Hybrid materials composed of transition‐metal compounds and nitrogen‐doped carbonaceous supports are promising electrocatalysts for various electrochemical energy conversion devices, whose activity ...enhancements can be attributed to the synergistic effect between metallic sites and N dopants. While the functionality of single‐metal catalysts is relatively well‐understood, the mechanism and synergy of bimetallic systems are less explored. Herein, the design and fabrication of an integrated flexible electrode based on NiCo2S4/graphitic carbon nitride/carbon nanotube (NiCo2S4@g‐C3N4‐CNT) are reported. Comparative studies evidence the electronic transfer from bimetallic Ni/Co active sites to abundant pyridinic‐N in underlying g‐C3N4 and the synergistic effect with coupled conductive CNTs for promoting reversible oxygen electrocatalysis. Theoretical calculations demonstrate the unique coactivation of bimetallic Ni/Co atoms by pyridinic‐N species (a Ni, Co–N2 moiety), which simultaneously downshifts their d‐band center positions and benefits the adsorption/desorption features of oxygen intermediates, accelerating the reaction kinetics. The optimized NiCo2S4@g‐C3N4‐CNT hybrid manifests outstanding bifunctional performance for catalyzing oxygen reduction/evolution reactions, highly efficient for realistic zinc–air batteries featuring low overpotential, high efficiency, and long durability, superior to those of physical mixed counterparts and state‐of‐the‐art noble metal catalysts. The identified bimetallic coactivation mechanism will shed light on the rational design and interfacial engineering of hybrid nanomaterials for diverse applications.
A novel free‐standing NiCo2S4/graphitic carbon nitride (g‐C3N4)/carbon nanotubes (CNTs) hybrid electrode is developed by combining a hydrothermal approach and vacuum filtration. Experimental and theoretical investigations demonstrate the coactivation of bimetallic Co and Ni sites by abundant pyridinic‐N in g‐C3N4 and the synergistic effect with coupled conductive CNTs contributes to substantially enhanced oxygen electrocatalytic activities and discharge/charge behaviors in Zn–air batteries.
Designing high‐performance and low‐cost electrocatalysts is crucial for the electrochemical production of hydrogen. Dislocation‐strained IrNi nanoparticles loaded on a carbon nanotube sponge ...(DSIrNi@CNTS) driven by unsteady thermal shock in an extreme environment are reported here as a highly efficient hydrogen evolution reaction (HER) catalyst. Experimental results demonstrate that numerous dislocations are kinetically trapped in self‐assembled IrNi nanoparticles due to the ultrafast quenching and different atomic radii, which can induce strain effects into the IrNi nanoparticles. Such strain‐induced high‐energy surface structures arising from bulk defects (dislocations), are more likely to be resistant to surface restructuring during catalysis. The catalyst exhibits outstanding HER activity with only 17 mV overpotential to achieve 10 mA cm−2 in an alkaline electrolyte with fabulous stability, exceeding state‐of‐the‐art Pt/C catalysts. These density functional theory results demonstrate that the electronic structure of as‐synthesized IrNi nanostructure can be optimized by the strain effects induced by the dislocations, and the free energy of HER can be tuned toward the optimal region.
Dislocation‐strained IrNi nanoparticles with competitive HER activity are realized by unsteady thermal shock progress in an extreme environment, and they are uniformly distributed within a carbon nanotube sponge (DSIrNi@CNTS). Numerous dislocations are generated in self‐assembled IrNi nanoparticles due to ultrafast quenching, inducing strain effects into the IrNi nanoparticles, which optimize the electronic structure of the active sites.
