Water electrolysis is a promising source of hydrogen; however, technological challenges remain. Intensive efforts have focused on developing highly efficient and earth‐abundant electrocatalysts for ...water splitting. An effective strategy is proposed, using a bifunctional tubular cobalt perselenide nanosheet electrode, in which the sluggish oxygen evolution reaction is substituted with anodic hydrazine oxidation so as to assist energy‐efficient hydrogen production. Specifically, this electrode produces a current density of 10 mA cm−2 at −84 mV for hydrogen evolution and −17 mV for hydrazine oxidation in 1.0 m KOH and 0.5 m hydrazine electrolyte. An ultralow cell voltage of only 164 mV is required to generate a current density of 10 mA cm−2 for 14 hours of stable water electrolysis.
Sweet electrocatalytic synergy: An effective strategy for energy‐saving water electrolysis is presented. The sluggish oxygen evolution reaction is replaced by anodic hydrazine oxidation on a low‐cost and bifunctional cobalt perselenide electrode.
Hydrogen economy by water splitting is the indispensable cornerstone for sustainable energy yet it is impeded by sluggish anodic water oxidation. Hence, the rational design of highly efficient ...electrocatalysts for oxygen evolution is the key to unlocking its wider use. Herein, cobalt-iron selenide nanoframes are reported for the efficient water oxidation, which need only 270 mV overpotential to give a 10 mA cm
−2
current density and outperforms most cobalt-based catalysts, and even the benchmarked commercial ruthenium oxides (RuO
2
). More profoundly, iron doping regulates the local spin state of cobalt species, which further accelerates charge transfer and formation of oxygenated intermediates, and consequently contributes to the enhanced oxygen evolution. This work demonstrates a highly efficient oxygen evolution electrocatalyst and may pioneer a promising approach which involves tuning the local electronic structure to achieve the improved electrocatalysis activities in energy conversion technologies.
Tuning local spin state of Co centres by Fe doping in cobalt-iron selenides is effective for boosting oxygen evolution.
The electrocatalytic carbon dioxide reduction reaction (CO2RR) to value‐added chemical products is an effective strategy for both greenhouse effect mitigation and high‐density energy storage. ...However, controllable manipulation of the oxidation state and porous structure of Cu‐carbon based catalysts to achieve high selectivity and current density for a particular product remains very challenging. Herein, a strategy derived from Cu‐based metal‐organic frameworks (MOFs) for the synthesis of controllable oxidation states and porous structure of Cu‐carbon (Cu‐pC, Cu2O‐pC, and Cu2O/Cu‐pC) is demonstrated. By regulating oxygen partial pressure during the annealing process, the valence state of the Cu and mesoporous structures of surrounding carbon are changed, leads to the different selectivity of products. Cu2O/CuO‐pC with the higher oxidation state exhibits FEC2H4 of 65.12% and a partial current density of −578 mA cm−2, while the Cu2O‐pC shows the FECH4 over 55% and a partial current density exceeding −438 mA cm−2. Experimental and theoretical studies indicate that porous carbon‐coated Cu2O structures favor the CH4 pathway and inhibit the hydrogen evolution reaction. This work provides an effective strategy for exploring the influence of the various valence states of Cu and mesoporous carbon structures on the selectivity of CH4 and C2H4 products in CO2RR.
A controllable oxidation strategy derived from Cu‐based metal organic frameworks (MOFs) is introduced for the synthesis of controllable oxidation states and porous structure of Cu‐carbon (Cu‐pC, Cu2O‐pC, and Cu2O/Cu‐pC) for selective CO2 electroreduction. The Cu2O/CuO‐pC with the higher oxidation state exhibits FEC2H4 of 65.12% and the Cu2O‐pC shows the FECH4 over 55%.
High current density hydrogen evolution reaction (HER) in alkaline water electrolysis plays crucial role in renewable and sustainable energy systems, while posing a great challenge to the ...highly‐efficient electrocatalysts. Here, the synthesis of Ni/NiO@MoO3−x composite nanoarrays is reported by a moderate reduction strategy, combining Ni/NiO nanoparticles (≈20 nm) with amorphous MoO3−x nanoarrays. The Ni/NiO@MoO3−x composite nanoarrays possess enhanced hydrophilicity, optimize reaction energy barriers, accelerate reactant diffusion/bubble detachment, and therefore display an ultrahigh alkaline HER activity with a low η10 overpotential of 7 mV as well as Tafel slope of 34 mV dec−1. More significantly, the Ni/NiO@MoO3−x nanoarrays only demand low overpotentials of 75 and 112 mV to deliver 100 and 200 mA cm−2 hydrogen production current, and can steadily work at 100 mA cm−2 for 40 h, which is more efficient and stable than the Pt/C catalyst.
