Solvothermal-Etching Process Induced Ti-Doped Fe₂O₃ Thin Film with Low Turn-On Voltage for Water Splitting

In this work, a thinning process of hematite film accompanied by simultaneous titanium (Ti) doping has been demonstrated. Ti⁴⁺ ion was incorporated into ultrathin Fe₂O₃ film by solvothermally etching a hematite film fabricated on titanium nanorod array substrate. As a consequence, the onset potential (<i>V</i>_on) of oxygen evolution reaction for final ultrathin Ti-doped Fe₂O₃ film shifted toward cathodic substantially, a very low <i>V</i>_on of 0.48 V_RHE was realized, approximately 0.53 V cathodic shift of the hematite film. Working mechanisms were investigated from both kinetic and thermodynamic ways. The ultrathin Ti-doped Fe₂O₃ film exhibited reduced Tafel slope and higher generated photovoltage than the pristine Fe₂O₃ electrode. Moreover, the highly doped Fe₂O₃ resulted in significant reduction of charge-transfer resistance at the Fe₂O₃∥electrolyte interface. The drastic cathodic-shift <i>V</i>_on is believed to be a result of combined factors including thermodynamic contribution, improved surface reaction kinetics, as well as facilitated charge transfer across bulk and interface

Iron–Nickel Nitride Nanostructures in Situ Grown on Surface-Redox-Etching Nickel Foam: Efficient and Ultrasustainable Electrocatalysts for Overall Water Splitting

Water splitting is widely considered to be a promising strategy for clean and efficient energy production. In this paper, for the first time we report an in situ growth of iron–nickel nitride nanostructures on surface-redox-etching Ni foam (FeNi₃N/NF) as a bifunctional electrocatalyst for overall water splitting. This method does not require a specially added nickel precursor nor an oxidizing agent, but achieves well-dispersed iron–nickel nitride nanostructures that are grown directly on the nickel foam surface. The commercial Ni foam in this work not only acts as a substrate but also serves as a slow-releasing nickel precursor that is induced by redox-etching of Fe³⁺. FeCl₂ is a more preferable iron precursor than FeCl₃ for no matter quality of FeNi₃N growth or its electrocatalytic behaviors. The obtained FeNi₃N/NF exhibits extraordinarily high activities for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with low overpotentials of 202 and 75 mV at 10 mA cm^–2, Tafel slopes of 40 and 98 mV dec^–1, respectively. In addition, the presented FeNi₃N/NF catalyst has an extremely good durability, reflecting in more than 400 h of consistent galvanostatic electrolysis without any visible voltage elevation

Responses of nutrient capture and fine root morphology of subalpine coniferous tree <i>Picea asperata</i> to nutrient heterogeneity and competition

<div><p>Investigating the responses of trees to the heterogeneous distribution of nutrients in soil and simultaneous presence of neighboring roots could strengthen the understanding of an influential mechanism on tree growth and provide a scientific basis for forest management. Here, we conducted two split-pot experiments to investigate the effects of nutrient heterogeneity and intraspecific competition on the fine root morphology and nutrient capture of <i>Picea asperata</i>. The results showed that <i>P</i>. <i>asperata</i> efficiently captured nutrients by increasing the specific root length (SRL) and specific root area (SRA) of first-and second-order roots and decreasing the tissue density of first-order roots to avoid competition for resources and space with neighboring roots. The nutrient heterogeneity and addition of fertilization did not affect the fine root morphology, but enhanced the P and K concentrations in the fine roots in the absence of a competitor. On the interaction between nutrient heterogeneity and competition, competition decreased the SRL and SRA but enhanced the capture of K under heterogeneous soil compared with under homogeneous soil. Additionally, the P concentration, but not the K concentration, was linearly correlated to root morphology in heterogeneous soil, even when competition was present. The results suggested that root morphological features were only stimulated when the soil nutrients were insufficient for plant growth and the nutrients accumulations by root were mainly affected by the soil nutrients more than the root morphology.</p></div

The concentrations of K and P in roots of different branch order affected by nutrients heterogeneity.

<p><b>Noted</b>: SHNF is the non-fertilizer compartment in SHF treatment; SHF is the fertilizer compartment in SHF treatment. Different letters indicate significant treatment effects between the means at <i>p</i><0.05 analyzed by post hoc Tukey’s HSD test (means ± SE, n = 8).</p

Bivariate correlation coefficients (r²) of fine root morphology and nutrient concentration in the competitive and non-competitive compartments respectively.

<p>Bivariate correlation coefficients (r²) of fine root morphology and nutrient concentration in the competitive and non-competitive compartments respectively.</p

Factorial ANOVA results (F values) of fine root morphology at different branch orders in the sub-experiment I and II affected by fertilization, competition, nutrient heterogeneity and compartment, as well as their interactions.

<p>Factorial ANOVA results (F values) of fine root morphology at different branch orders in the sub-experiment I and II affected by fertilization, competition, nutrient heterogeneity and compartment, as well as their interactions.</p

Factorial ANOVA results (<i>F</i> values) of nutrient concentration at different parts of shoots in the sub-experiment I and II affected by fertilization, competition or nutrient heterogeneity, as well as their interactions.

<p>Factorial ANOVA results (<i>F</i> values) of nutrient concentration at different parts of shoots in the sub-experiment I and II affected by fertilization, competition or nutrient heterogeneity, as well as their interactions.</p

Schematic of the experimental treatments.

<p>The sub-experiment I included the upper three treatments without competitors with applying fertilizer to one half compartment (SHF) of the container or both two compartments (SF) of the container, or no fertilizer in both compartments (SNF) of the container. SHNF is the non-fertilizer compartment in SHF treatment and SHF is the fertilizer compartment of the same container in SHF treatment. The sub-experimentIIincluded the lower four treatments with competitors roots which was set up by applying fertilizer to the competitive compartment (with competitors) of the container (FC), the non-competitive compartment (without competitors) of the container (FNC), and both the two compartments of the container (F), as well as no fertilizer being in both two compartments of the container (NF). The gray parts represent applying fertilizer. The figure has been modified from previous work by our team [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187496#pone.0187496.ref031" target="_blank">31</a>].</p

The concentrations of K (a) and P (b) in shoots of different parts under different treatments.

<p>Different letters indicate significant treatment effects between the means at <i>p</i><0.05 analyzed by post hoc Tukey’s HSD test (means ± SE, n = 8).</p

Factorial ANOVA results (<i>F</i> values) of nutrient concentration in roots of different branch order in the sub-experiment I and II affected by fertilization, competition, nutrient heterogeneity and compartment, as well as their interactions.

<p>Factorial ANOVA results (<i>F</i> values) of nutrient concentration in roots of different branch order in the sub-experiment I and II affected by fertilization, competition, nutrient heterogeneity and compartment, as well as their interactions.</p