Synergy of Self-redox Reaction of Fe₂O₃/MnO Heterojunction Electrocatalyst on Oxygen Evolution Reaction in Alkaline solution

김준영,강미숙 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

전기화학적 물 분해를 통해 에너지를 생산하는 과정은 태양 에너지와 같은 재생 에너지에서 생성된 잉여 전력을 이용하여 물분해 시스템에 이용할 수 있는 친환경적인 방법으로 알려져 있다. 물을 전기 화학적으로 분해하여 수소를 얻는 과정에서 가장 중요한 것은 최적의 HER 및 OER 촉매를 개발하는 것이다. 그 중에서도, OER의 반응 메커니즘은 복잡하고 반응 중에다양한 중간체가 형성되기 때문에 일반적으로 높은 과전압을 갖는다. 따라서, 과전압이 낮은 OER 전극 촉매의 개발은 고효율의 물 전기 분해를 위해 극복해야 할 큰 과제이다. 이 연구에서는 저렴하면서도 높은 효율을 갖는 OER 전극 촉매의 개발에 중점을 두었으며 기본 촉매로 Mn과 Fe을 선택하였다. 이들 입자를 니켈폼 상에 코팅하여, 산소 발생 반응을 진행하였다. 알칼리성 전해질에서 Fe₂O₃-MnO/NF 전극이 가장 안정적이고 가장 높은 OER 활성을 나타냈다. 또한, Mn 및 Fe의 효과적인 산화 환원 반응은 1000회 반복된 반응 후에도 안정적인 성능을 유지하는 것을 확인하였다.

Sol-Gel법을 이용한 Cu_xCo_3-xO₄ 산소 발생 촉매의 합성 및 전기화학 특성 분석

박유세,정창욱,김치호,구태우,석창규,권일영,김양도,Park, Yoo Sei,Jung, Changwook,Kim, Chiho,Koo, Taewoo,Seok, Changgyu,Kwon, Ilyeong,Kim, Yangdo 한국재료학회 2019 한국재료학회지 Vol.29 No.2

Transition metal oxide is widely used as a water electrolysis catalyst to substitute for a noble metal catalyst such as $IrO_2$ and $RuO_2$. In this study, the sol-gel method is used to synthesize the $Cu_xCo_{3-x}O_4$ catalyst for the oxygen evolution reaction (OER),. The CuxCo3-xO4 is synthesized at various calcination temperatures from $250^{\circ}C$ to $400^{\circ}C$ for 4 h. The $Cu_xCo_{3-x}O_4$ synthesized at $300^{\circ}C$ has a perfect spinel structure without residues of the precursor and secondary phases, such as CuO. The particle size of $Cu_xCo_{3-x}O_4$ increases with an increase in calcination temperature. Amongst all the samples studied, $Cu_xCo_{3-x}O_4$, which is synthesized at 300?, has the highest activity for the OER. Its onset potential for the OER is 370 mV and the overpotential at $10mA/cm^2$ is 438 mV. The tafel slope of $Cu_xCo_{3-x}O_4$ synthesized at $300^{\circ}C$ has a low value of 58 mV/dec. These results are mainly explained by the increase in the available active surface area of the $Cu_xCo_{3-x}O_4$ catalyst.

Randomly entangled and twisted 3D structures of N doped PDEB chain combined with Co single-atom as a high-efficiency oxygen reduction reaction catalyst

김관우,강태오,김주헌 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

The metal-air batteries are spotlighted as renewable energy storage system, because it has unlimited resources to use oxygen and their high theoretical energy density performance. However, the undesirable sluggish ORR & OER kinetics are main challenged to be solved. Here, we report the 3D material with a high catalytic activity site, which has not been reported previously, a carbon chain structure connected by a cobalt single atom. Tangled & twisted structure has a meso- to macro-porous characteristic, which provides a three-phases (gas/oxygen-liquid/electrolyte-solid/catalyst) coexist space that is advantageous for oxygen adsorption and desorption reaction. In addition, the single atom scale can control previous uncontrolled metal- supported bonds. Co, which has lost its charge to N, becomes more oxidized and has a higher potential as a bifunctional catalyst. Therefore, these fresh cathodic catalysts with metal-air battery may suggest the new direction and paradigm.

