Search

Noble metal Pt‐based catalysts have slow water dissociation kinetics at high pH conditions, making it difficult for water molecules to be electrochemically activated. Utilizing ligand effect and strain effect to tailor catalytic active sites is a common method, while the understanding of mechanism of their interaction remains obscure due to the complexity of the process. This study proposes a pulse‐induced torsional strained PtRu mesocrystals (PtRu MCs) with 20 times higher mass activity than commercial Pt/C. The combination of experimental results and theoretical calculations reveals that the ligand effect induced by Ru doping accelerates the kinetics of the water dissociation reaction, while the pulse‐induced torsion strained dominates the thermodynamic optimization of the hydrogen adsorption reaction. The structure‐activity relationship defined by the synergistic effect under the complementary advantages of the strain and doping provides guidance for the design of future basic hydrogen evolution catalysts. The catalyst can run stably at 1 A cm−2 for 500 h, showing potential for industrial application. [ABSTRACT FROM AUTHOR]

Atomically precise composite site‐based catalysts with new electrocatalytic synergistic mechanisms and enhanced electrocatalytic activities have emerged as a frontier in the electrocatalysis community. This topical review focuses on the recent research advances of atomically precise metal composite sites‐based electrocatalysts. This work first demonstrates an overview of the configurations of atomically precise composite sites, including a discussion of the advanced methods employed for understanding the composite sites. The review then provides a comprehensive organization of the previously reported methodologies of synthesizing electrocatalysts with atomically precise composite sites. Representative case studies are provided, starting from the simple one‐step pyrolysis strategy to the species‐by‐species multi‐step pyrolysis strategy. Based on the preceding discussions of the catalyst materials, the review further discusses the unique electrocatalysis mechanisms raised by the composite sites, that are different from the routine single species sites. The electrocatalytic systems mainly involve the oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, nitrogen reduction reaction, and carbon dioxide reduction reaction. The themes of this section include the true active center determination for composite sites and various types of electrocatalytic synergy mechanisms. Finally, critical unanswered questions and remaining challenges, as well as promising underexplored research directions are identified. [ABSTRACT FROM AUTHOR]

The sluggish kinetics and mutual interference of oxygen evolution and reduction reactions in the air electrode resulted in large charge/discharge overpotential and low energy efficiency of Zn‐air batteries. In this work, we designed a breathing air‐electrode configuration in the battery using P‐type Ca3Co4O9 and N‐type CaMnO3 as charge and discharge thermoelectrocatalysts, respectively. The Seebeck voltages generated from thermoelectric effect of Ca3Co4O9 and CaMnO3 synergistically compensated the charge and discharge overpotentials. The carrier migration and accumulation on the cold surface of Ca3Co4O9 and CaMnO3 optimized the electronic structure of metallic sites and thus enhanced their intrinsic catalytic activity. The oxygen evolution and reduction overpotentials were enhanced by 101 and 90 mV, respectively, at temperature gradient of 200 °C. The breathing Zn‐air battery displayed a remarkable energy efficiency of 68.1 %. This work provides an efficient avenue towards utilizing waste heat for improving the energy efficiency of Zn‐air battery. [ABSTRACT FROM AUTHOR]

Alloying platinum with early transition metals is a promising approach to optimize the adsorption behaviors of catalysts. Nevertheless, the large negative redox potential between early transition metals and Pt hinders the fabrication of such alloys. Herein, a strategy combining the thermal shock technique with electrochemical activation to prepare Pt3V alloy as a hydrogen evolution reaction catalyst is reported for the first time. Electrochemical tests show that the as‐prepared catalyst exhibits exceptional catalytic activity and durability in 0.5 m H2SO4, surpassing the state‐of‐the‐art 20 wt.% Pt/C. The catalyst can maintain its activity after 100 h tests without evident decay under the current density of 500 mA cm−2. Theoretical calculations demonstrate that the optimized hydrogen absorption and high vacancy formation energy of Pt3V contributes to the enhanced electrocatalytic activity and stability. This work may spur future research for other Pt‐based early transition metal alloy catalysts for electrocatalysis. [ABSTRACT FROM AUTHOR]

