ZnCo2O4 quantum dots anchored on nitrogen‐doped carbon nanotubes (N‐CNT) retain the high catalytic activity of ZnCo2O4 to oxidize water while enabling an efficient oxygen reduction performance ...thereby combining these desirable features. These advantages realize a bifunctional catalytic activity for ZnCo2O4/N‐CNT that can be used in rechargeable zinc–air batteries.
Photocatalytic hydrogen production is crucial for solar‐to‐chemical conversion process, wherein high‐efficiency photocatalysts lie in the heart of this area. A photocatalyst of hierarchically ...mesoporous titanium phosphonate based metal–organic frameworks, featuring well‐structured spheres, a periodic mesostructure, and large secondary mesoporosity, are rationally designed with the complex of polyelectrolyte and cathodic surfactant serving as the template. The well‐structured hierarchical porosity and homogeneously incorporated phosphonate groups can favor the mass transfer and strong optical absorption during the photocatalytic reactions. Correspondingly, the titanium phosphonates exhibit significantly improved photocatalytic hydrogen evolution rate along with impressive stability. This work can provide more insights into designing advanced photocatalysts for energy conversion and render a tunable platform in photoelectrochemistry.
A multi‐structured photocatalyst: A metal–organic framework (MOF) nanostructure synthesized by a surfactant‐directed strategy features a stable framework of titanium phosphates, a well‐defined sphere, and hierarchical nanopores. These features ensure competitive photoactivity in evolving hydrogen under both visible light and full‐spectrum simulator irradiation, along with high durability.
A new class of highly efficient oxygen evolution catalysts has been synthesized through the self‐assembly of graphitic carbon nitride nanosheets and carbon nanotubes, driven by π–π stacking and ...electrostatic interactions. Remarkably, the catalysts exhibit higher catalytic oxygen evolution activity and stronger durability than Ir‐based noble‐metal catalysts and display the best performance among the reported nonmetal catalysts. This good result is attributed to the high nitrogen content and the efficient mass and charge transfer in the porous three‐dimensional nanostructure.
Combining C and N to make O: 3D porous graphitic carbon nitride nanosheet–carbon nanotube composites have been synthesized through a spontaneous assembly process. The high nitrogen content, enhanced electron conductivity, and improved mass transport result in excellent catalytic oxygen evolution activity and strong durability, superior to those reported for other nonmetal catalysts and noble‐metal catalysts (see figure; OER: oxygen evolution reaction).
Abstract
Scalable and sustainable solar hydrogen production through photocatalytic water splitting requires highly active and stable earth-abundant co-catalysts to replace expensive and rare ...platinum. Here we employ density functional theory calculations to direct atomic-level exploration, design and fabrication of a MXene material, Ti
3
C
2
nanoparticles, as a highly efficient co-catalyst. Ti
3
C
2
nanoparticles are rationally integrated with cadmium sulfide via a hydrothermal strategy to induce a super high visible-light photocatalytic hydrogen production activity of 14,342 μmol h
−1
g
−1
and an apparent quantum efficiency of 40.1% at 420 nm. This high performance arises from the favourable Fermi level position, electrical conductivity and hydrogen evolution capacity of Ti
3
C
2
nanoparticles. Furthermore, Ti
3
C
2
nanoparticles also serve as an efficient co-catalyst on ZnS or Zn
x
Cd
1−
x
S. This work demonstrates the potential of earth-abundant MXene family materials to construct numerous high performance and low-cost photocatalysts/photoelectrodes.
Rational design and exploration of robust and low‐cost bifunctional oxygen reduction/evolution electrocatalysts are greatly desired for metal–air batteries. Herein, a novel high‐performance oxygen ...electrode catalyst is developed based on bimetal FeCo nanoparticles encapsulated in in situ grown nitrogen‐doped graphitic carbon nanotubes with bamboo‐like structure. The obtained catalyst exhibits a positive half‐wave potential of 0.92 V (vs the reversible hydrogen electrode, RHE) for oxygen reduction reaction, and a low operating potential of 1.73 V to achieve a 10 mA cm−2 current density for oxygen evolution reaction. The reversible oxygen electrode index is 0.81 V, surpassing that of most highly active bifunctional catalysts reported to date. By combining experimental and simulation studies, a strong synergetic coupling between FeCo alloy and N‐doped carbon nanotubes is proposed in producing a favorable local coordination environment and electronic structure, which affords the pyridinic N‐rich catalyst surface promoting the reversible oxygen reactions. Impressively, the assembled zinc–air batteries using liquid electrolytes and the all‐solid‐state batteries with the synthesized bifunctional catalyst as the air electrode demonstrate superior charging–discharging performance, long lifetime, and high flexibility, holding great potential in practical implementation of new‐generation powerful rechargeable batteries with portable or even wearable characteristic.
