Reducing the noble-metal catalyst content of acid Polymer Electrolyte Membrane (PEM) water electrolyzers without compromising catalytic activity and stability is a goal of fundamental scientific interest and substantial technical importance for cost-effective hydrogen-based energy storage. This study presents nanostructured iridium nanodendrites (Ir-ND) supported on antimony doped tin oxide (ATO) as efficient and stable water splitting catalysts for PEM electrolyzers. The active Ir-ND structures exhibited superior structural and morphological properties, such as particle size and surface area compared to commercial state-of-art Ir catalysts. Supported on tailored corrosion-stable conductive oxides, the Ir-ND catalysts exhibited a more than 2-fold larger kinetic water splitting activity compared with supported Ir nanoparticles, and a more than 8-fold larger catalytic activity than commercial Ir blacks. In single-cell PEM electrolyzer tests, the Ir-ND/ATO outperformed commercial Ir catalysts more than 2-fold at technological current densities of 1.5 A cm−2 at a mere 1.80 V cell voltage, while showing excellent durability under constant current conditions. We conclude that Ir-ND/ATO catalysts have the potential to substantially reduce the required noble metal loading, while maintaining their catalytic performance, both in idealized three-electrode set ups and in the real electrolyzer device environments.

/pdf/oxide-supported-ir-nanodendrites-with-high-activity-and-3w1edle4wp.pdf

Oxide-supported Ir nanodendrites with high activity and durability for the oxygen evolution reaction in acid PEM water electrolyzers

Electrochemical splitting of water is an attractive way to produce hydrogen fuel as a clean and renewable energy source. However, a major challenge is to accelerate the sluggish kinetics of the anodic half-cell reaction where oxygen evolution reaction (OER) takes place. Here, a seamlessly conductive 3D architecture is reported with a carbon-shelled Ni-Co nanowire network as a highly efficient OER electrocatalyst. Highly porous and granular Ni-Co nanowires are first grown on a carbon fiber woven fabric utilizing a cost-effective hydrothermal method and then conductive carbon shell is coated on the Ni-Co nanowires via glucose carbonization and annealing processes. The conductive carbon layer surrounding the nanowires is introduced to provide a continuous pathway for facile electron transport throughout the whole of the integrated 3D catalyst. This 3D hierarchical structure provides several synergistic effects and beneficial functions including a large number of active sites, easy accessibility of water, fast electron transport, rapid release of oxygen gas, enhanced electrochemical durability, and stronger structural integrity, resulting in a remarkable OER activity that delivers an overpotential of 302 mV with a Tafel slope of 43.6 mV dec−1 at a current density of 10 mA cm−2 in an alkaline medium electrolyte (1 m KOH).

Seamlessly Conductive 3D Nanoarchitecture of Core–Shell Ni-Co Nanowire Network for Highly Efficient Oxygen Evolution

Gelatinous fibres are specialized fibres, distinguished by the presence of an inner, gelatinous cell-wall layer. In recent years, they have attracted increasing interest since their walls have a desirable chemical composition (low lignin, low pentosan, and high cellulose contents) for applications such as saccharification and biofuel production, and they have interesting mechanical properties, being capable of generating high tensional stress. However, the unique character of gelatinous layer has not yet been widely recognized. The first part of this review presents a model of gelatinous-fibre organization and stresses the unique character of the gelatinous layer as a separate type of cell-wall layer, different from either primary or secondary wall layers. The second part discusses major current models of tensional stress generation by these fibres and presents a novel unifying model based on recent advances in knowledge of gelatinous wall structure. Understanding this mechanism could potentially lead to novel biomimetic developments in material sciences.

/pdf/tensional-stress-generation-in-gelatinous-fibres-a-review-1bk61b5a22.pdf

Tensional stress generation in gelatinous fibres: a review and possible mechanism based on cell-wall structure and composition

Pb(II) and Cr(VI) sorption by biochars pyrolyzed from the municipal wastewater sludge under different heating conditions.

New tannin–lignin aerogels

The mechanism for tree orientation in angiosperms is based on the production of high tensile stress on the upper side of the inclined axis. In many species, the stress level is strongly related to the presence of a peculiar layer, called G-layer, in the fibre wall. The structure of G-layer has been recently described as a hydrogel thanks to N2 adsorption-desorption isotherms of supercritically dried samples showing a high mesoporosity (pores size from 2 to 50 nm). This led us to revisit the concept of G-layer that was until now only described from anatomical observation. Adsorption isotherms of both normal wood and tension wood have been measured on six tropical species. Measurements show that mesoporosity is high in tension wood with typical thick G-layer while it is much less with thinner G-layer, sometimes no more than normal wood. The mesoporosity of tension wood species without G-layer is as low as in normal wood. Not depending on the amount of pores, the pore sizes distribution are always centred around 6-12 nm. These results suggest that, among species producing fibres with G-layer, large structural differences of G-layer exist between species

Guang-Jie Zhao

Papers

Mesoporosity as a new parameter for understanding tension stress generation in trees