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• Co doped MoS 2 was decorated on nitrogen-doped carbon fiber/carbon paper (NCFCP) by a solvothermal process. • The lattice spacing of (1 0 0) plane of Co-MoS 2 was slightly narrow than that of MoS 2. • The as-prepared Co-MoS 2 /NCFCP hybrids showed enhanced electrochemical activity for HER. In this paper, Co-doped MoS 2 (Co-MoS 2) with various Co/Mo mole ratio (6%–12%) decorated on nitrogen-doped carbon fiber/carbon paper (NCFCP) (Co-MoS 2 /NCFCP) is fabricated by a solvothermal method as an efficient electrocatalyst for hydrogen evolution reaction (HER). The NCFCP substrate is prepared by electrochemical deposition of polypyrrole on carbon paper followed by heat treatment. The obtained 9% Co-MoS 2 /NCFCP hybrid catalyst exhibits an excellent electrocatalytic HER activity with a low overpotential of 174 mV at 10 mA cm−2, a small Tafel slope of 52 mV dec−1 and long-term stability. Thus, Co-MoS 2 /NCFCP hybrid holds high potential as an efficient earth-abundant electrocatalyst material for HER. [ABSTRACT FROM AUTHOR]

Recently, two-dimensional phosphorene (2D BP) has become an ideal material for electrocatalysts due to its short charge transport distance, high carrier mobility and fully exposed surface active sites. However, the inadequate adsorption energy of oxygen-containing intermediates results in the sluggish reaction kinetics, and thus limits its practical application. In this paper, granular amorphous Ni2P on the surface of BP to construct Ni2P@ BP heterostructure were introduced, in order to improve its electrochemical stability and reaction activity. The results show that, compared with the pure BP and Ni2P catalysts, the Ni2P@ BP catalyst exhibits excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activities with an overpotential of 167 and 186 mV at a current density of 10 mA/cm², respectively. As a bifunctional electrocatalyst, Ni2P@ BP requires only 1. 54 V applied bias (Vapp) to achieve a current density of 10 mA/cm². Finally, over 7% solar to hydrogen (STH) coversion efficiency is achieved assisting with a-Si:H/a-SiGe:H/ a-SiGe:H triple-junction solar cell, which is 95% higher than that of pure BP as a bifunctional electrocatalyst. [ABSTRACT FROM AUTHOR]

Renewable electricity-powered hydrogen production is an attractive alternative to unsustainable industrial processes, but the large-scale implantation of such sustainable technology still requires efficient and noble-metal-free electrocatalysts for driving cathodic hydrogen evolution reaction (HER), especially under alkaline conditions. In this paper, CoP nanowire array was in-situ developed on porous graphite felt (CoP/GF) as a new 3D electrocatalyst in facilitating hydrogen evolution electrocatalysis. This CoP/GF presents outstanding HER activity, requiring a low overpotential of 130 mV to deliver a current density of 20 mA cm−2 as tested in 1.0 M KOH. Furthermore, this free-standing catalyst exhibits impressive long-term durability of up to 50 h under working conditions. • CoP nanowire array was developed on graphite felt as a 3D electrocatalyst. • CoP/GF presents outstanding hydrogen evolution reaction performance. • CoP/GF exhibits impressive long-term durability of up to 50 h under working conditions. [ABSTRACT FROM AUTHOR]

This paper used ultrasonic method or solvothermal method to prepare cobalt-based MOFs with the same structural composition but different morphology by adjusting the experimental conditions. The cobalt-based MOF with laminar nanostructure (named as Co-MOF-C) exhibits more outstanding OER electrocatalytic activity (overpotential of 342 mV at 10 mA cm−2), a smaller Tafel slope (119 mV dec−1) and robust stability in alkaline media than the other cobalt-based MOF with the lumpy and block morphology (named as Co-MOF-A and Co-MOF-B, respectively). [Display omitted] • The cobalt-based MOFs with the same structural composition but different morphologies were synthesized by ultrasonic method or solvothermal method by adjusting the experimental conditions through a facile and timesaving method. • The as-prepared Co-MOF-C with a more apparent laminar nanostructure morphology possess many intriguing features, such as a faster charge transfer and mass transport, an improvement in mechanical stability, and more accessible active centers. • The Co-MOF-C exhibits more outstanding OER electrocatalytic activity (overpotential of 342 mV at 10 mA cm−2), a smaller Tafel slope (119 mV dec−1) and robust stability in alkaline media than the lumpy Co-MOF-A and Co-MOF-B with block morphology. Developing productive and stable catalysts using common elements for the production of hydrogen via water splitting is highly desirable. Due to their well-designed composition, unique morphology, and highly crystalline structure, metal–organic frameworks (MOFs) exhibit good electrocatalytic performance and have attracted significant research interest as OER catalysts. The optimized Co-MOF-C catalyst reported herein exhibited a smaller overpotential at 10 mA cm−2 and Tafel slope (342 mV, 119 mV dec−1) than Co-MOF-A and Co-MOF-B in an alkaline solution for OER. Moreover, Co-MOF-C showed better long-term durability and stability with negligible deactivation compared with the other MOF catalysts. The apparent laminar nanomorphology of Co-MOF-C provided more accessible active metal centers, better electrical conductivity, and improved kinetics, explaining its better performance as an OER electrocatalyst. [ABSTRACT FROM AUTHOR]

