Water photolysis is a sustainable technology to convert natural solar energy and water into chemical fuels and is thus considered a thorough solution to the forthcoming energy crises. Unassisted ...water splitting that could directly harvest solar light and subsequently split water in a single device has become an important research theme. Three types of tandem devices including photoelectrochemical (PEC), photovoltaic (PV) cell/PEC and PV/electrolyser tandem cells are proposed to realize water photolysis at different levels of integration and component. Recent progress in tandem water splitting devices is summarized, and crucial issues on device optimization from the perspective of each photo‐absorber functionalities in band edge potential, light absorptivity and transmittance are discussed. By increasing the performances of stand‐alone PEC or PV devices, a 20% solar to hydrogen efficiency is predicted that is a significant value towards further application in practice. Accordingly, the challenges for materials development and configuration optimization are further outlined.
Tandem water splitting devices composed of two or more photoabsorbers could realize unassisted solar to hydrogen conversion. Various PEC electrodes and solar cells are proposed as photoabsorbers to be combined together for the tandem configurations, but the optimal device design is still not obvious. Recent progress in tandem water splitting devices is summarized and crucial issues on device optimization from the perspective of each photo‐absorber functionalities in band‐edge potential, light absorptivity and transmittance are discussed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In the past several years, surface-disordered TiO2, which is referred to as black TiO2 and can absorb both visible and near-infrared solar light, has triggered an explosion of interest for many ...important applications. Despite the excellent optical and electrical features of black TiO2 for various photoelectrochemical (PEC) and photochemical reactions, the current understanding of the photocatalytic mechanism is unsatisfactory and incomplete. On the basis of previous studies, we present new insight into the surface localization of defects and perspectives on the liquid/solid interface. The future prospects for understanding black TiO2 from this perspective suggest that defect engineering at the liquid/solid interface is a potential method of guiding nanomaterial design.
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IJS, KILJ, NUK, PNG, UL, UM
Inspired by the great success of graphite in lithium‐ion batteries, anode materials that undergo an intercalation mechanism are considered to provide stable and reversible electrochemical sodium‐ion ...storage for sodium‐ion battery (SIB) applications. Though MoS2 is a promising 2D material for SIBs, it suffers from deformation of its layered structure during repeated intercalation of Na+, resulting in undesirable electrochemical behaviors. In this study, vertically oriented MoS2 on nitrogenous reduced graphene oxide sheets (VO‐MoS2/N‐RGO) is presented with designed spatial geometries, including sheet density and height, which can deliver a remarkably high reversible capacity of 255 mA h g−1 at a current density of 0.2 A g−1 and 245 mA h g−1 at a current density of 1 A g−1, with a total fluctuation of 5.35% over 1300 cycles. These results are superior to those obtained with well‐developed hard carbon structures. Furthermore, a SIB full cell composed of the optimized VO‐MoS2/N‐RGO anode and a Na2V3(PO4)3 cathode reaches a specific capacity of 262 mA h g−1 (based on the anode mass) during 50 cycles, with an operated voltage range of 2.4 V, demonstrating the potentially rewarding SIB performance, which is useful for further battery development.
Vertically oriented MoS2 with controlled spatial geometry on N‐RGO favors rapid Na+ diffusion for sodium‐ion batteries, and the dense spatial distance due to the high sheet density and low height enables a high reversible capacity and long stability.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Alleviating charge recombination at the electrode/electrolyte interface by introducing an overlayer is considered an efficient approach to improve photoelectrochemical (PEC) water oxidation. A WO3 ...overlayer with dual oxygen and tungsten vacancies was prepared by using a solution‐based reducing agent, LEDA (lithium dissolved in ethylenediamine), which improved the PEC performance of the mesoporous WO3 photoanode dramatically. In comparison to the pristine samples, the interconnected WO3 nanoparticles surrounded by a 2–2.5 nm thick overlayer exhibited a photocurrent density approximately 2.4 times higher and a marked cathodic shift of the onset potential, which is mainly attributed to the facilitative effect on interface charge transfer and the improved conductivity by enhanced charge carrier density. This simple and effective strategy may provide a new path to improve the PEC performance of other photoanodes.
