In this Communication, we report the topotactic fabrication of self-supported nanoporous cobalt phosphide nanowire arrays on carbon cloth (CoP/CC) via low-temperature phosphidation of the corresponding Co(OH)F/CC precursor. The CoP/CC, as a robust integrated 3D hydrogen-evolving cathode, shows a low onset overpotential of 38 mV and a small Tafel slope of 51 mV dec(-1), and it maintains its catalytic activity for at least 80,00 s in acidic media. It needs overpotentials (η) of 67, 100, and 204 mV to attain current densities of 10, 20, and 100 mA cm(-2), respectively. Additionally, this electrode offers excellent catalytic performance and durability under neutral and basic conditions.

Progress in catalysis is driven by society's needs. The development of new electrocatalysts to make renewable and clean fuels from abundant and easily accessible resources is among the most challenging and demanding tasks for today's scientists and engineers. The electrochemical splitting of water into hydrogen and oxygen has been known for over 200 years, but in the last decade and motivated by the perspective of solar hydrogen production, new catalysts made of earth-abundant materials have emerged. Here we present an overview of recent developments in the non-noble metal catalysts for electrochemical hydrogen evolution reaction (HER). Emphasis is given to the nanostructuring of industrially relevant hydrotreating catalysts as potential HER electrocatalysts. The new syntheses and nanostructuring approaches might pave the way for future development of highly efficient catalysts for energy conversion.

The hydrogen evolution reaction (HER) is a crucial step in electrochemical water splitting and demands an efficient, durable and cheap catalyst if it is to succeed in real applications. For an energy-efficient HER, a catalyst must be able to trigger proton reduction with minimal overpotential and have fast kinetics. The most efficient catalysts in acidic media are platinum-based, as the strength of the Pt-H bond is associated with the fastest reaction rate for the HER. The use of platinum, however, raises issues linked to cost and stability in non-acidic media. Recently, non-precious-metal-based catalysts have been reported, but these are susceptible to acid corrosion and are typically much inferior to Pt-based catalysts, exhibiting higher overpotentials and lower stability. As a cheaper alternative to platinum, ruthenium possesses a similar bond strength with hydrogen (∼65 kcal mol), but has never been studied as a viable alternative for a HER catalyst. Here, we report a Ru-based catalyst for the HER that can operate both in acidic and alkaline media. Our catalyst is made of Ru nanoparticles dispersed within a nitrogenated holey two-dimensional carbon structure (Ru@CN). The Ru@CN electrocatalyst exhibits high turnover frequencies at 25 mV (0.67 H s in 0.5 M HSO solution; 0.75 H s in 1.0 M KOH solution) and small overpotentials at 10 mA cm (13.5 mV in 0.5 M HSO solution; 17.0 mV in 1.0 M KOH solution) as well as superior stability in both acidic and alkaline media. These performances are comparable to, or even better than, the Pt/C catalyst for the HER.

Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen production through electrolysis or photoelectrochemistry. Here we report nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decomposition of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete reduction and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves similar to 20 mA cm(-2) at a voltage of 1.5V, and which may be operated by a single-cell alkaline battery, is fabricated using cheap, non-precious metal-based electrocatalysts.

Improving the sluggish kinetics for the electrochemical reduction of water to molecular hydrogen in alkaline environments is one key to reducing the high overpotentials and associated energy losses in water-alkali and chlor-alkali electrolyzers. We found that a controlled arrangement of nanometer-scale Ni(OH)(2) clusters on platinum electrode surfaces manifests a factor of 8 activity increase in catalyzing the hydrogen evolution reaction relative to state-of-the-art metal and metal-oxide catalysts. In a bifunctional effect, the edges of the Ni(OH)(2) clusters promoted the dissociation of water and the production of hydrogen intermediates that then adsorbed on the nearby Pt surfaces and recombined into molecular hydrogen. The generation of these hydrogen intermediates could be further enhanced via Li(+)-induced destabilization of the HO-H bond, resulting in a factor of 10 total increase in activity.

The hydrogen evolution reaction (HER) is one of the two processes in electrolytic water splitting. Known for more than two centuries, the HER still receives great attention in fundamental and applied science in view of its apparent simplicity (only two electrons are transferred), fast kinetics in acidic media, and promising technological applications in electrolyzers. However, the exact nature of active catalytic sites for this reaction is often uncertain, especially at nonuniform metal electrodes. Identification of such centers is important, as the HER will probably be central in future energy provision schemes, and it is simultaneously a convenient model reaction to study structure-composition-activity relations in catalysis. In this work, using simple coordination-activity considerations, we outline the location and geometric configuration of the active sites at various model Pt single-crystal electrodes. We show that when the coordination of such surface sites is optimized and their density at the surface is maximized, the experimental-specific HER activities are among the highest reported in the literature for pure platinum with a well-defined surface structure under similar conditions.