The development of cost‐effective and highly efficient electrocatalysts to accelerate distinct electrochemical reactions is essential to help the industry to achieve a low‐carbon footprint. Single‐atom alloys (SAAs) with the characteristics of unique electronic structures, well‐defined active sites, and maximum atom utilization demonstrate promising potential to replace traditional noble metal catalysts. SAAs are expected to tailor the adsorption properties of reaction species, thus promoting electrocatalytic behaviors. Herein, representative synthetic strategies including wet chemistry, galvanic replacement, dealloying, and atomic layer deposition are introduced, followed by a summary of applications of SAAs in hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and ethanol electro‐oxidation to provide an in‐depth understanding of the structure–activity relationship. Moreover, the challenges and perspectives in this emerging field of SAAs are discussed. [ABSTRACT FROM AUTHOR]

Constructing novel heterostructures is an effective way for enhancing the oxygen electrocatalytic properties of the catalysts. In this work, a class of Janus homologous heterostructures, compositing transition metal alloys with their corresponding sulfides (TM/TMS), are controllably synthesized through an ultrafast high‐temperature shock (HTS) strategy. The ultrafast sintering rate and carbothermal reduction reaction lead to the formation of sulfides and partial reduction of sulfides to alloys, while the ultrafast cooling rate keeps the homologous heterostructure of TM/TMS stable. The components of TMs in the composites can be well controlled from unary to quaternary. Moreover, benefiting from the synergistic effect of the metallic sites in the interfaces, the adsorption and desorption energy barrier of the active intermediates are significantly optimized and thus leading to the enhanced oxygen catalytic performance. Impressively, the aqueous zinc‐air battery (ZAB) using the binary homologous nanocomposite FeCo/(FeCo)S as air cathodes achieves impressive durability (> 470 cycles) and power density (261.8 mW cm−2). The as‐assembled flexible ZAB can well power the wearable devices and can work for at least 300 cycles without obvious degradation. This work opens a new chemical space for designing homologous heterostructures for their application in energy storage and conversion systems. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides (TMCs) have been identified as pre‐electrocatalysts for the oxygen evolution reaction (OER) and the high valent TMs in the in situ generated oxyhydroxides are considered to be the real OER catalytic center. However, the role of chalcogens for OER process has been ignored and not fully elucidated. Herein, it is discovered that about 2.8–3.5% of chalcogens remain in as oxidized derivatives at a steady state, which plays a vital role for enhancing the catalytic activity. A facile and spontaneous sulfurizing method is developed to synthesize sulfur‐doped NiCo‐(oxy)hydroxysulfides (NCOSH) nanosheets, in which the sulfur can directly bond with high‐valence TMs and keep them stable for OER catalysis. Theoretical and experimental results suggest that the S‐coordination in NCOSH can cause bond length strengthening and electronic modulation between TM‐S and TM‐O, thus enhancing the oxidation activity and stability of high‐valence TMs in NCOSH. Consequently, the as‐obtained NCOSH exhibits superior bifunctional activities and durability for oxygen electrocatalytic reactions, and also serves as a superb air cathode in rechargeable solid state Zn‐air batteries. This work sheds light on the rational design of (oxy)hydroxysulfides as efficient electrocatalysts and gains deeper fundamental insights on the enhancing mechanism of S in oxyhydroxysulfides for diverse electrochemical applications. [ABSTRACT FROM AUTHOR]

Abundant surface structural defects can endow electrocatalysts with extraordinary physical and chemical characteristics. Herein, metastable Pd nanoparticles (NPs) with abundant twin boundaries (TBs) and atomic steps (ASs) anchored on a carbon substrate (TS‐Pd/C) are directly synthesized by a solid‐state thermal shock (TS) strategy. Molecular dynamics simulation indicates that the transient super cooling procedure after the TS synthesis can boost the formation of TBs. Benefitting from the abundant TBs and ASs, these metastable Pd NPs can serve as an advanced electrocatalyst for the ethanol oxidation reaction (EOR) with superior reactivity, stability, and CO tolerance in alkaline solutions, which far exceeds that of commercial Pd/C. The first‐principles calculations suggest that the defect structure dominated by TBs can achieve the spatial separation of the optimal adsorption sites for CO and OH. The CO can concentrate at optimal surface sites to minimize the number of poisoned active sites. The strong adsorption of OH can accelerate the EOR process and jointly promote the improvement of electrocatalytic reactivity. [ABSTRACT FROM AUTHOR]

