RESUMEN
Metallic materials with unique surface structure have attracted much attention due to their unique physical and chemical properties. However, it is hard to prepare bulk metallic materials with special crystal faces, especially at the nanoscale. Herein, we report an efficient method to adjust the surface structure of a Cu plate which combines ion implantation technology with the oxidation-etching process. The large number of vacancies generated by ion implantation induced the electrochemical oxidation of several atomic layers in depth; after chemical etching, the Cu(100) planes were exposed on the surface of the Cu plate. As a catalyst for acid hydrogen evolution reaction, the Cu plate with (100) planes merely needs 273 mV to deliver a current density of 10 mA/cm2 because the high-energy (100) surface has moderate hydrogen adsorption and desorption capability. This work provides an appealing strategy to engineer the surface structure of bulk metallic materials and improve their catalytic properties.
RESUMEN
Engineering high-performance electrocatalysts is of great importance for energy conversion and storage. As an efficient strategy, element doping has long been adopted to improve catalytic activity, however, it has not been clarified how the valence state of dopant affects the catalytic mechanism and properties. Herein, it is reported that the valence state of a doping element plays a crucial role in improving catalytic performance. Specifically, in the case of iridium doped nickel-iron layer double hydroxide (NiFe-LDH), trivalent iridium ions (Ir3+ ) can boost hydrogen evolution reaction (HER) more efficiently than tetravalent iridium (Ir4+ ) ions. Ir3+ -doped NiFe-LDH delivers an ultralow overpotential (19 mV @ 10 mA cm-2 ) for HER, which is superior to Ir4+ doped NiFe-LDH (44 mV@10 mA cm-2 ) and even commercial Pt/C catalyst (40 mV@ 10 mA cm-2 ), and reaches the highest level ever reported for NiFe-LDH-based catalysts. Theoretical and experimental analyses reveal that Ir3+ ions donate more electrons to their neighboring O atoms than Ir4+ ions, which facilitates the water dissociation and hydrogen desorption, eventually boosting HER. The same valence-state effect is found for Ru and Pt dopants in NiFe-LDH, implying that chemical valence state should be considered as a common factor in modulating catalytic performance.
RESUMEN
Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel-cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O2- /Co3+ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O2- and Co3+ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H2 evolution rate of 1.7â µmol h-1 under AMâ 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380â nm.
RESUMEN
Stapled hemorrhoidopexy has been used for years to treat hemorrhoids. Despite numerous systematic reviews and meta-analyses on the topic, inconsistent conclusions have left people uncertain about its effectiveness and raised doubts about the quality of these reviews.In order to provide reliable evidence for clinical practice, it is crucial to conduct an overview to assess the quality of MAs/SRs regarding the efficacy and complications of SH.A comprehensive search was performed across seven databases to identify MAs/SRs on the efficacy and complications of SH from inception to October 2023. The selected MAs/SRs were then assessed using three well-established tools: AMSTAR-2, PRISMA 2020and GRADE. These assessments provide a robust evaluation of the quality and reliability of the included MAs/SRs.We removed overlapping randomized controlled trials (RCTs) and conducted a new meta-analysis of the outcomes. The overview included 23 meta-analyses.In AMSTAR-2, three reviews were deemed moderate quality, nine reviews were classified as low quality, and eleven reviews were evaluated as critically low quality.In PRISMA 2020,certain deficiencies were exhibited, such as abstracts (0/23:0 %),final retrieval date (0/23:0 %), sensitivity analysis (6/23:26.09 %),publication bias assessment (11/23:47.83 %), the quality of evidence (2/23:8.70 %) and so on.In GRADE,twenty-six items were rated as moderate quality (27.96 %),forty-one items were rated as low quality (44.09 %) and twenty-six items were rated as critically low quality (27.96 %).SH has been found to be an effective intervention for reducing postoperative pain, shortening procedure time, and promoting wound healing. The re-analysis indicated that SH can reduce postoperative pain in hemorrhoid patients (odds ratio = 0.28, 95 % confidence interval [0.15,0.55], p = 0.0002; I2 = 74 %, p < 0.00001). But SH is associated with a higher risk of postoperative bleeding and recurrence of prolapse.Given that the reviews included in this overview were rated as low quality, caution should be exercised when interpreting the findings.
RESUMEN
A zinc-infiltration process was adopted to prepare silver-doped copper nanosheet arrays. The larger atomic radius of Ag introduces tensile stress, which lowers the electron density at the s-orbitals of Cu atoms and improves the adsorption capability for hydrogen atoms. As a catalyst for hydrogen evolution, these silver doped copper nanosheet arrays achieved a low overpotential of 103 mV at 10 mA cm-2 in 1 M KOH, which is 604 mV lower than that of pure copper foil.
RESUMEN
P-N depleted bulk BiOBr/α-Fe2O3 heterojunction (DBH) nanostructures with the growth of (001) BiOBr facets were prepared via a simple hydrothermal method. BiOBr possesses an average thickness of around 50 nm and shows preferential exposure of the (001) facets. α-Fe2O3 nanoparticles, with an average diameter of 5 nm, are attached on the surface of BiOBr as 20-50 nm clusters with an intimate contact interface. Such DBH nanostructures show high hydrogen evolution, and 193 mmol g-1 of H2 is produced with DBH containing 1 wt% Pt, which is 6.3 times higher than that of α-Fe2O3 nanoparticles. The structural features of DBH are considered to be important to obtain attractive properties in photocatalytic water splitting.