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Conspectus Photoelectrochemical water-splitting is a promising and sustainable way to store the energy of the sun in chemical bonds and use it to produce hydrogen gas, a clean fuel. The key components in photoelectrochemical cells (PECs) are photoelectrodes, including a photocathode that reduces water to hydrogen gas and a photoanode that oxidizes water to oxygen gas. Materials used in photoelectrodes for PECs must effectively absorb sunlight, yield photogenerated carriers, and exhibit electronic properties that enable the efficient shuttling of carriers to the surface to participate in relevant water-splitting reactions. Discovering and understanding the key characteristics of optimal photoelectrode materials is paramount to the realization of PEC technologies. Oxide-based photoelectrodes can satisfy many of these materials requirements, including stability in aqueous environments, band edges with reasonable alignment with the redox potentials for water splitting, and ease of synthesis. However, oxide photoelectrodes generally suffer from poor charge transport properties and considerable bulk electron–hole separation, and they have relatively large band gaps. Numerous strategies have been proposed to improve these aspects and understand how these improvements are reflected in the photoelectrochemical performance. Unfortunately, the structural and compositional complexity of multinary oxides accompanied by the inherent complexity of photoelectrochemical processes makes it challenging to understand the individual effects of composition, structure, and defects in the bulk and on the surface on a material’s photoelectrochemical properties. The integration of experiment and theory has great potential to increase our atomic-level understanding of structure–composition–property relationships in oxide photoelectrodes. In this Account, we describe how integrating experiment and theory is beneficial for achieving scientific insights at the microscopic scale. We highlight studies focused on understanding the role of (i) bulk composition via solid-state solutions, intercalation, and comparison with isoelectronic compounds, (ii) dopants for both the anion and cation and their interactions with oxygen vacancies, and (iii) surface/interface structure in the photocurrent generation and photoelectrochemical performance in oxide photoelectrodes. In each instance, we outline strategies and considerations for integrating experiment and theory and describe how this integration led to valuable insights and new directions in uncovering structure–composition–property relationships. Our aim is to demonstrate the unique value of combining experiment and theory in studying photoelectrodes and to encourage the continued effort to bring experiment and theory in closer step with each other.

5-Hydroxymethylfurfural (HMF), which can be derived from lignocellulosic biomass, is an important platform molecule that can be used to produce valuable biofuels and polymeric materials. Electrochemical reduction of HMF is of great interest as it uses water as the hydrogen source and achieves desired reduction reactions at room temperature and ambient pressure. Hydrogenation and hydrogenolysis are two important reactions for reductive HMF conversion. Therefore, elucidating key characteristics of electrocatalysts that govern the selectivity for hydrogenation and hydrogenolysis is critical in rationally developing efficient and selective electrocatalysts. In this study, combined experimental and computational investigations are used to demonstrate how the adsorption energy of HMF on metal surfaces and the resulting changes in the intramolecular bond lengths of adsorbed HMF directly impact the reduction pathways of HMF. These results make it possible to rationally understand a general trend in the behaviors observed when using various metal electrodes for HMF reduction.

The ability to engineer a photoelectrode surface is pivotal for optimizing the properties of any photoelectrode used for solar fuel production. Altering crystal facets exposed on the surface of photoelectrodes has been a major strategy to modify their surface structure. However, there exist numerous ways to terminate the surface even for the same facet, which can considerably alter the photoelectrode properties. Here we report tightly integrated experimental and computational investigations of epitaxial BiVO4 photoelectrodes with vanadium- and bismuth-rich (010) facets. Our study demonstrates that even for the same facet the surface Bi:V ratio has a remarkable impact on the interfacial energetics and photoelectrochemical properties. We also elucidate the microscopic origins of how the surface composition can affect the photoelectrochemical properties. This study opens an unexplored path for understanding and engineering surface energetics via tuning the surface termination/composition of multinary oxide photoelectrodes. Surface facets are known to influence the behaviour of photoelectrodes for solar fuel production; however, the role of surface composition, which can vary even for the same facet, is less well understood. Here the authors find that the surface Bi:V ratio is a key factor that affects properties of BiVO4 photoanodes.