Owing to its unique atomic arrangement and electronic structure, metallic glass (MG) has been widely investigated in the field of energy storage and conversion. In the past few decades, multiple strategies have been developed to synthesize bulk and nanosized MG based materials. Here, combining the structure–activity relationship of MG with electrochemical reaction kinetics, the substantial progress of glass structures in electrocatalytic processes are highlighted, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, methanol oxidation reaction, carbon dioxide reduction reaction, and nitrogen fixation. Meanwhile, applications of MG materials in energy storage devices, like supercapacitors and lithium‐ion batteries, are also introduced in detail. Finally, challenges and possibilities for reasonable design of highly‐efficient MG‐based electrode materials are proposed. The integration of high‐throughput methods, artificial intelligence technology, as well as advanced characterization techniques is fundamental to screen materials with remarkable performance. This review aims to deepen the understanding of the relationship between electronic structure and electrochemical performance, providing guidance for rational design of functional MG materials with outstanding activity, selectivity, and durability. [ABSTRACT FROM AUTHOR]

Rational design of bifunctional efficient electrocatalysts for both oxygen reduction (ORR) and oxygen evolution reactions (OER) is desirable—while highly challenging—for development of rechargeable metal–air batteries. Herein, an efficient bifunctional electrocatalyst is designed and fabricated by encapsulating Co nanoparticles in interconnected N‐doped hollow porous carbon nanofibers (designated as Co@N‐C/PCNF) using an ultrafast high‐temperature shock technology. Benefiting from the synergistic effect and intrinsic activity of the CoNC moiety, as well as porous structure of carbon nanofibers, the Co@N‐C/PCNF composite shows high bifunctional electrocatalytic activities for both OER (289 mV at 10 mA cm−2) and ORR (half‐wave potential of 0.85 V). The CoNC moiety in the composite can modulate the local environmental and electrical structure of the catalysts, thus optimizing the adsorption/desorption kinetics and decreasing the reaction barriers for promoting the reversible oxygen electrocatalysis. Co@N‐C/PCNF‐based aqueous Zn–air batteries (AZAB) provide high power density of 292 mW cm−2, and the assembled flexible ZAB can power wearable devices. [ABSTRACT FROM AUTHOR]

Highly efficient electrocatalysts play an integral part in developing renewable energy conversion and storage technologies. Despite considerable efforts devoted to synthesizing electrocatalysts with superior performance, the identification of active moieties and understanding of reaction mechanisms under practical conditions still remain elusive. Herein, the substantial progresses in unraveling the local electronic and atomic structure optimizations of nanocatalysts for gas‐involved electrocatalysis, disclosing real active sites, and clarifying their relationships with intrinsic activities by combining advanced characterization techniques with computational simulations are summarized. The continuous development of in situ and ex situ characterization tools, particularly at multi‐scale resolution, to monitor or even directly observe the active center structure is systematically discussed, which is divided into four main categories based on the type of active sites: atomically dispersed active sites, vacancies, heteroatom doping sites, and edge sites. Current challenges and perspectives in both fundamental area and industrial application are finally proposed for the future research direction of next‐generation electrode materials. The aim of this review is to provide mechanistic insights into the real catalytically active structure with the assistance of newly developed characterization techniques, guiding the rational design and structure engineering of advanced functional materials with outstanding activity, selectivity, and durability. [ABSTRACT FROM AUTHOR]

Developing superior electrocatalysts for formic acid oxidation (FAO) is the most crucial step in commercializing direct formic acid fuel cells. Herein, we electrodeposited palladium membranes with periodically ordered mesoporosity obtained by asymmetrically replicating the bicontinuous cubic phase structure of a lyotropic liquid‐crystal template. The Pd membrane with the largest periodicity and highest degree of order delivered up to 90.5 m2 g−1 of electrochemical active surface area and 3.34 A mg−1 electrocatalysis capability towards FAO, 3.8 and 7.8 times the values of the commercial Pd/C catalyst, respectively. By controlling the temperature and potential of the electrodeposition procedure, the periodicity area and order degree of the mesoporosity are highly tunable. These Pd membranes gave prototype formic acid fueled cells with 4.3 and 2.4 times the maximum current and power density of the commercial Pd/C catalyst. [ABSTRACT FROM AUTHOR]

