Energy Research Institute

Electricity-driven water splitting can facilitate the storage of electrical energy in the form of hydrogen gas. As a half-reaction of electricity-driven water splitting, the oxygen evolution reaction (OER) is the major bottleneck due to the sluggish kinetics of this four-electron transfer reaction. Developing low-cost and robust OER catalysts is critical to solving this efficiency problem in water splitting. The catalyst design has to be built based on the fundamental understanding of the OER mechanism and the origin of the reaction overpotential. In this article, we summarize the recent progress in understanding OER mechanisms, which include the conventional adsorbate evolution mechanism (AEM) and lattice-oxygen-mediated mechanism (LOM) from both theoretical and experimental aspects. We start with the discussion on the AEM and its linked scaling relations among various reaction intermediates. The strategies to reduce overpotential based on the AEM and its derived descriptors are then introduced. To further reduce the OER overpotential, it is necessary to break the scaling relation of HOO* and HO* intermediates in conventional AEM to go beyond the activity limitation of the volcano relationship. Strategies such as stabilization of HOO*, proton acceptor functionality, and switching the OER pathway to LOM are discussed. The remaining questions on the OER and related perspectives are also presented at the end.

Glucose-derived water-soluble crystalline graphene quantum dots (GQDs) with an average diameter as small as 1.65 nm (∼5 layers) were prepared by a facile microwave-assisted hydrothermal method. The GQDs exhibits deep ultraviolet (DUV) emission of 4.1 eV, which is the shortest emission wavelength among all the solution-based QDs. The GQDs exhibit typical excitation wavelength-dependent properties as expected in carbon-based quantum dots. However, the emission wavelength is independent of the size of the GQDs. The unique optical properties of the GQDs are attributed to the self-passivated layer on the surface of the GQDs as revealed by electron energy loss spectroscopy. The photoluminescence quantum yields of the GQDs were determined to be 7-11%. The GQDs are capable of converting blue light into white light when the GQDs are coated onto a blue light emitting diode.

Tremendous efforts have been dedicated into the development of high-performance energy storage devices with nanoscale design and hybrid approaches. The boundary between the electrochemical capacitors and batteries becomes less distinctive. The same material may display capacitive or battery-like behavior depending on the electrode design and the charge storage guest ions. Therefore, the underlying mechanisms and the electrochemical processes occurring upon charge storage may be confusing for researchers who are new to the field as well as some of the chemists and material scientists already in the field. This review provides fundamentals of the similarities and differences between electrochemical capacitors and batteries from kinetic and material point of view. Basic techniques and analysis methods to distinguish the capacitive and battery-like behavior are discussed. Furthermore, guidelines for material selection, the state-of-the-art materials, and the electrode design rules to advanced electrode are proposed.

We demonstrate strong potential of computational screening and germanium iodide perovskite compounds for photovoltaic applications.

A Ni3S2 nanorods/Ni foam composite electrode is prepared as a high-performance catalyst for the oxygen evolution reaction (OER), which exhibits excellent OER activity with a small overpotential of ∼157 mV based on the onset of catalytic current.

Electrocatalysts with single metal atoms as active sites have received increasing attention owing to their high atomic utilization efficiency and exotic catalytic activity and selectivity. This review aims to provide a comprehensive summary on the recent development of such single-atom electrocatalysts (SAECs) for various energy-conversion reactions. The discussion starts with an introduction of the different types of SAECs, followed by an overview of the synthetic methodologies to control the atomic dispersion of metal sites and atomically resolved characterization using state-of-the-art microscopic and spectroscopic techniques. In recognition of the extensive applications of SAECs, the electrocatalytic studies are dissected in terms of various important electrochemical reactions, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). Examples of SAECs are deliberated in each case in terms of their catalytic performance, structure-property relationships, and catalytic enhancement mechanisms. A perspective is provided at the end of each section about remaining challenges and opportunities for the development of SAECs for the targeted reaction.

Review: The conversion of sunlight into electricity can be achieved using a solar cell and is one of the most attractive future soruce of energy. Silicon‐based cells, while quite efficient, are difficult and expensive to produce, a fact that drives up the cost of electricity produced using them. The alternative, organic‐based cells (see Figure) have the potential advantages of ease of processing and cheapness if their efficiency can be brought up to reasonable levels. Recent progress made and future targets in this field are reviewed. equation image

Abstract The effect of combined hydrostatic pressure, P, and of uniaxial tension, [sgrave], on the rupture time of polycrystalline copper wire in the temperature range 400° to 500°c has been determined. All the specimens broke by intergranular fracture, due to the growth of voids along grain boundaries. Preliminary experiments indicated that the voids grow by the addition of vacancies under the action of the applied stress. A theory has been developed assuming that failure results from the growth of void nuclei on the grain boundary, which requires that the activation energy for failure is that of grain boundary diffusion and that the rupture time, tr, depends only on ([sgrave]-P). The experiments show that the activation energy is close to the expected value, and provided that [sgrave] is constant tr agrees with theory. Changes in [sgrave], when ([sgrave] - P) is constant, affect tr appreciably, and the results suggest that many of the void nuclei are stress induced.

This article reviews the fundamental photophysics and working mechanisms of perovskite solar cells and highlights the current state-of-the-art and open questions in this maturing field.

