergistic effects between Fe and Ni atoms. In addition, relevant theoretical calculation on the optimal catalyst, FeNi-NC-800, further demonstrated its efficient OER performance with effective Fe-doping in the Ni-based oxyhydroxides.

Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H₂O₂-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co₉Se₈@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co₉Se₈@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm^-2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm^-2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.

Coupling Transition Metal Catalysts with Ir for Enhanced Electrochemical Water Splitting Activity

Developing advanced electrocatalysts is of great significance for boosting electrochemical water splitting to produce hydrogen. The electrocatalytic activity of a catalyst is associated with the surface/interface, geometric structure, and electronic properties. Coupling Ir with transition metal compounds is an effective strategy to improve their electrocatalytic performance. In this review, we summarize the recent progress of Ir coupled transition metal compound catalysts for the application in driving electrochemical water splitting. The significant role of Ir played in the promotion of electrocatalytic performance is firstly illustrated. Then, the applications of Ir-based catalysts in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are comprehensively discussed, with an emphasis on correlating the structure-function relationships. Lastly, the challenges and future directions for the fabrication of more advanced Ir coupled electrocatalysts are also presented.

Heterojunction MnO2-nanosheet-decorated Ag nanowires with enhanced oxidase-like activity for the sensitive dual-mode detection of glutathione

The biocatalytic design of nanomaterials with enzyme-like activity is considered a reliable and promising toolkit for the generation of diagnostic agents in complex biological microenvironments. However, the preparation of nanomaterials while maintaining a high catalytic activity in tumor cells (pH 6.0-6.5) poses a prominent challenge. Herein, we constructed a biomimetic enzyme-trigged dual-mode system with colorimetry at 652 nm and photothermal biosensors to detect glutathione based on hollow MnO₂-nanosheet-decorated Ag nanowires (Ag@MnO₂) as an oxidase-like nanozyme. As expected, Ag@MnO₂ catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the absence of H₂O₂, leading to a blue-colored oxidized TMB (oxTMB) that displayed oxidase-like activity in pH 6.0. Interestingly, the portable dual-mode colorimetry and photothermal method for GSH was developed based on the redox reaction between GSH and oxTMB. This detection method exhibited a wide linear range of 0.1-55 μM for GSH with a low detection limit of 0.08 μM. This work highlights a new insight into nanotechnology by taking advantage of biomimetic design in biological analysis.

Hydrogen evolution reaction catalysis on RuM (M = Ni, Co) porous nanorods by cation etching

The development of efficient and stable nanomaterial electrocatalysts for the hydrogen evolution reaction (HER) is of great significance for renewable energy conversion via water electrolysis. Herein, we have developed a novel class of bimetallic RuM (M = Ni, Co) hollow nanorods (HNRs) through a facile Fe³⁺ etching strategy, as electrocatalysts for enhancing the HER. Morphological physical characterization and electrochemical tests demonstrated that RuM (M = Ni, Co) HNRs with hollow structures can effectively enhance electrocatalytic activity due to their high specific surface areas. Impressively, the RuNi HNRs exhibited superior HER performance with an overpotential of merely 25.6 mV in 1 M KOH solution at 10 mA cm^-2, which is significantly lower than that of commercial Pt/C (44.7 mV). Moreover, the as prepared RuNi HNRs showed excellent stability and could continuously work at a current density of 10 mA cm^-2 for 40 h with a negligible increase in potential. The Ru-based HNRs also showed high HER activity in an acidic solution. This study paves a new way for the universal fabrication of bimetallic hollow structured nanomaterials as efficient electrocatalysts for boosting the HER.

