Nieves López-Salas

Developing efficient and stable oxygen evolution reaction catalysts is crucial for practical water splitting. Herein, a mild room-temperature sulfidation strategy is employed to construct a hierarchical heterostructure composed of Fe-Co LDH nanoneedles and ultrathin Fe-CoSOH nanosheets on nickel foam. This nanoneedle-nanosheet architecture provides abundant active sites, optimized charge transfer pathways, and enhanced electrolyte wettability. Electrochemical tests show that the resulting catalyst exhibits excellent OER activity in 1.0 M KOH, requiring an overpotential of 230 mV to achieve a current density of 10 mA cm–2, with a Tafel slope of 35.37 mV dec–1. Notably, it maintains stable operation for over 600 h at a current density of 100 mA cm–2. Mechanism studies reveal that sulfur doping optimizes the electronic structure and promotes the reconstruction into the active CoOOH phase at a lower potential. Finite element simulations confirm that the hierarchical structure enhances the local electric field and reactant transport. This work provides an effective strategy for synergistically improving electrocatalytic performance through anion engineering and structural design.

SiOC(N)-based polymer-derived ceramic coatings are promising materials for biomedical surface engineering owing to their chemical stability and biofunctional potential, which stem from their tunable structure and composition. In this study, the effect of Cu and Zn on the structure and functional properties of SiOC(N) coatings deposited on AISI 316L stainless steel was investigated. Both metals induced significant structural and microstructural changes, including alterations of polymerization degree of the silicon-oxygen network, cleaving Si-C bonds and segregation of the free carbon phase. Zn-doped coatings remained amorphous and exhibited a stronger tendency to reorganise the SiOC(N) structure, indicating zinc's role as an effective network modifier. In contrast, incorporating Cu resulted in the formation of metallic nanoparticles within the SiOC(N) matrix. Electrochemical tests in PBS revealed modest improvement in the protective capabilities of unmodified and Cu-doped samples compared to the bare substrate. Zn-modified coatings exhibited the broadest passivation potential range and the highest stability under polarization. The SiOC(N)-based materials were hemocompatible, biocompatible, and osteoconductive. Additionally, the deposited coatings promoted osteogenic differentiation by stimulating the synthesis of early- and mid-stage osteogenesis markers. These results indicated that transition metal incorporation is an effective route for tailoring the structure and performance of SiOC(N)-based coatings for implantology-related applications.

Magnetron-sputtered CNx thin films are primarily employed as hard, low-friction protective and tribological coatings, as solar cells, and for catalytic applications. Lower growth rates and a reduced N content, favoring graphitic sp2 structures, hinder industrial scalability due to prolonged deposition times and produce softer, less dense films with inferior hardness, elasticity, and wear resistance. Carbon nitride films deposited by magnetron sputtering exhibit growth behavior strongly influenced by plasma–surface interactions. However, nitrogen resputtering and reduced film growth rates are commonly attributed to chemical etching by positive ions. We propose an additional, unreported power-dependent mechanism involving negative ions formed at the carbon target. These ions are accelerated through the plasma sheath, reaching the substrate with high kinetic energy and inducing both chemical and physical resputtering. This effect is localized to the geometrical projection of the target, as shown by spatially resolved analysis: ellipsometry reveals thickness reduction, and x-ray photoelectron spectroscopy and Raman spectroscopy indicate nitrogen depletion within this region. Correlation between stoichiometry and structural signatures confirms the decisive role of negative ions in modifying the film composition and microstructure. At the same time, the composition of the gas mixture exerts only a minor effect.