The surface of WO3 photoanodes is dramatically activated after in situ formation of an overlayer with dual tungsten and oxygen vacancies, presenting a photocurrent density of 2.81 mA cm−2 at 1.23 V (vs. RHE) and a negative shift of the onset potential.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Background and Aims The efficacy of palliative biliary drainage by using bilateral or unilateral self-expandable metal stents (SEMSs) for a malignant hilar biliary stricture (MHS) remains ...controversial. This prospective, randomized, multicenter study investigated whether bilateral drainage by using SEMSs is superior to unilateral drainage in patients with inoperable MHSs. Methods Patients with inoperable high-grade MHSs who underwent palliative endoscopic insertion of bilateral or unilateral SEMSs were enrolled. The main outcome measurements were the rate of primary reintervention for malfunction after successful placement of SEMSs, stent patency, technical and clinical success rates, adverse events, and survival duration. Results A total of 133 pathology-diagnosed patients were randomized to the bilateral group (n = 67) or the unilateral group (n = 66). The primary technical success rates were 95.5% (64/67) and 100% (66/66) in the bilateral and unilateral groups, respectively ( P = .244). The clinical success rates were 95.3% (61/64) and 84.9% (56/66), respectively ( P = .047). The primary reintervention rates based on the per-protocol analysis were 42.6% (26/61) in the bilateral group and 60.3% (38/63) in the unilateral group ( P = .049). The median cumulative stent patency duration was 252 days in the bilateral group and 139 days in the unilateral group. The risk of stent patency failure was significantly higher in the unilateral group (log-rank test; P < .01). In a multivariate Cox proportional hazard model to assess stent patency, bilateral SEMS placement was a favorable factor (adjusted hazard ratio 0.30, 95% confidence interval, 0.172-0.521; P < .001). Survival probability and late adverse events were not different between the 2 groups. Conclusions Unilateral and bilateral drainage strategies by using SEMSs had similar technical success rates, but bilateral drainage resulted in fewer reinterventions and more durable stent patency in patients with inoperable high-grade MHSs. (Clinical trial registration number: NCT02166970.)
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A high‐performance novel photodetector is demonstrated, which consists of graphene and CH3 NH3PbI3 perovskite layers. The resulting hybrid photodetector exhibits a dramatically enhanced photo ...responsivity (180 A/W) and effective quantum efficiency (5× 104%) over a broad bandwidth within the UV and visible ranges.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The current lithium-ion battery (LIB) electrode fabrication process relies heavily on the wet coating process, which uses the environmentally harmful and toxic N-methyl-2-pyrrolidone (NMP) solvent. ...In addition to being unsustainable, the use of this expensive organic solvent substantially increases the cost of battery production, as it needs to be dried and recycled throughout the manufacturing process. Herein, we report an industrially viable and sustainable dry press-coating process that uses the combination of multiwalled carbon nanotubes (MWNTs) and polyvinylidene fluoride (PVDF) as a dry powder composite and etched Al foil as a current collector. Notably, the mechanical strength and performance of the fabricated LiNi
Co
Mn
O
(NCM712) dry press-coated electrodes (DPCEs) far exceed those of conventional slurry-coated electrodes (SCEs) and give rise to high loading (100 mg cm
, 17.6 mAh cm
) with impressive specific energy and volumetric energy density of 360 Wh kg
and 701 Wh L
, respectively.
