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[Display omitted] Metal organic frameworks (MOFs) are considered as promising electrocatalytic materials due to their tunable porosity, functional organic ligands, and large specific surface area for oxygen evolution reaction (OER). Recently, most reported electrocatalysts focus on the establishing heterogeneous structures by thermal treatments to improve OER performance. However, the thermal treatments are accompanied by the complex synthetic process and destruction of the MOFs structure. Therefore, improving the catalytic performance of pristine MOFs remains a challenge. Here, a series of trimetallic M a M b M c -MOFs (M represents metal element) were synthesized by one-pot method. Modulating the Co/Ni ratio not only adjusts the morphology of FeCoNi-MOFs, but also effectively optimizes the electronic structure. The composition-optimized FeCo 0.5 Ni 2.5 -MOF nano-bundles (FeCo 0.5 Ni 2.5 -NBs) only required a low overpotential of 273 mV to achieve the current density of 10 mA cm−2 in alkaline solution, with a Tafel slope of 51.1 mV dec−1, lower than other FeCoNi-MOFs and commercial RuO 2 catalyst. The two-electrode couple FeCo 0.5 Ni 2.5 -NBs || Pt/C achieved the cell voltage of 1.55 V, delivering current density of 10 mA cm−2 for overall water splitting. [ABSTRACT FROM AUTHOR]

Fe@CoMo 2 S 4 /Ni 3 S 2 /NF catalysts with enhanced conductivity, enlarged electochemical active areas and modulated electronic structure for efficient water splitting. [Display omitted] Oxygen evolution reaction (OER) is a multi-electron transfer process, whose intrinsic sluggish dynamic restricts the whole process of overall water splitting (OWS). To address this issue, a porous transition metal sulfide (TMS) catalyst with rich heterojunctions was prepared by vulcanization and trace Fe doping of CoMo-based metal–organic framework (MOF). In this work, the nanoflower composed of ultrathin 2D nanosheets anchored on a nickel foam presents a layered interface that contributes to the exposure of active regions. The resulting electrode denoted as Fe@CoMo 2 S 4 /Ni 3 S 2 /NF required a low overpotential (η 10 = 167 mV @ 10 mA cm−2, η 50 = 260 mV @ 50 mA cm−2) in 1.0 M KOH for OER and a small cell voltage (E = 1.513 V @ 10 mA cm−2) to power OWS when coupled with commercial Pt/C. It also exhibited splendid morphological and chemical stability with virtually invariant polarization curve and flower-like appearance after 1000 CV cycles, as well as long-term durability over 100 h with a constant current density of 10 mA cm−2. This work revealed the multi-anionic regulation mechanism in the surface reconstruction of sulfide electrocatalysts, and verified that Co/Mo/Ni-based oxysulfide was the true active substance of OER, which inspired the understanding and design of multi-anionic regulated electrocatalysts. [ABSTRACT FROM AUTHOR]

A sequential template-engaged method was applied to design and construct unique Pt-NiCoFeP@NiCoFe-PBA hollow nanocages. Impressively, constructing heterointerfaces and incorporating ultralow Pt could induce strong synergistic effects and modify electronic configurations to optimize the binding energy of intermediates, thus achieving prominent electrocatalytic performance. [Display omitted] • Exploiting a partial phosphidation strategy to ingeniously construct heterostructures. • Ultralow Pt-loading to regulate electronic structure and increase active sites of catalysts. • Three-dimensional cage-like nanostructure could promote efficient charge transfer. • Pt-NiCoFeP@NiCoFe-PBA exhibits admirable electrocatalytic activity toward OER. Developing highly efficient electrocatalysts based on appropriate heterojunction engineering and electronic structure modification for the oxygen evolution reaction (OER) has been extensively recognized as an effective approach to increase the efficiency of water splitting. Herein, ultralow Pt-loaded (1 %) NiCoFeP@NiCoFe-PBA hollow nanocages with well-defined heterointerfaces and modified electronic environment are successfully fabricated. As expected, the obtained Pt-NiCoFeP@NiCoFe-PBA exhibits outstanding performance with a low overpotential of 255 mV at 10 mA cm−2 and a small Tafel slope of 57.2 mV dec-1. More specifically, the highly open three-dimensional structure, exquisite interior voids and abundant surface defects endow Pt-NiCoFeP@NiCoFe-PBA nanocages with more electrochemical active sites. Meanwhile, experimental results and mechanism studies also reveal that the construction of heterogeneous interfaces as well as incorporation of noble metals could readily induce strong synergistic effects and significantly tailor electronic configurations to optimize the binding energy of the intermediates, thereby achieving prominent OER performance. [ABSTRACT FROM AUTHOR]

A series of CoNi-based CoNiM (M= Fe, Cd, Ce, Cu, Mn, Zn) LTHs nanocatalysts with ultrathin nanosheet configuration are prepared as efficient electrocatalysts for OER. [Display omitted] • We developed a simple MOF-mediated method for synthetizing ultrathin 2D CoNiFe LTHs. • The modified electronic structure leads to high OER activity of the CoNiFe LTHs. • This work will boost the synthesis of ternary layer hydroxide catalysts. Developing low-budget, stable, and high-performance electrocatalyst toward oxygen evolution reaction (OER) is of pivotal significance in the fields of energy conversion and storage. Herein, a universal metal organic framework (MOF)-mediated method for the synthesis of two-dimensional (2D) layered triple hydroxides (LTHs) nanosheets with ultrathin nature has been developed. It is interesting to disclose that the CoNi-based LTHs possess better electrochemical catalytic performance, giving superior performance to commercial RuO 2 catalysts. Remarkably, benefitting from the ultrathin nanosheet configuration, optimized electronic structure, and strong synergistic effect, the optimized CoNiFe LTHs nanosheets show excellent OER performance with an ultralow overpotential of 262 mV at a current density of 10 mA cm−2 and a small Tafel slope of 88.1 mV dec-1. This work provides a promising avenue to develop low-cost and high-performance layered ternary hydroxide electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amorphization/crystallization methods of TM-based catalysts are summarized. • Various kinds of a/c TM-based catalysts are reviewed. • Perspectives and challenges of a/c TM-based catalysts for water splitting are outlined. The rational phase engineering on transition-metal-based (TM-based) catalysts is an efficient strategy to improve the catalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in water splitting. Combining high conductivity from crystalline phase with orderly atomic arrangement and high activity from amorphous phase with abundant unsaturated sites, more amorphous/crystalline (a/c) heterostructure TM-based catalysts with optimized electronic structures have been confirmed to exhibit superior OER and HER properties with well-balanced activity and stability. However, the rational design of the a/c TM-based catalysts for water splitting is often ignored. In this review, we firstly summarized the amorphization/crystallization strategies for constructing a/c TM-based catalysts including pyrolysis method, composition-tuned approach, electrochemical method, chemical etching and other strategies. Then, we introduced various kinds of a/c TM-based catalysts such as a/c TM-based alloys, oxides and hydroxides, nitrides/phosphides/sulfides, and composites. In addition, the roles of a/c interfaces on the performance promotion for OER and HER have been analyzed, which involved the active sites increasement with optimized d-band center, catalytic kinetics acceleration with fast electron transfer, and stability enhancement with electron density redistribution. Finally, we proposed the existing challenges and further perspectives referring to the precise synthesis, in-depth activity investigation and performance promotion. [ABSTRACT FROM AUTHOR]