Development of a non-noble-metal hydrogen-producing catalyst is essential to the development of solar water-splitting devices. Improving both the activity and the stability of the catalyst remains a ...key challenge. In this Communication, we describe a two-step reaction for preparing three-dimensional electrodes composed of CoSe2 nanoparticles grown on carbon fiber paper. The electrode exhibits excellent catalytic activity for a hydrogen evolution reaction in an acidic electrolyte (100 mA/cm2 at an overpotential of ∼180 mV). Stability tests though long-term potential cycles and extended electrolysis confirm the exceptional durability of the catalyst. This development offers an attractive catalyst material for large-scale water-splitting technology.
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A micro‐/nanostructured “superaerophilic” electrode constructed by direct growth of cobalt‐incorporated and nitrogen‐doped carbon‐nanotube arrays with subsequent hydrophobic modification is ...demonstrated for a high‐performance oxygen‐reduction‐reaction electrode, superior to the Pt/C–air electrode. This high performance is attributed to the simultaneously accelerated gas‐diffusion and electron‐transport processes induced by the unique structural advantages.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Layered double hydroxides (LDHs) are a family of layer materials that receive heightened attention. Herein a ternary NiFeMn-LDH is investigated with superior oxygen evolution activity, which is ...attributed to the Mn(4+) doping in the intralayer, which modifies the electronic structure and improves the conductivity of the electrocatalyst.
Tungsten carbide is one of the most promising electrocatalysts for the hydrogen evolution reaction, although it exhibits sluggish kinetics due to a strong tungsten-hydrogen bond. In addition, ...tungsten carbide's catalytic activity toward the oxygen evolution reaction has yet to be reported. Here, we introduce a superaerophobic nitrogen-doped tungsten carbide nanoarray electrode exhibiting high stability and activity toward hydrogen evolution reaction as well as driving oxygen evolution efficiently in acid. Nitrogen-doping and nanoarray structure accelerate hydrogen gas release from the electrode, realizing a current density of -200 mA cm
at the potential of -190 mV vs. reversible hydrogen electrode, which manifest one of the best non-noble metal catalysts for hydrogen evolution reaction. Under acidic conditions (0.5 M sulfuric acid), water splitting catalyzed by nitrogen-doped tungsten carbide nanoarray starts from about 1.4 V, and outperforms most other water splitting catalysts.
Fabricating active materials into specific macrostructures is critical in the pursuit of high electro-catalytic activity. Herein we demonstrate that a three-dimensional (3D) architecture of NiFe ...layered double hydroxide (NiFe-LDH) significantly reduced the onset potential, yielded high current density at small overpotentials, and showed outstanding stability in electrochemical oxygen evolution reaction.
Molybdenum disulfide (MoS2) with the two-dimensional layered structure has been widely studied as an advanced catalyst for hydrogen evolution reaction (HER). Intercalating guest species into the van ...der Waals gaps of MoS2 has been demonstrated as an effective approach to tune the electronic structure and consequently improve the HER catalytic activity. In this work, by constructing nanostructured MoS2 particles with largely exposed edge sites on the three-dimensional substrate and subsequently conducting Li electrochemical intercalation and exfoliation processes, an ultrahigh HER performance with 200 mA/cm2 cathodic current density at only 200 mV overpotential is achieved. We propose that both the high surface area nanostructure and the 2H semiconducting to 1T metallic phase transition of MoS2 are responsible for the outstanding catalytic activity. Electrochemical stability test further confirms the long-term operation of the catalyst.
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Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is ...important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (∼20 nm) are electrochemically transformed into ultra-small diameter (2-5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm(-2) water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts.
Electrocatalysis is of great importance to a variety of energy conversion processes, where developing highly efficient catalysts is critical. While common strategies involve screening a wide range of ...materials with new chemical compositions or structures, a different approach to continuously, controllably, and effectively tune the electronic properties of existing catalytic materials for optimized activities has been demonstrated recently. Inspired by studies in lithium‐ion batteries, systematical lithium electrochemical tuning (LiET) methods such as Li intercalation, extraction, cycling, and strain engineering, are employed to effectively tune the electronic structures of different existing catalysts and thus improve their catalytic activities dramatically. Herein, the advantages of the LiET method in electrocatalysis are introduced, and then some recent representative examples in improving the performances of important electrochemical reactions are reviewed briefly. Lastly, a few promising directions on extending the applications of the LiET method in electrocatalysis are proposed.
Lithium electrochemical tuning (LiET) methods, such as intercalation and extraction, have been demonstrated to be effective in tuning the electronic structures of existing catalysts and improving their electrocatalytic activities dramatically. The advantages of the LiET method in electrocatalysis are summarized, some representative examples in important electrochemical reactions are briefly reviewed, and a few promising directions for extending its applications are proposed.
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Layered double hydroxides (LDHs) are a family of high‐profile layer materials with tunable metal species and interlayer spacing, and herein the LDHs are first investigated as bifunctional ...electrocatalysts. It is found that trinary LDH containing nickel, cobalt, and iron (NiCoFe‐LDH) shows a reasonable bifunctional performance, while exploiting a preoxidation treatment can significantly enhance both oxygen reduction reaction and oxygen evolution reaction activity. This phenomenon is attributed to the partial conversion of Co2+ to Co3+ state in the preoxidation step, which stimulates the charge transfer to the catalyst surface. The practical application of the optimized material is demonstrated with a small potential hysteresis (800 mV for a reversible current density of 20 mA cm−2) as well as a high stability, exceeding the performances of noble metal catalysts (commercial Pt/C and Ir/C). The combination of the electrochemical metrics and the facile and cost‐effective synthesis endows the trinary LDH as a promising bifunctional catalyst for a variety of applications, such as next‐generation regenerative fuel cells or metal–air batteries.
It is found that incorporating Co into NiFe‐layered double hydroxides (LDHs) can significantly improve the oxygen reduction reaction (ORR) activity and both the ORR and oxygen evolution reaction activities of trinary NiCoFe‐LDHs can be significantly improved by a preoxidation process. This improvement is attributed to the formation of Co3+ in the intralayer, and results in the conductivity improvement of the material.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Modern lithium ion batteries are often desired to operate at a wide electrochemical window to maximize energy densities. While pushing the limit of cutoff potentials allows batteries to provide ...greater energy densities with enhanced specific capacities and higher voltage outputs, it raises key challenges with thermodynamic and kinetic stability in the battery. This is especially true for layered lithium transition-metal oxides, where capacities can improve but stabilities are compromised as wider electrochemical windows are applied. To overcome the above-mentioned challenges, we used atomic layer deposition to develop a LiAlF4 solid thin film with robust stability and satisfactory ion conductivity, which is superior to commonly used LiF and AlF3. With a predicted stable electrochemical window of approximately 2.0 ± 0.9 to 5.7 ± 0.7 V vs Li+/Li for LiAlF4, excellent stability was achieved for high Ni content LiNi0.8Mn0.1Co0.1O2 electrodes with LiAlF4 interfacial layer at a wide electrochemical window of 2.75–4.50 V vs Li+/Li.
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