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Developing efficient, low-cost and bifunctional catalysts with predominant durability for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is an extraordinary challenge in the preparation of green hydrogen energy by electrochemical water splitting. Three-dimensional (3D) transition metal compounds have become a research hotspot as OER electrocatalysts, which can replace noble metal oxides such as RuO 2 and IrO 2 to reduce application costs. Herein, we synthesized a novel three-dimensional pine-tree-like bimetallic sulfide arrays on nickel foam (FeCoS/NF) using various optimization strategies such as morphology optimization, in situ growth and introduction of heterogeneous structures. The as-synthesized FeCoS/NF electrocatalyst only requires relatively low overpotential of 156 mV to achieve a current density of 20 mA cm−2 for OER, with a Tafel slope of only 37 mV dec−1. It also has a small charge transfer resistance, an electrochemical surface area and good electrochemical stability in alkaline electrolytes. The excellent performance of FeCoS/NF can be attributed to the synergistic effect and amorphous phase of FeCoS as well as the well-defined pine-tree-like array architecture with a large surface area, abundant active sites, and sufficient gas and electrolyte diffusion channels. [Display omitted] • A 3D pine-tree-like structure of FeCoS/NF electrocatalyst was synthesized. • The FeCoS/NF exhibits excellent electrocatalytic activity for OER. • FeCoS/NF-based zinc-air battery shows an open-circuit voltage of 1.27 V. [ABSTRACT FROM AUTHOR]

The design of low-cost, short time, mass preparation and high-efficiency of electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and zinc air batteries are highly challenging. Herein, we design a bifunctional chrysanthemum-like electrocatalysts (Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF) for highly efficient electrochemical water splitting by a simple and highly controllable two-step method in a few hours. This unique hierarchical electrocatalyst has porous structure and short diffusion paths, which can promote charge transfer, ion and water diffusion, and rapidly release hydrogen and oxygen bubbles. The obtained Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF composite exhibits low overpotentials of 57 mV at −10 mA cm−2 toward the HER, which is superior to most of the previously reported CoMoO 4 -based electrocatalysts. And the Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF exhibits excellent performance of 355 mV at 100 mA cm−2 toward the OER. Benefiting from the unique hierarchical heterostructure and the coupling effect between the inner and outer layers, the Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF catalysts were endowed with high activity for water splitting. [Display omitted] [ABSTRACT FROM AUTHOR]

The design and synthesis of high-performance catalysts for hydrogen evolution reaction (HER) is of significant importance for electrocatalysis reaction. In this study, 0D Ag nanoparticles were successfully loaded onto 2D Ni(OH)2 nanosheets by a one-step hydrothermal method for enhancing the electrocatalytic ability. The special structure of Ni(OH)2 with only 2 wt% Ag on 3D nickel foam (NF) exhibited a high surface area and excellent charge transfer channels. Furthermore, the synergistic effect as well as the transfer of electron density between Ag and Ni(OH)2 contributed to a high HER activity. As a result, Ni(OH)2–Ag/NF exhibited excellent HER performance with an overpotential of 89 mV to obtain a current of 10 mA cm−2 in an alkaline electrolyte, 155 mV lower than that of Ni(OH)2/NF. After 10 hours of stability test and more than 1000 cycles, negligible loss of the initial catalytic activity to drive a current density of 10 mA cm−2 verified excellent stability during the alkaline HER process. This research provides a new idea to integrally construct ultralow noble metal catalysts with outstanding HER performance and results in new advances in the field of hydrogen evolution. [ABSTRACT FROM AUTHOR]

