Metal–organic frameworks (MOFs) with carboxylate ligands as co‐catalysts are very efficient for the oxygen evolution reaction (OER). However, the role of local adsorbed carboxylate ligands around the ...in‐situ‐transformed metal (oxy)hydroxides during OER is often overlooked. We reveal the extraordinary role and mechanism of surface‐adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs for OER electrocatalytic activity enhancement. The results of X‐ray photoelectron spectroscopy (XPS), synchrotron X‐ray absorption spectroscopy, and density functional theory (DFT) calculations show that the carboxylic groups around metal (oxy)hydroxides can efficiently induce interfacial electron redistribution, facilitate an abundant high‐valence state of nickel species with a partially distorted octahedral structure, and optimize the d‐band center together with the beneficial Gibbs free energy of the intermediate. Furthermore, the results of in situ Raman and FTIR spectra reveal that the surface‐adsorbed carboxylate ligands as Lewis base can promote sluggish OER kinetics by accelerating proton transfer and facilitating adsorption, activation, and dissociation of hydroxyl ions (OH−).
In the oxygen evolution reaction (OER), surface‐adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs demonstrate a synergistic effect. As a Lewis base the carboxylate ligands promote the sluggish OER by accelerating proton transfer and facilitating adsorption, activation, and dissociation of OH− ions, while also facilitating intrinsic electron redistribution and a partially distorted octahedral structure.
The study of cost‐efficient and high‐performance electrocatalysts for oxygen evolution reaction (OER) has attracted much attention. Here, porous microrod arrays constructed by carbon‐confined ...NiCo@NiCoO2 core@shell nanoparticles (NiCo@NiCoO2/C PMRAs) are fabricated by the reductive carbonization of bimetallic (Ni, Co) metal–organic framework microrod arrays (denoted as NiCo‐MOF MRAs) and subsequent controlled oxidative calcination. They successfully combine the desired merits including large specific surface areas, high conductivity, and multiple electrocatalytic active sites for OER. In addition, the oxygen vacancies in NiCo@NiCoO2/C PMRAs significantly improve the conductivity of NiCoO2 and accelerate the kinetics of OER. The above advantages obviously enhance the electrocatalytic performance of NiCo@NiCoO2/C PMRAs. The experimental results demonstrate that the NiCo@NiCoO2/C PMRAs as electrocatalysts exhibit high catalytic activity, low overpotential, and high stability for OER in alkaline media. The strategy reported will open up a new route for the fabrication of porous bimetallic composite electrocatalysts derived from MOFs with controllable morphology for electrochemical energy conversion devices.
Porous microrod arrays (PMRAs) constructed by carbon‐confined NiCo@NiCoO2 core@shell nanoparticles (NiCo@NiCoO2/C PMRAs) are designed and successfully fabricated by the reductive carbonization of bimetallic metal–organic frameworks and subsequent controlled oxidative calcinations in air. They exhibit superior electrocatalytic activity, low overpotential, and high stability for the oxygen evolution reaction in alkaline media.
The integration of Fe dopant and interfacial FeOOH into Ni‐MOFs Fe‐doped‐(Ni‐MOFs)/FeOOH to construct Fe−O−Ni−O−Fe bonding is demonstrated and the origin of remarkable electrocatalytic performance of ...Ni‐MOFs is elucidated. X‐ray absorption/photoelectron spectroscopy and theoretical calculation results indicate that Fe‐O−Ni−O−Fe bonding can facilitate the distorted coordinated structure of the Ni site with a short nickel–oxygen bond and low coordination number, and can promote the redistribution of Ni/Fe charge density to efficiently regulate the adsorption behavior of key intermediates with a near‐optimal d‐band center. Here the Fe‐doped‐(Ni‐MOFs)/FeOOH with interfacial Fe−O−Ni−O−Fe bonding shows superior catalytic performance for OER with a low overpotential of 210 mV at 15 mA cm−2 and excellent stability with ≈3 % attenuation after a 120 h cycle test. This study provides a novel strategy to design high‐performance Ni/Fe‐based electrocatalysts for OER in alkaline media.
Iron doping and FeOOH decorating leads to interfacial Fe−O−Ni−O−Fe bonding in Fe‐doped‐(Ni‐MOF)/FeOOH. This interfacial bonding can regulate the active Ni site to give the appropriate adsorption behavior of intermediates for the oxygen evolution reaction (OER). As a result, Fe‐doped‐(Ni‐MOF)/FeOOH shows outstanding catalytic performance with low overpotential, small Tafel slope, and high durability.
Iron‐substituted CoOOH porous nanosheet arrays grown on carbon fiber cloth (denoted as FexCo1−xOOH PNSAs/CFC, 0≤x≤0.33) with 3D hierarchical structures are synthesized by in situ anodic oxidation of ...α‐Co(OH)2 NSAs/CFC in solution of 0.01 m (NH4)2Fe(SO4)2. X‐ray absorption fine spectra (XAFS) demonstrate that CoO6 octahedral structure in CoOOH can be partially substituted by FeO6 octahedrons during the transformation from α‐Co(OH)2 to FexCo1−xOOH, and this is confirmed for the first time in this study. The content of Fe in FexCo1−xOOH, no more than 1/3 of Co, can be controlled by adjusting the in situ anodic oxidation time. Fe0.33Co0.67OOH PNSAs/CFC shows superior OER electrocatalytic performance, with a low overpotential of 266 mV at 10 mA cm−2, small Tafel slope of 30 mV dec−1, and high durability.
