The mean SOC contents at five depths and the corresponding fitting model.

<p>The mean SOC contents at five depths and the corresponding fitting model.</p

CuO Nanosheets Prepared by Dielectric Barrier Discharge Microplasma as Catalysts for the Oxygen Evolution Reaction

A method for constructing transition metal catalysts for the oxygen evolution reaction (OER) is proposed. Facile preparation is realized in the case of no added metal source via dielectric barrier discharge (DBD) microplasma under 10 min, and the thickness of the nanosheet is only 6.5 nm. The prepared ultrathin CuO nanosheets on copper foam (CuO UTNS/CF) display a catalytic activity of 262 mV overpotential (η) at 10 mA cm–2 for the OER in alkaline media. The as-prepared electrocatalyst guarantees appealing long-term durability (>90 h) and a high turnover frequency (TOF) of 0.488 mol O2 s–1 at 426 mV. Compared to CuO/CF prepared traditionally, the overpotential of CuO UTNS/CF can be directly reduced to 38 mV. Moreover, hydroxyl radicals (•OH) were identified as the intermediate products and a possible synthesis mechanism was preliminarily put forward. As a facile technology for the OER catalyst, we believe that DBD microplasma will provide a broad perspective for researchers

Parameters of the three-dimensional semivariogram of the residuals.

<p><i>C</i>₀ is nugget value; <i>C</i>₁ is the structural variance; a_horizontal and a_vertical are the spatial correlation distance in horizontal and vertical directions, respectively.</p><p>Parameters of the three-dimensional semivariogram of the residuals.</p

Statistical characteristics of soil organic carbon in five different depths.

<p>^a Standard deviation;</p><p>^b Coefficient of variation;</p><p>^c Type of distribution. Different letters in the same column indicate significantly different at <i>P</i> < 0.05.</p><p>Statistical characteristics of soil organic carbon in five different depths.</p

Effects of soil texture and land use types on SOC content.

<p>The letters above the bars of a given soil layer denote significant differences between soil texture and land use types for that layer (P < 0.05). The error bars denote the standard errors of the mean.</p

The flow chart of kriging combined with profile depth function of soil organic carbon (KPDF) interpolation procedures.

<p>The flow chart of kriging combined with profile depth function of soil organic carbon (KPDF) interpolation procedures.</p

The map of soil texture, three-dimensional distribution map of SOC content in the Quzhou county and the corresponding four cross-section maps of SOC content at 0–0.05 m (a), 0.25–0.30 m (b), 0.55–0.60 m (c), and 0.95–1.00 m (d).

<p>The map of soil texture, three-dimensional distribution map of SOC content in the Quzhou county and the corresponding four cross-section maps of SOC content at 0–0.05 m (a), 0.25–0.30 m (b), 0.55–0.60 m (c), and 0.95–1.00 m (d).</p

Comparison of the measured SOC content with the predictions using kriging combined with profile depth distribution function (KPDF) interpolation.

<p>Comparison of the measured SOC content with the predictions using kriging combined with profile depth distribution function (KPDF) interpolation.</p

Locations of soil sampling sites in Quzhou County in the North China Plain (NCP).

<p>Open circles represent calibration data (91 profiles and 455 samples) and solid triangles represent validation sites (30 profiles and 150 samples).</p

Experimental variograms (circles) and corresponding fitted models (solid lines) for the residual in the two directions (a—horizontal direction, b—vertical direction).

<p>Experimental variograms (circles) and corresponding fitted models (solid lines) for the residual in the two directions (a—horizontal direction, b—vertical direction).</p