As the cost-effective and nontoxic alternative for hydrogen evolution reaction (HER), Co 9 S 8 has attracted much attention. This paper explores the regulation of Zn doping impacted the unique nanostructure and electrocatalytic performance on Co 9 S 8. Herein, utilizing copper foam (CF) as substrate, a series of different nanostructure of (Zn-)Co 9 S 8 @CF has been synthesized by accurately varying the ratio of Zn2+ to Co2+. Compared with aggregated pure Co 9 S 8 and other different ratios contrast samples, Zn–Co 9 S 8 @CF-(1-1) with a zinc to cobalt ratio of 1 possesses highly dispersity which can be attributed to the novel nano-neuron network structure. The electrochemical measurements for HER demonstrate that Zn–Co 9 S 8 @CF-(1-1) not only reveals superior activity with small overpotentials to achieve a current density of 10 mA cm−2 in acidic (278 mV) and alkaline (273 mV) media, but also exhibits long-time durability in the solution with a wide range of pH. The excellent performance of Zn–Co 9 S 8 @CF-(1-1) can be attributed to the unique reticular structure which can facilitate exposure of numerous active sites and favorable long-term stability. The substrate of three-dimensional CF can provide the remarkable conductivity. This work provides a precise and effective approach to regulate three-dimensional nanostructure of Zn-doped electrocatalysts for HER. Image 1 • Zn–Co 9 S 8 on copper foam (CF) with a nano-neuron network structure is synthesized. • The ratios of Zn2+ to Co2+ can affect the structure of Zn–Co 9 S 8 @CF. • Zn–Co 9 S 8 @CF exhibits excellent activity and long-time durability with a wide range of pH. • Zn doping is a promising method for construct the novel structure of electrocatalysts. [ABSTRACT FROM AUTHOR]

In this paper, we present a solvothermal synthesis of iron phosphide electrocatalysts using a triphenylphosphine (TPP) precursor. The synthetic protocol generates Fe 2 P phase at 300 °C and FeP phase at 350 °C. To enhance the catalytic activities of obtained iron phosphide particles heat-treatments were carried out at elevated temperatures. Annealing at 500 °C under reductive atmosphere induced structural changes in the samples: (i) Fe 2 P provided a pure Fe 3 P phase (Fe 3 P−500 °C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe 2 P/FeP−500 °C). Pure Fe 2 P films was prepared under argon atmosphere at 450 °C (Fe 2 P−450 °C). The electrocatalytic activities of heat-treated Fe 2 P−450 °C, Fe 3 P−500 °C, and Fe 2 P/FeP−500 °C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4. The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with Fe 2 P/FeP−500 °C catalyst. Image 1 • Iron phosphides catalyst were synthesized via a wet-chemistry method. • Spin-coating of iron phosphide particles onto graphite substrates yielded uniform thin films. • Heat treatment of iron phosphides at 500 °C resulted in structural changes. • The iron phosphide films were used as electrocatalysts for efficient hydrogen evolution. [ABSTRACT FROM AUTHOR]

