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Catalysts of multiphase nickel sulfide coupling with CeO 2 (NiS x /CeO 2 /NF) are fabricated through one step hydrothermal and calcination process. The as-obtained NiS x /CeO 2 /NF exhibits excellent activity towards overall water splitting reaction with a low potential of 1.53 V for 10 mA cm−2 in 1 M KOH. [Display omitted] Constructing nanostructured electrocatalysts with heterointerface and finetuning their electronic properties are essential for high-efficient overall water splitting. Here, we prepared a well-designed nano-flower-like multiphase and hybrid material of NiS/NiS 2 /CeO 2 /NF (NiS x /CeO 2 /NF) with rich heterointerfaces and abundant active sites through solvothermal reaction and post-annealing treatment. The as-fabricated NiS x /CeO 2 /NF exhibits exceptional catalytic performance for OER and HER. Specifically, in 1 M KOH solution, it requires the low overpotentials of 326 and 92 mV to achieve the current density of 200 and 10 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. More satisfactorily, when NiS x /CeO 2 /NF is used as the bifunctional catalyst, a low voltage of only 1.53 V is required to achieve a current density of 10 mA cm−2 for overall water splitting. The excellent catalytic performance should be attributed to its special heterogeneous structure and the synergy effect between NiS x and CeO 2. This work emphasizes the important significance of constructing efficient bifunctional electrocatalysts by reasonably designing heterostructures and multiphase components for overall water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] Designing heterojunction catalysts with energy effects at the interface, particularly combining the surface structure advantages of super-hydrophilic interfaces with the high activity advantages of bimetal synergistic optimisation, is the key to developing economical and efficient industrial electrocatalytic water-splitting catalysts. In this study, a coupled nanoflower-like NiFe(OH) x /(Ni, Fe)Se heterostructure catalyst supported on Ni foam (NF) (NFSe@NFOH/NF) was designed and successfully prepared using hydrothermal and electrodeposition strategies. Owing to the electron interaction at the heterogeneous amorphous (NFOH)/crystalline (NFSe) interface and the bimetallic synergistic effect of Ni and Fe, the prepared NFSe@NFOH/NF exhibited excellent and stable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalytic properties, with low overpotentials of 214/276 mV at 100 mA⋅cm−2 and 262/340 mV at 500 mA⋅cm−2. The assembled water electrolyser comprising NFSe@NFOH/NF || NFSe@NFOH/NF needed only small voltages of 1.73 and 1.85 V to yield current densities of 100 and 500 mA⋅cm−2, respectively. This study offers an innovative design idea for the rational adoption of interface engineering and amorphous–crystalline engineering techniques to construct catalysts with excellent catalytic activity and stability for electrocatalytic overall water splitting (EOWS) at a high current density, which further facilitates the advancement of sustainable energy technology in the future. [ABSTRACT FROM AUTHOR]

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] Exploration of highly efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is of crucial importance for the development of water splitting. In recent years, Cu-based materials have been widely concerned in OER due to their non-toxicity, rich reserves and highest reversibility. Meanwhile, Cu x O nanorods is easy to be prepared in industry. Herein, we report a fast preparation method to construct an integrated Cu x O@CoNi-LDH electrocatalyst with a unique 1D nanowire-2D nanosheet hierarchical core–shell structure by electrodepositing CoNi-LDH nanosheet arrays directly onto Cu x O nanorods (Cu x O were in situ-created on the Cu foam) at a large deposition voltage of −3.0 V vs SCE. The unique heterogeneous core–shell nanostructure, large deposition amount of CoNi-LDH and the synergistic effects between Cu x O core and CoNi-LDH shell can provide abundant active sites, rich open-channels and reduced charge transfer resistance (R ct) for effective oxygen release and facile electron transport. Consequently, the optimized Cu x O@CoNi-LDH/CF exhibits a low overpotential of 207 mV in 1 M KOH solution at the current density of 10 mV cm−2 and a small Tafel slope of 50.1 mV dec−1. After 60 h of long-term stability test, the catalytic performance is only slightly weakened. This work demonstrates a new approach to design the high-performance LDH and Cu-related OER catalysts by constructing a unique hierarchical core–shell nanostructure. [ABSTRACT FROM AUTHOR]

• Mo 3 S 4 /Co 1-x S nanosheets are synthesized by a simple one-step hydrothermal method. • Mo 3 S 4 /Co 1-x S@CF-8 has high hydrophilicity. • The bimetallic sulfide compound has high catalytic activity. • Mo 3 S 4 /Co 1-x S@CF-8 can achieve efficient overall water splitting. Hydrogen generation through electrochemical water decomposition is a promising method to address the global energy crisis. Herein, we report the synthesis of a series of flower-like Mo 3 S 4 /Co 1-x S composites on Co foil (Mo 3 S 4 /Co 1-x S@CF) as high-performance electrochemical water-splitting catalysts in an alkaline environment. The flower-like array structure of Mo 3 S 4 /Co 1-x S@CF not only increases the electrochemically active surface area of ​​the catalyst, but also facilitates the release of bubbles generated, resulting in enhanced catalytic activity. For the hydrogen evolution reaction, the Mo 3 S 4 /Co 1-x S@CF electrode exhibits good stability and excellent catalytic activity in 1.0 M KOH (η 10 = 105 mV), 1.0 M PBS (η 10 = 92 mV) and 0.5 M H 2 SO 4 (η 10 = 68 mV) solutions. For the oxygen evolution reaction, the electrode displays excellent stability and catalytic activity in 1.0 M KOH solution (η 10 = 215 mV). When used for overall water splitting in 1.0 M KOH solution, Mo 3 S 4 /Co 1-x S@CF achieves a current density of 10 mA cm−2 at a low potential of 1.58 V and maintains it stably for 40 h. This study presents a simple method for preparing transition metal-based bimetallic composite catalysts for efficient hydrogen production. [ABSTRACT FROM AUTHOR]