Selective oxidation of alcohols to their corresponding aldehyde or carboxylic acid is one of the most important classes of organic synthesis reactions. In addition, electrochemical alcohol oxidation is considered a viable anode reaction that can be paired with H2 evolution or other reductive fuel production reactions in electrochemical and photoelectrochemical cells. NiOOH, a material that has been extensively studied as an oxygen evolution catalyst, is among the most promising electrocatalysts for selective alcohol oxidation. Electrochemical alcohol oxidation by NiOOH has been understood since the 1970s to proceed through a hydrogen atom transfer to NiOOH. In this study, we establish that there is a second, more dominant general alcohol oxidation pathway on NiOOH enabled at more positive potentials. Using a three-step electrochemical procedure we developed, we deconvoluted the currents corresponding to these two pathways for various alcohols and aldehydes. The results show that alcohols and aldehydes have a distinct difference in their respective preferences for the two oxidation pathways. Our three-step electrochemical procedure also allowed us to evaluate the Ni valence involved with the different oxidation pathways to elucidate their mechanistic differences. Using these experimental results coupled with a computational investigation, we propose that the new pathway entails hydride transfer from the substrate to Ni4+ sites in NiOOH. This study offers an essential foundation to understand various oxidative electrochemical dehydrogenation reactions on oxide and hydroxide-based catalytic electrodes.

Oxide-based photoelectrodes recently have been at the forefront of research for photoelectrochemical water splitting. While most oxide-based photoanodes suffer from severe electron–hole recombinati...

Nickel hexacyanoferrate (NiHCF), a type of Prussian blue analogue (PBA), has recently emerged as one of the most promising Na-storage electrodes for use in electrochemical desalination. Previous studies have revealed that NiHCF can be prepared with both cubic and rhombohedral symmetries depending on the oxidation state of Fe (Fe

The electrochemical oxidation of water to oxygen gas is the primary counter reaction to the formation of hydrogen gas via water splitting. In acidic media, the only well-established and active oxyg...

Photoelectrochemical N2 reduction enables the production of NH3 under ambient conditions using water as the hydrogen source. Furthermore, by utilizing solar energy, photoelectrochemical N2 reductio...

Bismuth vanadate (BiVO4) is a widely studied oxide in solar water splitting, known for its ease of synthesis, high charge extraction yields, and advantageous band alignment with water. We present a combined first-principles and experimental study of the electronic structure of the (010) surface of BiVO4 aimed at disentangling the impact of the surface and bulk oxygen vacancies on the electronic structure and transport properties. We found that oxygen vacancies are deep donors at the surface as they are in the bulk; our calculations on defect and polaron formation energies suggest that, while polarons formed from oxygen vacancies in the bulk can contribute to conductivity, those at the surface likely do not. Our results also show that out-of-plane structural relaxations at the surface contribute to the relatively immobile nature of electron polarons derived from surface oxygen vacancies. The structural model derived from first-principles calculation was validated by comparing computed results with experimental measurements of single-crystal and epitaxially grown single-crystalline BiVO4 samples. We also found a reasonably good agreement between our calculated and measured work functions for BiVO4 samples with and without oxygen vacancies.

The electrochemical N2 reduction reaction (ENRR) that can produce NH3 using water as the hydrogen source at ambient temperature and pressure can be an exciting alternative to the Haber–Bosch process. The major challenge for electrochemical NH3 production is the competing hydrogen evolution reaction (HER), which seriously limits the faradaic efficiency (FE) for NH3 production. To date, noble metal electrocatalysts that are inactive for the HER have mainly been investigated for the ENRR. Studies reporting a FE greater than 10% for NH3 production using non-noble metal catalysts in the low overpotential region (E ≤ 0.2 V vs. RHE) are very rare. This study reports effective electrochemical surface modification strategies that drastically increase the ENRR activity of a non-noble Bi electrode in the low overpotential region and achieve a FE for NH3 production as high as 13.2% at −0.2 V vs. RHE in pH 7.5 phosphate buffer. The effect of each of the surface modifications on the activity for the ENRR and the electrode stability during the ENRR were systematically elucidated, which may be used to develop general strategies to enhance the ENRR activities of other non-noble metal electrodes in the low overpotential region.

As editors of a materials chemistry journal, we are thrilled at the awarding of the 2019 Nobel Prize in Chemistry to John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino, for their contributions that have led to the modern lithium ion battery (Figure 1). As the Nobel Prize Committee states succinctly, “They created a rechargeable world.”(1) The commercial and societal rewards of experimental research typically require decades to reach fruition, and lithium ion batteries were no different, with crucial leads dating back to the 1960s, and even earlier.(2) Materials chemistry journals only emerged 30 years ago with the advent of Chemistry of Materials, the Journal of Materials Chemistry, and Advanced Materials in 1989. Much of the earlier work in battery materials appeared beforehand in electrochemistry, physics, and solid state journals. The key fundamental discovery underpinning the lithium ion battery was the understanding and application of ion intercalation, in this case,(3) lithium ions inserted between the layers in graphite, metal sulfides, and, eventually, oxides that were commercialized. This Nobel Prize was evenly split three ways because, as the Nobel committee correctly observed, the contributions of all three inventors were essential to the success of the commercialization of the lithium ion battery.

