Plasma Enhanced Chemical Vapor Deposition (PECVD) was used to prepare vanadium oxide thin films as cathodes for rechargeable lithium batteries. The reactants consisted of a high vapor pressure liquid source of vanadium (VOCl 3 ) and hydrogen and oxygen gas. Deposition parameters such as the flow rates of H 2 , O 2 and VOCl 3 , the substrate temperature and the Rf power were optimized, and high deposition rate of 11 Å/s was obtained. Vanadium oxide films with high discharge capacities of up to 408 mAh/g were prepared. The films also showed a superior cycling stability between 4 and 1.5 V at a C/0.2 rate for more than 4400 cycles. The films were amorphous up to a deposition temperature of 300°C, however, deposition on to substrates with textured surfaces facilitated the formation of crystalline films. We demonstrate that both the vanadium oxide material and the PECVD deposition method are very attractive for constructing thin-film rechargeable lithium batteries with high capacity and long-term cyclic stability.

Extensive fragmentation of copper current collectors was observed after spherical indentation on prismatic and large-format pouch Li-ion cells by 3D X-ray computed tomography (XCT). Microscopic analysis including scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and x-ray photoelectron microscopy (XPS) was carried out on copper current collectors from used commercial cells and pristine anodes. The copper-graphite cross-section images showed rough interface areas affected by reactions and diffusion in the used cell. Electron probe micro-analyzer (EPMA) element mapping showed the interface area was rich in oxygen and phosphorus. A detectable amount of phosphorus was also uniformly distributed inside the current collector. The same oxygen and phosphorus distributions were confirmed by STEM/EDS analysis. XPS depth profiles on multiple elements revealed the interface area of the aged anode was rich in Li, F, P, O and C and diffused at least 50 nm into the copper. In comparison, the pristine anode showed a very smooth C/Cu interface. No other elements were detected. For commercial cells, the reactions in the interface area and diffusion of multiple elements into the lattice and grain boundaries were responsible for the embrittlement of the copper current collectors. Permanent cell capacity loss was observed in electrochemical performance of the indented cells. (C) 2020 Elsevier Ltd. All rights reserved.

We report on investigations of V2O5 thin film cathodes prepared by pulsed laser deposition and the phase transformations which occur during electrochemical cycling. Our experimental results on PLD-grown, textured V2O5 crystalline films concur with reports in the literature that there is a voltage threshold above which, cycling appears to be completely reversible and below which, cycling appears to be irreversible. Crystalline films discharged beyond the threshold to 2.0 V vs. Li exhibited an immediate and continuous fade in capacity as well as a ∼90% decrease in XRD peak intensity and a similar decrease in Raman signal intensity in as few as 10 cycles. We have made co-phase material by both electrochemically discharging virgin, crystalline V2O5 and by further discharging previously cycled films which showed irreversible structural changes.

In this chapter, we discuss the prerequisites for high-efficiency water splitting and their implementation with tandem cells based on absorbers of the III–V semiconductor material class. A brief outline of efficiency-limiting factors shows that at a given set of boundary conditions, such as catalyst performance, the optimum tandem absorbers require a very precise control of opto-electronic properties, as facilitated by the III–V compounds. After a short history of high efficiency solar energy conversion, we present recent implementations of highly efficient water splitting systems with solar-to-hydrogen efficiencies of 14–16% together with an outlook on further improvements. Even if other absorber systems turn out to be more cost-competitive, the III–V systems currently serve as a testbed for high-efficiency water splitting in general, with lessons to be learned for catalyst requirements, cell design, and efficiency validation. We conclude with a discussion of appropriate efficiency benchmarking routines, outlining potential pitfalls for multi-junction absorbers and how to avoid them.

Electrolysis converts electrical energy into chemical energy by storing electrons in the form of stable chemical bonds. The chemical energy can be used as a fuel or converted back to electricity when needed. Water electrolysis to hydrogen and oxygen is a well-established technology, whereas fundamental advances in CO2 electrolysis are still needed to enable short-term and seasonal energy storage in the form of liquid fuels. This paper discusses the electrolytic reactions that can potentially enable renewable energy storage, including water, CO2 and N2 electrolysis. Recent progress and major obstacles associated with electrocatalysis and mass transfer management at a system level are reviewed. We conclude that knowledge and strategies are transferable between these different electrochemical technologies, although there are also unique complications that arise from the specifics of the reactions involved.

