Designing a highly active electrocatalyst with optimal stability at low cost is must and non-negotiable if large-scale implementations of fuel cells are to be fully realized. Zeolitic-imidazolate frameworks (ZIFs) offer rich platforms to design multifunctional materials due to their flexibility and ultrahigh surface area. Herein, an advanced Co-N x /C nanorod array derived from 3D ZIF nanocrystals with superior electrocatalytic activity and stability toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) compared to commercial Pt/C and IrO 2 , respectively, is synthesized. Remarkably, as a bifunctional catalyst (E j = 10 (OER) − E 1/2 (ORR) ≈ 0.65 V), it further displays high performance of Zn-air batteries with high cycling stability even at a high current density. Such supercatalytic properties are largely attributed to the synergistic effect of the chemical composition, high surface area, and abundant active sites of the nanorods. The activity origin is clarified through post oxygen reduction X-ray photoelectron spectroscopy analysis and density functional theory studies. Undoubtedly, this approach opens a new avenue to strategically design highly active and performance-oriented electrocatalytic materials for wider electrochemical energy applications.
Replacement of noble‐metal platinum catalysts with cheaper, operationally stable, and highly efficient electrocatalysts holds huge potential for large‐scale implementation of clean energy devices. Metal–organic frameworks (MOFs) and metal dichalcogenides (MDs) offer rich platforms for design of highly active electrocatalysts owing to their flexibility, ultrahigh surface area, hierarchical pore structures, and high catalytic activity. Herein, an advanced electrocatalyst based on a vertically aligned MoS2 nanosheet encapsulated Mo–N/C framework with interfacial Mo–N coupling centers is reported. The hybrid structure exhibits robust multifunctional electrocatalytic activity and stability toward the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. Interestingly, it further displays high‐performance of Zn–air batteries as a cathode electrocatalyst with a high power density of ≈196.4 mW cm−2 and a voltaic efficiency of ≈63 % at 5 mA cm−2, as well as excellent cycling stability even after 48 h at 25 mA cm−2. Such outstanding electrocatalytic properties stem from the synergistic effect of the distinct chemical composition, the unique three‐phase active sites, and the hierarchical pore framework for fast mass transport. This work is expected to inspire the design of advanced and performance‐oriented MOF/MD hybrid‐based electrocatalysts for wider application in electrochemical energy devices.
Highly active, stable, and cheap Pt-free catalysts for the hydrogen evolution reaction (HER) are under increasing demand for future energy conversion systems. However, developing HER electrocatalysts with Pt-like activity that can function at all pH values still remains as a great challenge. Herein, based on our theoretical predictions, we design and synthesize a novel N,P dual-doped carbon-encapsulated ruthenium diphosphide (RuP @NPC) nanoparticle electrocatalyst for HER. Electrochemical tests reveal that, compared with the Pt/C catalyst, RuP @NPC not only has Pt-like HER activity with small overpotentials at 10 mA cm (38 mV in 0.5 m H SO , 57 mV in 1.0 m PBS and 52 mV in 1.0 m KOH), but demonstrates superior stability at all pH values, as well as 100 % Faradaic yields. Therefore, this work adds to the growing family of transition-metal phosphides/heteroatom-doped carbon heterostructures with advanced performance in HER.
Structural and compositional engineering of atomic-scaled metal-N-C catalysts is important yet challenging in boosting their performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Here, boron (B)-doped Co-N-C active sites confined in hierarchical porous carbon sheets (denoted as Co-N,B-CSs) were obtained by a soft template self-assembly pyrolysis method. Significantly, the introduced B element gives an electron-deficient site that can activate the electron transfer around the Co-N-C sites, strengthen the interaction with oxygenated species, and thus accelerate reaction kinetics in the 4e processed ORR and OER. As a result, the catalyst showed Pt-like ORR performance with a half-wave potential (E) of 0.83 V versus (vs) RHE, a limiting current density of about 5.66 mA cm, and higher durability (almost no decay after 5000 cycles) than Pt/C catalysts. Moreover, a rechargeable Zn-air battery device comprising this Co-N,B-CSs catalyst shows superior performance with an open-circuit potential of ∼1.4 V, a peak power density of ∼100.4 mW cm, as well as excellent durability (128 cycles for 14 h of operation). DFT calculations further demonstrated that the coupling of Co-N active sites with B atoms prefers to adsorb an O molecule in side-on mode and accelerates ORR kinetics.
A series of noble metal diphosphides (IrP2@NC, RhP2@NC and Pd5P2@NC) have been designed and fabricated, and among which IrP2@NC exhibits ultrahigh hydrogen evolution reaction performance.
Here first a 2D dual-metal (Co/Zn) and leaf-like zeolitic imidazolate framework (ZIF-L)-pyrolysis approach is reported for the low-cost and facile preparation of Co nanoparticles encapsulated into nitrogen-doped carbon nanotubes (Co-N-CNTs). Importantly, the reasonable Co/Zn molar ratio in the ZIF-L is the key to the emergence of the encapsulated microstructure. Specifically, high-dispersed cobalt nanoparticles are fully encapsulated in the tips of N-CNTs, leading to the full formation of highly active Co-N-C moieties for oxygen reduction and evolution reactions (ORR and OER). As a result, the obtained Co-N-CNTs present superior electrocatalytic activity and stability toward ORR and OER over the commercial Pt/C and IrO 2 as well as most reported metal-organic-framework-derived catalysts, respectively. Remarkably, as bifunctional air electrodes of the Zn-air battery, it also shows extraordinary charge-discharge performance. The present concept will provide a guideline for screening novel 2D metal-organic frameworks as precursors to synthesize advanced multifunctional nanomaterials for cross-cutting applications.
Theoretical calculations reveal that intrinsic pentagons in the basal plane can contribute to the local electronic redistribution and the contraction of band gap, making the carbon matrix possess superior binding affinity and electrochemical reactivity. To experimentally verify this, a pentagon‐defect‐rich carbon nanomaterial was constructed by means of in situ etching of fullerene molecules (C60). The electrochemical tests show that, relative to hexagons, such a carbon‐based material with abundant intrinsic pentagon defects makes much greater contribution to the electrocatalytic oxygen reduction activity and electric double layer capacitance. It shows a four‐electron‐reaction mechanism similar to commercial Pt/C and other transition‐metal‐based catalysts, and a higher specific capacitance than many reported metal‐free carbon materials. These results show the influence of intrinsic pentagon defects for developing carbon‐based nanomaterials toward energy conversion and storage devices.
Developing highly efficient and stable electrocatalysts plays an important role in energy-related electrocatalysis fields. Transition-metal phosphides (TMPs) possess a series of advantages, such as high conductivity, earthabundance reserves, and good physicochemical properties, therefore arousing wide attention. In this review, the electrochemical activity origin of TMPs, allowing the rational design and construction of phosphides toward various energy-relevant reactions is first discussed. Subsequently, their unique energy-related electrocatalysis nature toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO 2 RR), nitrogen reduction reaction (NRR), urea oxidation reaction (UOR), methanol oxidation reaction (MOR), and others is highlighted. Then, the TMPs' synthetic strategies are analyzed and summarized systematically. Finally, the existing key issues, countermeasures, and the future challenges of TMPs toward efficient energy-related electrocatalysis are briefly discussed.
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