The size effect of transition‐metal nanoparticles on electrocatalytic performance remains ambiguous especially when decreasing the size to the atomic level. Herein, we report the spatial isolation of cobalt species on the atomic scale, which was achieved by tuning the zinc dopant content in predesigned bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo‐ZIFs), and led to the synthesis of nanoparticles, atomic clusters, and single atoms of Co catalysts on N‐doped porous carbon. This synthetic strategy allowed an investigation of the size effect on electrochemical behavior from nanometer to Ångström dimensions. Single‐atom Co catalysts showed superior bifunctional ORR/OER activity, durability, and reversibility in Zn–air batteries compared with the other derivatives and noble‐metal Pt/C+RuO2, which was attributed to the high reactivity and stability of isolated single Co atoms. Our findings open up a new avenue to regulate the metal particle size and catalytic performance of MOF derivatives. The spatial isolation of cobalt species on the atomic scale was achieved by tuning the zinc dopant content in predesigned bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo‐ZIFs), and enabled the generation of nanoparticles, atomic clusters, and single atoms of cobalt on N‐doped porous carbon. The single‐atom Co catalysts showed superior bifunctional ORR/OER activity, durability, and reversibility in Zn–air batteries. [ABSTRACT FROM AUTHOR]

Abstract: Tuning the catalytic active sites plays a crucial role in developing low cost and highly durable oxygen electrode catalysts with precious metal‐competitive activity. In an attempt to engineer the active sites in Co3O4 spinel for oxygen electrocatalysis in alkaline electrolyte, herein, controllable synthesis of surface‐tailored Co3O4 nanocrystals including nanocube (NC), nanotruncated octahedron (NTO), and nanopolyhedron (NP) anchored on nitrogen‐doped reduced graphene oxide (N‐rGO), through a facile and template‐free hydrothermal strategy, is provided. The as‐synthesized Co3O4 NC, NTO, and NP nanostructures are predominantly enclosed by {001}, {001} + {111}, and {112} crystal planes, which expose different surface atomic configurations of Co2+ and Co3+ active sites. Electrochemical results indicate that the unusual {112} plane enclosed Co3O4 NP on rGO with abundant Co3+ sites exhibit superior bifunctional activity for oxygen reduction and evolution reactions, as well as enhanced metal–air battery performance in comparison with other counterparts. Experimental and theoretical simulation studies demonstrate that the surface atomic arrangement of Co2+/Co3+ active sites, especially the existence of octahedrally coordinated Co3+ sites, optimizes the adsorption, activation, and desorption features of oxygen species. This work paves the way to obtain highly active, durable, and cost‐effective electrocatalysts for practical clean energy devices through regulating the surface atomic configuration and catalytic active sites. [ABSTRACT FROM AUTHOR]

Highlights from the article: Electrocatalysis: Mesoporous Decoration of Freestanding Palladium Nanotube Arrays Boosts the Electrocatalysis Capabilities toward Formic Acid and Formate Oxidation (Adv. Keywords: electrocatalysis; formate oxidation; formic acid oxidation; mesoporosity; Pd nanotube arrays Electrocatalysis, formate oxidation, formic acid oxidation, mesoporosity, Pd nanotube arrays.

Fabricating high‐performance electrocatalysts is the most critical step in commercializing direct formic acid or formate fuel cells. In this work, a dual‐template electrodeposition method is used to create freestanding mesoporosity decorated palladium nanotube arrays (P‐PdNTA) as a bifunctional electrocatalyst toward formic acid and formate oxidation (FAO/FOR). The phytantriol‐based soft template modifies the superficial chemistry of aluminum anodic oxide inner surfaces, thereby facilitating the regulated electrodeposition of highly stable palladium nanotubes. The sacrifice of the soft template generates substantial mesoporosity on the nanotubes, resulting in a 189% increase in the electrochemically active surface area with respect to the mesopore‐free PdNTA baseline. In addition, the soft template significantly increases the density of catalytically active sites per unit area via perturbation on routine nanotube growth, as evidenced by the doubled areal catalytic activity of P‐PdNTA versus PdNTA. Remarkably, the P‐PdNTA delivered gravimetric catalytic currents of 3.65 and 3.87 A mg−1 for FAO and FOR, which are 8.5 and 6.5 times higher, respectively, than those of commercial Pt/C. These values are among the most favorable reported and benefit from the unique synergy of fast substance transport, large electrochemical active surface area and high areal population of catalytically active sites. [ABSTRACT FROM AUTHOR]

The front cover artwork is provided by the group of Dr. Cheng Zhong, Tianjin University (Tianjin, China). The image shows the presence of a high density of catalytically active defect sites such as surface atomic steps on the flower-like Pt-based particles, as revealed by atomic-resolution spherical-aberration-corrected transmission electron microscopy. Read the full text of the Article at . [ABSTRACT FROM AUTHOR]