Metal‐organic frameworks (MOFs) have been considered as promising platforms for preparing the efficient oxygen evolution reaction (OER) catalysts, but few of them are directly employed as active components due to their poor electrical conductivity. Herein, a lamellar bimetallic MFN (MIL‐53(FeNi)) encapsulated in graphene aerogel‐grafted Ni foam has been developed (denoted as MFN@GA/NF). The graphene aerogel (GA) provides abundant space for the in‐situ growth of MFN and functions as a "bridge" to connect nickel foam (NF) with MFN by virtue of good conductivity. Benefitting from its structural integrity, the obtained hierarchical MFN@GA/NF exhibited excellent OER performances in alkaline media with an overpotential of 250 mV (20 mA cm−2) and 326 mV (200 mA cm−2), as well as remarkable stability in continuous electrolysis for over 100 h. This work provides a new channel for engineering MOF‐based functional materials with featured architectures. [ABSTRACT FROM AUTHOR]

The fabrication of cost‐effective and performance‐advanced electrocatalysts is in great requirements for water splitting to achieve sustainable oxygen production. A simple and effective precursor of ZIF‐67 particles mounted on Cu(OH)2 nanorods was induced by a template alignment method. After annealing, hierarchical CoO polyhedron‐decorated CuO/Cu2O (CuOx) nanorods on Cu foam (denoted as CuOx@CoO NRs/CF) were achieved, which displayed the heterojunction in CuOx components, hierarchical configuration and outward active sites. These features, verified by HRTEM, SEM, XPS and EDX, optimized the oxygen evolution reaction (OER) electrocatalyst. Benefiting from its large electrochemical surface area and the synergetic effect between CuOx and CoO, CuOx@CoO NRs/CF exhibited considerable catalytic activity with a low overpotential of 254 mV to obtain a current density of 10 mA cm−2 in alkaline electrolyte and a scarce loss of the initial catalyst activity over 24 h and over 5000 cycles. This work provides a channel to enhance the performance in OER. [ABSTRACT FROM AUTHOR]

• Composite of CePO 4 with Ni as a HER catalyst is reported. • CePO 4 lead to enhanced electrical conductivity and H 2 desorption ability. • Ni/CePO 4 shows excellent electrocatalytic HER performance at high current density. • Mechanism of photocatalytic HER over CePO 4 -Ni with Eosin Y photosensitizer and electrocatalytic HER are proposed. Developing suitable electrocatalyst/photocatalyst cocatalyst with electron transfer and desorption of hydrogen active sites is extremely significance for hydrogen evolution reaction (HER). Herein, we develop a series of Ni/(m)CePO 4 catalyst with rich interfaces via thermal treatment at low temperature with Ni-BTC/CePO 4 as precursor. The as-synthesized Ni/(m)CePO 4 heterojunction possess compact heterogeneous interface, and large specific surface area by loading Ni nanosphere on CePO 4 nanowire. By carefully designing method, the powerfully intimated heterointerface between Ni and CePO 4 conducive to the conversion of adsorption energy toward H atoms and electron conductivity, which enhance the synergic effect for electro-/photo-catalytic HER performances. Impressively, the Ni/0.1CePO 4 catalyst renders outstanding electrocatalytic HER activity with an lowest overpotential of −120 mV at −10 mA cm−2 and a optimal Tafel slope of 72 mV dec−1. The overpotential of Ni/0.1CePO 4 catalyst is −288 mV at −100 mA cm−2, close to 20 wt% Pt/C. With Eosin Y as photosensitizer, the photocatalytic performance for H 2 generation speed is around 64 umol h−1. Additionally, the Ni/0.1CePO 4 catalyst exhibits wonderful cycle stability in both electro-/photo-catalytic HER. The possible speculation of mechanisms of HER have also been proposed. This work provides a new insight into design HER catalysts for electro-/photo-catalytic hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Developing high-performance nonprecious-metal electrocatalysts for the oxygen evolution reaction (OER) is crucial for efficient water splitting. Therefore, the reasonable design principle of catalyst, leading to high activity catalytic center and improving the accessibility of active sites, is undoubtedly crucial. Here, we used a kind of Prussian blue analogue (CoFe-PBA) nanoparticles to anchor the nitrogen-carbon doped CoFe 2 O 4 (CoFe 2 O 4 @NC) species to reduced graphene oxide aerogels as OER catalysts. The strong interaction between nanosized CoFe 2 O 4 @NC and the graphitic carbon shell led to synergistic effects in the OER, and the protection of the carbon shell guaranteed stability of the catalyst. As a result, the aerogel electrocatalyst exhibits more excellent activity and stability than the most advanced RuO 2 catalyst in OER under the same mass load in alkaline medium. It shows smaller overpotential of 250 mV to afford a current density of 10 mA cm−2 in a continuous working time of more than 70 hours. [Display omitted] • The catalyst has highly exposed active surface, multi-dimensional mass transfer pathway and good charge transfer ability. • The in-situ formation of nitrogen-carbon doped structure can greatly improve the catalytic activity and stability. • The binary active sites on the conductive GA network reduce the interfacial resistance and enhance catalytic activity. • The "Plum Pudding Model" structure integrates multiple requirements for catalyst design strategies. [ABSTRACT FROM AUTHOR]

