新型钴基硒化物电极材料的制备及催化释氢性能研究

发布时间：2018-04-19 22:31

本文选题：过渡金属硒化物 + 电/光电催化制氢　；参考：《浙江大学》2017年博士论文

【摘要】：随着能源危机,环境污染等问题的日益突出,人类社会对以氢能为代表的清洁能源的需求越来越迫切,水分解制氢作为理想的获取氢能的方法成为研究的热点。由于水分解产氢反应(Hydrogen Evolution Reaction,HER)是一个耗能的上坡反应,实际外加电压往往要高于理论值。电催化和光电催化作为两种重要的水分解制氢的方式,其核心问题是如何实现电能和太阳能向化学能的高效转化。研究表明,在电极表面负载产氢催化剂改善反应动力学是提升反应速率的关键,但是目前在电催化和光电催化分解水体系以Pt等为代表的贵金属催化剂由于成本等问题不适宜于水分解制氢的大规模应用。钴基硒化物由于具有适宜的结合氢原子的能力,且价格低廉,储量丰富,被认为是理想的Pt释氢催化剂替代材料。但如何实现钴基硒化物的简便合成、晶相调控以及如何与半导体材料耦合仍面临很大挑战。本论文通过创新催化材料的制备方法制备了高效的钴基硒化物,并系统探究不同工艺条件下钴基硒化物的形成机理、物相组成、微观形貌。针对目前过渡金属化合物电催化释氢材料制备工艺复杂的问题,我们提出一种简便的气相反应方法,即在Se蒸气的氛围里,使钴基无机盐直接转化为黄铁矿型CoSe_2晶体。进一步地,针对块状晶体催化活性位点少,催化能力差等问题,提出通过设计混晶结构来提高晶体材料催化活性的研究思路;首先利用电沉积合成CoSex,然后通过改变煅烧温度实现CoSe_2晶体结构从斜方晶型(o-CoSe_2)到立方晶型(c-CoSe_2)的调控,首次合成了由(c-CoSe_2)和(o-CoSe_2)组成的混晶CoSe_2(-CoSe_2)。混晶结构中不同晶型晶体界面处的原子的周期性排列发生剧烈变化,原子具有更高的自由度,由此产生的晶面缺陷进一步提高了 CoSe_2晶体的电催化活性,其释氢Tafel斜率为30mV/decade(与Pt相同),而且具有优异稳定性。在光电催化体系中,实现催化剂与半导体的有效耦合非常困难,特别是对以硅为基底的光电阴极,由于硅基底与催化剂界面相容性差、催化剂阻碍硅基对光的吸收等问题,大多数晶体电催化材料不能直接应用于光电催化体系。此外,常规催化剂负载工艺会在硅表面引入缺陷,影响光电转化效率。针对上述问题,为了构建高效半导体-催化剂体系,我们有针对性地设计出电催化性能优异(Tafe1～39 mV/decade)且透光性良好的三元钴基无定形薄膜(NiCoSex)。利用温和的光辅助-电沉积的方法,以吸光性能良好的三维硅纳米柱阵列(p-SiNP)为基底,构建了具有“核-壳”结构的p-Si/NiCoSexNP异质结复合电极,100 mW/cm2的模拟太阳光条件下,释氢光电流为-37.5 mA/cm2,是目前以p-Si为基底的光电阴极电流的最高值。本论文以制备高效的水分解释氢催化材料为目标,系统研究了不同钴基硒化物结构与催化析氢性能的构效关系;构建了“半导体-催化剂”高效光电催化体系,实现了光生电子的有效收集和利用。本论文将为设计其它具有类似结构的催化材料提供有益的借鉴,并为Si基半导体析氢材料走向工业化提供新材料和新思路。
[Abstract]:As the energy crisis, environmental pollution and other problems become increasingly prominent, the demand for clean energy represented by hydrogen energy is becoming more and more urgent in human society. Water decomposition and hydrogen production as an ideal method for obtaining hydrogen energy has become a hot spot. Because of the water decomposition hydrogen production (Hydrogen Evolution Reaction, HER) is a energy consuming upslope reaction, practical The applied voltage is often higher than the theoretical value. Electrocatalysis and photoelectrocatalysis are two important ways of water decomposition and hydrogen production. The core problem is how to realize the efficient conversion of electric energy and solar energy to chemical energy. The precious metal catalysts, such as Pt and so on, are not suitable for the large-scale application of hydrogen production. The cobalt based selenide is considered to be a substitute for the Pt hydrogen release catalyst because it has the ability to combine the hydrogen atom with the suitable hydrogen atom, and is considered to be the substitute for the hydrogen release catalyst. The simple synthesis of cobalt based selenide, the regulation of crystal phase and how to coupling with semiconductor materials are still facing great challenges. In this paper, a highly efficient cobalt based selenide is prepared by the preparation of innovative catalytic materials. The formation mechanism, phase composition and Micromorphology of cobalt based selenide under different technological conditions are systematically explored. A complex process for the preparation of electrocatalytic hydrogen release materials for metal compounds, we have proposed a simple method of gas phase reaction, that is, the cobalt based inorganic salts are converted directly into pyrite type CoSe_2 crystals in the atmosphere of Se vapor. The structure is used to improve the catalytic activity of crystal materials. First, CoSex is synthesized by electrodeposition, and then the CoSe_2 crystal structure is regulated from o-CoSe_2 to cubic (c-CoSe_2) by changing the calcination temperature. The mixed crystal CoSe_2 (-CoSe_2) composed of (c-CoSe_2) and (o-CoSe_2) is synthesized for the first time. The different crystal structure in the mixed crystal structure is synthesized. The periodic arrangement of atoms at the interface of the type crystal occurs violently, and the atom has a higher degree of freedom. The resulting crystal surface defects further improve the electrocatalytic activity of the CoSe_2 crystal. The Tafel slope of the hydrogen release is 30mV/decade (the same as that of Pt), and has excellent stability. In the photoelectrocatalysis system, the catalyst and the semi conductance are realized. The effective coupling of the body is very difficult, especially for the silicon based photocathode. Because the compatibility of the silicon substrate and the catalyst interface is poor, the catalyst hinders the absorption of the silicon base to the light, most of the crystal electrocatalysis materials can not be directly applied to the photoelectrocatalysis system. In addition, the conventional catalyst loading process will introduce defects on the silicon surface. In order to build an efficient semiconductor catalyst system, we have designed a three element cobalt based amorphous film (NiCoSex) with excellent electrocatalytic performance (Tafe1 ~ 39 mV/decade) and good transmittance in order to construct an efficient semiconductor catalyst system. A p-Si/NiCoSexNP heterojunction composite electrode with a "nuclear shell" structure is constructed on the base of p-SiNP, which is the highest value of the photocurrent current on the base of p-Si under the simulated solar light condition of 100 mW/cm2, which is the highest value of the photocurrent current on the basis of p-Si. The structure-activity relationship between the structure of different cobalt based selenides and the catalytic hydrogen evolution performance was studied. The efficient photoelectric catalysis system of "semiconductor catalyst" was constructed, and the effective collection and utilization of photogenerated electrons were realized. This paper will provide useful reference for the design of other similar structure catalytic materials and walk for the Si based semiconductor hydrogen evolution material. Provide new materials and new ideas for industrialization.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.2

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