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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]

The development of highly efficient, economical, and sustainable electrocatalysts based on non‐noble metals for hydrogen evolution reaction (HER) is of vital significance for large‐scale renewable energy storage. Herein, an effective synthetic strategy for the construction of MoO2 nanoflowers decorated with metallic Cu/Cu2O nanoparticles (NPs) on Ni foam (NF) (Cu2O/MoO2@Cu/NF) with a simple two‐step method is reported. The prepared Cu2O/MoO2@Cu/NF as an electrocatalyst exhibits outstanding reactivity and remarkable stability in alkaline solution. The onset overpotential of Cu2O/MoO2@Cu/NF approaches 0 V. An overpotential as low as 32 mV is obtained to afford a current density of 10 mA cm−2, comparable with Pt/C catalysts. The Tafel slope is low at 40 mV dec−1 as well. The involvement of zero‐valent Cu greatly reduces the resistance. The well‐dispersed Cu/Cu2O NPs on the sphere‐like MoO2 nanoflowers exaggerate the surface area. The ringent channels provide the fast release of evolved bubbles. Furthermore, the enhanced conductivity and large surface area lead to significant activity in HER. Herein, a novel design and facile synthesis of a highly efficient electrocatalyst with catalytic activity that is comparable to a Pt/C catalyst is provided. [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]

In order to develop efficient and earth-abundant catalysts for large-scale hydrogen evolution via water splitting, a Ni/Ni(OH)2 dual composition electrocatalyst was manufactured via a two-step electrodeposition procedure. The stepwise fabricated 3D hierarchical nanoarrays as well as the concurrent dual composition electrodeposition yielded a papillae-like hybrid crystal structure. The high electrochemically active surface area, defect-rich hybrid crystal structure, and synergistic effects of the dual composition provided an elevated catalytic performance. Only 53 mV overpotential was needed to deliver a current density of 10 mA cm−2 with a small Tafel slope of 54.5 mV dec−1 to catalyze the HER in alkaline media. Approximately 81% catalytic activity could be maintained after 20 h of continuous testing, demonstrating long-term stability. Our findings offer an efficient approach to design and fabricate efficient noble-metal-free alkaline HER electrocatalysts. [ABSTRACT FROM AUTHOR]

To achieve a cost‐effective and performance‐enhanced electrocatalyst for the hydrogen evolution reaction (HER), Mo‐doped Cu/Co hybrid oxides were prepared through the processes of hydrothermal chemistry and dehydration/reduction. Hybrid structures consisting of a polycrystalline hybrid crystal structure and an amorphous structure, and hybrid constituents including at least Cu, Cu2O, CuO, CoO, CuCoO2, and Cu2CoO3 were identified and characterized by using SEM, HR‐TEM, XPS as well as electrochemical analysis. Interestingly, no information of the doped Mo appeared in the XRD patterns. The reasonable deduction is that Mo might be confined in the amorphous area. The highly developed interface, enhanced conductivity, larger active surface area, abundant oxygen vacancies, and redistribution of electrons among these elements resulted in the significantly enhanced electrocatalytic activity. The optimized Mo‐doped hybrid Cu/Co oxide exhibited catalytic activity with an overpotential of 88 mV to obtain a current density of 10 mA cm−2 in alkaline electrolyte with scarce loss of the initial catalyst activity for 28 h and over 5000 cycles. This work may provide a channel to enhance the performance in the HER. Better code of conduct: The Mo‐doped hybrid Cu/Co oxide exhibits significantly enhanced electrocatalytic activity, owing to the highly developed interface, better conductivity, larger active surface area, and abundant oxygen vacancies. [ABSTRACT FROM AUTHOR]

