Nanoporous Metal Oxide and Nitride Derived from Organic-Inorganic Hybrid Precursors as Electrode Materials

Abstract

Development of bifunctional catalysts for oxygen/hydrogen evolution reaction has received greatly attention lately as fuel cells whose sources are oxygen and hydrogen are one of the possible alternatives for the current fossil fuel based energy resources. In particular, it has been important to design a materials that enables both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline electrolyte due to the difficulties of OER. Herein, porous ZnCo2O4 has been successfully synthesized as a bifunctional electrocatalyst by calcining a precursor derived from zeolitic imidazolate frameworks and characterized by various analytic porous ZnCo2O4 shows a much lower overpotential at 10 mA/cm2 than that of Co3O4 and IrO2 which is an OER benchmarking catalyst. Furthermore, ZnCo2O4 also exhibits the electrocatalytic activity for HER in alkaline environment. The electrocatalytic performances have been investigated by electrochemical analyses. Supercapacitors have been regarded as next generation energy storage due to their high power density, fast charging, and semi-permanent cycle lives. Pseudo-capacitors, a kind of supercapacitors, have been attractive because of their higher power and energy density than those of electrochemical double layer capacitors. In this work, titanium oxynitride hexagonal nanorod was firstly introduced. Titanium oxynitride hexagonal nanorod was induced from hydroxyl titanium oxalate precursor by two-step synthesis, which allows porosity and high surface area. This newly synthesized titanium oxynitride has been adopted as a pseudo-capacitive material to take advantages of high surface area and electrical conductivity, and specific capacitance of 186.71 F/g was obtained at 2 mV/s. |현재 산소와 수소를 원료로 하는 연료 전지가 현재 화석 연료 기반 에너지 자원의 가능한 대안 중 하나이기 때문에 최근 산소 및 수소 발생 반응을 위한 양쪽성 촉매 개발이 주목 받고 있다. 특히, 산소 발생 반응의 어려움으로 인해 알칼라인 전해액에서 산소 발생 반응과 수소 발생 반응을 동시에 가능하게 하는 전극물질을 개발하는 것이 새로운 과제로 대두되고 있다. 본 연구에서는 Zeolitic Imidazolate Framework 전구체로부터 유도된 아연-코발트 산화물(ZnCo2O4)이 전극 촉매로서 합성되었으며 다양한 방법을 통해 분석되었다. 개발된 아연-코발트 산화물이 코발트 산화물(Co3O4) 및 산소 발생 반응의 대표적인 촉매인 이산화 이리듐(IrO2)보다 훨씬 낮은 과전압을 갖는 것이 확인되었다. 나아가, 아연-코발트 산화물은 알칼라인 환경에서 수소 발생 반응에 대한 전기 촉매 활성을 보이는 것 또한 관찰되었다. 얻어진 결과는 전기 화학적 분석에 의해 설명되었다. 슈퍼캐패시터는 높은 출력 밀도, 빠른 충전 및 반영구적인 사이클 수명으로 인해 차세대 에너지 저장 장치로 간주되어왔고, 특히 슈퍼캐패시터의 일종인 유사(pseudo-)캐패시터는 전기이중층 캐패시터보다 높은 출력 및 에너지 밀도를 가지는 것이 두드러진다. 이 연구에서는 새로운 물질인 육각막대 모양의 티타늄 옥시나이트라이드가 유사캐패시터의 전극물질로 최초로 제안되었다. 메조 기공을 갖는 티타늄 옥시나이트라이드 육각막대는 금속 및 유기골격체인 수산화 옥살산 티타늄(HTO)으로부터 합성되었다. 새로이 개발된 티타늄 옥시나이트라이드의 높은 표면적 및 전기 전도성의 이점을 취하기 위해 유사캐패시터의 물질로 채택되었으며, 2 mV/s에서 186.71 F/g의 용량이 얻어졌다.; Development of bifunctional catalysts for oxygen/hydrogen evolution reaction has received greatly attention lately as fuel cells whose sources are oxygen and hydrogen are one of the possible alternatives for the current fossil fuel based energy resources. In particular, it has been important to design a materials that enables both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline electrolyte due to the difficulties of OER. Herein, porous ZnCo2O4 has been successfully synthesized as a bifunctional electrocatalyst by calcining a precursor derived from zeolitic imidazolate frameworks and characterized by various analytic porous ZnCo2O4 shows a much lower overpotential at 10 mA/cm2 than that of Co3O4 and IrO2 which is an OER benchmarking catalyst. Furthermore, ZnCo2O4 also exhibits the electrocatalytic activity for HER in alkaline environment. The electrocatalytic performances have been investigated by electrochemical analyses. Supercapacitors have been regarded as next generation energy storage due to their high power density, fast charging, and semi-permanent cycle lives. Pseudo-capacitors, a kind of supercapacitors, have been attractive because of their higher power and energy density than those of electrochemical double layer capacitors. In this work, titanium oxynitride hexagonal nanorod was firstly introduced. Titanium oxynitride hexagonal nanorod was induced from hydroxyl titanium oxalate precursor by two-step synthesis, which allows porosity and high surface area. This newly synthesized titanium oxynitride has been adopted as a pseudo-capacitive material to take advantages of high surface area and electrical conductivity, and specific capacitance of 186.71 F/g was obtained at 2 mV/s.