It remains an ongoing challenge to develop cheap, highly active, and stable electrocatalysts to promote the sluggish electrocatalytic oxygen evolution, oxygen reduction, and hydrogen evolution ...reactions for rechargeable metal–air batteries and water-splitting systems. In this work, we report the morphology-controllable synthesis of zinc cobalt mixed sulfide (Zn–Co–S) nanoarchitectures, including nanosheets, nanoplates, and nanoneedles, grown on conductive carbon fiber paper (CFP) and the micronanostructure dependent electrochemical efficacy for catalyzing hydrogen and oxygen in zinc-air batteries and water electrolysis. The formation of different Zn–Co–S morphologies was attributed to the synergistic effect of decomposed urea products and the corrosion of NH4F. Among synthesized Zn–Co–S nanostructures, the nanoneedle arrays supported on CFP exhibit superior trifunctional activity for oxygen reduction, oxygen evolution, and hydrogen evolution reactions than its nanosheet and nanoplate counterparts through half reaction testing. It also exhibited better catalytic durability than Pt/C and RuO2. Furthermore, the Zn–Co–S nanoneedle/CFP electrode enables rechargeable Zn-air batteries with low overpotential (0.85 V), high efficiency (58.1%), and long cycling lifetimes (200 cycles) at 10 mA cm–2 as well as considerable performance for water splitting. The superior performance is contributed to the integrated nanoneedle/CFP nanostructure, which not only provides enhanced electrochemical active area, but also facilitates ion and gas transfer between the catalyst surface and electrolyte, thus maintaining an effective solid–liquid–gas interface necessary for electrocatalysis. These results indicate that the Zn–Co–S nanoneedle/CFP system is a low cost, highly active, and durable electrode for highly efficient rechargeable zinc–air batteries and water electrolysis in alkaline solution.
Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction (OER) and the impairment ...of chlorine electrochemistry at anode. Herein, we report a heterostructure of Ni
3
S
2
nanoarray with secondary Fe-Ni(OH)
2
lamellar edges that exposes abundant active sites towards seawater oxidation. The resultant Fe-Ni(OH)
2
/Ni
3
S
2
nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater. It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm
−2
and the Tafel slope is as low as 46 mV·dec
−1
. The 27-hour chronopotentiometry operated at high current density of 100 mA·cm
−2
shows negligible deterioration, suggesting good stability of the Fe·Ni(OH)
2
/Ni
3
S
2
@NF electrode. Faraday efficiency for oxygen evolution is up to ∼ 95%, revealing decent selectivity of the catalyst in saline water. Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites. The density functional theory (DFT) calculations indicate that the OER has lower theoretical overpotential than Cl
2
evolution reaction in Fe sites, which is contrary to that of Ni sites. The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.
Directly harvesting solar energy for battery charging represents an ultimate solution toward low-cost, green, efficient and sustainable electrochemical energy storage. Here, we design a sunlight ...promotion strategy into rechargeable zinc-air battery with significantly reduced charging potential below the theoretical cell voltage of zinc-air batteries. The sunlight-promoted zinc-air battery using BiVO
or α-Fe
O
air photoelectrode achieves a record-low charge potential of ~1.20 and ~1.43 V, respectively, under illumination, which is lowered by ~0.5-0.8 V compared to the typical charge voltage of ~2 V in conventional zinc-air battery. The band structure and photoelectrochemical stability of photoelectrodes are found to be key factors determining the charging performance of sunlight-promoted zinc-air batteries. The introduction of photoelectrode as an air electrode opens a facile way for developing integrated single-unit zinc-air batteries that can efficiently use solar energy to overcome the high charging overpotential of conventional zinc-air batteries.
Grid-level large-scale electrical energy storage (GLEES) is an essential approach for balancing the supply–demand of electricity generation, distribution, and usage. Compared with conventional energy ...storage methods, battery technologies are desirable energy storage devices for GLEES due to their easy modularization, rapid response, flexible installation, and short construction cycles. In general, battery energy storage technologies are expected to meet the requirements of GLEES such as peak shaving and load leveling, voltage and frequency regulation, and emergency response, which are highlighted in this perspective. Furthermore, several types of battery technologies, including lead–acid, nickel–cadmium, nickel–metal hydride, sodium–sulfur, lithium-ion, and flow batteries, are discussed in detail for the application of GLEES. Moreover, some possible developing directions to facilitate efforts in this area are presented to establish a perspective on battery technology, provide a road map for guiding future studies, and promote the commercial application of batteries for GLEES.