The synthesis of Ni/NiO@MoO3−x composite nanoarrays to accelerate reaction and diffusion kinetics for alkaline high current density hydrogen evolution reaction.
Hard carbons (HCs) with high sloping capacity are considered as the leading candidate anode for sodium‐ion batteries (SIBs); nevertheless, achieving basically complete slope‐dominated behavior with ...high rate capability is still a big challenge. Herein, the synthesis of mesoporous carbon nanospheres with highly disordered graphitic domains and MoC nanodots modification via a surface stretching strategy is reported. The MoOx surface coordination layer inhibits the graphitization process at high temperature, thus creating short and wide graphite domains. Meanwhile, the in situ formed MoC nanodots can greatly promote the conductivity of highly disordered carbon. Consequently, MoC@MCNs exhibit an outstanding rate capacity (125 mAh g−1 at 50 A g−1). The “adsorption‐filling” mechanism combined with excellent kinetics is also studied based on the short‐range graphitic domains to reveal the enhanced slope‐dominated capacity. The insight in this work encourages the design of HC anodes with dominated slope capacity toward high‐performance SIBs.
Mesoporous carbon nanospheres with highly disordered graphitic domains and MoC nanodots modification are developed via a surface stretching strategy. The MoOx surface coordination layer inhibits the graphitization process at high temperature, while the in situ formed MoC nanodots can greatly promote the conductivity of highly disordered carbon. Consequently, MoC@MCNs exhibit enhanced slope‐dominated capacity, as well as outstanding rate capability and cycle performance.
Water splitting is limited by the sluggish kinetics of anodic oxygen evolution, thus extensive studies have focused on developing highly efficient electrocatalysts for water oxidation. Nevertheless, ...replacing sluggish water oxidation with smart anodic reactions would greatly lower the overall cost of energy and the electrode by using earth-abundant electrocatalysts. Herein, a Ni3Se4 nanorod array is prepared by an in situ hydrothermal selenization method and demonstrates excellent activity for anodic reactions. Assisted by this versatile Ni3Se4 nanorod array, only 240 mV overpotential is required to drive 10 mA cm−2 of oxygen evolution current steadily. By substituting oxygen evolution with urea and hydrazine oxidation, the anodic potential can be reduced from 1.47 V to 1.38 V and even further to 0.32 V to afford 10 mA cm−2 anodic current density. Substituting anodic reactions coupled with the non-precious electrocatalyst demonstrated in the hybrid water electrolysis in this study has promising potential for future energy conversion, environmental treatment and valuable chemical upgrading.
The high‐current‐density Zn–air battery shows big prospects in next‐generation energy technologies, while sluggish O2 reaction and diffusion kinetics barricade the applications. Herein, the ...sequential assembly is innovatively demonstrated for hierarchically mesoporous molybdenum carbides/carbon microspheres with a tunable thickness of mesoporous carbon layers (Meso‐Mo2C/C‐x, where x represents the thickness). The optimum Meso‐Mo2C/C‐14 composites (≈2 µm in diameter) are composed of mesoporous nanosheets (≈38 nm in thickness), which possess bilateral mesoporous carbon layers (≈14 nm in thickness), inner Mo2C/C layers (≈8 nm in thickness) with orthorhombic Mo2C nanoparticles (≈2 nm in diameter), a high surface area of ≈426 m2 g−1, and open mesopores (≈6.9 nm in size). Experiments and calculations corroborate the hierarchically mesoporous Mo2C/C can enhance hydrophilicity for supplying sufficient O2, accelerate oxygen reduction kinetics by highly‐active Mo2C and N‐doped carbon sites, and facilitate O2 diffusion kinetics over hierarchically mesopores. Therefore, Meso‐Mo2C/C‐14 outputs a high half‐wave potential (0.88 V vs RHE) with a low Tafel slope (51 mV dec−1) for oxygen reduction. More significantly, the Zn–air battery delivers an ultrahigh power density (272 mW cm−2), and an unprecedented 100 h stability at a high‐current‐density condition (100 mA cm−2), which is one of the best performances.
The hierarchically mesoporous Mo2C/C microspheres synthesized by the novel sequential assembly strategy are composed of mesoporous Mo2C/C nanosheets with a tunable thickness of mesoporous carbon layers. Besides, the hierarchically mesoporous structure can accelerate the oxygen reduction reaction and oxygen diffusion kinetics toward high‐current‐density Zn–air battery, which outperforms Pt/C and other electrocatalysts.