Bamboo‐like FeCo alloy encapsulated in nitrogen‐doped carbon nanotubes exhibits superior catalytic oxygen reduction and oxygen evolution performance than that of noble metal benchmarks, which benefits from the nitrogen‐rich and defect‐rich catalyst surface. The all‐solid‐state zinc–air batteries equipped by the synthesized materials show low charging/discharging overpotentials, long lifetime, and high flexibility, suitable for practical application.
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.
An unusual {112} facet enclosed Co3O4 nanopolyhedron supported on N‐doped graphene exhibits superior oxygen reduction reaction/oxygen evolution reaction bifunctional and Zn–air battery performance than those of {100} and {100} + {111} surrounded Co3O4 nanocubes and nanotruncated octahedron owning to the unique surface atomic configuration of Co2+/Co3+ active sites, which favors the adsorption, activation of oxygen species, and the kinetics of O22−/OH− displacement.
In spite of recent advances in the synthesis of hollow micro/nanostructures, the fabrication of three‐dimensional electrodes on the basis of these structures remains a major challenge. Herein, we ...develop an electrochemical sacrificial‐template strategy to fabricate hollow Co3O4 microtube arrays with hierarchical porosity. The resultant unique structures and integrated electrode configurations impart enhanced mass transfer and electron mobility, ensuring high activity and stability in catalyzing oxygen and hydrogen evolution reactions. Impressively, the apparent performance can rival that of state‐of‐the‐art noble‐metal and transition‐metal electrocatalysts. Furthermore, this bifunctional electrode can be used for highly efficient overall water splitting, even competing with the integrated performance of Pt/C and IrO2/C.
Hollow and hierarchical: An electrochemical self‐templating strategy was developed for the fabrication of hollow Co3O4 microtube arrays with hierarchical porosity. The resultant structures showed excellent electrocatalytic activity and durability towards oxygen and hydrogen evolution and are thus capable of catalyzing full water splitting.
Atomically and electronically coupled Pt and CoO hybrid nanocatalysts are fabricated for electrocatalytic oxygen reduction reaction. The atomic coupling between the Pt and the CoO endows precise ...control of the atomic interface between the Pt and the CoO, which directly results in electron donation from the CoO to the Pt, and thus favorable tuning of the electronic structure of the Pt.
Free‐standing flexible films, constructed from two‐dimensional graphitic carbon nitride and titanium carbide (with MXene phase) nanosheets, display outstanding activity and stability in catalyzing ...the oxygen‐evolution reaction in alkaline aqueous system, which originates from the Ti–Nx motifs acting as electroactive sites, and the hierarchically porous structure with highly hydrophilic surface. With this excellent electrocatalytic ability, comparable to that of the state‐of‐the‐art precious‐/transition‐metal catalysts and superior to that of most free‐standing films reported to date, they are directly used as efficient cathodes in rechargeable zinc–air batteries. Our findings reveal that the rational interaction between different two‐dimensional materials can remarkably promote the oxygen electrochemistry, thus boosting the entire clean energy system.
A fascinating catalyst structure: Free‐standing flexible films composed of strongly coupled carbon nitride and titanium carbide nanosheets through Ti–Nx interactions (see picture) exhibited outstanding electrocatalytic activity and stability towards the oxygen‐evolution reaction (OER). The films could be directly used as efficient cathodes in rechargeable Zn–air batteries.
Flexible non‐metal oxygen electrodes fabricated from phosphorus‐doped graphitic carbon nitride nano‐flowers directly grown on carbon‐fiber paper exhibit high activity and stability in reversibly ...catalyzing oxygen reduction and evolution reactions, which is a result of N, P dual action, enhanced mass/charge transfer, and high active surface area. The performance is comparable to that of the state‐of‐the‐art transition‐metal, noble‐metal, and non‐metal catalysts. Remarkably, the flexible nature of these oxygen electrodes allows their use in folded and rolled‐up forms, and directly as cathodes in Zn–air batteries, featuring low charge/discharge overpotential and long lifetime.
Electrodes, on a roll: Flexible and reversible oxygen electrodes composed of nanostructured P‐doped graphitic carbon nitrides grown on carbon‐fiber paper exhibit outstanding catalytic activity and stability towards both oxygen reduction (ORR) and oxygen evolution reactions (OER) in different folded and rolled‐up forms. They can be used as efficient air cathodes in Zn–air batteries.
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