Nickel Phosphide Electrocatalysts for Hydrogen Evolution Reaction

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

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

Asymmetrical radial strain energy strategy of M–N–SWCNT single atom catalysts for highly efficient hydrogen evolution: A high-throughput DFT study

Formation of ReS2/ReO3 semiconductor-metal heterostructure boosts electrocatalytic performance of pristine ReS2 nanoparticles in hydrogen evolution reaction

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.

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.

Fe-B alloy coupled with Fe clusters as an efficient cocatalyst for photocatalytic hydrogen evolution

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.

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

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.

Urchin-like Co0.8-Mn0.2-P/CC nanowires array: a high-performance and cost-effective hydrogen evolution electrocatalyst

One promising way to tune the physicochemical properties of materials and optimize their performance in various potential applications is to engineer material structures at the atomic level. As is well known, the performance of Pd-based catalysts has long been constrained by surface contamination and their single structure. Here, we employed an unadulterated top-down synthesis method, known as laser fragmentation in liquid (LFL), to modify pristine PdPS crystals and obtained a kind of metastable palladium-sulfur compound nanoparticles (LFL-PdS NPs) as a highly efficient electrocatalyst for hydrogen evolution reaction (HER). Laser fragmentation of the layered PdPS crystal led to a structural reorganization at the atomic level and resulted in the formation of uniform metastable LFL-PdS NPs. Noteworthy, the LFL-PdS NPs show excellent electrocatalytic HER performance and stability in acidic media, with an overpotential of –66 mV at 10 mA⋅cm−2, the Tafel slope of 42 mV⋅dec−1. The combined catalytic performances of our LFL-PdS NPs are comparable to the Pt/C catalyst for HER. This work provides a top-down synthesis strategy as a promising approach to design highly active metastable metal composite electrocatalysts for sustainable energy applications.

Molybdenum carbide/phosphide hybrid nanoparticles embedded P, N co-doped carbon nanofibers for highly efficient hydrogen production in acidic, alkaline solution and seawater

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