Abstract A new method is described for setting up the effective potential for electrons in non-transition metals, including liquid metals and alloys. It is based on a model potential fitted to the spectroscopically measured energy levels of the free ions. The potential between the atomic cores is obtained from the dielectric screening calculation of Cohen and Phillips (1961) with some refinements. The method is tested on the band structures of the (solid) alkali metals. The Fermi surfaces of K, Rb and Cs are found to be considerably less distorted than calculated by Ham (1962), and thus in better agreement with experiment.

Abstract Formulae are obtained for the concentration in a poorly diffusing half space bisected by a thin well-diffusing slab, at different times after the edge of the half-space has been suddenly raised from zero to unit concentration. This represents a simplified model for studying 'grain boundary' diffusion of one metal into another. The problem also has obvious application to the study of heat flow in a poorly conducting solid with a metallic fin.

Thermally removable nanoparticle templates were used for the fabrication of self-supported N-doped mesoporous carbons with a trace amount of Fe (Fe-N/C). Experimentally Fe-N/C was prepared by pyrolysis of poly(2-fluoroaniline) (P2FANI) containing a number of FeO(OH) nanorods that were prepared by a one-pot hydrothermal synthesis and homogeneously distributed within the polymer matrix. The FeO(OH) nanocrystals acted as rigid templates to prevent the collapse of P2FANI during the carbonization process, where a mesoporous skeleton was formed with a medium surface area of about 400 m(2)/g. Subsequent thermal treatments at elevated temperatures led to the decomposition and evaporation of the FeO(OH) nanocrystals and the formation of mesoporous carbons with the surface area markedly enhanced to 934.8 m(2)/g. Electrochemical measurements revealed that the resulting mesoporous carbons exhibited apparent electrocatalytic activity for oxygen reduction reactions (ORR), and the one prepared at 800 °C (Fe-N/C-800) was the best among the series, with a more positive onset potential (+0.98 V vs RHE), higher diffusion-limited current, higher selectivity (number of electron transfer n > 3.95 at +0.75 V vs RHE), much higher stability, and stronger tolerance against methanol crossover than commercial Pt/C catalysts in a 0.1 M KOH solution. The remarkable ORR performance was attributed to the high surface area and sufficient exposure of electrocatalytically active sites that arose primarily from N-doped carbons with minor contributions from Fe-containing species.

A ZnO compact layer formed by electrodeposition and ZnO nanorods grown by chemical bath deposition (CBD) allow the processing of low-temperature, solution based and flexible solid state perovskite CH3NH3PbI3 solar cells. Conversion efficiencies of 8.90% were achieved on rigid substrates while the flexible ones yielded 2.62%.

Demonstration of band-gap tuning of mixed anion lead halide perovskites (MAPb(I_1−xBr_x)₂ (0 ≤ <italic>x</italic> ≤ 1)) by means of a sequential deposition process.

Converting solar energy into fuel via photo-assisted water splitting to generate hydrogen or drive CO2 reduction is an attractive scientific and technological goal to address the increasing global demand for energy and to reduce the impact of energy production on climate change. Engineering an efficient, low-cost photocatalyst is necessary to achieve this technological goal. A photocatalyst combines a photosensitiser and an electrocatalyst to capture light and accelerate the chemical reactions in the same device. In this perspective paper, we first describe the recent developments of some families of semiconductors that are attractive candidates for engineering photocatalysts. We then discuss the use of semiconductors as light harvesting agents, combined with a bio-catalyst, synthetic bio-mimetic molecular catalyst or synthetic all-inorganic catalyst, in photocatalytic hybrid systems for water splitting and CO2 reduction. To highlight the advantages of semiconductors for engineering efficient and robust photocatalysts, we compare these systems to examples of homogeneous photocatalytic systems constructed from molecular photosensitisers (dyes). We conclude that all-inorganic catalysts coupled to appropriate semiconductors look more promising for the construction of robust photocatalytic hybrid systems for producing solar fuels.

This review provides an overview of factors affecting film morphology and how together with device architecture they impact perovskite cell performance.

A three-dimensional graphene network (3DGN) grown on nickel foam is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. Ni(OH)2nanosheets coated onto single-crystal Ni3S2nanorods grown on the surface of the 3DGN (referred to as the Ni3S2@Ni(OH)2/3DGN) are synthesized using a one-step hydrothermal reaction. SEM, TEM, XRD and Raman spectroscopy are used to investigate the morphological and structural evolution of the Ni3S2@Ni(OH)2/3DGN. Detailed electrochemical characterization shows that the Ni3S2@Ni(OH)2/3DGN exhibits high specific capacitance (1277 F g−1 at 2 mV s−1 and 1037.5 F g−1 at 5.1 A g−1) and areal capacitance (4.7 F cm−2 at 2 mV s−1 and 3.85 F cm−2 at 19.1 mA cm−2) with good cycling performance (99.1% capacitance retention after 2000 cycles).

This handbook has been prepared by the Solar Energy Research Institute under the US Department of Energy /bold Solar Technical Information Program/. It is intended as a guide to the design, testing, operation, and manufacture of small-scale (less than 200 kW (270 hp)) gasifiers. A great deal of the information will be useful for all levels of biomass gasification. The handbook is meant to be a practical guide to gasifier systems, and a minimum amount of space is devoted to questions of more theoretical interest.

Analyzing the commercialization potential of g-C₃N₄photocatalysts for solar H₂generation from an economic viewpoint and for large-scale production.

A lead-free low bandgap organic–inorganic hybrid perovskite, formamidinium tin iodide, is introduced as a photovoltaic material.