Self-supported ZIF-coated Co2P/V3P bifunctional electrocatalyst for high-efficiency water splitting

Yuying Yang,Jingyue Yang,Qin Zhou,Dalan Qian,Yaling Xiong,Zhongai Hu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-

Exploring high-efficiency dual-functional electrocatalysts to drive electrochemical water splitting is ofgreat importance for advancement of renewable hydrogen energy. Herein, a hierarchical core–shell structureelectrocatalyst ZIF-Co2P/V3P is in situ grown on Ni foam (abbreviated as ZIF-Co2P/V3P@NF) by a stepwisemethod. Firstly, Co, V layered double hydroxides (CoV-LDHs) is grown directly on Ni foam (NF)substrate by solvothermal method. Secondly, CoV-LDHs@NF is transferred into 2-MeIm solution andits surface is coated with a layer of imidazolate zeolite skeleton (ZIF). Finally, ZIF-Co2P/V3P@NF catalystis obtained by low-temperature phosphorization method. The performance of hydrogen evolution reaction(HER) and oxygen evolution reaction (OER) can be adjusted by tuning molar ratio of Co/V, and theoptimized ZIF-Co2P/V3P@NF-2 manifests superior performance due to its core–shell structure coveredby ZIF skeleton, rich heterogeneous interfaces, as well as the positive synergistic interaction betweenthe Co2P and V3P. The overpotentials are only 57 mV@10 mA cm2 for HER and 261 mV@10 mA cm2for OER. Remarkably, the alkaline electrolyzer assembled with ZIF-Co2P/V3P@NF-2 catalyst acquires asmall operating voltage of 1.54 V to drive the current density of 10 mA cm2 and displays excellentlong-term durability. This work provides a novel opinion for design and preparation of non-noble metalelectrocatalysts.

Design of Ru-based oxygen evolution reaction (OER) electrocatalyst with efficient catalytic activity and stability

임철완,오형석,이재경 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Clean energy is attracting attention as a solution to the current energy economy system problems caused by fossil fuels. On that point, hydrogen resources produced by electrochemical water splitting have advantages of no pollution for operations and high energy density and so on. There have 2-electrochemical reactions on the electrochemical water splitting system; hydrogen evolution reaction (HER) on cathode and oxygen evolution reaction (OER) on anode. Ruthenium (Ru) element is known promising catalyst because it can achieve high performance, but there has a decline of durability caused by dissolution. To improve that issue, we focused on modification of the electronic structure of Ru based electrocatalysts by introducing platinum (Pt). Especially, on accout of RuO2 and PtO2 have structurally similarity, which can change the electrochemical structure without crystal structural strain. As a result of designing of catalysts system, enhanced stability can be interpreted.

Morphology controlled synthesis of 2-D Ni–Ni3S2 and Ni3S2 nanostructures on Ni foam towards oxygen evolution reaction

CHAUDHARINITIN KADUBA,Oh Aram,Sa Young Jin,Jin Haneul,백현석,Kim Sang Gu,이석중,주상훈,Lee Kwangyeol 나노기술연구협의회 2017 Nano Convergence Vol.4 No.7

Catalysts for oxygen evolution reactions (OER) are at the heart of key renewable energy technologies, and development of non-precious metal catalysts with high activity and stability remain a great challenge in this field. Among various material candidates, metal sulfides are receiving increasing attention. While morphology-dependent catalytic performances are well established in noble metal-based catalysts, relatively little is known for the morphology‒catalytic performance relationship in metal sulfide catalysts. In this study, uniform spider web-like Ni nanosheets–Ni3S2 and honeycomb-like Ni3S2 structures are deposited on nickel foam (Ni3S2/NF) by a facile one-step hydrothermal synthetic route. When used as an oxygen evolution electrode, the spider web-like Ni–Ni3S2/NF with the large exposed surface area shown excellent catalytic activity and stability with an overpotential of ~310 mV to achieve at 10 mA/cm2 and a Tafel slope of 63 mV/dec in alkaline media, which is superior to the honeycomb-like structure without Ni nanosheet. The low Tafel slope of the spider web-like Ni–Ni3S2/NF represents one of the best OER kinetics among nickel sulfide-based OER catalysts. The results point to the fact that performance of the metal sulfide electrocatalysts might be fine-tuned and optimized with morphological controls.

Enhanced catalytic activity of electrodeposited Ni-Cu-P toward oxygen evolution reaction

Kim, Byung Keun,Kim, Soo-Kil,Cho, Sung Ki,Kim, Jae Jeong Elsevier 2018 Applied Catalysis B Vol.237 No.-

<P><B>Abstract</B></P> <P>The slow kinetics of the oxygen evolution reaction (OER) and the high cost of the precious metal catalysts for the OER limit the efficiency and cost-effectiveness of water splitting. In this study, we introduce electrodeposited nickel-copper-phosphorous (NiCuP) as an efficient OER electrocatalyst in alkaline medium. The addition of Cu into the NiP electrocatalyst significantly enhanced the OER activity. Optimization of the electrodeposition conditions revealed that Ni<SUB>59</SUB>Cu<SUB>19</SUB>P<SUB>9</SUB> in terms of atomic percent exhibited the best activity with a reduced Tafel slope and charge transfer resistance for the OER, compared to NiP. The Ni<SUB>59</SUB>Cu<SUB>19</SUB>P<SUB>9</SUB> catalyst successfully endured the OER operation at 10 mA/cm<SUP>2</SUP> for up to 30 h while maintaining a Faradaic efficiency of over 99%. The X-ray photoelectron spectroscopy showed that the amount of active Ni hydroxide (NiOOH) species increased with the addition of Cu, which likely contributed to the enhanced of catalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A Ni-Cu-P electrocatalyst for the oxygen evolution reaction (OER) was prepared via electrodeposition. </LI> <LI> The addition of Cu into the NiP electrocatalyst enhanced the catalytic activity, and Ni59Cu19P9 exhibited the maximum OER performance. </LI> <LI> Ni59Cu19P9 required only 307 mV overpotential to deliver 10 mA/cm2 with a 42.5 mV/dec Tafel slope. </LI> <LI> The catalytic activity of Ni59Cu19P9 was sustained for 30 h with almost 100% Faradaic efficiency. </LI> <LI> The increase in the activity with Cu addition is likely associated with the increase in the amount of NiOOH in the NiCuP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Gold nanodots-decorated nickel hydroxide nanoflowers for enhanced electrochemical oxygen evolution activity

