七钼酸根离子在水中稳定镍掺杂的羟基氧化铁核以改善电化学析氧反应,ACS Applied Energy Materials

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七钼酸根离子在水中稳定镍掺杂的羟基氧化铁核以改善电化学析氧反应
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2023-12-22 , DOI: 10.1021/acsaem.3c02631
Krishna Samanta ₁ , Laxmikanta Mallick ₁ , Biswarup Chakraborty ₁

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杂金属掺杂的羟基氧化镍或高熵多金属氧化物表现出显着的电催化活性。在此，采用一种容易获得的安德森型多金属氧酸盐（POM）阴离子七钼酸盐（[Mo ₇ O ₂₄ ] ^6–）作为无机配体来稳定镍（II）掺杂的羟基氧化铁纳米核。通过水热法制备了核心( 1-3 )中具有不同比例的Ni(II)和Fe(III)的[Mo ₇ O ₂₄ ] ^6–配位Ni _x Fe _{1– x} O( OH )纳米材料。ICP-MS 和随后对材料的 PXRD 研究发现，大约 1.5-2% 的镍被纳入 γ-FeO(OH) 核中，而不会改变其二维层状晶格结构。多种光谱和显微技术证明， 4-5 nm 高度结晶的 Ni _x Fe _1-_x O(OH) 核表面存在大量共价连接的 POM 。1-3的负 zeta 电位表示由于带负电的 POM 的存在而导致材料的离子表面，这使得它们在水中高度分散和稳定。使用1-3作为电催化剂，研究了碱性条件下的析氧反应（OER）。对于催化 OER，与未掺杂的核心材料 Mo _x O _y @FeO(OH) 以及不含 POM 的裸 FeO(OH) 和 Ni _x Fe相比，泡沫镍 (NF) 电极上的1-3需要低近 20 mV 的过电势_1–_xO (OH)。更好的 OER 活性可以与更好的电动学相关，这是通过塔菲尔斜率和电荷转移电阻 ( R _ct ) 实现的。所制备的电极1 @NF不仅在OER条件下表现出长期稳定性，而且可以制备成使用石墨棒作为阴极的水分解电解槽，以产生法拉第效率约为1的绿色氢气。72%。在这项研究中，Anderson 型 POM 被用作潜在的配体，衍生出量子点大小的 Ni _x Fe _1–_x O(OH) 核，作为 OER 的反应性电催化剂。在广泛的背景下，这种策略，即使用POM作为纯无机配体来稳定反应性金属氧化物纳米核，可以进一步适应设计各种多金属或混合价金属氧化物材料。

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Stabilization of Nickel-Doped Iron-oxy-hydroxide Core in Water by Heptamolybdate Ions to Improve the Electrochemical Oxygen Evolution Reaction

Heterometal-doped nickel-oxy-hydroxides or high-entropy multimetallic oxides show notable electrocatalytic activity. Herein, a readily available Anderson-type polyoxometalate (POM) anion, heptamolybdate ([Mo₇O₂₄]^6–), is taken as an inorganic ligand to stabilize the nickel(II)-doped iron-oxy-hydroxide nanocore. [Mo₇O₂₄]^6–-ligated Ni_xFe_1–xO(OH) nanomaterials with different ratios of Ni(II) and Fe(III) in the core (1–3) are prepared via a hydrothermal route. ICP–MS and the subsequent PXRD study of the materials have found out that approximately 1.5–2% nickel is incorporated into the γ-FeO(OH) core without altering its two-dimensional-layered lattice structure. The presence of numerous POMs covalently linked on the surface of 4–5 nm highly crystalline Ni_xFe_1–xO(OH) core is proven by multiple spectroscopic and microscopic techniques. Negative zeta potential of 1–3 infers the ionic surface of the materials due to the presence of negatively charged POMs which makes them highly dispersed and stable in water. Using 1–3 as electrocatalysts, oxygen evolution reaction (OER) is studied under alkaline condition. For catalytic OER, 1–3 on the nickel foam (NF) electrode require almost 20 mV less overpotential compared to the undoped core material Mo_xO_y@FeO(OH) and the POM-free bare FeO(OH) and Ni_xFe_1–xO(OH). The better OER activity can be correlated to better electrokinetics, realized from the Tafel slope and charge-transfer resistance (R_ct). The fabricated electrode 1@NF not only shows a long-term stability under the OER condition but also can be fabricated to a water-splitting electrolyzer using a graphite rod as the cathode to produce green hydrogen with Faradaic efficiency of ca. 72%. In this study, Anderson-type POM is used as a potential ligand to derive the quantum-dot-sized Ni_xFe_1–xO(OH) core as a reactive electrocatalyst for OER. In a broad context, this strategy, i.e., the use of POM as a pure inorganic ligand to stabilize a reactive metal oxide nanocore, can further be adapted to design a variety of multimetallic or mixed-valence metal oxide materials.

更新日期：2023-12-22

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