Designing ultrahigh energy density and mass-loading of electrocatalysts for hydrogen evolution is highly desirable but remains a great challenge. Herein, a 3D high-rise architectural structure consisting of dense Ni(OH) 2 nanoparticles on CuMoO 4 nanocube heterostructure arrays on Ni foam (Ni(OH) 2 /CuMoO 4 /NF) is developed via a hydrothermal reaction, calcination and electrodeposition method. Benefitting from the optimized electronic configuration, hierarchical high-rise architecture, and large specific surface area and mesoporous, the Ni(OH) 2 /CuMoO 4 /NF exhibits superior hydrogen evolution reaction (HER) activity in 1.0 M KOH solution. Ni(OH) 2 /CuMoO 4 /NF only requires low overpotential of 70 mV achieving a current density of 10 mA cm−2 with a low Tafel slope of 80 mV dec−1, and superior long-term stability toward HER. This work provides a new structural design to high-rise architectural structures for efficient catalytic application. [Display omitted] • A highly topological nickel hydroxide doped copper molybdate oxide composite was synthesized. • The high-topology structure with a heterogeneous interface enhances the conductivity. • The typical structure and proper components contribute to the electrochemical activity. [ABSTRACT FROM AUTHOR]

Developing highly efficient, low-cost and superior stable electrocatalysts for the oxygen evolution reaction (OER) is essential for coping with global energy shortage and environmental crisis. In this article, a polymetallic catalyst of ultrathin Fe(OH) 3 nanosheets uniformly embedded in NiCo 2 O 4 porous nanotube arrays (Fe(OH) 3 -NiCo 2 O 4 /NF) was synthesized via a simple hydrothermal-annealing and electrodeposition method. Benefits from the synergistic effect and their unique interactions between Fe(OH) 3 and NiCo 2 O 4 , the Fe(OH) 3 -NiCo 2 O 4 /NF triggers optimum electronic properties, rich multiple active sites, and favorite free adsorption energy, resulting in excellent OER catalytic activities. Meanwhile, the highly porous of Fe(OH) 3 and NiCo 2 O 4 effectively promotes a multichannel architecture for charge transfer and gas/ion diffusion to improve stability. Such core-shell Fe(OH) 3 -NiCo 2 O 4 /NF hybrid was used as a polymetallic catalyst, exhibiting a small overpotential of 268 mV at a current density of 50 mA cm−2 and low Tafel slope of 73.1 mV dec−1 for OER in 1 M KOH. In the battery system with Fe(OH) 3 -NiCo 2 O 4 /NF as the cathode and zinc sheet as the anode, the zinc-air battery (ZAB) exhibits an open-circuit voltage of 1.32 V and an instantaneous current of 0.96 A. This material provides a new idea for the coupling of amorphous materials and transition metal compound, and the application of ZAB. [Display omitted] [ABSTRACT FROM AUTHOR]