Hien Duy Mai,Suncheol Kim,Hyojong Yoo 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-

Oxygen evolution reaction (OER) is considered a major challenge in the production of efficientelectrochemical water splitting devices. To overcome the challenge, the development of inexpensiveelectrochemical catalysts with high energy conversion efficiencies is vital. Nanohybrids composed ofnoble metal nanoparticles and transition metal hydroxides often possess catalytically active sites that arebeneficial for OER performance. In this study, we report a successful synthesis of Ni(OH)2 nanoflowerswith a high degree of crystallinity and uniformity. The as-prepared Ni(OH)2 nanoflowers are employed astemplates for effective and controllable loading of Au nanodots to obtain Ni(OH)2@Au nanohybrids. Anexamination of the OER activity reveals that Ni(OH)2@Au nanohybrids exhibit a considerably loweroverpotential (h) value (390 mV) at a current density of 5 mA cm–2 and a smaller Tafel slope (120 mV dec–1) than those of Ni(OH)2 nanoflowers (540 mV and 324 mV dec–1, respectively). The OER enhancementeffect is mainly attributed to the decoration of Au nanodots, inducing charge transfer from Ni to Au andthereby stabilizing the Ni species at high oxidation levels. Moreover, the uniform loading of Au nanodotson the anisotropic Ni(OH)2 nanoflowers provides more active interfacial surfaces, which are expedient toOER.

Bimetallic Mn-Fe Oxide Electrode Material for Improved Oxygen Evolution Reaction

김준영,강미숙 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

수소를 생산하는 다양한 방법 중에서 전기화학적으로 물을 분해하여 수소를 제조하는 방법이 있다. 이 방법은 시스템이 간단하고, 풍력이나 태양 에너지와 같은 재생 가능한 에너지로부터 생성된 잉여 전력을 이용하여 친환경적으로 수소를 생산 할 수 있어, 가장 유망한 기술 중에 하나로 알려져 있다. 한편, 물 전기분해시 각 전극에 걸리는 과전압을 줄여, 낮은 과전압에서도 충분한 양의 수소를 생산하기 위한 전극을 개발하기 위한 연구가 많이 이루어지고 있다. 따라서 본 연구에서는 양쪽 전극 중에서 산소 발생 반응(OER)에서 낮은 과전압을 가질 수 있는 전극 촉매를 개발하고자 하였다. 비교적 저렴하면서도 우수한 물분해 산화 촉매 물질로 알려져 있는 Mn과 Fe을 Mn-Fe Oxide 형태로 사용하였다. 합성한 전극 촉매는 XRD, SEM, TEM을 통해 표면의 물리적, 화학적 특성을 분석하였다. 전극의 성능은 LSV, CV, Tafel plot을 이용하여 평가하였다.

음이온 교환막 수전해에 사용되는 Cu0.72Co2.28O4 산소 발생 촉매의 합성 및 특성 분석

박성민,장명제,박유세,정재엽,정재훈,이주영,최민관,노유성,서민호,김형주,양주찬,김양도,최승목 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.1

In this study, we investigated the morphological, crystal structural, electronic structural, and electrocatalytic properties of the inverse spinel structured copper cobalt oxide (Cu0.72Co2.28O4) catalysts. The materials were prepared by coprecipitation using various copper and cobalt precursors, and subsequent oxidation treatment. Electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer Emmett Teller (BET) analyses were employed to characterize the Cu0.72Co2.28O4 catalysts. The Cu0.72Co2.28O4 catalyst, synthesized with acetate based precursors, exhibited higher activity for the oxygen evolution reaction than commercial precious IrO2 catalyst. This performance was attributed to its high surface area, sheet morphology and ratio of Co3+. The Cu0.72Co2.28O4 catalyst also showed excellent stability with a performance of 99% after 300 hours. The Cu0.72Co2.28O4 catalyst anode electrode was coupled with a Pt/C cathode electrode to construct an anion exchange membrane water electrolysis (AEMWE) cell. Our AEMWE cell achieved a current density of 644 mA/cm2 and an energy efficiency of 85% at a cell voltage of 1.8 V in 1M KOH.