2,5-Furandicarboxylic acid (FDCA) is a near-market monomer that has been identified as a viable biomass-derived replacement for petroleum-derived terephthalic acid in the synthesis of polyethylene terephthalate (PET). FDCA can be produced from the oxidation of 5-hydroxymethylfurfural (HMF), which is a versatile biomass intermediate produced from the dehydration of C-6 monosaccharides obtained from cellulosic biomass. In this study, we comparatively investigated the use of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 4-acetamido-TEMPO (ACT) for electrochemical HMF oxidation to FDCA. The distinct advantage of TEMPO- and ACT-mediated electrochemical oxidation of HMF is that they can efficiently achieve HMF oxidation in mildly basic conditions (pH 9–10), while other heterogeneous catalysts typically require the use of more basic media. Since HMF oxidation in a strongly basic condition increases the chance to form humins, which are difficult to separate from FDCA and decrease the commercial viability of FDCA and FDCA-derived products, TEMPO- and ACT-mediated HMF oxidation may offer a critical advantage for producing commercial-grade FDCA. In this study, the stabilities, electrochemical properties, and electrocatalytic performances of TEMPO and ACT, which has been identified as a less expensive alternative to TEMPO, were comparatively examined for electrochemical HMF oxidation. Through investigating the effect of pH, applied potential, and ratio of nitroxyl radical to HMF in solution on HMF oxidation, two different regeneration pathways of TEMPO and ACT in the catalytic cycle and the factors that affect their regeneration pathways were identified. The stability and catalytic activity of TEMPO and ACT for electrochemical HMF oxidation at an elevated temperature were also studied. On the basis of this investigation, optimal electrochemical conditions to efficiently oxidize a concentrated HMF solution (100 mM), which is relevant to large-scale electrochemical FDCA production, were identified.

In this work, spectroelectrochemical techniques are employed to analyse the catalytic water oxidation performance of a series of three nickel/iron oxyhydroxide electrocatalysts deposited on FTO and BiVO4, at neutral pH. Similar electrochemical water oxidation performance is observed for each of the FeOOH, Ni(Fe)OOH and FeOOHNiOOH electrocatalysts studied, which is found to result from a balance between degree of charge accumulation and rate of water oxidation. Once added onto BiVO4 photoanodes, a large enhancement in the water oxidation photoelectrochemical performance is observed in comparison to the un-modified BiVO4. To understand the origin of this enhancement, the films were evaluated through time-resolved optical spectroscopic techniques, allowing comparisons between electrochemical and photoelectrochemical water oxidation. For all three catalysts, fast hole transfer from BiVO4 to the catalyst is observed in the transient absorption data. Using operando photoinduced absorption measurements, we find that water oxidation is driven by oxidised states within the catalyst layer, following hole transfer from BiVO4. This charge transfer is correlated with a suppression of recombination losses which result in remarkably enhanced water oxidation performance relative to un-modified BiVO4. Moreover, despite similar electrocatalytic behaviour of all three electrocatalysts, we show that variations in water oxidation performance observed among the BiVO4/MOOH photoanodes stem from differences in photoelectrochemical and electrochemical charge accumulation in the catalyst layers. Under illumination, the amount of accumulated charge in the catalyst is driven by the injection of photogenerated holes from BiVO4, which is further affected by the recombination loss at the BiVO4/MOOH interface, and thus leads to deviations from their behaviour as standalone electrocatalysts., Elucidating the role of charge accumulation and reaction kinetics in governing the performance of Ni/Fe oxyhydroxides as electrocatalysts and as co-catalysts on BiVO4 photoanodes water oxidation.

(Photo)electrochemical cells that produce fuels have often relied on water oxidation to complete the redox cycle. Here, the authors discuss alcohol oxidation as an alternative reaction and consider general mechanistic features of oxidation electrocatalysts.

A new electrochemical, solution-based synthesis method to prepare uniform multinary oxide photoelectrodes was developed. This method involves solubilizing multiple metal ions as metal-catechol complexes in a pH condition where they are otherwise insoluble. When some of the catechol ligands are electrochemically oxidized, the remaining metal complexes become insoluble and are deposited as metal-catechol films on the working electrode. The resulting films are then annealed to form crystalline multinary oxide electrodes. Because catechol can serve as a complexing agent for a variety of metal ions, the newly developed method can be used to prepare a variety of multinary oxide films. In the present study, we used this method to prepare n-type Fe2TiO5 photoanodes and investigated their photoelectrochemical properties for use in a photoelectrochemical water-splitting cell. We also performed a computational investigation with two goals. The first goal was to investigate small electron polaron formation in Fe2TiO5. Charge transport in most oxide photoelectrodes involves small polaron hopping, but small polaron formation in Fe2TiO5 has not been examined prior to this work. The second goal was to investigate the effect of substitutional Sn doping at the Fe site on the electronic band structure and the carrier concentration of Fe2TiO5. The combined experimental and theoretical results presented in this study greatly improve our understanding of Fe2TiO5 for use as a photoanode.