In situ anodic oxidation of α‐Co(OH)2 is developed to fabricate 3D FexCo1−xOOH porous nanosheet arrays for water oxidation. During the transformation from α‐Co(OH)2 to FexCo1−xOOH, the partial CoO6 octahedrons in CoOOH can be substituted by the unsaturated FeO6 octahedrons. The FexCo1−xOOH PNSAs/CFC exhibits the outstanding electrocatalytic performance for OER with low onset potential, small Tafel slope, and excellent durability.
Water splitting into hydrogen and oxygen in order to store light or electric energy requires efficient electrocatalysts for practical application. Cost‐effectiveness, abundance, and efficiency are ...the major challenges of the electrocatalysts. Herein, this paper reports the use of low‐cost 304‐type stainless steel mesh as suitable electrocatalysts for splitting of water. The commercial and self‐support stainless steel mesh is subjected to exfoliation and heteroatom doping processes. The modified stainless steel electrocatalyst displays higher oxygen evolution reaction property than the commercial IrO2, and comparable hydrogen evolution reaction property with that of Pt. More importantly, an all‐stainless‐steel‐based alkaline electrolyzer (denoted as NESSP//NESS) is designed for the first time, which possesses outstanding stability along with lower overall voltage than the conventional Pt//IrO2 electrolyzer at increasing current densities. The remarkable electrocatalytic properties of the stainless steel electrode can be attributed to the unique exfoliated‐surface morphology, heteroatom doping, and synergistic effect from the uniform distribution of the interconnected elemental compositions. This work creates prospects to the utilization of low‐cost, highly active, and ultradurable electrocatalysts for electrochemical energy conversion.
Surface engineering of cost‐effective commercial stainless‐steel mesh is employed as 3D self‐supportive electrocatalysts for electrochemical water splitting. Benefiting from the highly active exfoliated surfaces and heteroatoms‐doping, the surface‐engineered stainless‐steel mesh displays outstanding oxygen evolution reaction, hydrogen evolution reaction, and overall water‐splitting performance, coupled with excellent ultralong stability.
Herein, we developed FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams for oxygen evolution reaction (OER). The inner Co metal cores serve as highly conductive layers to provide ...reliable electronic transmission, and can overcome the poor electrical conductivity of FeOOH efficiently. DFT calculations demonstrate the strong electronic interactions between Co and FeOOH in the FeOOH/Co/FeOOH HNTAs, and the hybrid structure can lower the energy barriers of intermediates and thus promote the catalytic reactions. The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long‐term durability, and they are promising electrocatalysts for OER in alkaline solution.
FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams were developed for the oxygen evolution reaction (OER). The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long‐term durability, and are promising electrocatalysts for OER in alkaline solution.
Porous CoFe2O4/C NRAs supported on nickel foam@NC (denoted as NF@NC‐CoFe2O4/C NRAs) are directly fabricated by the carbonization of bimetal–organic framework NRAs grown on NF@poly‐aniline(PANI), and ...they exhibit high electrocatalytic activity, low overpotential, and high stability for the oxygen evolution reaction in alkaline media.
Low-cost transition-metal dichalcogenides (MS2) have attracted great interest as alternative catalysts for hydrogen evolution. However, a significant challenge is the formation of sulfur–hydrogen ...bonds on MS2 (S–Hads), which will severely suppress hydrogen evolution reaction (HER). Here we report Cu nanodots (NDs)-decorated Ni3S2 nanotubes (NTs) supported on carbon fibers (CFs) (Cu NDs/Ni3S2 NTs-CFs) as efficient electrocatalysts for HER in alkaline media. The electronic interactions between Cu and Ni3S2 result in Cu NDs that are positively charged and can promote water adsorption and activation. Meanwhile, Ni3S2 NTs are negatively charged and can weaken S–Hads bonds formed on catalyst surfaces. Therefore, the Cu/Ni3S2 hybrids can optimize H adsorption and desorption on electrocatalysts and can promote both Volmer and Heyrovsky steps of HER. The strong interactions between Cu and Ni3S2 cause the Cu NDs/Ni3S2 NTs-CFs electrocatalysts to exhibit the outstanding HER catalytic performance with low onset potential, high catalytic activity, and excellent stability.
Constructing inorganic–organic hybrids with superior properties in terms of water adsorption and activation will lead to catalysts with significantly enhanced electrocatalytic activity in the ...hydrogen evolution reaction (HER) in environmentally benign neutral media. Herein, we report SiO2–polypyrrole (PPy) hybrid nanotubes supported on carbon fibers (CFs) (SiO2 /PPy NTs–CFs) as inexpensive and high‐performance electrocatalysts for the HER in neutral media. Because of the strong electronic interactions between SiO2 and PPy, the SiO2 uniquely serves as the centers for water adsorption and activation, and accordingly promotes the HER. The metal‐free SiO2 /PPy NTs–CFs displayed high catalytic activity in the HER in neutral media, such as a low onset potential and small Tafel slope, as well as excellent long‐term durability.
Working better together: SiO2/polypyrrole (PPy) hybrid nanotubes were designed as metal‐free electrocatalysts for the hydrogen evolution reaction (HER) in neutral media. The electronic interactions between SiO2 and PPy effectively enhance the adsorption and activation of water molecules, which leads to superior electrocatalytic activity and stability in the HER at neutral pH (NTs=nanotubes, CFs=carbon fibers).
FeOOH/CeO2 heterolayered nanotubes supported on Ni foam as efficient oxygen evolution electrocatalysts are reported. The hybrid structure can obviously promote the catalytic performance for the ...oxygen evolution reaction, such as low onset potential, high electroactivity, and excellent long‐term durability. This study provides a new route to the design and fabrication of electrocatalysts with high electroactivity and durability for oxygen evolution.