Defect and Interface Engineering of Three-Dimensional Open Nanonetcage Electrocatalysts for Advanced Electrocatalytic Oxygen Evolution Reaction

Defect engineering and interface engineering are two efficient approaches to promote the electrocatalytic performance of transition metal oxides (TMOs) by modulating the local electronic structure and inducing a synergistic effect but usually require costly and complicated processes. Herein, a facile electrochemical etching method is proposed for the controllable tailoring of the defects in a three-dimensional (3D) open nanonetcage CoZnRuO_x heterostructure via the in situ electrochemical etching to remove partial ZnO. The highly open 3D nanostructures, numerous defects, and multicomponent heterointerfaces endow the CoZnRuO_x nanonetcages with more accessible active sites, moderated local electronic structure, and strong synergistic effect, thereby enabling them to not only deliver an ultralow overpotential (244 mV @ 10 mA cm^-2) for oxygen evolution reaction (OER) but also high-performance overall water electrolysis by coupling with commercial Pt/C, with a potential of 1.52 V at 10 mA cm^-2. Moreover, experiments and characterizations also reveal that the remaining Zn²⁺ can facilitate OH^- adsorption and charge transfer, which also further improves the electrocatalytic OER performance. This work proposes a promising strategy for creating surface defects in heterostructured TMOs and provides insights to understand the defect- and interface-induced enhancement of OER electrocatalysis.

Recent advances in hollow nanomaterials with multiple dimensions for electrocatalytic water splitting

Electrocatalytic water splitting has great research prospects in the production of green hydrogen energy, and electrocatalysts are the prerequisite. As widely employed efficient electrocatalysts, hollow nanostructures have attracted a lot of research attention due to their excellent catalytic activity and structural stability. Moreover, the abundant catalytically active sites and tunable morphology also make hollow nanomaterials promising electrocatalysts for water splitting. Despite these advantages, the industrial applications of these hollow nanocatalysts are impeded by limitations like the lack of effective synthesis methods and unclear formation mechanisms. Therefore, extensive efforts have been devoted to the development of efficient synthesis strategies to boost the development of more efficient hollow electrocatalysts, and great progress has been achieved in recent years. To gain a better understanding of the rapid development of hollow nanocatalysts for water splitting, we herein organize a review to summarize the recent synthetic methods and advantages of hollow materials with different dimensions. The specific advantages of hollow nanomaterials in electrocatalytic water splitting, such as abundant active sites, a stable structure, high mass transfer efficiency, and reduced aggregation of catalytic particles, are also summarized. Finally, the challenges and prospects of hollow nanostructures with multiple dimensions in electrocatalytic water splitting are further explored.

Hierarchical Hollow CoWO4-Co(OH)2 Heterostructured Nanoboxes Enabling Efficient Water Oxidation Electrocatalysis

Rational design and construction of well-defined hollow heterostructured nanomaterials assembled by ultrathin nanosheets overtakes crucial role in developing high-efficiency oxygen evolution reaction (OER) electrocatalysts. Herein, a reliable metal-organic framework-mediated and cation-exchange strategy to tune the geometric structure and multicomponent heterostructures has been proposed for the fabrication of hollow CoWO₄-Co(OH)₂ hierarchical nanoboxes assembled by rich ultrathin nanosheets. Benefiting from the hierarchical hollow nanostructure, the CoWO₄-Co(OH)₂ nanoboxes offer plenty of metal active centers available for reaction intermediates. Moreover, the well-defined nanointerfaces between CoWO₄ and Co(OH)₂ can function as the bridge for boosting the efficient electron transfer from CoWO₄ to Co(OH)₂. As a consequence, the optimized CoWO₄-Co(OH)₂ nanoboxes can exhibit outstanding electrocatalytic performance toward OER by delivering 10 mA cm^-2 with a low overpotential of 280 mV and a small Tafel slope of 70.6 mV dec^-1 as well as outstanding electrochemical stability. More importantly, this CoWO₄-Co(OH)₂ heterostructured nanocatalyst can couple with Pt/C to drive overall water splitting to achieve 10 mA cm^-2 with a voltage of 1.57 V.