Solar water splitting using photoelectrochemical cells (PECs) has emerged as one of the most promising routes to produce hydrogen as a clean and renewable fuel source. Among various semiconductors that have been considered as photoelectrodes for use in PECs, oxide-based photoanodes are particularly attractive because of their stability in aqueous media in addition to inexpensive and facile processing compared to other types of semiconductors. However, they typically suffer from poor charge carrier separation and transport. In the past few years, there has been tremendous progress in developing ternary oxide-based photoelectrodes, specifically, photoanodes. The use of ternary oxides provides more opportunities to tune the composition and electronic structure of the photoelectrode compared to binary oxides, thus providing more freedom to tune the photoelectrochemical properties. In this article, we outline the important characteristics to analyze when evaluating photoanodes and review the major recent progress made on the development of ternary oxide-based photoanodes. For each system, we highlight the favorable and unfavorable features and summarize the strategies utilized to address the challenges associated with each material. Finally, by combining our analyses of all the photoanodes surveyed in this review, we provide possible future research directions for each compound and an outlook for constructing more efficient oxide-based PECs. Overall, this review will provide a critical overview of current ternary oxide-based photoanodes and will serve as a platform for the design of future oxide-based PECs.

2,5-Furandicarboxylic acid (FDCA) has received increasing attention as a near-market platform chemical that can potentially replace terephthalic acid in the production of commercial and high-perfor...

Summary Aim Major hepatic resection of a cirrhotic liver may result in a fatal clinical course. Preoperative erythropoietin (EPO) treatment has been shown to have protective properties and to stimulate liver regeneration. This study aims to investigate the effect of preoperative EPO on survival following major hepatic resection in a cirrhotic rat model. Methods Cirrhotic liver was induced by intraperitoneal injection of thioacetamide (200 mg/kg/mL) in 72 Lewis rats. Each 36 rats received EPO (1 IU/g, every second day, 5 times preoperatively) or saline (control) and major hepatectomy (removal of the left and half of the median lobe) was performed. Biochemical and immunohistochemical parameters, cytokines and overall survival were compared following surgery. Results Rats that received preoperative EPO had decreased hepatic aspartate aminotransferase, alanine aminotransferase and interleukin (IL)-1β expression, 48 hours following surgery. They had increased hepatocyte growth factor and vascular endothelial growth factor expression at 1 hour, increased IL-6 expression at 24, 48 and 120 hours and increased Ki-67, 120 hours following surgery. Overall, survival was significantly improved among EPO-treated rats (P = 0.034). Conclusion Preoperative EPO treatment has a protective effect and stimulates liver regeneration, leading to improved overall survival following major hepatectomy in a cirrhotic rat model.

Titanium dioxide (TiO2) deposited by atomic layer deposition (ALD) has been the most commonly used protection layer to enhance chemical and photoelectrochemical stabilities of photoelectrodes. In this study, we report a new electrochemical deposition method that can place a thin, conformal TiO2 coating layer on a photoelectrode. This method takes

Maleic acid (MA) is a platform chemical used for various industrial processes. In this study, a new electrochemical oxidation method that can convert furfural, which is one of the most important C5 platform chemicals derived from cellulosic biomass, to MA is reported. This method can produce MA in aqueous media under ambient temperature and pressure without the use of oxidizing agents. The use of acidic media, which promotes opening of the furan ring during oxidation, was critical for the formation of MA. PbO2, MnO2, and Pt, which are stable in acidic solutions under strongly oxidizing potentials, were investigated as anodes for furfural oxidation. The results showed that PbO2 is the only catalyst that can convert furfural to MA as the major product. It was also revealed that the electrochemical conversion of furfural to MA proceeds with 2-furanol as an intermediate.

2,5-Furandicarboxylic acid (FDCA) has become an increasingly desirable platform chemical to replace terephthalic acid in the production of a variety of polymeric materials, including polyethylene terephthalate. FDCA can be produced by the oxidation of 5-hydroxymethylfurfural (HMF), which can be derived from cellulosic biomass. Oxidation of HMF to FDCA is typically performed under basic conditions. Separation of FDCA is most easily accomplished by lowering the pH until FDCA is insoluble and filtering it from solution. In a large-scale process, this would lead to a high operating cost to purchase the required acid and base and to dispose of the resulting salt waste. In this study, electrochemical oxidation of HMF was carried out in acidic media by using a manganese oxide (MnOx ) anode to remove the need to vary the pH to separate FDCA. The MnOx anode afforded a FDCA yield of 53.8 % in a pH 1 H2 SO4 solution, in which FDCA precipitation occurred spontaneously from the same reaction solution without altering the pH or other aspects of the solution composition. Electrochemical oxidation in acidic media offers a new pathway to convert HMF into maleic acid, which is another desirable biomass-derived platform molecule. The performance of the MnOx anode was investigated in comparison with that of a Pt anode to identify unique electrocatalytic properties of the MnOx anode for HMF oxidation.

