The biopolymer lignin is deposited in the cell walls of vascular cells and is essential for long-distance water conduction and structural support in plants. Different vascular cell types contain distinct and conserved lignin chemistries, each with specific aromatic and aliphatic substitutions. Yet, the biological role of this conserved and specific lignin chemistry in each cell type remains unclear. Here, we investigated the roles of this lignin biochemical specificity for cellular functions by producing single cell analyses for three cell morphotypes of tracheary elements, which all allow sap conduction but differ in their morphology. We determined that specific lignin chemistries accumulate in each cell type. Moreover, lignin accumulated dynamically, increasing in quantity and changing in composition, to alter the cell wall biomechanics during cell maturation. For similar aromatic substitutions, residues with alcohol aliphatic functions increased stiffness whereas aldehydes increased flexibility of the cell wall. Modifying this lignin biochemical specificity and the sequence of its formation impaired the cell wall biomechanics of each morphotype and consequently hindered sap conduction and drought recovery. Together, our results demonstrate that each sap-conducting vascular cell type distinctly controls their lignin biochemistry to adjust their biomechanics and hydraulic properties to face developmental and environmental constraints.
Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, we report for the first time, the creation of Fe vacancies as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe vacancies were produced by chemical leaching of Mg that was introduced into FeP as “sacrificial dopant”. The obtained Fevacancy‐rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg‐doped FeP, achieving a current density of 10 mA cm−2 at overpotentials of 108 mV in 1 m KOH and 65 mV in 0.5 m H2SO4, with a near‐100 % Faradaic efficiency. Our theoretical and experimental analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near‐optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe‐vacancy‐rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochemical water splitting.
Oxygen evolution catalysts (OEC)
are often employed on the surface
of photoactive, semiconducting photoanodes to boost their kinetics
and stability during photoelectrochemical water oxidation. However,
the necessity of using optically transparent OEC to avoid parasitic
light absorption by the OEC under front-side illumination is often
neglected. Here, we show that furnishing the surface of a WO3 photoanode with suitable loading of FeOOH as a transparent OEC improved
the photocurrent density by 300% at 1 V versus RHE and the initial
photocurrent-to-O2 Faradaic efficiency from ∼70
to ∼100%. The data from the photovoltammetry, electrochemical
impedance, and gas evolution measurements show that these improvements
were a combined result of reduced hole-transfer resistance for water
oxidation, minimized surface recombination of charge carriers, and
improved stability against photocorrosion of WO3. We demonstrate
the utility of transparent FeOOH-coated WO3 in a solar-powered,
tandem water-splitting device by combining it with a double-junction
Si solar cell and a Ni–Mo hydrogen evolution catalyst. This
device performed at a solar-to-hydrogen conversion efficiency of 1.8%
in near-neutral K2SO4 electrolyte.
Low-concentration cobalt doping improves the intrinsic activity and charge transport of hematite thin-film electrocatalyst for high-performance acidic water oxidation.
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