Superior Performances of Electroless-Deposited Ni–P Films Decorated with an Ultralow Content of Pt for Water-Splitting Reactions

The design of highly efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) is a critical endeavor, especially in alkaline electrolytes. Herein, we report the development of ultralow-amount Pt-decorated Ni–P catalysts on nickel foam substrates (Pt/Ni–P/NF) via a facile electroless deposition of Ni–P alloys subsequently decorated with a very small amount of Pt nanoparticles through a dip-coating procedure. Benefiting from the 3D porous backbone of the NF substrate and from the synergistic effect between Ni–P and Pt, the present Pt/Ni–P/NF catalyst demonstrates superior HER activity compared to most of the state-of-the-art Pt-based electrocatalysts, with a very low overpotential (22 mV at 10 mA cm–2) and Tafel slope (30 mV dec–1) and a high turnover frequency (1.78 s–1) at η = 50 mV. Furthermore, a full alkaline electrolyzer is constructed using Pt/Ni–P/NF as the cathode and undecorated Ni–P as the anode, which can drive overall water splitting with a low potential of 1.64 V at 10 mA cm–2. This work engenders novel possibilities toward the design of advanced ultralow-content Pt electrocatalysts fulfilling both excellent HER performance and low-cost requirements

Engineering Hexagonal/Monoclinic WO₃ Phase Junctions for Improved Electrochemical Hydrogen Evolution Reaction

Electrochemical hydrogen evolution reaction (HER) is one of the most promising green methods used to produce renewable and sustainable energy. The development of a highly efficient Pt-free electrocatalyst for HER is a crucial point for the ecosustainability and cost reduction of this method. Herein, WO3 nanorods were synthesized by a hydrothermal method and calcinated in air at 400 °C for different times (30, 60, and 90 min). Experimental investigation involved SEM, TEM, XRD, and electrochemical analyses such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Mott Schottky analysis. Calcination at 400 °C induces a peculiar crystal phase transition driven by the formation of hexagonal/monoclinic WO3 phase junctions. The best HER performance (170 mV overpotential for 10 mA/cm2) is obtained when WO3 nanorods show comparable volumes of hexagonal and monoclinic phases (after 60 min annealing). The effect of phase junction on HER catalysis sustained by WO3 nanorods is investigated in detail, opening the route of efficient, Pt-free catalysts for HER application

Band Engineering versus Catalysis: Enhancing the Self-Propulsion of Light-Powered MXene-Derived Metal–TiO₂ Micromotors To Degrade Polymer Chains

Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal–TiO2 micromotors with different metal materials to investigate the impact of electronic properties of the metal–semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti3C2Tx MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal–semiconductor interface. Under UV light irradiation, Au–TiO2 micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H2O2, Ag–TiO2 micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H2O2 decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au–TiO2 micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal–semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications

Band Engineering versus Catalysis: Enhancing the Self-Propulsion of Light-Powered MXene-Derived Metal–TiO₂ Micromotors To Degrade Polymer Chains

Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal–TiO2 micromotors with different metal materials to investigate the impact of electronic properties of the metal–semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti3C2Tx MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal–semiconductor interface. Under UV light irradiation, Au–TiO2 micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H2O2, Ag–TiO2 micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H2O2 decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au–TiO2 micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal–semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications

Band Engineering versus Catalysis: Enhancing the Self-Propulsion of Light-Powered MXene-Derived Metal–TiO₂ Micromotors To Degrade Polymer Chains

Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal–TiO2 micromotors with different metal materials to investigate the impact of electronic properties of the metal–semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti3C2Tx MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal–semiconductor interface. Under UV light irradiation, Au–TiO2 micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H2O2, Ag–TiO2 micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H2O2 decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au–TiO2 micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal–semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications

Band Engineering versus Catalysis: Enhancing the Self-Propulsion of Light-Powered MXene-Derived Metal–TiO₂ Micromotors To Degrade Polymer Chains

Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal–TiO2 micromotors with different metal materials to investigate the impact of electronic properties of the metal–semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti3C2Tx MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal–semiconductor interface. Under UV light irradiation, Au–TiO2 micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H2O2, Ag–TiO2 micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H2O2 decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au–TiO2 micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal–semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications

Band Engineering versus Catalysis: Enhancing the Self-Propulsion of Light-Powered MXene-Derived Metal–TiO₂ Micromotors To Degrade Polymer Chains