While selenium has recently been proposed as a lithium battery cathode as a promising alternative to a lithium–sulfur battery, dissolution of intermediate species should be resolved to improve its cycle stability. Here, we report the promising results of transition-metal disulfides as an anchoring material and the underlying origin for preventing active material loss from the electrode using density functional theory calculations. Group 5 and 4 disulfides (VS2, NbS2, TaS2, TiS2, ZrS2, and HfS2) in particular show anchoring capabilities superior to those of group 6 disulfides (CrS2, MoS2, and WS2). The governing interaction controlling the latter relative anchoring strengths is shown to be charge transfer as understood by crystal-field theory. The current findings and methodologies provide novel chemical insight for the further design of inorganic anchoring materials for both lithium–selenium and lithium–sulfur batteries.

2,5-Furandicarboxylic acid (FDCA) is a key near-market platform chemical that can potentially replace terephthalic acid in various polyesters such as polyethylene terephthalate (PET). FDCA can be obtained from oxidation of 5-hydroxymethylfurfural (HMF), which can be derived from cellulosic biomass through isomerization and dehydration of hexoses. In this study, electrochemical oxidation of HMF to FDCA is demonstrated using Cu, one of the cheapest transition metals, as the catalytic anode. The oxidized Cu surface is not catalytic for water oxidation, which is the major reaction competing with HMF oxidation in aqueous media. Therefore, a wide potential window to oxidize HMF without inducing water oxidation was available, enabling high Faradaic efficiencies for FDCA production. Cu was prepared as nanocrystalline and bulk electrodes by electrodeposition, and key differences in their surface oxidation and electrochemical HMF oxidation were investigated. The oxide and hydroxide layers formed on the nanocrystall...

The development of new and inexpensive semiconductor electrodes that possess suitable band gap energies and band positions for solar water splitting is of great interest in the field of solar fuel production. In this study, n-type Cu11V6O26 that has a band gap energy of 1.9 eV was produced as a pure, high-quality photoanode, and its properties and stability for photoelectrochemical water splitting were systematically investigated in pH 9.2 and 13 solutions. As Cu11V6O26 photoanodes appeared to suffer from poor charge transport properties, Mo and W doping into the V site was also examined, which considerably improved the photocurrent generation of Cu11V6O26. The band gap energy, band edge positions, flatband potential, photocurrent generation, and photostability of pristine and doped Cu11V6O26 electrodes are discussed in comparison to elucidate the effect of Mo and W doping and to evaluate the promise and limitations of Cu11V6O26 as a photoanode for use in a water splitting photoelectrochemical cell.

LaFeO3 is a p-type oxide that has an ideal bandgap and band edge positions for overall solar water splitting. This study reports an electrochemical synthesis method to produce LaFeO3 as a high surface area, nanoporous photocathode. The resulting electrode generated a photocurrent density of −0.1 mA/cm2 at a potential as positive as 0.73 V vs RHE for photoelectrochemical oxygen reduction with a photocurrent onset potential very close to its flatband potential of 1.45 V vs RHE. Furthermore, without a protection layer, it showed stable photocurrent generation with no sign of photocorrosion. Due to the poor catalytic nature of the LaFeO3 surface for water reduction, the photocurrent obtained for water reduction was not substantial. However, its photostability and its ability to achieve a photovoltage for water reduction greater than 1.2 V encourage further studies on doping to enhance electron–hole separation as well as interfacing appropriate hydrogen evolution catalysts.

Materials that can selectively store Na and Cl ions in the bulk of their structures and release these ions with good cycle stability can enable the construction of a high capacity, rechargeable desalination cell for use in seawater desalination. In this study, the ability of a nanocrystalline Bi foam electrode to serve as an efficient and high capacity Cl-storage electrode using its conversion to BiOCl was investigated. When Bi as a Cl-storage electrode was coupled with NaTi2(PO4)3 as a Na-storage electrode, a new type of rechargeable desalination cell, which is charged during desalination and discharged during salination, was constructed. The resulting Bi-NaTi2(PO4)3 cell was tested under various salination and desalination conditions to investigate advantages and potential limitations of using Bi as a Cl-storage electrode. Slow Cl– release kinetics of BiOCl in neutral conditions and an imbalance in Cl and Na storage (i.e., Cl storage requires three electrons/Cl, while Na storage requires one electron/Na...