Ru doping boosts electrocatalytic water splitting

Heteroatom doping plays a crucial role in improving the electrocatalytic performance of catalysts towards water splitting. Owing to the existence of Ru-O moieties, Ru is thus emerging as an ideal dopant for promoting the electrocatalytic performance for water splitting by modifying the electronic structure, introducing extra active sites, improving electronic conductivity, and inducing a strong synergistic effect. Benefitting from these advantages, Ru-doped nanomaterials have been widely investigated and employed as advanced electrocatalysts for water splitting, and many excellent Ru-doped electrocatalysts have been successfully developed. In an effort to obtain a better understanding of the influence of Ru doping on the electrocatalytic water splitting performance of nanocatalysts, we herein summarize the recent progress of Ru-doped electrocatalysts by focusing on the synthesis strategies and advantageous merits. Applications of these new materials in water electrolysis technology are also discussed with emphasis on future directions in this active field of research.

Fabrication of cobaltous telluride and carbon composite as a promising carrier for boosting electro oxidation of ethylene glycol on palladium in alkaline medium

The development of highly active and earth-rich electrocatalysts remains a formidable challenge for the commercialization of fuel cells. Herein, a composite carrier composed of cobaltous telluride (CoTe) and carbon (C) has been designed for the first time to enhance the electrocatalytic performance of palladium (Pd) nanoparticles (NPs) for the electro-oxidation of ethylene glycol (EG). Remarkably, the mass activity for the as-prepared Pd/CoTe-C catalyst during the ethylene glycol oxidation reaction (EGOR) is found to reach up to 3917.3 mA mg^-1, which is 2.2 times higher than that of Pd/Co-C (1785.0 mA mg^-1) and 4.1 times greater than that of commercial Pd/C catalyst (962.4 mA mg^-1), exceeding that obtained for most Pd-based electrocatalysts reported thus far. In particular, the Pd/CoTe-C catalyst shows better electrochemical stability toward the EGOR than the Pd/Co-C and commercial Pd/C catalysts. Thus, the Pd/CoTe-C electrocatalyst is expected to exhibit broad application prospects in the field of fuel cells.

Recent advances in fuel cell reaction electrocatalysis based on porous noble metal nanocatalysts

As the center of fuel cells, electrocatalysts play a crucial role in determining the conversion efficiency from chemical energy to electrical energy. Therefore, the development of advanced electrocatalysts with both high activity and stability is significant but challenging. Active site, mass transport, and charge transfer are three central factors influencing the catalytic performance of electrocatalysts. Endowed with rich available surface active sites, facilitated electron transfer and mass diffusion channels, and highly active components, porous noble metal nanomaterials are widely considered as promising electrocatalysts toward fuel cell-related reactions. The past decade has witnessed great achievements in the design and fabrication of advanced porous noble metal nanocatalysts in the field of electrocatalytic fuel oxidation reaction (FOR) and oxygen reduction reaction (ORR). Herein, the recent research advances regarding porous noble metal nanocatalysts for fuel cell-related reactions are reviewed. In the discussions, the inherent structural features of porous noble metal nanostructures for electrocatalytic reactions, advanced synthetic strategies for the fabrication of porous noble metal nanostructures, and the structure-performance relationships are also provided.

Engineering NiMoO4/NiFe LDH/rGO multicomponent nanosheets toward enhanced electrocatalytic oxygen evolution reaction

Rational hybridization of two-dimensional (2D) nanomaterials with extrinsic species has shown great promise for boosting the electrocatalytic oxygen evolution reaction (OER). To date, the rational design and engineering of heterojunctions based on three or more components has been rather limited. Herein, by taking advantage of the high intrinsic activity of NiFe layered double hydroxide (LDH), strong synergistic effects between different components, and good electronic conductivity of reduced graphene oxide (rGO), we demonstrate the successful synthesis of NiMoO₄/NiFe LDH/rGO nanosheets. As a proof-of-concept demonstration, the multicomponent nanosheet catalyst with a well-modified electronic structure is applied to boost the electrochemical OER and achieve decent electrocatalytic activity in 1 M KOH electrolyte, which can deliver a current density of 10 mA cm^-2 with an overpotential of merely 270 mV and a small Tafel slope of 76.2 mV dec^-1, which are markedly superior to those of the commercial RuO₂ catalyst (303 mV, 131.9 mV dec^-1). This work is expected to provide new insights into furnishing multi-component heterostructures with extended functionalities and more advantageous merits.

