Dual-Functional N Dopants in Edges and Basal Plane of MoS2 Nanosheets Toward Efficient and Durable Hydrogen Evolution
TL;DR: In this article, the dual-functions of N dopants in molybdenum disulfide (MoS2) catalyst through a combined experimental and first-principles approach were revealed.
Abstract: Herein, the authors explicitly reveal the dual-functions of N dopants in molybdenum disulfide (MoS2) catalyst through a combined experimental and first-principles approach. The authors achieve an economical, ecofriendly, and most efficient MoS2-based hydrogen evolution reaction (HER) catalyst of N-doped MoS2 nanosheets, exhibiting an onset overpotential of 35 mV, an overpotential of 121 mV at 100 mA cm-2 and a Tafel slope of 41 mV dec(-1). The dual-functions of N dopants are (1) activating the HER catalytic activity of MoS2 S-edge and (2) enhancing the conductivity of MoS2 basal plane to promote rapid charge transfer. Comprehensive electrochemical measurements prove that both the amount of active HER sites and the conductivity of N-doped MoS2 increase as a result of doping N. Systematic first-principles calculations identify the active HER sites in N-doped MoS2 edges and also illustrate the conducting charges spreading over N-doped basal plane induced by strong Mo 3d-S 2p-N 2p hybridizations at Fermi level. The experimental and theoretical research on the efficient HER catalysis of N-doped MoS2 nanosheets possesses great potential for future sustainable hydrogen production via water electrolysis and will stimulate further development on nonmetal-doped MoS2 systems to bring about novel high-performance HER catalysts.
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TL;DR: The fundamentals of HER are summarized and the recent state-of-the-art advances in the low-cost and high-performance catalysts based on noble and non-noble metals, as well as metal-free HER electrocatalysts are reviewed.
Abstract: Hydrogen fuel is considered as the cleanest renewable resource and the primary alternative to fossil fuels for future energy supply. Sustainable hydrogen generation is the major prerequisite to realize future hydrogen economy. The electrocatalytic hydrogen evolution reaction (HER), as the vital step of water electrolysis to H2 production, has been the subject of extensive study over the past decades. In this comprehensive review, we first summarize the fundamentals of HER and review the recent state-of-the-art advances in the low-cost and high-performance catalysts based on noble and non-noble metals, as well as metal-free HER electrocatalysts. We systemically discuss the insights into the relationship among the catalytic activity, morphology, structure, composition, and synthetic method. Strategies for developing an effective catalyst, including increasing the intrinsic activity of active sites and/or increasing the number of active sites, are summarized and highlighted. Finally, the challenges, perspectives, and research directions of HER electrocatalysis are featured.
1,387 citations
TL;DR: Insightful insights gathered in the process of studying TMS are provided, and valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies are described.
Abstract: Heterogenous electrocatalysts based on transition metal sulfides (TMS) are being actively explored in renewable energy research because nanostructured forms support high intrinsic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, it is described how researchers are working to improve the performance of TMS-based materials by manipulating their internal and external nanoarchitectures. A general introduction to the water-splitting reaction is initially provided to explain the most important parameters in accessing the catalytic performance of nanomaterials catalysts. Later, the general synthetic methods used to prepare TMS-based materials are explained in order to delve into the various strategies being used to achieve higher electrocatalytic performance in the HER. Complementary strategies can be used to increase the OER performance of TMS, resulting in bifunctional water-splitting electrocatalysts for both the HER and the OER. Finally, the current challenges and future opportunities of TMS materials in the context of water splitting are summarized. The aim herein is to provide insights gathered in the process of studying TMS, and describe valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies.
899 citations
TL;DR: This Review systematically introduces and discusses the classic synthesis methods, advanced characterization techniques, and various catalytic applications toward two-dimensional materials confining single-atom catalysts.