New electrochemical synthesis methods were developed to produce copper hydroxy double salt(Cu-HDS) films with four different intercalated anions (NO3–, SO42–, Cl–, and dodecyl sulfate (DS)) as pure crystalline films as deposited (Cu2NO3(OH)3, Cu4SO4(OH)6, Cu2Cl(OH)3, and Cu2DS(OH)3). These methods are based on p-benzoquinone reduction, which increases the local pH at the working electrode and triggers the precipitation of Cu2+ and appropriate anions as Cu-HDS films on the working electrode. The resulting Cu-HDS films could be converted to crystalline Cu(OH)2 and CuO films by immersing them in basic solutions. Because Cu-HDS films were composed of 2D crystals as a result of the atomic-level layered structure of HDS, the CuO films prepared from Cu-HDS films have unique low-dimensional nanostructures, creating high surface areas that cannot be obtained by direct deposition of CuO, which has a 3D atomic-level crystal structure. The resulting nanostructures allowed the CuO films to facilitate electron–hole sep...

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Photoelectrochemical cells (PECs), which use semiconductor electrodes (photoelectrodes) to absorb solar energy and perform chemical reactions, constitute one of the most attractive strategies to produce chemical fuels using renewable energy sources. Oxide-based photoelectrodes specifically have been intensively investigated for the construction of PECs due to their relatively inexpensive processing costs and better stability in aqueous media compared with other types of photoelectrodes. Although there have been many advancements in the development of oxide-based photoanodes, our understanding of oxide-based photocathodes remains limited. The goal of this Perspective is to examine the recent progress made in the field of oxide-based photocathodes and discuss future research directions. The photocathode systems considered here include binary and ternary Cu-based photocathodes and ternary Fe-based photocathodes. We assessed the characteristics and major advantages and drawbacks of each system and identified the most critical research gaps. The insights and discussions provided in this Perspective will serve as useful resources for the design of future studies, leading to the development of more efficient and practical PECs.

Ni/Fe oxyhydroxides are the best performing Earth-abundant electrocatalysts for water oxidation. However, the origin of their remarkable performance is not well understood. Herein, we employ spectroelectrochemical techniques to analyse the kinetics of water oxidation on a series of Ni/Fe oxyhydroxide films: FeOOH, FeOOHNiOOH, and Ni(Fe)OOH (5% Fe). The concentrations and reaction rates of the oxidised states accumulated during catalysis are determined. Ni(Fe)OOH is found to exhibit the fastest reaction kinetics but accumulates fewer states, resulting in a similar performance to FeOOHNiOOH. The later catalytic onset in FeOOH is attributed to an anodic shift in the accumulation of oxidised states. Rate law analyses reveal that the rate limiting step for each catalyst involves the accumulation of four oxidised states, Ni-centred for Ni(Fe)OOH but Fe-centred for FeOOH and FeOOHNiOOH. We conclude by highlighting the importance of equilibria between these accumulated species and reactive intermediates in determining the activity of these materials., Multimetallic oxyhydroxides are highly active electrocatalysts for water oxidation but their mechanism and the role of each metal is poorly understood. Here, authors use spectroelectrochemical techniques to probe the species accumulated during catalysis in Ni/Fe oxyhydroxide films.

A spatial confiment of polysulfides using the metal compound additives having polar surfaces has been considered to be a promising approach to address the insufficient rate capability and cyclability of lithium–sulfur batteries. Herein, we report a more effective approach outperforming this conventional one: a heterogeneous catalysis to promote polysulfide fragmentations. It was revealed using combined computational and experimental approaches that an ultrastrong adsorption of elemental sulfur on TiN surfaces resulted in a spontaenous fragmentation into shorter chains of polysulfides. This heterogeneous catalysis reaction improved the sluggish kinetics of polysulfide reduction because of the chemical disproportionation at the second plateau. A markedly enhanced rate capability was finally obtained, exhibiting a discharge capacity of 700 mAh g–1 at a scan rate of 5C.

Electrochemical synthesis methods were developed to produce CuBi2O4, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi2O4 at 450 °C in air. Ag-doped CuBi2O4 electrodes were also prepared by adding a trace amount of Ag+ in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi2O4, Ag+ ions substitutionally replaced Bi3+ ions and increased the hole concentration in CuBi2O4. As a result, photocurrent enhancements for both O2 reduction and water reduction were achieved. Furthermore, while undoped CuBi2O4 electrodes suffered from anodic photocorrosion during O2 reduction due to poor hole transport, Ag-doped CuBiO4 effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi2O4 and Ag-doped CuBi2O4 electrodes prepared in this ...