Light-powered micro- and nanomotors based on photocatalytic semiconductors convert light into mechanical energy, allowing self-propulsion and various functions. Despite recent progress, the ongoing quest to enhance their speed remains crucial, as it holds the potential for further accelerating mass transfer-limited chemical reactions and physical processes. This study focuses on multilayered MXene-derived metal–TiO2 micromotors with different metal materials to investigate the impact of electronic properties of the metal–semiconductor junction, such as energy band bending and built-in electric field, on self-propulsion. By asymmetrically depositing Au or Ag layers on thermally annealed Ti3C2Tx MXene microparticles using sputtering, Janus structures are formed with Schottky junctions at the metal–semiconductor interface. Under UV light irradiation, Au–TiO2 micromotors show higher self-propulsion velocities due to the stronger built-in electric field, enabling efficient photogenerated charge carrier separation within the semiconductor and higher hole accumulation beneath the Au layer. On the contrary, in 0.1 wt % H2O2, Ag–TiO2 micromotors reach higher velocities both in the presence and absence of UV light irradiation, owing to the superior catalytic properties of Ag in H2O2 decomposition. Due to the widespread use of plastics and polymers, and the consequent occurrence of nano/microplastics and polymeric waste in water, Au–TiO2 micromotors were applied in water remediation to break down polyethylene glycol (PEG) chains, which were used as a model for polymeric pollutants in water. These findings reveal the interplay between electronic properties and catalytic activity in metal–semiconductor junctions, offering insights into the future design of powerful light-driven micro- and nanomotors with promising implications for water treatment and photocatalysis applications

Enhanced Quality, Growth Kinetics, and Photocatalysis of ZnO Nanowalls Prepared by Chemical Bath Deposition

ZnO nanowalls (NWLs) represent a nontoxic, abundant, and porous material, with promising applications in sensing and photocatalysis. They can be grown by low-cost solution methods on Al (covered) substrates; Al­(OH)₄^– generated in situ is assumed to be responsible for engendering the NWL morphology. Here, we grew ZnO NWLs by chemical bath deposition (at 70–95 °C). The roles of pH, concentration of Al­(OH)₄^–, and growth time on the thickness and quality of NWL film were experimentally investigated, and the growth kinetics was explained in terms of a self-screening model. Increasing the chemical bath pH from 5.7 to 7.4 led to a 40% thicker film and more NWLs per unit area of the substratedue to increased concentration of Al­(OH)₄^–but these were accompanied by the presence of embedded micro-/nanoparticles. We propose the use of anodized Al as a way to enhance the growth rate and density of the NWLs with no detrimental effect on film quality. Compared with non-anodized Al, NWL film grown on anodized Al (at the lower pH) showed a higher growth rate, an excellent film quality, and a higher photocatalytic activity in the degradation of toxic methyl orange

Double Role of HMTA in ZnO Nanorods Grown by Chemical Bath Deposition

ZnO nanorods (NRs) grown by chemical bath deposition (CBD) are among the most promising semiconducting nanostructures currently investigated for a variety of applications. Still, contrasting experimental results appear in the literature on the microscopic mechanisms leading to high aspect ratio and vertically aligned ZnO NRs. Here, we report on CBD of ZnO NRs using Zn nitrate salt and hexamethylenetetramine (HMTA), evidencing a double role of HMTA in the NRs growth mechanism. Beyond the well-established pH buffering activity, HMTA is shown to introduce a strong steric hindrance effect, biasing growth along the <i>c</i>-axis and ensuring the vertical arrangement. This twofold function of HMTA should be taken into account for avoiding detrimental phenomena such as merging or suppression of NRs, which occur at low HMTA concentration

Flexible Organic/Inorganic Hybrid Field-Effect Transistors with High Performance and Operational Stability

The production of high-quality semiconducting nanostructures with optimized electrical, optical, and electromechanical properties is important for the advancement of next-generation technologies. In this context, we herein report on highly obliquely aligned single-crystalline zinc oxide nanosheets (ZnO NSs) grown via the vapor–liquid–solid approach using r-plane (01–12) sapphire as the template surface. The high structural and optical quality of as-grown ZnO NSs has been confirmed using high-resolution transmission electron microscopy and temperature-dependent photoluminescence, respectively. To assess the potential of our NSs as effective building materials in high-performance flexible electronics, we fabricate organic (parylene C)/inorganic (ZnO NS) hybrid field-effect transistor (FET) devices on flexible substrates using room-temperature assembly processes. Extraction of key FET performance parameters suggests that as-grown ZnO NSs can successfully function as excellent n-type semiconducting modules. Such devices are found to consistently show very high on-state currents (Ion) > 40 μA, high field-effect mobility (μeff) > 200 cm2/(V s), exceptionally high on/off current modulation ratio (Ion/off) of around 109, steep subthreshold swing (s-s) < 200 mV/decade, very low hysteresis, and negligible threshold voltage shifts with prolonged electrical stressing (up to 340 min). The present study delivers a concept of integrating high-quality ZnO NS as active semiconducting elements in flexible electronic circuits