CuGaSe2 (CGS) is a semiconductor that has potential use as a photo electrode for solar water splitting. Its wide band gap and high absorption coefficient make it an ideal candidate for the top absorber in tandem structures. CGS can be synthesized by several techniques, being electrodeposition the most advantageous from a technical standpoint. Many reports show that electrodeposition of these films for producing the desired precursor atomic composition can be aided by using a complexing agent. However, the use of supporting electrolyte and the type of the electrolyte to improve the atomic composition in the films has never been reported. Using cyclic voltammetry, with complexing agents and deposition potentials between -0.5 and -0.9 V vs. Ag/AgCl reference electrode atomic ratios close to the ideal values ([Cu]/[Ga] = 1 and [Se]/[Cu+Ga] = 1), based on atomic composition and morphology analysis are reported in this work. From the X-ray diffraction (XRD), the as-deposited films exhibit poor crystallinity; however, the XRD patterns evidence the formation CuGaSe2 after annealing of the samples. (C) 2018 Elsevier B.V. All rights reserved.

Solar water splitting via multi-junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance-of-systems costs. For sufficient photovoltage, water-splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water-splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p-doped photocathodes by using a buried p–n junction. Advanced on-sun benchmarking, spectrally corrected and validated with incident photon-to-current efficiency, yields over 16% solar-to-hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high-efficiency tandem III–V device. Solar water-splitting efficiency can be enhanced by careful bandgap selection in multi-junction semiconductor structures. Young et al. demonstrate a route that allows independent bandgap tuning of each junction in an immersed water-splitting device, enabling a solar-to-hydrogen efficiency of over 16%.

Achieving solar-to-hydrogen efficiencies above 15% is key for the commercial success of photoelectrochemical water-splitting devices. While tandem cells can reach those efficiencies, increasing the catalytic activity and long-term stability remains a significant challenge. Here we show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity (current density of 11 mA cm−2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination) and stability (retention of 80% of initial photocurrent density over a 20 h durability test) for the hydrogen evolution reaction. Microscopy and spectroscopy reveal that annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2. Our findings demonstrate the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production. Solar water splitting is often performed in highly corrosive conditions, presenting materials stability challenges. Gu et al. show that an efficient and stable hydrogen-producing photocathode can be realized through the application of a graded catalytic–protective layer on top of the photoabsorber.

Efficient water splitting using light as the only energy input requires stable semiconductor electrodes with favorable energetics for the water-oxidation and proton-reduction reactions. Strategies to tune electrode potentials using molecular dipoles adsorbed to the semiconductor surface have been pursued for decades but are often based on weak interactions and quickly react to desorb the molecule under conditions relevant to sustained photoelectrolysis. Here, we show that covalent attachment of fluorinated, aromatic molecules to p-GaAs(100) surfaces can be employed to tune the photocurrent onset potentials of p-GaAs(100) photocathodes and reduce the external energy required for water splitting. Results indicate that initial photocurrent onset potentials can be shifted by nearly 150 mV in pH -0.5 electrolyte under 1 Sun (1000 Wm(-2)) illumination resulting from the covalently bound surface dipole. Though Xray photoelectron spectroscopy analysis reveals that the covalent molecular dipole attachment is not robust under extended 50h photoelectrolysis, the modified surface delays arsenic oxide formation that results in a p-GaAs(100) photoelectrode operating at a sustained photocurrent density of -20.5 mA cm(-2) within -0.5 V of the reversible hydrogen electrode.