Single-atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential-cycling method to synthesize a catalyst comprising single Pt atoms on CoP-based nanotube arrays supported by a Ni foam, termed PtSA-NT-NF. This binder-free catalyst is centimeter-scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA-NT-NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large-scale production strategy for binder-free Pt SAC electrodes for efficient HER in neutral media.© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Platinum-based catalysts have been considered the most effective electrocatalysts for the hydrogen evolution reaction in water splitting. However, platinum utilization in these electrocatalysts is extremely low, as the active sites are only located on the surface of the catalyst particles. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their efficiency by utilizing nearly all platinum atoms. Here we report on a practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique. The single platinum atom catalysts are investigated for the hydrogen evolution reaction, where they exhibit significantly enhanced catalytic activity (up to 37 times) and high stability in comparison with the state-of-the-art commercial platinum/carbon catalysts. The X-ray absorption fine structure and density functional theory analyses indicate that the partially unoccupied density of states of the platinum atoms' 5d orbitals on the nitrogen-doped graphene are responsible for the excellent performance.

Yan, Binghai; Felser, Claudia Max Planck Inst Chem Phys Solids, D-01187 Dresden, Germany. Yan, Binghai Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany. Yan, Binghai ShanghaiTech Univ, Sch Phys Sci & Technol, Shanghai 200031, Peoples R China. Stadtmueller, Benjamin; Haag, Norman; Jakobs, Sebastian; Seidel, Johannes; Jungkenn, Dominik; Cinchetti, Mirko; Aeschlimann, Martin Univ Kaiserslautern, Dept Phys, D-67653 Kaiserslautern, Germany. Stadtmueller, Benjamin; Haag, Norman; Jakobs, Sebastian; Seidel, Johannes; Jungkenn, Dominik; Cinchetti, Mirko; Aeschlimann, Martin Univ Kaiserslautern, Res Ctr OPTIMAS, D-67653 Kaiserslautern, Germany. Mathias, Stefan Univ Gottingen, Inst Phys 1, D-37077 Gottingen, Germany.

The physical property investigation (like transport measurements) and ultimate application of the topological insulators usually involve surfaces that are exposed to ambient environment (1 atm and room temperature). One critical issue is how the topological surface state will behave under such ambient conditions. We report high resolution angle-resolved photoemission measurements to directly probe the surface state of the prototypical topological insulators, Bi(2)Se(3) and Bi(2)Te(3), upon exposing to various environments. We find that the topological order is robust even when the surface is exposed to air at room temperature. However, the surface state is strongly modified after such an exposure. Particularly, we have observed the formation of two-dimensional quantum well states near the exposed surface of the topological insulators. These findings provide key information in understanding the surface properties of the topological insulators under ambient environment and in engineering the topological surface state for applications.

Shekhar, Chandra; Nayak, Ajaya K.; Sun, Yan; Schmidt, Marcus; Nicklas, Michael; Schnelle, Walter; Borrmann, Horst; Grin, Yuri; Felser, Claudia; Yan, Binghai Max Planck Inst Chem Phys Solids, D-01187 Dresden, Germany. Nayak, Ajaya K. Max Planck Inst Microstruct Phys, D-06120 Halle, Germany. Leermakers, Inge; Zeitler, Uli Radboud Univ Nijmegen, HFML EMFL, NL-6525 ED Nijmegen, Netherlands. Skourski, Yurii; Wosnitza, Jochen Helmholtz Zentrum Dresden Rossendorf, Dresden High Magnet Field Lab HLD EMFL, D-01328 Dresden, Germany. Liu, Zhongkai Diamond Light Source, Harwell OX11 0QX, Berks, England. Chen, Yulin Univ Oxford, Dept Phys, Oxford OX1 3PU, England. Yan, Binghai Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany.

The vital role of electrocatalysts in determining the efficiency of renewable energy conversion inspired the uncovering of the relation between the catalytic efficiency and electronic structure, in which the volcano-type plot based on adsorption energies and d-band model has achieved great success. At the same time, catalysts with nontrivial topological electronic structures have received considerable attention because of their robust topological surface states and high-mobility electrons, which favor the electrons transfer processes in the heterogeneous catalysis reactions. Under the guidance of this theory, excellent catalysts were reported among topological materials. Inspired by the current development of catalyst and topological materials, we tried to extract a pure intrinsic physical parameter, projected Berry phase (PBP), that only depends on the bulk electronic structure. Applying this parameter to the well-known nonmagnetic transition-metal electrocatalysts, we found a linear relationship between PBP and catalytic efficiency of hydrogen evolution reaction (HER) after considering the symmetry constraint. This can be used as a descriptor for the prediction and designing of promising catalysts for HER, which is realized experimentally in PtCu nanostructures. This work illustrates the importance of the pure bulk band structure effect on electrochemical activities and implies an effective way to understand the mechanism of HER catalysts.Copyright © 2020 American Chemical Society.

The pace of materials discovery for heterogeneous catalysts and electrocatalysts could, in principle, be accelerated by the development of efficient computational screening methods. This would require an integrated approach, where the catalytic activity and stability of new materials are evaluated and where predictions are benchmarked by careful synthesis and experimental tests. In this contribution, we present a density functional theory-based, high-throughput screening scheme that successfully uses these strategies to identify a new electrocatalyst for the hydrogen evolution reaction (HER). The activity of over 700 binary surface alloys is evaluated theoretically; the stability of each alloy in electrochemical environments is also estimated. BiPt is found to have a predicted activity comparable to, or even better than, pure Pt, the archetypical HER catalyst. This alloy is synthesized and tested experimentally and shows improved HER performance compared with pure Pt, in agreement with the computational screening results.