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Ru@Fe-Ni(OH) 2 /NF catalyst fabricated through Fe-doped and interfacial Ru nanoclusters co-engineering of Ni(OH) 2 nanosheets directly grafted on Ni foam exhibits excellent activity towards oxygen evolution reaction (OER) in alkaline media with an overpotential of 266.4 mV to achieving a current density of 50 mA cm−2 in 1 M KOH. Our results show that we have successfully developed an efficient OER catalyst for green and efficient electrocatalytic hydrolysis to produce H 2 and O 2 , providing a promising method for clean H 2 production. [Display omitted] The creation of inexpensive, high-performance catalysts to reduce the overpotential of the oxygen evolution reaction (OER) process is critical for the electrolysis of water for hydrogen production. Therefore, we applied a one-step hydrothermal method using cation exchange reaction (CER) to prepare Fe-doped and interfacial Ru nanoclusters co-engineered Ni(OH) 2 nanosheets directly grafted on Ni foam (Ru@Fe-Ni(OH) 2 /NF) for OER process. Results of electrochemical tests reveal that Ru@Fe-Ni(OH) 2 /NF has excellent OER activity, and its overpotential (η) is only 266.4 mV when the current density is 50 mA cm−2 in 1 M KOH solution, even lower than that of commercial OER catalyst RuO 2 (355 mV). The Tafel slope also decreases from 133.8 mV dec−1 for pristine Ni(OH) 2 /NF material to 24.1 mV dec−1 for Ru@Fe-Ni(OH) 2 /NF, indicating the higher charge transfer rates and fastest kinetics for water oxidation. At an overpotential of 300 mV the optimal turnover frequency (TOF) of 0.062 s−1 for Ru@Fe-Ni(OH) 2 /NF is achieved compared to that of Ni(OH) 2 /NF (0.014 s−1, NN), demonstrating the fast reaction kinetics of the as-prepared electrocatcalyst. After 24 h stability test, the catalytic activity of Ru@Fe-Ni(OH) 2 /NF was only attenuated by 2 %, showing excellent OER stability and durability. Our results show that we have successfully developed an efficient OER catalyst for green and efficient electrocatalytic hydrolysis to produce H 2 and O 2 , providing a promising method for clean H 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study realizes rational construction of the hierarchical wing-like iron/molybdenum oxide heterojunction on nickel foam (FMO/NF). • Hierarchical porous structure composed of the nanoparticle-micron sheets facilitates electrolyte/catalyst contact and bubble release. • The synergistic effect of Fe and Mo combined with the interfacial effect of the heterojunction optimizing structural configurations. • FMO/NF exhibits distinguished performance for overall water splitting in alkaline solution. Designing heterojunction catalysts with high-energy interfacial effects, especially combining the geometrical advantages of hierarchical micro-nano structures with the advantages of bi- or multi-metal syergistically optimised electronic coordination environments, is crucial for achieving efficient and stable water splitting. In this study, a simple one-step hydrothermal method was used to construct a hierarchical wing-like iron/molybdenum oxide heterojunction with a porous structure on nickel foam (FMO/NF). The synergistic effect of Fe, Mo, and the heterostructures can enrich structural defects, overcome the disadvantages of the individual components, and improve material performance by optimising the structural configurations and electronic properties and exploiting the electronic interactions that occur between interfaces composed of different phases. In addition, owing to the high porosity of the hierarchical micro-nano structure and abundant active sites, the wing-like FMO/NF was utilised as an efficient bifunctional catalyst for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), presenting low overpotentials of 278.06 and 263.72 mV, respectively, at a current density of 100 mA·cm−2 in 1 mol/L KOH. Furthermore, assembling FMO/NF as both the anode and cathode (FMO/NF || FMO/NF) required a cell voltage of 1.87 V to drive 100 mA·cm−2 in 1 mol/L KOH, and it proceeded continuously for 110 h with negligible cell voltage decay. This work provides a rational synthetic route for the preparation of innovative double transition metal-based micro-nano hierarchical heterostructured electrocatalysts with a synergistic effect and further advances the development of energy-conversion technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-supported hierarchical Co 3 S 4 /CeO 2 nanorod array is fabricated via a facile one-step hydrothermal method. • Hierarchical heterostructured Co 3 S 4 /CeO 2 acts as efficient catalyst for overall water splitting, demonstrating superior activity and stability. • The introduction of CeO 2 greatly enhances the OER catalytical activity of Co 3 S 4 as illustrated by DFT calculation. Herein, a hierarchical Co 3 S 4 / CeO 2 nanorod array on cobalt foam (Co 3 S 4 / CeO 2 -CF) was successfully constructed via a facile one-step hydrothermal method. The fabrication of Co 3 S 4 / CeO 2 -CF was confirmed by X-ray diffraction, scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM). It is observed that CeO 2 nanorod was fully covered with Co 3 S 4 nanosheets, forming a hierarchical core–shell nanostructure. Furthermore, CeO 2 and Co 3 S 4 were doped with each other during the one-step hydrothermal process, forming a heterogeneous Co 3 S 4 / CeO 2 nanostructure. Density functional theory (DFT) calculations suggest that the introduction of CeO 2 in Co 3 S 4 is effective in reducing the free energy barrier of OER process. To achieve current density of 10 mA cm−2, only small overpotentials of 74.9 mV and 213 mV are required for HER and OER in 1.0 M KOH solution, respectively. In particular, the Co 3 S 4 / CeO 2 -CF based electrolysis cell for overall water splitting only needs an output voltage of 1.64 V in the alkaline medium, lower than that of Pt/C–RuO 2 -based electrolysis cells (1.70 V). Such hierarchical heterogeneous catalyst also shows ultra-stable catalytic activity. Therefore, with the favorable heterointerfaces and hierarchical structures, Co 3 S 4 / CeO 2 -CF could be a promising bifunctional electrocatalyst for overall water splitting and this study may also provide a facile method for the preparation of hierarchical heterogeneous nanostructured materials. [ABSTRACT FROM AUTHOR]

