Polymers of intrinsic microporosity in electrocatalysis:Novel pore rigidity effects and lamella palladium growth

Two polymers (i) the polymer of intrinsic microporosity (or PIM) ethanoanthracene TB-PIM (P1, PIM-EA-TB, MW 70 kDa, BET surface area 1027 m2 g−1) and (ii) the structurally less rigid polymer based on dimethyldiphenylmethane units (P2, BDMPM-TB, MW 100 kDa, BET surface area 47 m2g−1) are compared to highlight the benefits of the newly emerging PIM membrane materials in electrocatalysis and nanostructure formation. Binding sites and binding ability/capacity in aqueous environments are compared in films deposited onto glassy carbon electrodes for (i) indigo carmine dianion immobilisation (weakly binding from water–ethanol) and (ii) PdCl42− immobilisation (strongly binding from acidic media). Nano-lamella growth for Pd metal during electro-reduction of PdCl42− is observed. Electrocatalytic oxidation of formic acid (at pH 6) is investigated for P1 and P2 as a function of film thickness. The more rigid high BET surface area PIM material P1 exhibits “open-pore” characteristics with much more promising electrocatalytic activity at Pd lamella within polymer pores

Intrinsically microporous polymer slows down fuel cell catalyst corrosion

The limited stability of fuel cell cathode catalysts causes a significant loss of operational cell voltage with commercial Pt-based catalysts, which hinders the wider commercialization of fuel cell technologies. We demonstrate beneficial effects of a highly rigid and porous polymer of intrinsic microporosity (PIM-EA-TB with BET surface area 1027 m2 g−1) in accelerated catalyst corrosion experiments. Porous films of PIM-EA-TB offer an effective protective matrix for the prevention of Pt/C catalyst corrosion without impeding flux of reagents. The results of electrochemical cycling tests show that the PIM-EA-TB protected Pt/C (denoted here as PIM@Pt/C) exhibit a significantly enhanced durability as compared to a conventional Pt/C catalyst. Keywords: Electrocatalysis, Fuel cells, Membrane, Stabilization, Corrosio

Alkaline Hydrogen Oxidation Reaction Catalysts: Insight into Catalytic Mechanisms, Classification, Activity Regulation and Challenges

Hydrogen oxidation reaction (HOR) is an important semi‐cell reaction in the renewable energy conversion technology such as fuel cells. However, due to the slow reaction rate, the development of highly active catalysts remains a major challenge in alkaline fuel cells. Based on fundamental understanding of the sluggish kinetics toward the reaction mechanism in alkaline electrolytes, noble and non‐noble metal catalysts and their regulation strategies including geometry, composition, atom‐doping, oxyphilic site and substrate engineerings are analyzed and summarized in this review to seek for the possible breakthrough toward HOR catalytic performance enhancement. Eventually, challenges and opportunities faced by alkaline HOR, and potential future research trends are proposed. This review not only deepens the understanding of the hydrogen electrocatalysis mechanism, but also provides guidelines for the rational design of advanced HOR catalysts

Facile Synthesis of α-MnO2 with a 3D Staghorn Coral-like Micro-Structure Assembled by Nano-Rods and Its Application in Electrochemical Supercapacitors

Abstract: Manganese oxides with an alpha crystal structure are synthesized via combined solid-state reaction and wet chemical processing, which is a simple and inexpensive synthetic route easy for mass production. The effects of the synthetic reaction duration and the temperature of acid treatments on crystal structure, morphology, and electrochemical capacitive properties of α-MnO2 are discussed. It is evidenced that the samples treated in acid for a longer time at 25 °C display the uniform nanorods that are aggregated to form micro-buildings with fine features on the surface of rods. This microstructure possesses large surface areas and more active sites that are easy to access electrochemically, leading to a better electrochemical capacitive performance. We expected that these results would provide the practical information for shape- and morphology-controlled synthesis for nanostructured functional materials in supercapacitor applications

FUELCELL2006-97192 SINGLE CELL PERFORMANCE OF CATALYST COATED MEMBRANE BASED ON SUPERTHIN PROTON EXCHANGE MEMBRANE

ABSTRACT The superthin PEM (≤ 30µm in thickness) can be used in CCMs(Catalyst coated membranes) and helpful to lower the cost of fuel cells. In this paper, the CCM based on Nafion NRE® 211 membrane (thickness ~25µm) was prepared and assembled into a single fuel cell. The activation time, the V-I curves and the voltage vs time plot were used to characterize the performance of CCMs under variuos hydrogen/air humidifying conditions at ambient pressure. The experimental results showed that the fuel cell with CCMs based on NRE® 211 membrane had a shorter activation time and higher performance under humidifying conditions compared to that based on nafion NRE® 212 membrane (thickness ~50µm). However, it's important to remove water from anode in order to maintain a stable performance of fuel cell. Moreover, the performance of the single fuel cell using superthin membranes could be improved at a high current density under non-humidifying conditions

RuRh Bimetallene Nanoring as High‐efficiency pH‐Universal Catalyst for Hydrogen Evolution Reaction

Abstract Electrocatalysis of the hydrogen evolution reaction (HER) is a vital and demanding, yet challenging, task to produce clean energy applications. Here, the RuRh2 bimetallene nanoring with rich structural defects is designed and successfully synthesized by a mixed‐solvent strategy, displaying ascendant HER performance with high mass activity at −0.05 and −0.07 V, separately higher than that of the commercial Pt catalyst. Also, it maintains steady hydrogen bubble evolution even after 30 000 potential cycles in acid media. Furthermore, the RuRh2 bimetallene nanoring shows an outstanding activity in both alkaline and neutral media, outperforming that of Pt catalysts and other reported HER catalysts. A combination of atomic‐scale structure observation and density functional theory calculations demonstrates that both the grain boundaries and symmetry breaking of RuRh2 bimetallene cannot only weaken the adsorption strength of atomic hydrogen, but also facilitate the transfer of electrons and the adsorption of reactants, further boosting the HER electrocatalytic performance in all pH values

Surface-dopylated carbon nanoparticles sense gas-induced ph changes

Carbon nanoparticles of ca. 9-18 nm diameter (Emperor 2000™) are surface-modified by covalently linking l-dopa-boc (boc-protected l-3,4-dihydroxyphenylalanine) with a surface coverage of approximately 100 per particle (or 3 × 10 13 cm -2). In solution environments these redox-active nanoparticles provide chemically stable and pH-sensitive voltammetirc responses (reversible 2-electron 2-proton oxidation) over a pH range from 2 to 12. When mixed into Dowex 50 Wx4 cation exchanger or Dowex 50 1x2 anion exchanger and placed in contact with a glassy carbon electrode in a flow of humidified gas, the l-dopa-boc-modified carbon nanoparticles provide pH-sensitive surface probes to monitor the surface conditions. In a two-terminal cell it is demonstrated that gas flow measurements are possible with both modified cation and anion exchanger particles in contact to glassy carbon electrodes. The anion exchanger particles allow pH control after pre-conditioning in phosphate buffer. Loading-dependent sensitivity to ammonia gas is investigated and high sensitivity to ammonia is observed for Dowex 50 1x2 anion exchanger pre-equilibrated in phosphate buffer pH 3 and decorated with l-dopa-boc-modified carbon nanoparticles. Responses are observed with sequential injections of 1 cm 3 ammmonia into a gas flow-through device