Multiple exciton generation (MEG) in quantum dots (QDs) has the potential to greatly increase the power conversion efficiency in solar cells and in solar-fuel production. During the MEG process, two electron–hole pairs (excitons) are created from the absorption of one high-energy photon, bypassing hot-carrier cooling via phonon emission. Here we demonstrate that extra carriers produced via MEG can be used to drive a chemical reaction with quantum efficiency above 100%. We developed a lead sulfide (PbS) QD photoelectrochemical cell that is able to drive hydrogen evolution from aqueous Na2S solution with a peak external quantum efficiency exceeding 100%. QD photoelectrodes that were measured all demonstrated MEG when the incident photon energy was larger than 2.7 times the bandgap energy. Our results demonstrate a new direction in exploring high-efficiency approaches to solar fuels. Multiple exciton generation has been shown to improve the performance of quantum-dot-based solar cells. Yan et al. now apply it to photoinduced hydrogen production and present a system using PbS quantum-dot photoelectrodes that yields an external quantum efficiency of over 100%.

CuGaSe2 is an important thin film electronic material that possesses several attributes that make it appealing for solar energy conversion. Due to its properties it can be incorporated in to various devices, among the greatest highlights are photovoltaic cells, as well as its potential use as photocathodes for hydrogen production, via the photoelectrolysis. There are several methods of its preparation, most notably electrodeposition that has the potential for large areas and high volumes. Electrodeposition of ternary and/or quaternary semiconductors generally proceeds via the formation of a binary, which is subsequently reacted to form the ternary compound. Several conditions must be controlled to form binary compounds that include the use of complexing agents, buffers, temperature, etc. In this paper, we discuss the effect of anion composition in the electrolytic bath and the type of lithium salts, in order to manipulate the atomic concentration of CuGaSe2 during the electrodeposition of thin films, yielding copper-rich, gallium-rich or stoichiometric thin films. We also present the results of a study on the morphology and structure obtained using two types of substrates both before and after performing a heat treatment.

In order to economically generate renewable hydrogen fuel from solar energy using semiconductor-based devices, the U.S. Department of Energy Fuel Cells Technology Office has established technical targets of over 20% solar-to-hydrogen (STH) efficiency with several thousand hours of stability under operating conditions [1]. We have modeled attainable efficiencies of tandem absorbers that, for the first time, considered the absorption of sunlight by water [2]. We used this modeling to identify top and bottom semiconductor bandgap combinations that should be targeted to achieve maximal STH efficiency. We had to employ several key solid-state technological advances to achieve STH efficiencies exceeding 16%. The first improvement was to increase the device current via a non-lattice-matched 1.2 eV InGaAs grown using the inverted metamorphic multijunction technique developed by NREL’s III-V photovoltaics group. The second modification was to add a thin n-GaInP2 layer to p-GaInP2 to generate a "buried junction", which increased the photocurrent onset or Voc of the device by several hundred mV and enabled 14% STH efficiency. Finally, we increased the top junction photon conversion efficiency by adding an AlInP "window layer", which is commonly used in solid-state PV devices to reduce surface recombination. Through the use of a collimating tube, we measured our devices outdoors under direct solar illumination and verified over 16% STH conversion efficiency. I will also briefly introduce pitfalls of common experimental procedures that can influence the accuracy of measured STH efficiencies, which can be exaggerated for mulitjunction absorbers. The largest loss in our current system is reflection at the semiconductor/electrolyte interface, so I will address the photon management strategies we use to achieve greater parity between measured efficiency and the theoretical limit. Capturing a significant portion of the ~25% of photons lost to reflection at this interface should allow the realization of devices that exceed 20% STH efficiency. [1] http://energy.gov/sites/prod/files/2015/06/f23/fcto_myrdd_production.pdf [2] H. Döscher et al., Energy Environ. Sci. 7, 2951 (2016).

Our goal is to improve solar-to-hydrogen (STH) efficiency from just over 10% to over 20% via novel tandem semiconductor materials and configurations. Our primary focus is to develop inverted metamorphic multijunction (IMM) III-V semiconductors that have bandgaps optimized for water splitting. We will also discuss measurement challenges in appraising STH efficiency, some of which are specific to tandem absorbers. Using more stringent measurement standards, we have confirmed 16.2% STH on our most advanced IMM devices.