A promising approach to resolving insufficient freshwater resources is utilizing solar energy for steam generation. Although various types of photothermal conversion materials have been developed, there are still some obstacles, such as complicated system structure fabrication and low energy utilization, that severely hinder their practical application. Herein, we designed and produced a self-floating porous carbon/polyaniline foam (PCPF) evaporator via impregnating melamine foam with porous carbon generated following the bottom-up pyrolytic method and polyaniline, followed by thermal treatment, for efficient solar steam generation. The PCPF obtained with a porous carbon (PC) to polyaniline (PAN) mass ratio of 3:5 (PCPF-3) exhibited a rich pore structure, good hydrophilicity, low thermal conductivity (0.0413 W m−1 K−1), and excellent light absorption (96.1%). Our results show that, without additional thermal insulators, the evaporation rate of PCPF-3 reached 1.496 kg m−2 h−1, and the photothermal conversion efficiency reached 87.3% under one sun irradiation. Furthermore, it also exhibited good durability and desalination performance. This type of environmentally friendly, low-cost, and stable photothermal conversion material could be used in water treatment and seawater desalination. [ABSTRACT FROM AUTHOR]

Manganese dioxide (MnO 2) with high theoretical capacity (1380 F g−1), high natural abundance and low cost has been considered as one of the most competitive active materials for preparing the electrode of supercapacitors. However, the poor electrical conductivity limits its broad applications. To solve this problem, we design a hierarchical Cu(OH) 2 @MnO 2 core-shell nanorods array on copper foam (CF), in which the one-dimensional (1D) Cu(OH) 2 nanorod core provides the scaffold for the growth of MnO 2 nanosheets and a short ion and electronic diffusion pathway and the two-dimensional (2D) MnO 2 nanosheets shell provides enormous active sites due to their large surface area. The obtained Cu(OH) 2 @MnO 2 /CF nanorods array displays an excellent areal capacitance of 708.62 mF cm−2 at the current density of 2 mA cm−2 (283.45 F g−1 at 0.8 A g−1). Additionally, the assembled Cu(OH) 2 @MnO 2 /CF//activated carbon (AC) asymmetric supercapacitor shows an outstanding energy density of 18.36 Wh kg−1 at a power density of 750 W kg−1. Two such capacitors connected in series can light up a red LED bulb for over fifteen minutes. [ABSTRACT FROM AUTHOR]

Compressible and flexible supercapacitors have aroused enormous interest of many scientific researchers for potential applications in wearable electronic products. However, the design and construction of the electrode with superior mechanical as well as electrical properties still face a lot of challenges. In present work, melamine foam/polypyrrole (MF/PPy) electrode with high deformation-tolerance and excellent electrochemical performance is prepared by in-situ interfacial polymerization of polypyrrole on commercial melamine foam, where PPy nanoparticles with size of 700 nm are uniformly anchored on the MF skeletons. The electrochemical characterizations show that the electrode exhibits excellent specific area capacitance of 2.685 F cm−2 at 2 mA cm−2 and good cyclic stability with more than 80% of capacitance remained after 3000 cycles. Furthermore, a symmetrical aqueous supercapacitor is assembled and exhibits an excellent energy density up to 75.95 μWh cm−2 at the power density of 5.82 mW cm−2 and excellent cycling stability as the current density increases by 10 times. Even under a high strain of 70%, about 95.76% of the initial capacitance is retained after 500 consecutive compressions. These outstanding performances enable the MF/PPy composite a promising candidate for potential applications in compressible and flexible electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]