Polymer-Mediated Self-Assembly of TiO₂@Cu₂O Core–Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation

Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu2O on TiO2 nanowire array (NWA) to form a truly core–shell TiO2@Cu2O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm–2 at 1.23 V vs RHE in 0.5 M Na2SO4 solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO2-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO2@Cu2O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO2@Cu2O core–shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core–shell nanoarchitectures for broad applications

Self-Improvement of Ti:Fe₂O₃ Photoanodes: Photoelectrocatalysis Improvement after Long-Term Stability Testing in Alkaline Electrolyte

Hematite photoanode is a widely accepted stable photoelectrode in a strong alkali solution, such as NaOH aqueous solution. However, no one systematically investigates the photoelectrochemical stability of hematite-based photoanodes. More importantly, there are some contradictory results about the stability of hematite photoanodes in the literature. Herein we investigate the long-term stability of a Ti doped hematite (Ti:Fe₂O₃) photoanode in 1.0 M NaOH under visible light. Ti:Fe₂O₃ photoanode exhibits the significant photocurrent enhancement and the cathodic shift of the onset potential after long-term working in a strong alkali solution. Detailed characterizations reveal that an FeOOH layer, which serves as cocatalyst for self-improvement of Ti:Fe₂O₃ photoanodes, is formed at the interface of the Ti:Fe₂O₃/electrolyte junction

Additional file 1: Figure S1. of DNA@Mn3(PO4)2 Nanoparticles Supported with Graphene Oxide as Photoelectrodes for Photoeletrocatalysis

AFM images of (A) GO drop-casted on freshly cleaved mica surface, (B) DNA drop-casted on freshly cleaved mica surface. Figure S2. XRD pattern of Mn3(PO4)2 powders. A. Mn3(PO4)2; B. Standard XRD pattern of Mn3(PO4)2 from the PDF card of 33–0901. Figure S3. Absorbance of DNA solution before and after react with MnSO4 and K3PO4 (A); concentration vs. absorbance calibration of DNA solution (B). Figure S4. Linear sweep voltammetry curves of (a) ssDNA, dsDNA, and lmDNA synthesized nanocomposite (c) different concentrations of GO synthesized nanocomposite (e) different concentration of Mn3(PO4)2; and photocurrent response of (b) ssDNA, dsDNA, and lmDNA synthesized nanocomposite (d) different concentrations of GO synthesized nanocomposite (f) different concentrations of Mn3(PO4)2. Figure S5. (a) UV-vis diffuses reflectance spectra of Mn3(PO4)2 powder, (b) first derivative absorption spectra of Mn3(PO4)2 powder. (c) Cyclic voltammetry (CV) curve of Mn3(PO4)2 on glassy carbon electrode in 0.1 M KCl solution. (DOCX 2269 kb

Additional file 1: Figure S1. of DNA@Mn3(PO4)2 Nanoparticles Supported with Graphene Oxide as Photoelectrodes for Photoeletrocatalysis

AFM images of (A) GO drop-casted on freshly cleaved mica surface, (B) DNA drop-casted on freshly cleaved mica surface. Figure S2. XRD pattern of Mn3(PO4)2 powders. A. Mn3(PO4)2; B. Standard XRD pattern of Mn3(PO4)2 from the PDF card of 33–0901. Figure S3. Absorbance of DNA solution before and after react with MnSO4 and K3PO4 (A); concentration vs. absorbance calibration of DNA solution (B). Figure S4. Linear sweep voltammetry curves of (a) ssDNA, dsDNA, and lmDNA synthesized nanocomposite (c) different concentrations of GO synthesized nanocomposite (e) different concentration of Mn3(PO4)2; and photocurrent response of (b) ssDNA, dsDNA, and lmDNA synthesized nanocomposite (d) different concentrations of GO synthesized nanocomposite (f) different concentrations of Mn3(PO4)2. Figure S5. (a) UV-vis diffuses reflectance spectra of Mn3(PO4)2 powder, (b) first derivative absorption spectra of Mn3(PO4)2 powder. (c) Cyclic voltammetry (CV) curve of Mn3(PO4)2 on glassy carbon electrode in 0.1 M KCl solution. (DOCX 2269 kb

DataSheet_1_Tidal variation modulates the dissolved silicate behavior and exchange flux across the semi-enclosed bay‐coastal water continuum, China.xlsx