Abstract: Two-dimensional materials and single-atom catalysts are two frontier research fields in catalysis. A new category of catalysts with the integration of both aspects has been rapidly developed in recent years, and significant advantages were established to make it an independent research field. In this Review, we will focus on the concept of two-dimensional materials confining single atoms for catalysis. The new electronic states via the integration lead to their mutual benefits in activity, that is, two-dimensional materials with unique geometric and electronic structures can modulate the catalytic performance of the confined single atoms, and in other cases the confined single atoms can in turn affect the intrinsic activity of two-dimensional materials. Three typical two-dimensional materials are mainly involved here, i.e., graphene, g-C3N4, and MoS2, and the confined single atoms include both metal and nonmetal atoms. First, we systematically introduce and discuss the classic synthesis methods, advanced ...
647 citations
TL;DR: In this paper, a facile and controllable synthesis strategy for nickel-cobalt bimetal phosphide nanotubes as highly efficient electrocatalysts for overall water splitting via low-temperature phosphorization from a bimetallic metal-organic framework (MOF-74) precursor is reported.
Abstract: The design of highly efficient, stable, and noble-metal-free bifunctional electrocatalysts for overall water splitting is critical but challenging. Herein, a facile and controllable synthesis strategy for nickel–cobalt bimetal phosphide nanotubes as highly efficient electrocatalysts for overall water splitting via low-temperature phosphorization from a bimetallic metal-organic framework (MOF-74) precursor is reported. By optimizing the molar ratio of Co/Ni atoms in MOF-74, a series of CoxNiyP catalysts are synthesized, and the obtained Co4Ni1P has a rare form of nanotubes that possess similar morphology to the MOF precursor and exhibit perfect dispersal of the active sites. The nanotubes show remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic performance in an alkaline electrolyte, affording a current density of 10 mA cm−2 at overpotentials of 129 mV for HER and 245 mV for OER, respectively. An electrolyzer with Co4Ni1P nanotubes as both the cathode and anode catalyst in alkaline solutions achieves a current density of 10 mA cm−2 at a voltage of 1.59 V, which is comparable to the integrated Pt/C and RuO2 counterparts and ranks among the best of the metal-phosphide electrocatalysts reported to date.
568 citations
TL;DR: In this article, a rational design of hollow Mo-doped CoP (Mo-CoP) nanoarrays, which simultaneously combine electronic structure modification through doping with a high density of reaction sites through nanostructuring, is reported.
558 citations
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
IBM1
TL;DR: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way and can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function.
Abstract: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.
61,450 citations
TL;DR: In this article, a method for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector is given, where the integration can be over the entire zone or over specified portions thereof.
Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.
51,059 citations
TL;DR: A way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects as well as significant interconfigurational and interterm errors remain.
Abstract: Generalized gradient approximations (GGA's) seek to improve upon the accuracy of the local-spin-density (LSD) approximation in electronic-structure calculations. Perdew and Wang have developed a GGA based on real-space cutoff of the spurious long-range components of the second-order gradient expansion for the exchange-correlation hole. We have found that this density functional performs well in numerical tests for a variety of systems: (1) Total energies of 30 atoms are highly accurate. (2) Ionization energies and electron affinities are improved in a statistical sense, although significant interconfigurational and interterm errors remain. (3) Accurate atomization energies are found for seven hydrocarbon molecules, with a rms error per bond of 0.1 eV, compared with 0.7 eV for the LSD approximation and 2.4 eV for the Hartree-Fock approximation. (4) For atoms and molecules, there is a cancellation of error between density functionals for exchange and correlation, which is most striking whenever the Hartree-Fock result is furthest from experiment. (5) The surprising LSD underestimation of the lattice constants of Li and Na by 3--4 % is corrected, and the magnetic ground state of solid Fe is restored. (6) The work function, surface energy (neglecting the long-range contribution), and curvature energy of a metallic surface are all slightly reduced in comparison with LSD. Taking account of the positive long-range contribution, we find surface and curvature energies in good agreement with experimental or exact values. Finally, a way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects.
17,848 citations