Cu2O is a typical photoelectrocatalyst for sustainable hydrogen production, while the fast charge recombination hinders its further development. Herein, Ni2+ cations have been doped into a Cu2O ...lattice (named as Ni‐Cu2O) by a simple hydrothermal method and act as electron traps. Theoretical results predict that the Ni dopants produce an acceptor impurity level and lower the energy barrier of hydrogen evolution. Photoelectrochemical (PEC) measurements demonstrate that Ni‐Cu2O exhibits a photocurrent density of 0.83 mA cm−2, which is 1.34 times higher than that of Cu2O. And the photostability has been enhanced by 7.81 times. Moreover, characterizations confirm the enhanced light‐harvesting, facilitated charge separation and transfer, prolonged charge lifetime, and increased carrier concentration of Ni‐Cu2O. This work provides deep insight into how acceptor‐doping modifies the electronic structure and optimizes the PEC process.
Taking charge: A nickel (Ni) electron acceptor has been successfully doped into a Cu2O lattice without forming impurity phases. Both theoretical and experimental results demonstrate that Ni dopants attract electrons from neighboring atoms, therefore facilitating charge separation and transfer. Consequently, the obtained Ni‐Cu2O exhibits a significantly enhanced photoelectrochemical performance.
Cobalt-based nanomaterials have been widely studied as catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to their remarkable bifunctional catalytic activity, ...low cost, and easy availability. However, controversial results concerning OER/ORR performance exist between different types of cobalt-based catalysts, especially for Co(OH)2 and Co3O4. To address this issue, we develop a facile electrochemical deposition method to grow Co(OH)2 directly on the skeleton of carbon cloth, and further Co3O4 was obtained by post thermal treatment. The entire synthesis strategy removes the use of any binders and also avoids the additional preparation process (e.g., transfer and slurry coating) of final electrodes. This leads to a true comparison of the ORR/OER catalytic performance between Co(OH)2 and Co3O4, eliminating uncertainties arising from the electrode preparation procedures. The surface morphologies, microstructures, and electrochemical behaviors of prepared Co(OH)2 and Co3O4 catalysts were systemically investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and electrochemical characterization methods. The results revealed that the electrochemically deposited Co(OH)2 was in the form of vertically aligned nanosheets with average thickness of about 4.5 nm. After the thermal treatment in an air atmosphere, Co(OH)2 nanosheets were converted into mesoporous Co3O4 nanosheets with remarkably increased electrochemical active surface area (ECSA). Although the ORR/OER activity normalized by the geometric surface area of mesoporous Co3O4 nanosheets is higher than that of Co(OH)2 nanosheets, the performance normalized by the ECSA of the former is lower than that of the latter. Considering the superior apparent overall activity and durability, the Co3O4 catalyst has been further evaluated by integrating it into a Zn–air battery prototype. The Co3O4 nanosheets in situ supported on carbon cloth cathode enable the assembled Zn–air cells with large peak power density of 106.6 mW cm–2, low charge and discharge overpotentials (0.67 V), high discharge rate capability (1.18 V at 20 mA cm–2), and long cycling stability (400 cycles), which are comparable or even superior to the mixture of state-of-the-art Pt/C and RuO2 cathode.
It remains challenging to develop economical and bifunctional electrocatalysts toward oxygen/hydrogen evolution reactions (OER/HER). Herein, we construct Co
9
S
8
nanoflakes decorated Co
3
O
4
...nanoarrays with enriched heterogeneous interface zones on Ni foam (Co
9
S
8
@Co
3
O
4
/NF) via a novel step-wise approach. The Co
9
S
8
@Co
3
O
4
/NF hybrid manifests excellent performance with low overpotentials of 130 mV for HER (10 mA·cm
−2
) and 331 mV for OER (100 mA·cm
−2
), delivering a small voltage of 1.52 V for water splitting at 10 mA·cm
−2
as well as outstanding catalytic durability, which surpasses precious metals and previously reported earth-abundant nanocatalysts. Further experimental and theoretical investigations demonstrate that the excellent performance is attributed to the followings: (i) Highly conductive Ni facilitates the efficient charge transfer; (ii) porous core-shell nanoarchitecture benefits the infiltration and transportation of gases/ions; (iii) heterogeneous interface zones synergistically lower the chemisorption energy of hydrogen/oxygen intermediates. This work will shed light on the controllable synthesis and engineering of heterostructure nanomaterials for clean energy storage and conversion technologies.
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