Polymer Modification of Surface Electronic Properties of Electrocatalysts

Oxygen vacancies enhanced electrocatalytic water splitting of P-FeMoO4 initiated via phosphorus doping

Transition metal oxides (TMOs) are abundant and cost-effective materials. However, poor conductivity and low intrinsic activity limit their application in electrolyzed water catalysts. Herein, we prepared P-FeMoO4 in situ on nickel foam (P-FMO@NF) by phosphorylation-modified FeMoO4 to optimize its electrocatalytic properties. Interestingly, phosphorus doping is accompanied by the generation of oxygen vacancies and surface phosphates. Oxygen vacancies accelerated Mo dissolution during the oxygen evolution reaction (OER), leading to the rapid reconfiguration of P-FMO@NF to FeOOH and regulating the electronic structure of P-FMO@NF. The formation of phosphates is caused by the substitution of some molybdates with phosphates, which further increases the amount of oxygen vacancies. Hence, the OER overpotential of P-FMO@NF at a current density of 10 mA cm-2 is only 206 mV, and the hydrogen evolution reaction (HER) overpotential is 154 mV. It was assembled into a water splitting cell with a voltage of just 1.59 V at 10 mA cm-2 and shows excellent stability over 50 h. These excellent electrocatalytic properties are mainly attributed to the oxygen vacancies, which improve the interfacial charge transfer properties of the catalysts. This study provides new insights into phosphorus doping and offers a new perspective on the design of electrocatalysts.

Shish-kebab structure fiber with nano and micro diameter regulate macrophage polarization for anti-inflammatory and bone differentiation

Biopolymer grafts often have limited biocompatibility, triggering excessive inflammatory responses similar to foreign bodies. Macrophage phenotype shifts are pivotal in the inflammatory response and graft success. The effects of the morphology and physical attributes of the material itself on macrophage polarization should be the focus. In this study, we prepared electrospun fibers with diverse diameters and formed a shish-kebab (SK) structure on the material surface by solution-induced crystallization, forming electrospun fiber scaffolds with diverse pore sizes and roughness. In vitro cell culture experiments demonstrated that SK structure fibers could regulate macrophage differentiation toward M2 phenotype, and the results of in vitro simulation of in vivo tissue reconstruction by the microenvironment demonstrated that the paracrine role of M2 phenotype macrophages could promote bone marrow mesenchymal stem cells (BMSCs) to differentiate into osteoblasts. In rats implanted with a subcutaneous SK-structured fiber scaffold, the large-pore size and low-stiffness SK fiber scaffolds demonstrated superior immune performance, less macrophage aggregation, and easier differentiation to the anti-inflammatory M2 phenotype. Large pore sizes and low-stiffness SK fiber scaffolds guide the morphological design of biological scaffolds implanted in vivo, which is expected to be an effective strategy for reducing inflammation when applied to graft materials in clinical settings.

Local hydrophobicity allows high-performance electrochemical carbon monoxide reduction to C2+ products

While CO can already be produced at industrially relevant current densities via CO₂ electrolysis, the selective formation of C₂₊ products seems challenging. CO electrolysis, in principle, can overcome this barrier, hence forming valuable chemicals from CO₂ in two steps. Here we demonstrate that a mass-produced, commercially available polymeric pore sealer can be used as a catalyst binder, ensuring high rate and selective CO reduction. We achieved above 70% faradaic efficiency for C₂₊ products formation at j = 500 mA cm^-2 current density. As no specific interaction between the polymer and the CO reactant was found, we attribute the stable and selective operation of the electrolyzer cell to the controlled wetting of the catalyst layer due to the homogeneous polymer coating on the catalyst particles' surface. These results indicate that sophistically designed surface modifiers are not necessarily required for CO electrolysis, but a simpler alternative can in some cases lead to the same reaction rate, selectivity and energy efficiency; hence the capital costs can be significantly decreased.

Tailored BiVO4 Photoanode Hydrophobic Microenvironment Enables Water Oxidative H2 O2 Accumulation

Direct photoelectrochemical 2-electron water oxidation to renewable H₂ O₂ production on an anode increases the value of solar water splitting. BiVO₄ has a theoretical thermodynamic activity trend toward highly selective water oxidation H₂ O₂ formation, but the challenges of competing 4-electron O₂ evolution and H₂ O₂ decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO₄ -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O₂ , where coating BiVO₄ with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H₂ O₂ . Also, the hydrophobicity is responsible for the H₂ O₂ production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO₄ surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO₄ photoanode. The accumulated H₂ O₂ concentration can reach 150 µm at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.

Polymer Coated Functional Catalysts for Industrial Applications

Surface engineering of conventional catalysts using polymeric coating has been extensively explored for producing hybrid catalytic material with enhanced activity, high mechanical and thermal stability, enhanced productivity, and selectivity of the desired product. The present review discusses in detail the state-of-the-art knowledge on surface modification of catalysts, namely photocatalysts, electrocatalysts, catalysts for photoelectrochemical reactions, and catalysts for other types of reactions, such as hydrodesulfurization, carbon dioxide cycloaddition, and noble metal-catalyzed oxidation/reduction reactions. The various techniques employed for the polymer coating of catalysts are discussed and the role of polymers in enhancing the catalytic activity is critically analyzed. The review further discusses the applications of biodegradable and biocompatible natural polysaccharide-based polymers, namely, chitosan and polydopamine as prospective coating material.

Fluorine-containing nano-objects with the same compositions but different segment distributions: synthesis, characterization and comparison

PHOS-b-PPFS nano-objects and PPFS-b-PHOS nano-objects can be prepared by RAFT PISA and MISA processes, respectively. These nano-objects have the same compositions but different segment distributions and distinct hydrophilic/hydrophobic properties.