Low-cost and earth-rich electrocatalysts with excellent catalytic activity in the electrochemical hydrogen evolution reaction (HER) are essential for large-scale renewable energy storage. Herein, we report a new type of core-shell Ni 2 P@CoP nanoarrays supported on nickel foam (NF) (Ni 2 P@CoP/NF) with large specific surface area, serving as an efficient cathode for hydrogen evolution reaction (HER). Plenty of tiny Ni 2 P nanosheets were tightly wrapped on the CoP nanowires, forming a rich heterostructure interface, which can provide more active sites and improve conductivity, thereby increasing their catalytic performance. What's more, the synergistic effect between Ni 2 P and CoP can promote the rapid electron transfer and improve the catalytic efficiency. The obtained Ni 2 P@CoP/NF NAs exhibited excellent HER activity with a low overpotential of 61 mV at 10 mA cm−2 and good durability in the alkaline media. The core-shell nanoarray structure of Ni 2 P@CoP/NF provides a novel method for the preparation of other heterojunction metal phosphides, which can be used to develop high performance HER electrocatalysts. [Display omitted] • Designed a new type of core-shell Ni 2 P@CoP nanoarrays supported on nickel foam. • The catalyst has a large specific surface area and rich heterostructure interfaces, which can provide more active sites. • The synergistic effect between Ni 2 P and CoP can promote the rapid electron transfer. • The obtained catalyst exhibits remarkable enhanced HER activities compared to pure Ni 2 P and CoP nanostructures. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D MOFs-based nanosheets with rich oxygen vacancies were designed. • The Kirkendall effect successfully regulated the oxygen vacancies. • The presence of oxygen vacancies improved the photocatalytic ability of the cathode. • PFOA degradation and TOC removal efficiency reached 93 % and 92 % in 180 min. • The mechanism of adsorption and degradation of PFOA in heterogeneous systems was described clearly. In heterogeneous solar photo-electro-Fenton (SPEF) degradation of perfluorooctanoic acid (PFOA), improving the binding energy between the catalyst and PFOA on a surface molecular level to facilitate absorption, diffusion, and degradation is a great challenge. Herein, we attained this goal in two steps: First, developing of two-dimensional (2D) MOFs-based CoFe nanosheets with layered structures as photo-electrocatalysts, which own abundant unsaturated coordination sites to accelerate rapid mass transport and charge transfer. Secondly, the construction of abundant oxygen vacancies (OVs) at low temperatures in 2D CoFe causes hybridization of the d-band of Fe and LUMO orbital of O in PFOA, enhancing PFOA's binding capacity by theoretical analysis. OVs also reduced the band gap of CoFe and increased the efficiency of electron-hole separation, thereby improving photo-electrocatalytic activity and enabling rapid degradation of PFOA. Moreover, it can maintain a good degradation effect in complex ionic background conditions and actual water samples. These findings extend the applications of catalysts and consolidate the effect of OVs on photo-electrocatalysis for wide environmental applications. [ABSTRACT FROM AUTHOR]

Due to the advantages of large specific surface area, high mass transfer efficiency and easy access to active sites, two dimensional (2D) nanomaterials provide a great opportunity for the construction of new versatile electrocatalysts with superior properties. Herein, a graphene-templated growth of MoS 2 -Ni 3 S 2 heterostructure with porous structure is successfully prepared on the Ni foam (MoS 2 /Ni 3 S 2 @G/NF) by one pot hydrothermal method. The electronic structure and surface properties of 2D chalcogenides are modified by heterogeneous interface and component engineering, so as to prepare a high-performance transition metal composite catalytic electrode for electrochemical reaction. The optimized MoS 2 /Ni 3 S 2 @G/NF shows excellent bifunctional activity and durability in alkaline medium. It only needs 53 mV and 265 mV overpotential to reach 10 mA cm−2 current density of HER and 20 mA cm−2 current density for OER, respectively. When the composite is used as an advanced electrocatalyst for water splitting, the 1.47 V voltage required to achieve a current density of 10 mA cm−2, which is better than the most non-noble metal electrocatalysts. The heterostructures between MoS 2 , Ni 3 S 2 and graphene are conducive to the synchronous chemical adsorption of hydrogen and oxygen-containing intermediates, which can improve the catalytic activity of overall water splitting. [Display omitted] • The synergy between MoS 2 nanosheets and Ni 3 S 2 particles enhances the intrinsic electrochemical activity of the material. • Graphene increases the load of active substances and regulates the interaction between electrons with faster carrier. • 3D nickel foam provides a binder free framework for catalytic reaction, greatly reducing charge transfer resistance. [ABSTRACT FROM AUTHOR]