The demand for sustainable chemical production methods has led to significant advancements in photocatalysis. This study explores the photocatalytic production of hydrogen peroxide (H₂O₂) from water using a covalent organic framework (CYANO-COF) synthesized from triformylphloroglucinol (Tp) and 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarbonitrile (Bp-CN) via Schiff-base condensation. The synthesized COF material exhibited a predominantly AB stacking structure with an optimal band gap (2.22 eV) for visible-light absorption and effective charge separation. Furthermore, the photoelectrochemical characterizations revealed the photoresponsive nature of the material by creating a high charge density under illumination. Under illumination, the photocatalyst demonstrated efficient H₂O₂ generation with production rates of 550 μmolg^-1h^-1 using only water and 371 μmolg^-1h^-1 in the presence of ethanol. The sacrificial-agent-free system aligns with green chemistry principles, simplifying reaction conditions and reducing the environmental impact. Mechanistic studies confirmed the role of photoinduced electron-hole pairs in water oxidation and oxygen reduction. This research underscores the potential of CYANO-COF materials in sustainable H₂O₂ production using only water and sunlight thus highlighting avenues for optimizing long-term stability and efficiency.

Via a one-pot synthetic approach, the obtained tin oxides/g-C ₃ N ₄ could directly split pure water only with the assistance of ultrasonication, yielding a production rate of 4427.2 µmol g ⁻¹ h ⁻¹ (H ₂ ) and 809.3 µmol g ⁻¹ h ⁻¹ (H ₂ O ₂ ), respectively.

Driven by the urgent need for a green, safe, and cost‐effective approach to producing H₂ and H₂O₂—both highly valuable in green energy and environmental protection fields—piezocatalysis, which converts mechanical energy into valuable chemicals, has emerged as a promising solution. However, current catalyst systems face challenges due to the need for materials with both a strong piezoelectric effect and favorable catalytic activity. Herein, the construction of an oxidized carbon nitride (g‐C₃N₄) matrix anchored with TiO₂ nanoparticles via alkaline hydrothermal treatment is reported. Under ultrasonication, the g‐C₃N₄/TiO₂ composite exhibits optimal performance under carefully controlled alkaline hydrothermal conditions. With a low concentration of Ba(OH)₂ during hydrothermal treatment, Ba(OH)₂ provides an alkaline medium, oxidizing the g‐C₃N₄ species and introducing structural defects into the g‐C₃N₄ framework. The disruption of the g‐C₃N₄ matrix, along with its interaction with TiO₂ nanoparticles, enhances the piezoelectric effect. Consequently, the oxidized g‐C₃N₄/TiO₂ composite achieves a remarkable H₂ production rate of 4427.2 μmol g⁻¹ and an H₂O₂ production rate of 809.3 μmol g⁻¹ within 1 h without the addition of any sacrificial agents or cocatalysts. This work presents an effective strategy for the structural optimization of g‐C₃N₄‐based materials and may inspire new approaches for designing advanced piezocatalysts.

Enhanced bifunctional electrocatalysis via CuSe₂/FeSe₂ heterojunctions for efficient water splitting was achieved.

Driven by the urgent need for a green, safe, and cost-effective approach to producing H2 and H2O2- both highly valuable in green energy and environmental protection fields- piezocatalysis, which converts mechanical energy into valuable chemicals, has emerged as a promising solution. However, current catalyst systems face challenges due to the need for materials with both a strong piezoelectric effect and favorable catalytic activity. Here, we report the construction of an oxidized carbon nitride (g-C3N4) matrix anchored with TiO2 nanoparticles via alkaline hydrothermal treatment. Under ultrasonication, the g-C3N4/TiO2 composite exhibits optimal performance under carefully controlled alkaline hydrothermal conditions. With a low concentration of Ba(OH)2 during hydrothermal treatment, Ba(OH)2 provides an alkaline medium, oxidizing the g-C3N4 species and introducing structural defects into the g-C3N4 framework. The disruption of the g-C3N4 matrix, along with its interaction with TiO2 nanoparticles, enhances the piezoelectric effect. Consequently, the CN-1BT composite achieves a remarkable H2 production rate of 4427.2 µmol g-1 and an H2O2 production rate of 809.3 µmol g-1 within one hour without the addition of any sacrificial agents or cocatalysts. This work presents an effective strategy for the structural optimization of g-C3N4-based materials and may inspire new approaches for designing advanced piezocatalysts.