Engineering Heterostructured Pd-Bi2Te3 Doughnut/Pd Hollow Nanospheres for Ethylene Glycol Electrooxidation

The electrooxidation of ethylene glycol (EG) is of vital significance for the conversion from biomass energy into electrical energy via direct fuel cells. However, the EG oxidation reaction (EGOR) suffers from poor efficiency due to the limitation of high-performance electrocatalysts for cleaving the C-C bonds. Herein, this limitation is successfully addressed by fabricating the doughnut-shaped Pd-Bi₂Te₃ heterostructured catalyst. Notably, the heterojunction Pd-Bi₂Te₃ nanocatalyst has been demonstrated to be highly active toward the EGOR with superb activity and durability, in which a mass activity as high as 2420.8 mA mg^-1 is achieved in alkaline media, being 1.7 times higher than that of the commercial Pd/C catalyst. Upon combination of experimental results with mechanism studies, it is indicated that the remarkable EGOR performance is attributed to the enlarged active areas that stemmed from the doughnut-like structure, as well as the strong synergistic effect from Pd-Bi₂Te₃ and Pd. More importantly, the highly electroactive Pd-Bi₂Te₃ can accelerate charge transfer and boost the oxidation of CO-like intermediates, which are conducive to the enhancement in electrochemical stability.

Engineering transition metal catalysts for large-current-density water splitting

Electrochemical water splitting plays a crucial role in transferring electricity to hydrogen fuel and appropriate electrocatalysts are crucial to satisfy the strict industrial demand. However, the successfully developed non-noble metal catalysts have a small tested range and the current density is usually less than 100 mA cm^-2, which is still far away from the practical application standards. Aiming to provide guidance for the fabrication of more advanced electrocatalysts with a large current density, we herein systematically summarize the recent progress achieved in the field of cost-efficient and large-current-density electrocatalyst design. Beginning by illustrating the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) mechanisms, we elaborate on the concurrent issues of non-noble metal catalysts that are required to be addressed. In view of large-current-density operating conditions, some distinctive features with regard to good electrical conductivity, high intrinsic activity, rich active sites, and porous architecture are also summarized. Next, some representative large-current-density electrocatalysts are classified. Finally, we discuss the challenges associated with large-current-density water electrolysis and future pathways in the hope of guiding the future development of more efficient non-noble-metal catalysts to boost large-scale hydrogen production with less electricity consumption.

Vanadium-Doped Nickel Cobalt Layered Double Hydroxide: A High-Performance Oxygen Evolution Reaction Electrocatalyst in Alkaline Medium

Vast attention from researchers is being given to the development of suitable oxygen evolution reaction (OER) electrocatalysts via water electrolysis. Being highly abundant, the use of transition-metal-based OER catalysts has been attractive more recently. Among the various transition-metal-based electrocatalysts, the use of layered double hydroxides (LDHs) has gained special attention from researchers owing to their high stability under OER conditions. In this work, we have reported the synthesis of trimetallic NiCoV-LDH via a simple wet-chemical method. The synthesized NiCoV-LDH possesses aggregated sheet-like structures and is screened for OER studies in alkaline medium. In the study of OER activity, the as-prepared catalyst demanded 280 mV overpotential and this was 42 mV less than the overpotential essential for pristine NiCo-LDH. Moreover, doping of a third metal into the NiCo-LDH system might lead to an increase in TOF values by almost three times. Apart from this, the electronic structural evaluation confirms that the doping of V³⁺ into NiCo-LDH could synergistically favor the electron transfer among the metal ions, which in turn increases the activity of the prepared catalyst toward the OER.