Exploring efficient and earth-abundant bifunctional electrocatalysts for overall water splitting is of paramount significance for clean and sustainable hydrogen energy generation. In this work, ...amorphous Co–Ni–B–O nanosheets (CNBO-NSs) are synthesized by the chemical reduction of bimetallic Prussian blue analogues (Co–Ni PBAs) using sodium borohydride. The as-prepared CNBO-NSs exhibit excellent electrochemical catalytic activity and stability. They can steadily afford 10 mA cm
−2
current density at overpotentials of 140 mV for hydrogen evolution and 300 mV for oxygen evolution during 24 h operation. The formation of a metal–boron bond and the improved surface area along with the enhanced conductivity in the resultant CNBO-NS structures are factors responsible for the enhanced catalytic activities. This work could offer new clues for the utilization of metal–organic frameworks for designing functional nanomaterials, and more importantly valuable insights into crystallinity engineering in efficient electrolysis for energy conversion and beyond.
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•Nickel-doped α-MnO2 was prepared via a novel ethylene glycol reduction strategy.•Ni-MnO2 showed excellent low-temperature performance for toluene combustion.•Synergistic effect of Mn ...and Ni was related to the enhanced catalytic properties.•Ni doping significantly improved the toluene adsorption on the α-MnO2 catalyst.
A series of metal-doped α-MnO2 catalysts (M-MnO2, M = Ni, Cu, Co) were synthesized via a novel ethylene glycol (EG) reduction strategy for the first time, based on initial reduction of KMnO4 with EG and subsequent heteroatom doping at room temperature, and used for catalytic toluene combustion. The obtained catalysts have been full characterized by XRD, XRF, N2 adsorption, SEM, TEM, XPS, H2-TPR, O2-TPD, and C7H8-TPSR. It was found that the catalytic properties of α-MnO2 can be significantly improved by nickel doping, a remarkable low-temperature performance (T90 = 199 °C) has been achieved over Ni-MnO2 catalyst, which is among the best reported values. Meanwhile, Ni-MnO2 has also exhibited high catalytic stability with strong water tolerance (5 vol%) in the oxidation of toluene. Herein, the relationship between catalyst structure and catalytic activity has been elucidated. The outstanding catalytic properties can be related to the synergistic effect between Mn and doped Ni species for the adsorption and activation of toluene. Significantly, the substitutional doping of Ni2+ into octahedra MnO6 frameworks could not only improve the redox properties, lattice oxygen mobility and the formation of more active lattice oxygen, but also promote the toluene adsorption. Additionally, a potential catalytic reaction process base on the Mars and van Krevelen mechanism was also proposed. Hence, this work paves a new way for the design and synthesis of high efficient catalysts for the elimination of volatile organic compounds.
Hydrogen production via water electrolysis is promising but impeded by sluggish cathodic and anodic reactions. Consequently, highly-efficient and earth-abundant electrocatalysts are attracting ...considerable attention. Herein we report a bifunctional NiMo alloy nanotube for efficient hydrogen production coupled with anodic urea oxidation in a hybrid water electrolysis system. Specifically, ultralow potentials of −44 mV and 1.36 V (vs. RHE) are required to deliver 10 mA cm−2 current density for cathodic and anodic reactions, respectively. Density functional theory (DFT) calculation results show the Mo center is the main reaction site for the chemisorption and OH bond cleavage of H2O while Ni center is identified as the hydrogen-evolving site. Based on this bifunctional NiMo electrocatalyst, a hybrid water electrolysis cell is proposed and the overall cell voltage of ∼1.43 V is achieved for outputting 10 mA cm−2 current density during the 10 h operation. The understandings in alternative electrode reactions coupled with highly-efficient and earth-abundant electrocatalysts for hybrid water electrolysis in this work holds encouraging potential in future energy conversion technologies and urea-related water treatments.
Nickel-molybdenum nanotube demonstrates the bifunctional and excellent electrocatalytic activity in the hybrid water electrolysis for energy-efficient and cost-effective hydrogen production assisting by anodic urea oxidation. Display omitted
•we report a bifunctional NiMo alloy nanotube for efficient hydrogen production coupled with anodic urea oxidation.•The Mo center is main reaction site for chemisorption and OH bond cleavage of H2O, while the Ni center is identified as the hydrogen-evolving site.•A hybrid water electrolysis cell with a voltage of 1.43 V is achieved for steadily outputting 10 mA cm−2 current density of hydrogen production.