CoP 3 is a promising electrocatalyst for the hydrogen evolution reaction, however it is still challenging for CoP 3 -based catalyst to deliver excellent activities in a wide pH range. In this work, the self-standing Ni-doped CoP 3 nanowire arrays (Ni-CoP 3 NWs) on carbon fiber paper were synthesized by hydrothermal method followed with an in situ phosphating process. The results show that the Ni doping effectively boosts the electrocatalytic hydrogen evolution for CoP 3 NWs over the wide pH range with good stability. The Ni doped CoP 3 NWs sample with the Ni: Co mole ratio of 10% (Ni-CoP 3 -10%) shows a low overpotential of 66 mV to afford the current density of 10 mA cm−2 in 0.5 M H 2 SO 4 , which is the optimal catalytic performance in this work. Furthermore, Ni-CoP 3 -10% sample also shows excellent electrocatalytic performance in alkaline and neutral conditions, which needs the overpotential of 114 and 131 mV to afford the current density of 10 mA cm−2 in 1 M KOH and 1 M PBS, respectively. The enhanced electrocatalytic activity can be ascribed to that the Ni doping improves the electron transport, increases the electrochemical active surface area and optimizes the Gibbs free energy of hydrogen adsorption for the CoP 3 NWs, which develops it as a promising electrochemical catalyst for hydrogen evolution. • Ni doped CoP 3 nanowire arrays are prepared by vacuum encapsulation technique. • Ni doping boosts the HER activity for CoP 3 in wide pH media. • The reasons of the enhanced HER performance for Ni doped CoP 3 is revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/CoTe was prepared via precipitation, reflux-hydrothermal, and hydrogen treatment. • The unique 3D structure promotes the exposure of active sites and ions diffusion. • Well-defined heterointerfaces improve the kinetics of OER and electrical conductivity. In this study, a three-step process involving precipitation, reflux-hydrothermal method, and hydrogen treatment leads to the formation of a Prussian blue analog (PBA)-derived Co/CoTe heterostructure featuring a unique hierarchical 3D structure. This framework facilitates efficient exposure of the catalytically active sites and fast diffusion of the electrolyte. Additionally, the well-defined metal/semiconductor heterointerfaces result in an overall electrical conductivity enhancement and promote the oxygen evolution reaction (OER) kinetics by lowering the activation energy. Owing to the synergistic effect of Co and CoTe, the Co/CoTe heterostructure displays high electrocatalytic activity for OER, attaining an overpotential of 400 mV to deliver a current density of 50 mA cm−2 and a low Tafel slope of 94.1 mV dec−1, which is superior to pure CoTe and Co counterparts. Furthermore, the Co/CoTe exhibits outstanding durability over 50 h without obvious change in alkaline media. The synthetic strategy reported in this paper provides new insights into the design and preparation of high-performance heterostructured materials of interest in energy-related applications. [ABSTRACT FROM AUTHOR]

• Ammonium polyphosphate as a green phosphorus source is reported for the first time; • The supramolecular precursor is self-assembly by coordination and electrostatic interactions; • MoP/MoNiP@NC exhibits remarkable and stable HER performance; • Density functional theory (DFT) calculation assigns negative P sites as best active sites. Transition metal phosphides (TMPs) have increasingly become the research focus of hydrogen evolution catalysts. In this paper, bimetallic phosphide electrocatalyst (MoP/MoNiP@NC) is prepared by predesigned supramolecular gels as precursors via a simple carbonization and phosphorating process, which experience a self-assembly process of ammonium polyphosphate (APP), phosphomolybdic acid hydrate (PMo 12), polyaniline (PANI) and Ni2+ ions via electrostatic and coordination interaction during heating in aqueous solutions. Ammonium polyphosphate as a new phosphorus source with non-toxicity and non-corrosive gas is reported for the first time and exhibits strong coordination ability with metal ions and polyoxometalate. MoP/MoNiP@NC displays satisfactory hydrogen evolution activity with low overpotentials of 94 and 137 mV at 10 mA cm−2 as well as excellent durability for 24 h in 1.0 M KOH and 0.5 M H 2 SO 4 , respectively. It is worth noted that the hydrogen evolution performance of the electrocatalyst is superior to the commercial Pt/C at a current density greater than 80 mA cm−2 under alkaline solution. The remarkable HER activity can be attributed to the synergistic effect of MoNiP and MoP nanoparticles, N-doped porous carbon layers protecting the nanoparticles from corrosion, exposing large amount of active sites and enhancing the mass transfer process. Density functional theory (DFT) calculations illustrate that the best active sites come from the negative P sites of MoNiP nanoparticles. This work provides an environment friendly and reproducible strategy for using APP as a green phosphorus source to synthesize transition metal phosphides as efficient electrocatalysts for energy conversion. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2) is one of the promising candidates for hydrogen evolution reaction (HER), it's HER properties can be extremely enhanced by the construction of nanostructure and the regulation of electronic structure. In this paper, hierarchical composites with MoS 2 and carbon nanotubes (CNTs) as the noble metal-free electrocatalysts for HER were fabricated through calcination and hydrothermal processes, in which the MoS 2 nanosheets with Ni atoms incorporation were vertically grown on the outsides of nitrogen (N)-doped CNTs. The constructed hierarchical structures provide large specific surface area of about 150 m2 g−1 and high structure stability. Importantly, the MoS 2 nanosheets with enlarged interlayer spacing possess ultrathin structure of about 4 nm in thickness. Owing to the incorporation of Ni atoms, abundant unsaturated S atoms are obtained in the basal plane, which leading to more active sites exposed during HER processes. Meanwhile, N-doped CNTs can act as the substrate for MoS 2 nanosheets growing and simultaneously improve the conductivity of catalyst. Based on the synergy of hierarchical structure, increased active sites and enhanced conductivity, the as-prepared electrocatalysts exhibit superior HER activity with low overpotentials, small Tafel slopes and long-time durability in both acidic and alkaline electrolytes. The overpotentials of 158 and 179 mV were required to drive HER current density up to 10 mA cm−2 in 0.5 M H 2 SO 4 and 1.0 M KOH, respectively. This work reports a highly efficient MoS 2 -based electrocatalyst for HER via fabricating hierarchical structure and doping Ni atoms. Image 1 [ABSTRACT FROM AUTHOR]