Older adults who are hospitalized are prone to multiple hazards such as falls, and significant functional mobility decline often resulting in institutionalization, and readmission to the hospital after discharge. Patients are often mobilized late in their hospital stay due to Nursing Sraff awaiting clearance from physical therapy. We sought to determine the effectiveness of an early mobilization protocol established to improve mobility and function in hospitalized older adults Project Setting was a 953 Bed academically affiliated safety net hospital. Participants included older adults 75yrs and older or patients 65 years and older identified to have 1 or more geriatric syndromes admitted to the Acute Care for the Elderly Service. All patients were evaluated by Nursing Staff on admission to determine their Get up and Go score ranging from a score of 1(patient able to get up and go without assistance) to 9 (bed rest ordered). Patients were mobilized early by Nursing based on their Get up and Go scores following the protocol on amount of mobilization required. Physical Therapy and Occupational Therapy also saw the patient early in their hospital stay to evaluate for further functional and mobility needs and implement physical and occupational therapy as needed. Initial data show a significant improvement in mobility scores for patients based on the Get Up and Go scores on admission and at the time of discharge with lower scores indicating improved mobility. Pre Intervention, the mobility scores on admission were 4.4 and increased to 4.53 at discharge. Post intervention, mobility scores were 4.37 on admission and 3.65 at discharge. In conclusion, the Get up and Go protocol is a useful mobilization program to improve functional mobility in hospitalized older adults.

Background: Older adults who are hospitalized are prone to multiple hazards such as falls, delirium, pressure ulcers, malnutrition, hospital-acquired infections and functional decline resulting in institutionalization, and readmission to the hospital after discharge. Geriatric-focused models of inpatient care offer effective ways to transform inpatient care for older adults and have been shown to improve outcomes. The role of these models of care in urban safety net hospitals has not been reported. We sought to determine the effectiveness of an Acute Care for the Elderly Service at our safety net hospital established 9mos ago. Project Setting is a 953 Bed academically affiliated safety net hospital. Participants were older adults 75yrs and older or patients 65 years and older identified to have 1 or more geriatric syndromes. All patients who met criteria were admitted to the ACE Service run by an interdisciplinary team constituting of a Geriatrician, Nurse Practitioner. Pharmacist, Dietitian, Case Management/ Social Work, Nursing Staff, Rehab personnel including PT, OT, ST, Team members reviewed the patients and made recommendations regarding the patient’s care. The focus of he service was to manage the following aspects of patient care – cognition, mood, functional status, nutrition, medication safety, skin care, transitions of care, A team of volunteers from our Senior Services Division also focused on involving patients in individual and congregate functional and cognitive activities to help preserve cognition and functional status. Community Health Workers provided support regarding the patients transition to other care settings with their providing support and care coordination immediately pre-discharge and in the discharge care setting for a period of 6 months post discharge for patients meeting criteria. Initial data show a significant improvement in delirium and cognition scores as measured by the Nudesc and Six Item screen scores, on admission compared to discharge. There was a drop in the Nudesc Scores by 14.9% at discharge compared to admission scores. There was also significant improvement in mobility scores for patients pre ACE intervention and post intervention., though there was some decline in the Katz and Lawton functional scores, There was also a positive response by the primary hospital teams in reducing the number of beers medications that the patient was taking. An ACE service with its care processes is a useful mechanism to improve cognition, mobility and medication safety in hospitalized older adults in a safety net hospital

Current artificial photosynthesis (APS) systems are promising for the storage of solar energy via transportable and storable fuels, but the anodic half-reaction of water oxidation is an energy intensive process which in many cases poorly couples with the cathodic half-reaction. Here we demonstrate a self-sustaining microbial photoelectrosynthesis (MPES) system that pairs microbial electrochemical oxidation with photoelectrochemical water reduction for energy efficient H2 generation. MPES reduces the overall energy requirements thereby greatly expanding the range of semiconductors that can be utilized in APS. Due to the recovery of chemical energy from waste organics by the mild microbial process and utilization of cost-effective and stable catalyst/electrode materials, our MPES system produced a stable current of 0.4 mA/cm2 for 24 h without any external bias and ∼10 mA/cm2 with a modest bias under one sun illumination. This system also showed other merits, such as creating benefits of wastewater treatment and facile preparation and scalability.