Successive Anion/Cation Exchange Enables the Fabrication of Hollow CuCo2S4 Nanorods for Advanced Oxygen Evolution Reaction Electrocatalysis

Hollow CuCo₂S₄ nanorods (H-CCS-Ns) have been successfully developed via a facile successive anion/cation-exchange method. The outstanding electrocatalytic performance of H-CCS-Ns is mainly attributed to its distinctive hollow structure, which accelerates the electron transfer rate and provides abundant active sites. Moreover, a mechanism study indicates that H-CCS-Ns has highly active octahedral Co³⁺, and the existence of Co³⁺ cations optimizes the adsorption of oxygen-involved intermediates, making H-CCS-Ns a promising OER electrocatalyst. Optimized H-CCS-Ns only need an ultralow overpotential of 220 mV to drive a current density of 10 mA·cm^-2 and exhibit distinguished cycling stability with a negligible fluctuation for 30 h. More impressively, when H-CCS-Ns are assembled with Pt/C for overall water splitting, a voltage as low as 1.545 V is required at a current density of 10 mA·cm^-2, and the catalyst shows outstanding stability for as long as 38 h. This study offers a feasible strategy to design hollow spinel catalysts for efficient OER catalysis.

Interfacial engineering of a tri-phase CoFe/CoFeOx/Co–Fe3O4 electrocatalyst for promoting the oxygen evolution reaction

A tri-phase interfacial structure of CoFe alloy/CoFe oxide/cobalt-doped iron oxide as a highly efficient and cost-effective oxygen evolution reaction electrocatalyst was elaborately constructed by a one-step chemical bath deposition approach.

Recent Progress on Polyvinyl Alcohol-Based Materials for Energy Conversion

Electrocatalytic energy conversion shows a promising “bridge” to mitigate energy shortage issues and minimizes the ecological implications by synergy with the sustainable energy sources, which calls for low-cost, highly active,...

Electronic and architecture engineering of hammer-shaped Ir–NiMoO4-ZIF for effective oxygen evolution

Electronic and architecture engineering is realized via doping an ultralow amount of Ir into NiMoO4-ZIF hammers to achieve outstanding electrocatalytic OER performance.

Boosted Electrocatalysis of Bimetallic Sulfide Particles Incorporated in Fe/Co-based Metal-Organic Framework Ultrathin Nanosheets toward Oxygen Evolution Reaction

The development of inexpensive, high-performance, and long-lasting electrocatalysts toward oxygen evolution reaction (OER) proves crucial to enhance the efficiency of water splitting to obtain clean and sustainable energy. Herein, Fe/Co-based...

Electrospun one-dimensional electrocatalysts for boosting electrocatalysis

Electrocatalytic reaction plays a crucial role in determining the energy conversion efficiency in advanced technology. However, it is limited by the sluggish reaction kinetics and high energy barrier. These shortcomings...

Surface nitriding to improve the catalytic performance of FeNi3 for the oxygen evolution reaction

In the oxygen evolution reaction, optimized Fe/Ni–Nx@FeNi3 nanosheets exhibit an overpotential of 251 mV to achieve a current density of 10 mA cm−2 and an excellent durability of 210 h.

Electronic structure optimization boosts Pd nanocrystals for ethanol electrooxidation realized by Te doping

Te doping greatly modifies the electronic structure of Pd and promotes the electrocatalytic performance towards EOR.

Engineering atomically dispersed single Cu–N3 catalytic sites for highly selective oxidation of benzene to phenol

A single-atom Cu catalyst with a CuN3 structure is prepared by a facile and practical strategy, the pyrolysis method, showing desirable conversion and selectivity for the oxidation reaction of benzene to phenol.

Engineering Thiospinel-Based Hollow Heterostructured Nanoarrays for Boosting Electrocatalytic Oxygen Evolution Reaction

Thiospinel, known as a member of spinel, has been demonstrated to be promising for boosting electrocatalytic oxygen evolution reaction (OER), while their practical application is severely impeded by the limited...