Coastal water is the key transition zone for the circulation and transport of nutrients. Their role in transporting nutrients is important to understanding global dissolved silicate (DSi) cycles and sources of nutrients supporting the biological pump and ocean carbon cycle. However, the understanding of controlling DSi exchange flux between the semi-enclosed bay and coastal water was still scarcely due to limitations in continuous observation. In this study, we conducted continuous investigations during spring tide (ST) and neap tide (NT) in 2021 in Shuidong Bay (SDB), China, to explore the impacts of different tidal cycles on DSi in SDB and the fluxes across SDB and South China Sea (SCS) coastal water. The findings demonstrated that there were significant differences in DSi concentrations and nutrients ratios between ST and NT in S1 station (P < 0.05). In addition, the DSi concentrations were 32.01 ± 27.21 μmol/L and 51.48 ± 48.44 μmol/L in ST and NT, respectively. Besides, the net export of DSi from SDB to SCS was 0.18 t throughout the entire early of autumn tidal cycle, suggesting SDB was the source of DSi, and its behavior across the semi-enclosed bay‐coastal water continuum was largely controlled by tidal characteristics (tidal height, flow velocity), water physicochemical parameters (salinity, pH), biological uptake and terrestrial sources input. SDB in ST has higher proportions of DSi: DIN (dissolved inorganic nitrogen) (1.49 ± 1.28) and DSi: DIP (dissolved inorganic phosphorus) (58.6 ± 43.73) compared with NT, DSi: DIN and DSi: DIP for the NT period were 1.45 ± 1.15 and 43.99 ± 28.59, indicating that phosphorus (P) is the limiting trophic factor for SDB. The tidal cycle in SDB would alter the DSi stoichiometry and mitigated the impact of eutrophication caused by terrestrial sources. This study provides new insights in the Si tidal cycling across the semi-enclosed bay‐coastal water continuum, which was implications for understanding DSi biogeochemical process and primary production dynamics in coastal water.</p

Transparently Passivating Catalyst of Hydrated Manganese Phosphate for Photoelectrochemical O₂ Generation

A transparently hydrated manganese phosphate (“Mn–Pi”) catalyst is coated onto a Ti-doped hematite (Ti:Fe2O3) photoanode by the photo-assisted electrochemical deposition. Under a visible light illumination of 100 mW cm–2, the photocurrent density of Ti:Fe2O3/Mn–Pi reaches 0.28 mA cm–2 at 1.2 VRHE, which is around two times higher than that obtained with the pristine Ti:Fe2O3 electrode in a neutral electrolyte, and the “onset” potential reduces by 100 mV. The passivating role of the Mn–Pi catalyst is revealed experimentally. The surface states of hematite are significantly passivated after Mn–Pi deposition, which relieves the degree of Fermi level pinning of hematite and enhances the surface band bending of hematite. Therefore, the photovoltage and the charge separation are improved. Moreover, due to the valence change of the Mn element in Mn–Pi, the charge transfer through the Mn–Pi layer is favorable, which has a low charge transfer resistance for photogenerated holes. The suitability of this transparently passivating catalyst for concentrating light is also identified. This work demonstrates that Mn–Pi can be applied for photoelectrochemical water splitting as a transparently passivating catalyst

Hydrothermally Treating High-Ti Cinder for a Near Full-Sunlight-Driven Photocatalyst toward Highly Efficient H₂ Evolution

A major drawback of conventional photocatalysts like TiO₂ is the limit of only working under ultraviolet irradiation. As a solution, visible-light-driven photocatalysts have been explored in recent years but full-sunlight-driven photocatalysts are still lacking. Herein, multielement-codoped (Mn, Fe, Si, Al, S, F, etc.) TiO₂ nanomaterials were prepared from an industrial high-Ti cinder (HiTi) by a two-step hydrothermal method using NaOH and NH₄F (or H₂O) as morphology controlling agents. The prepared HiTi photocatalyst exhibits a strong absorption at near full-sunlight spectrum (300–800 nm). Among all TiO₂-based photocatalysts without any noble metal cocatalyst, the photocatalytic H₂ evolution rate on NaOH- and H₂O-hydrothermally treated HiTi (HiTi-TiO₂) is remarkably superior to the reference P25 TiO₂ powders by a factor of 3.8 and thus is the highest. However, NaOH- and NH₄F-treated HiTi (HiTi-TiO₂-F) shows a lower photoreactivity than HiTi-TiO₂ does. Mechanistic studies show that the multielement-doped TiO₂ can synergistically harvest full span sunlight to greatly increase light absorption, while suppressing the charge recombination and reducing the reaction barriers for efficient water splitting. Importantly, the amount of produced industrial cinder is huge in China, and it is dumped on the ground in very large mounds, which results in serious pollution. This study may open a promising recycling approach to treat the waste for sustainable energy use

Defective Metal–Organic Framework Assisted with Nitrogen Doping Enhances the Photoelectrochemical Performance of BiVO₄

