PMMA-TiO2 Fibers for the Photocatalytic Degradation of Water Pollutants

Titanium dioxide (TiO2) is a promising photocatalyst that possesses a redox potential suitable for environmental remediation applications. A low photocatalytic yield and high cost have thus far limited the commercial adoption of TiO2-based fixed-bed reactors. One solution is to engineer the physical geometry or chemical composition of the substrate to overcome these limitations. In this work, porous polymethyl methacrylate (PMMA) substrates with immobilized TiO2 nanoparticles in fiber forms were fabricated and analyzed to demonstrate the influence of contaminant transport and light accessibility on the overall photocatalytic performance. The influences of (i) fiber porosity and (ii) fiber architecture on the overall photocatalytic performance were investigated. The porous structure was fabricated using wet phase inversion. The core-shell-structured fibers exhibited much higher mechanical properties than the porous fibers (7.52 GPa vs. non-testability) and maintained the same degradation rates as porous structures (0.059 vs. 0.053/min) in removing methylene blue with comparable specific surface areas. The highest methylene blue (MB) degradation rate (kMB) of 0.116 min−1 was observed due to increases of the exposed surface area, pointing to more efficient photocatalysis by optimizing core-shell dimensions. This research provides an easy-to-manufacture and cost-efficient method for producing PMMA/TiO2 core-shell fibers with a broad application in water treatment, air purification, and volatile sensors

N-Doped Porous Carbon from <i>Sargassum</i> spp. as Efficient Metal-Free Electrocatalysts for O₂ Reduction in Alkaline Fuel Cells

This work reports the synthesis of N-doped porous carbon (NPC) with a high surface area from Sargassum spp. as a low-cost alternative for electrocatalyst production for the oxygen reduction reaction (ORR). Sargassum spp. was activated with potassium hydroxide at different temperatures (700, 750, and 800 &#176;C) and then doped with pyridine (N700, N750, and N800). As a result of the activation process, the 800 &#176;C sample showed a high surface area (2765 m2 g&#8722;1) and good onset potential (0.870 V) and current density (4.87 mA cm&#8722;2). The ORR performance of the electrocatalysts in terms of their current density was N800 &gt; N750 &gt; N700 &gt; 750 &gt; 800 &gt; 700, while the onset potential decreased in the following order: N800 &gt; 800 &gt; 750 &gt; 700 &gt; N700 &gt; N750. The fuel cell performance of the membrane electrode assembly (MEA) prepared with electrocatalyst synthesized at 750 &#176;C and doped with pyridine was 12.72 mW cm&#8722;2, which was close to that from Pt/C MEA on both the anode and cathode (14.42 mW cm&#8722;2). These results indicate that NPCs are an alternative to the problem of Sargassum spp. accumulation in the Caribbean due to their high efficiency as electrocatalysts for ORR

Highly Porous MIL-100(Fe) for the Hydrogen Evolution Reaction (HER) in Acidic and Basic Media

The present study reports the synthesis of a porous Fe-based MOF named MIL-100(Fe) by a modified hydrothermal method without the HF process. The synthesis gave a high surface area with the specific surface area calculated to be 2551 m2 g–1 and a pore volume of 1.407 cm3 g–1 with an average pore size of 1.103 nm. The synthesized electrocatalyst having a high surface area is demonstrated as an excellent electrocatalyst for the hydrogen evolution reaction investigated in both acidic and alkaline media. As desired, the electrochemical results showed low Tafel slopes (53.59 and 56.65 mV dec–1), high exchange current densities (76.44 and 72.75 mA cm–2), low overpotentials (148.29 and 150.57 mV), and long-term stability in both media, respectively. The high activity is ascribed to the large surface area of the synthesized Fe-based metal–organic framework with porous nature

Renewable Energy Sources for Green Hydrogen Generation in Colombia and Applicable Case of Studies

Electrification using renewable energy sources represents a clear path toward solving the current global energy crisis. In Colombia, this challenge also involves the diversification of the electrical energy sources to overcome the historical dependence on hydropower. In this context, green hydrogen represents a key energy carrier enabling the storage of renewable energy as well as directly powering industrial and transportation sectors. This work explores the realistic potential of the main renewable energy sources, including solar photovoltaics (8172 GW), hydropower (56 GW), wind (68 GW), and biomass (14 GW). In addition, a case study from abroad is presented, demonstrating the feasibility of using each type of renewable energy to generate green hydrogen in the country. At the end, an analysis of the most likely regions in the country and paths to deploy green hydrogen projects are presented, favoring hydropower in the short term and solar in the long run. By 2050, this energy potential will enable reaching a levelized cost of hydrogen (LCOH) of 1.7, 1.5, 3.1 and 1.4 USD/kg-H2 for solar photovoltaic, wind, hydropower and biomass, respectively

Is the H2 economy realizable in the foreseeable future? Part II: H2 storage, transportation, and distribution

The goal of the review series on the H2 economy is to highlight the current status, major issues, and opportunities associated with H2 production, storage, transportation, distribution and usage in various energy sectors. In particular, Part I discussed the various H2 (grey and green) production methods including the futuristic ones such as photoelectrochemical for small, medium, and large-scale applications. Part II of the H2 economy review identifies the developments and challenges in the areas of H2 storage, transportation and distribution with national and international initiatives in the field, all of which suggest a pathway for establishing greener H2 society in the near future. Currently, various methods, comprising physical and chemical routes are being explored with a focus on improving the H2 storage density, capacity, and reducing the cost. H2 transportation methods by road, through pipelines, and via ocean are pursued actively in expanding the market for large scale applications around the world. As of now, compressed H2 and its transportation by road is the most realistic option for the transportation sector.Peer reviewe

Protein hot spots at bio-nano interfaces

10.1016/S1369-7021(11)70167-5Materials Today147-8360-36