Anthropogenic activities such as the use of water softeners and road deicers have artificially increased the Cl− concentration in freshwater resources, threatening sustainable water ecosystems worldwide. Currently, there is no energy-efficient and sustainable method to selectively remove Cl− from water to regulate the Cl− concentration in water treatment processes. In this study, we report new electrochemical and photoelectrochemical strategies that can not only selectively remove Cl− but also recover and valorize Cl− to Cl2, HOCl, and ClO−. These methods are based on the use of Bi as a Cl-storage/release electrode for the construction of Cl-removal and Cl-recovery cells. We demonstrate the operation of proof-of-concept electrochemical and photoelectrochemical cells where the Cl− storage/release reactions are coupled with various reactions to generate electricity, fuels, and chemicals.

N-type bismuth vanadate (BiVO4) has emerged as one of the most promising photoanodes for use in water-splitting photoelectrochemical cells in recent years. However, its photoelectrochemical properties may be further enhanced by optimizing its band gap and its charge-transport properties. Doping at the V5+ and O2– sites of BiVO4 has proven to be an effective strategy to alter the oxide electronic band structure and/or charge-transport properties, but the effect of doping at the Bi3+ site is not nearly as well understood. In this study, we performed a combined experimental and theoretical study of BiVO4 doped with lanthanide (Ln) elements (La, Ce, Sm, and Yb) at the Bi3+ site, and we elucidated the effect of doping on the electronic band structure and charge-transport properties of BiVO4. Furthermore, we performed density functional theory calculations to investigate the combined effect of the Ln doping and oxygen vacancies, which are intrinsic defects in BiVO4. Our results showed that for some cases, the simultaneous consideration of Ln doping and O vacancy leads to changes that cannot be obtained by the sum of the changes caused by Ln doping alone and O vacancy alone, which was critical for understanding the experimental results. The various ways that the Ln dopants modified the electronic band structure and charge-transport properties of BiVO4 demonstrated in this study can provide useful guidelines for the tuning of the composition of oxide-based photoelectrodes.

Reductive biomass conversion has been conventionally conducted using H2 gas under high-temperature and -pressure conditions. In this study, efficient electrochemical reduction of 5-hydroxymethylfurfural (HMF), a key intermediate for biomass conversion, to 2,5-bis(hydroxymethyl)furan (BHMF), an important monomer for industrial processes, was demonstrated using Ag catalytic electrodes. This process uses water as the hydrogen source under ambient conditions and eliminates the need to generate and consume H2 for hydrogenation, providing a practical and efficient route for BHMF production. By systematic investigation of HMF reduction on the Ag electrode surface, BHMF production was achieved with the Faradaic efficiency and selectivity nearing 100%, and plausible reduction mechanisms were also elucidated. Furthermore, construction of a photoelectrochemical cell (PEC) composed of an n-type BiVO4 semiconductor anode, which uses photogenerated holes for water oxidation, and a catalytic Ag cathode, which uses photo...

BiVO4 photoanodes have mainly been investigated under neutral conditions because BiVO4 gradually dissolves under extreme pH conditions. In this study, the possibility of utilizing ZnFe2O4 as a protection layer to stabilize BiVO4 in a 0.1 M KOH solution was investigated. A 10-15 nm thick ZnFe2O4 layer was conformally placed on a nanoporous BiVO4 electrode by photodepositing a FeOOH layer, followed by drop casting a zinc nitrate solution and annealing. The resulting BiVO4/ZnFe2O4 electrode generated a photocurrent density of2 mA/cm(2) at 1.23 V versus RHE with a significantly improved stability compared with the pristine BiVO4 electrode. The incident and absorbed photon-to-current conversion efficiencies along with absorption spectra suggested that the ZnFe2O4 protection layer also contributes to photocurrent generation by increasing photon absorption and electron-hole separation. These results suggest that further investigation of protection and catalyst layers can enable more stable and efficient operation of BiVO4-based photoanodes in basic media.

2,5-Hexanedione (HD), which can be produced by reduction of 5-hydroxymethylfurfural (HMF), one of the most important biomass intermediates, can serve as a precursor to produce various biofuels and key building block chemicals. The conversion of HMF to HD requires reduction of both the alcohol and aldehyde groups to alkane groups as well as opening of the furan ring. In this study, a direct electrochemical conversion of HMF to HD at ambient pressure and temperature was demonstrated without using H2 or precious metal catalysts. Water was used as the hydrogen source and zinc was used as the catalytic electrode, which enabled hydrogenolysis and Clemmensen reduction coupled with furan ring opening. Optimum conditions to achieve high Faradaic efficiency (FE) and selectivity for HD production were investigated and plausible mechanisms were proposed. The environmentally benign one-step procedure to produce HD reported in this study will serve as a new route to valorize biomass intermediates.