BiVO4 is a promising n-type semiconductor for photoelectrochemical (PEC) water splitting, which can serve as a photoanode. However, severe surface recombination and slow water oxidation kinetics hinder the realization of its highly theoretical PEC performance. Single-atom catalyst-like metal–organic frameworks (MOFs) and their derived metal oxides have been broadly investigated to enhance the kinetics of BiVO4 photoanodes. According to the principle of catalysis, only coordinatively unsaturated atoms can participate in the catalytic reaction. Herein, a defective cobalt-based MOF (d-CoMOF) with missing linker defects is modified onto the surface of N-doped BiVO4 (N:BVO) photoanodes. The photocurrent density of d-CoMOF/N:BVO is 3.59 times higher than that of pristine BVO (0.56 mA/cm2) at 1.23 VRHE. The onset potential of d-CoMOF/N:BVO shows a cathodic shift of 300 mV relative to BVO. The roles of the d-CoMOF overlayer and N doping are experimentally revealed. The d-CoMOF modification and N doping could increase the electron density, passivate the surface states, and promote the catalysis kinetics of BVO. Thus, the kinetic parameters, such as the charge separation/injection efficiency, onset potential, and photocurrent density, are significantly enhanced. This work provides a way to use MOFs for PEC water splitting by the introduction of defects

Image_3_No evidence of a genetic causal relationship between ankylosing spondylitis and iron homeostasis: A two-sample Mendelian randomization study.TIF

BackgroundAnkylosing spondylitis (AS) is an immune-mediated chronic inflammatory disease that leads to bone hyperplasia and spinal ankylosis. Iron homeostasis plays a very important role in the inflammatory response and is closely related to the pathogenesis of AS. This study aimed to use large-scale genome-wide association study (GWAS) summary data to study the genetic causal relationship between AS and iron homeostasis using Mendelian randomization (MR).MethodsGenome-wide association study summary data of AS and iron homeostasis-related indicators were obtained from the FinnGen consortium and the DeCODE genetics database, respectively. We used four iron homeostasis-related indicators: ferritin, serum iron, total iron binding capacity (TIBC), and transferrin saturation (TSAT) for two-sample MR analyses to test for genetic causal association with AS using the “TwoSampleMR” package of the R software (version 4.1.2). The random-effects inverse variance weighted (IVW) method was the main analysis method used for MR. We examined the MR analysis results for heterogeneity, horizontal pleiotropy, and possible outliers. In addition, we confirmed the robustness of the MR analysis by testing whether the results were affected by a single SNP and whether they followed a normal distribution.ResultsThe random-effects IVW results showed that ferritin [p = 0.225, OR 95% confidence interval (CI) = 0.836 (0.627–1.116)], serum iron [p = 0.714, OR 95% CI = 0.948 (0.714–1.260)], TIBC [p = 0.380, OR 95% CI = 0.917 (0.755–1.113)], and TSAT [p = 0.674, OR 95% CI = 0.942 (0.713–1.244)] have no genetic causal relationship with AS. We detected no heterogeneity，horizontal pleiotropy and possible outliers in our MR analysis (p > 0.05). In addition, our MR analysis results were not affected by a single SNP, and were normally distributed.ConclusionOur study did not detect a genetic causal relationship between AS and iron homeostasis. Nonetheless, this does not rule out a relationship between the two at other mechanistic levels.</p

Image_2_No evidence of a genetic causal relationship between ankylosing spondylitis and iron homeostasis: A two-sample Mendelian randomization study.tif

BackgroundAnkylosing spondylitis (AS) is an immune-mediated chronic inflammatory disease that leads to bone hyperplasia and spinal ankylosis. Iron homeostasis plays a very important role in the inflammatory response and is closely related to the pathogenesis of AS. This study aimed to use large-scale genome-wide association study (GWAS) summary data to study the genetic causal relationship between AS and iron homeostasis using Mendelian randomization (MR).MethodsGenome-wide association study summary data of AS and iron homeostasis-related indicators were obtained from the FinnGen consortium and the DeCODE genetics database, respectively. We used four iron homeostasis-related indicators: ferritin, serum iron, total iron binding capacity (TIBC), and transferrin saturation (TSAT) for two-sample MR analyses to test for genetic causal association with AS using the “TwoSampleMR” package of the R software (version 4.1.2). The random-effects inverse variance weighted (IVW) method was the main analysis method used for MR. We examined the MR analysis results for heterogeneity, horizontal pleiotropy, and possible outliers. In addition, we confirmed the robustness of the MR analysis by testing whether the results were affected by a single SNP and whether they followed a normal distribution.ResultsThe random-effects IVW results showed that ferritin [p = 0.225, OR 95% confidence interval (CI) = 0.836 (0.627–1.116)], serum iron [p = 0.714, OR 95% CI = 0.948 (0.714–1.260)], TIBC [p = 0.380, OR 95% CI = 0.917 (0.755–1.113)], and TSAT [p = 0.674, OR 95% CI = 0.942 (0.713–1.244)] have no genetic causal relationship with AS. We detected no heterogeneity，horizontal pleiotropy and possible outliers in our MR analysis (p > 0.05). In addition, our MR analysis results were not affected by a single SNP, and were normally distributed.ConclusionOur study did not detect a genetic causal relationship between AS and iron homeostasis. Nonetheless, this does not rule out a relationship between the two at other mechanistic levels.</p