Multi-dimensional MoS2/S-doped-CoP heterostructure nanoarrays as an efficient electrocatalyst for hydrogen evolution reaction

Keplerate polyoxomolybdate nanoball mediated controllable preparation of metal-doped molybdenum disulfide for electrocatalytic hydrogen evolution in acidic and alkaline media

The production of hydrogen through electrochemical water splitting driven by clean energy becomes a sustainable route for utilization of hydrogen energy, while an efficient hydrogen evolution reaction (HER) electrocatalyst is required to achieve a high energy conversion efficiency. Nickel phosphides have been widely explored for electrocatalytic HER due to their unique electronic properties, efficient electrocatalytic performance, and a superior anti-corrosion feature. However, the HER activities of nickel phosphide electrocatalysts are still low for practical applications in electrolyzers, and further studies are necessary. Therefore, at the current stage, a specific comprehensive review is necessary to focus on the progresses of the nickel phosphide electrocatalysts. This review focuses on the developments of preparation approaches of nickel phosphides for HER, including a mechanism of HER, properties of nickel phosphides, and preparation and electrocatalytic HER performances of nickel phosphides. The progresses of the preparation and HER activities of the nickel phosphide electrocatalysts are mainly discussed by classification of the preparation method. The comparative surveys of their HER activities are made in terms of experimental metrics of overpotential at a certain current density and Tafel slope together with the preparation method. The remaining challenges and perspectives of the future development of nickel phosphide electrocatalysts for HER are also proposed.

Facile synthesis of interlaced flower-like layered double hydroxides grown on porous CoMoP as a highly efficient electrocatalyst for hydrogen evolution reaction

Powder sintered Ni–P/CNTs composites as three-dimensional self-supported efficient electrocatalysts for hydrogen evolution reaction

Design and construction of robust nickel-based MOFs for promoting HER catalytic activity

Electricity driven proton exchange membrane-based water electrolysis (PEMWE) has demonstrated considerable credibility in recent years, establishing high competency enabling PEMWE technology for rapid generation of clean hydrogen fuel 1-7. In order to attain the high efficiency needed and successful commercialization of PEMWE, there is a critical need to identify highly active, robust, and earth-abundant electrocatalysts for accelerating the hydrogen evolution reaction (HER) with minimum energy input 8. In the pursuit of achieving this goal, in the present work, employing the density functional theory (DFT) based calculations for rationalizing the thermodynamics and reaction kinetics of HER, we have investigated the platinum group metal (PGM)-free, earth-abundant, transition metal non-oxide (TMN) based electrocatalysts for acid mediated HER in PEMWE. Based on the theoretical calculations, the as-synthesized TMN electrocatalyst compositions reveal optimized hydrogen adsorption free energies (ΔGH *) and beneficial electronic structures modification, offering superior charge transfer kinetics, lower reaction barrier, low water contact angle (7o) suggesting high wettability (Fig. 1), and high electrocatalytic activity for HER. Furthermore, the highly active electrocatalyst compositions display excellent long term electrochemical HER stability in acidic media, with no significant obvious degradation in current density. The as-synthesized electrocatalysts thus, has propensity for exhibiting robust HER performance with excellent structural and mechanical integrity. The experimental results are in excellent agreement with the DFT calculations which further accentuate the incorporation of suitable PGM-free dopants into the TMN compositions resulting in optimized electronic structures lowering the HER reaction barriers. The system therefore offers improved electrocatalytic performance for HER which is comparable to state-of-the-art Pt/C electrocatalysts. Accordingly, the as-synthesized PGM-free electrocatalysts can be considered as reliable HER candidates, vital for the development of acid mediated PEM based water splitting employing PGM-free electrocatalysts. Results of this study will be presented and discussed. Acknowledgements: Financial support of NSF-CBET grant# 1511390, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) is acknowledged.

Optimizing the electronic and synergistic effect of hybrid electrocatalysts based on Pt and Pt-based nanocatalysts is of tremendous importance towards a superior hydrogen evolution performance under both acidic and alkaline conditions. However, developing an ideal Pt-based hydrogen evolution reaction (HER) electrocatalyst with moderated electronic structure as well as strong synergistic effect is still a challenge. Herein, we fabricated boron (B)-doped PtNi nanobundles by a two-step method using NaBH4 as the boron source to obtain PtNi/Ni4 B3 heterostructures with well-defined nanointerfaces between PtNi and Ni4 B3 , achieving an enhanced catalytic HER performance. Especially, the PtNi/Ni4 B3 nanobundles (PtNi/Ni4 B3 NBs) can deliver a current density of 10 mA cm-2 at the overpotential of 14.6 and 26.5 mV under alkaline and acidic media, respectively, as well as outstanding electrochemical stability over 40 h at the current density of 10 mA cm-2 . Remarkably, this approach is also universal for the syntheses of PtCo/Co3 B and PtFe/Fe49 B with outstanding electrocatalytic HER performance.

Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required. In this work, we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo2C on carbon fiber paper (Ni-Mo2CCB/CFP) for hydrogen evolution reaction (HER). The effects of nickel nitrate concentration on the phase composition, morphology, and electrocatalytic HER performance of Ni-doped Mo2C@CFP electrocatalysts was investigated. With the continuous increase of Ni(NO3)2 concentration, the morphology of Mo2C gradually changes from granular to flower-like, providing larger specific surface area and more active sites. Doping nickel (Ni) into the crystal lattice of Mo2C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity. The as-developed Mo2C-3 M Ni(NO3)2/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm−2. This catalyst has a fast HER kinetics, as demonstrated by a very small Tafel slope of 27.4 mV·dec−1, and persistent long-term stability. A further higher Ni concentration had an adverse effect on the electrocatalytic performance. Density functional theory (DFT) calculations further verified the experimental results. Ni doping could reduce the binding energy of Mo-H, facilitating the desorption of the adsorbed hydrogen (Hads) on the surface, thereby improving the intrinsic catalytic activity of Ni-doped Mo2C-based catalysts. Nevertheless, excessive Ni doping would inhibit the catalytic activity of the electrocatalysts. This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity, but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.

Large‐scale development of low‐cost, efficient, and stable powder electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions is a key step toward commercial hydrogen production. Herein, a hierarchical NiMo‐MoO3-x hollow nanotube (NiMo‐MoO3-x‐HNT) with bifunctional groups as an efficient HER electrocatalyst was strategically invented using an MoO3 nanorod (MoO3−NR) as the precursor. The synthesis mechanism of the NiMo‐MoO3-x‐HNT is established based on in‐depth investigations using diffraction, spectral, and microscopy results. Experimental results suggest that the NiMo‐MoO3-x‐HNT exhibits excellent electrocatalytic HER performance in 1 M KOH, with a low overpotential of 26.5 mV@10.0 mA cm-2 and a small Tafel slope of 32.6 mV dec–1. These values are comparable to those of cutting‐edge electrocatalysts based on platinum‐group metals. Moreover, it exhibits an almost unaffected cyclic stability over 50,000 cycles and robust durability over 98 h. This remarkable performance is attributed to its bifunctional groups and the porous hierarchical hollow nanotubular morphology. In summary, this study proposes a novel, efficient, and cost‐effective strategy for the development of noble metal‐free, high‐performance HER electrocatalysts.

Exploring catalysts with low cost and excellent performance for the hydrogen evolution reaction (HER) is still a significant challenge. In this work, zeolitic imidazolate framework 8 (ZIF-8), hybridized with polyvinylpyrrolidone, was used to prepare Zn, Ni co-loaded N-doped porous carbon (ZnNi/NPC) via a straightforward absorption and pyrolysis process. The as-prepared ZnNi/NPC was used as a catalyst for the HER. This experiment showed that the porous structure and Ni doping have a significant influence on the HER activity of the catalyst. Compared with Zn/NC and Zn/NPC, ZnNi/NPC exhibits superior HER activity with an overpotential of 198 mV and a Tafel slope of 69.2 mV dec−1. ZnNi/NPC also shows excellent physical and chemical stability during the HER process. Considering the lower cost and excellent HER performance of ZnNi/NPC, this work provides an attractive solution to fabricate non-precious materials and offers a possible new strategy to replace Pt-based electrocatalysts for HER.

Two facile routes to an AB&Cu-MOF composite with improved hydrogen evolution reaction

Iron-incorporated NiS/Ni(OH)2 composite as an efficient electrocatalyst for hydrogen evolution reaction from water in a neutral medium

Ruthenium decorated 2D N-doped carbon nanocone arrays for pH-universal electrocatalytic hydrogen evolution

Boosting the hydrogen evolution of layered double hydroxide by optimizing the electronic structure and accelerating the water dissociation kinetics

Though transition-metal-based materials have emerged as the most promising alternatives to Pt-based electrocatalysts in hydrogen evolution reaction (HER), only a few of them (Fe-, Co-, Ni-, W-, and Mo-based materials) are used as efficient HER electrocatalysts, while others are generally considered as HER-inactive materials with poor activities. Here, a theory-guided experiment is carried out to activate titanium dioxide as a new efficient HER electrocatalyst. First-principles simulations indicate that the hydrogen adsorption free energy could be optimized through tuning the structural and electronic properties of TiO2. Then Cu-doped amorphous TiO2 is successfully prepared based on the theoretical results. The activated TiO2 expectedly shows excellent HER performance with a low overpotential of 92 mV at 10 mA cm-2 in alkaline media, which is far superior to that of the crystalline TiO2 (over 400 mV). The origin of HER activity is further investigated in detail. The corrugation of the amorphous surface helps stabilize the adsorbed water molecule, crucial for the water dissociation of the Volmer step. The Cu doping can strengthen the orbital hybridization of H1s and O2p favoring the hydrogen adsorption/desorption and improve the electrical conductivity. Our work highlights the great potential of traditionally inactive materials in HER electrocatalysis and helps deepen our understanding of the catalytic mechanism.