Electrochemical reductive amination uses water as the hydrogen source without requiring other chemicals as the reducing agent, providing reaction conditions that are more environmentally benign. The catalytic abilities and efficiencies of various metal electrodes (Ag, Cu, Pt, Sn, Zn) were investigated for the electrochemical reductive amination of 5-hydroxymethylfurfural (HMF), a key intermediate for biomass conversion, with methylamine (CH3NH2). For each metal electrode, the potentials necessary to initiate reductive amination as well as potential dependent Faradaic efficiency (FE) and selectivity were investigated systematically. Based on the results, reduction conditions and a high surface area Ag electrode that can achieve a FE and a selectivity nearing 100% were reported. Furthermore, reductive amination of HMF derivatives such as 5-methylfurfural (5-MF), 2,5-diformylfuran (DFF), and 5-formyl-2-furancarboxylic acid (FFCA) using methylamine as well as reductive amination of HMF using ethanolamine (NH2CH2CH2OH) were conducted to establish electrochemical reductive amination as a general route for the reductive amination of furfural-based biomass intermediates.

We report an atomic force microscopy (AFM) based method to characterize the adhesion between metal nanoparticles and carbon support that plays an important role in determining the durability of fuel cells. This adhesion is related to the electrochemical active surface area (ECSA). Force–distance curves measured with a Pt-coated AFM tip on the surface of the support allows us to probe the adhesion between a Pt nanoparticle and the support because an asperity between a Pt-coated AFM tip and carbon support can mimic the nanoscale interface between Pt nanoparticles and carbon. We found that acid-based surface treatment of the carbon support increases the adhesion force by a factor of 4, compared with the as-received carbon support. Meanwhile, surface treatment using acid on the carbon support can lead to a higher ECSA, which is consistent with the higher adhesion force probed with AFM. We attribute the higher adhesion between the Pt probe and the acid-treated carbon to stronger chemical interaction by the C/O functional groups.

Tin has been widely used to solder, tin plated steel, bronze alloy, sputtering target for transparent electrode and chemical additives. It has been widely reported to the recycling technologies for tin scraps because of the scarcity and economic efficiency of the reserve. This study was analyzed by using open/registered patents KR, US, CN, JP and EP related to recycling technologies for processing scrap, sludges, waste fluid for plating process and spent alloy containing tin in between 1970 and 2013. Patents were collected using key-words searching and filtered by filtering criteria. The trends of the patents were analyzed by year, country, appliant and technology.

A Boost for Bismuth Vanadate In theory, given its light-absorption spectrum, bismuth vanadate should be an effective photoanode for solar water-splitting. However, in prior studies, few of the “holes” generated upon photoexcitation have persisted long enough to strip electrons from water. Kim and Choi (p. 990 , published online 13 February) now show that the use of a hydrophobic vanadium source in the semiconductor's synthesis results in a high-surface-area morphology with substantially enhanced hole lifetimes. Deposition of two successive catalyst layers enhanced the proportion of holes that reacted with water at the surface, thereby raising the efficiency of the oxygen evolution reaction.

Objectives We aimed to determine the prevalence of cholesterol gallstones, the compositional changes of gallstones and its predisposing factors in Korea with this single-center study. Methods Data of 365 patients who underwent cholecystectomy for cholecystolithiasis from July 2008 to September 2011 were reviewed. Based on the compositional analysis of the gallstones, patients were assigned to either cholesterol gallstone group or pigment gallstone group. The characteristics of the patients and the gallstones were summarized and compared. Results After eight patients with mixed gallstones were excluded, 357 patients were enrolled in the study, including cholesterol gallstones in 175 (49.0%) and pigment gallstones in 182 (51.0%). The number of patients with cholecystolithiasis increased but the prevalence of cholesterol gallstone decreased with age. Compared with the pigment gallstone group, the cholesterol gallstone group was associated with young age (

Harvesting energy directly from sunlight as nature accomplishes through photosynthesis is a very attractive and desirable way to solve the energy challenge. Many efforts have been made to find appropriate materials and systems that can utilize solar energy to produce chemical fuels. One of the most viable options is the construction of a photoelectrochemical cell that can reduce water to H(2) or CO(2) to carbon-based molecules. Bismuth vanadate (BiVO(4)) has recently emerged as a promising material for use as a photoanode that oxidizes water to O(2) in these cells. Significant advancement in the understanding and construction of efficient BiVO(4)-based photoanode systems has been made within a short period of time owing to various newly developed ideas and approaches. In this review, the crystal and electronic structures that are closely related to the photoelectrochemical properties of BiVO(4) are described first, and the photoelectrochemical properties and limitations of BiVO(4) are examined. Subsequently, the latest efforts toward addressing these limitations in order to improve the performances of BiVO(4)-based photoanodes are discussed. These efforts include morphology control, formation of composite structures, composition tuning, and coupling oxygen evolution catalysts. The discussions and insights provided in this review reflect the most recent approaches and directions for general photoelectrode developments and they will be directly applicable for the understanding and improvement of other photoelectrode systems.