Rational assembly and hetero-growth of hybrid structures consisting of multiple components with distinctive features are a promising and challenging strategy to develop materials for energy storage ...applications. Herein, we propose a supercapacitor electrode comprising a three-dimensional self-supported hierarchical MnCo-layered double hydroxides@Ni(OH) 2 MnCo-LDH@Ni(OH) 2 core–shell heterostructure on conductive nickel foam. The resultant MnCo-LDH@Ni(OH) 2 structure exhibited a high specific capacitance of 2320 F g −1 at a current density of 3 A g −1 , and a capacitance of 1308 F g −1 was maintained at a high current density of 30 A g −1 with a superior long cycle lifetime. Moreover, an asymmetric supercapacitor was successfully assembled using MnCo-LDH@Ni(OH) 2 as the positive electrode and activated carbon (AC) as the negative electrode. The optimized MnCo-LDH@Ni(OH) 2 //AC device with a voltage of 1.5 V delivered a maximum energy density of 47.9 W h kg −1 at a power density of 750.7 W kg −1 . The energy density remained at 9.8 W h kg −1 at a power density of 5020.5 W kg −1 with excellent cycle stability.
Solar energy-assisted water oxidative hydrogen peroxide (H2O2) production on an anode combined with H2 production on a cathode increases the value of solar water splitting, but the challenge of the ...dominant oxidative product, O2, needs to be overcome. Here, we report a SnO2–x overlayer coated BiVO4 photoanode, which demonstrates the great ability to near-completely suppress O2 evolution for photoelectrochemical (PEC) H2O oxidative H2O2 evolution. Based on the surface hole accumulation measured by surface photovoltage, downward quasi-hole Fermi energy at the photoanode/electrolyte interface and thermodynamic Gibbs free energy between 2-electron and 4-electron competitive reactions, we are able to consider the photoinduced holes of BiVO4 that migrate to the SnO2–x overlayer kinetically favor H2O2 evolution with great selectivity by reduced band bending. The formation of H2O2 may be mediated by the formation of hydroxyl radicals (OH·), from 1-electron water oxidation reactions, as evidenced by spin-trapping electron paramagnetic resonance (EPR) studies conducted herein. In addition to the H2O oxidative H2O2 evolution from PEC water splitting, the SnO2–x /BiVO4 photoanode can also inhibit H2O2 decomposition into O2 under either electrocatalysis or photocatalysis conditions for continuous H2O2 accumulation. Overall, the SnO2–x /BiVO4 photoanode achieves a Faraday efficiency (FE) of over 86% for H2O2 generation in a wide potential region (0.6–2.1 V vs reversible hydrogen electrode (RHE)) and an H2O2 evolution rate averaging 0.825 μmol/min/cm2 at 1.23 V vs RHE under AM 1.5 illumination, corresponding to a solar to H2O2 efficiency of ∼5.6%; this performance surpasses almost all previous solar energy-assisted H2O2 evolution performances. Because of the simultaneous production of H2O2 and H2 by solar water splitting in the PEC cells, our results highlight a potentially greener and more cost-effective approach for “solar-to-fuel” conversion.
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IJS, KILJ, NUK, PNG, UL, UM
A novel approach for improving the thermal and dimensional stability of a polymer based separator is investigated. The surface of the micropores in the polyolefin based separator is fully covered by ...a thin layer of SiO2 deposited by the chemical vapor deposition method. Through this new process, the thermal and dimensional stability of the microporous separators is greatly enhanced, thus allowing the commercialization of polymer based separators for large sized battery systems. The morphology of the modified separators as a function of the thickness of the inorganic layer is considered to be a key factor for the optimization of their thermal and dimensional stability without sacrificing their ionic conductivity for the sake of the cell performance. At the optimum thickness of the thin and conformal layer of SiO2, we obtain a polymer separator which is highly stable at high temperature, even above the melting point of the polymer membrane, with satisfactory cell performance, such as its ion conductivity, C-rate and cycle life.
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► The surface of the polyolefin based separator is covered by a thin layer of SiO2. ► The dimensional stability of a polymer based separator is improved. ► This study introduces a new paradigm for the separators of Li-ion batteries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
