TAILORING NOVEL MATERIALS FOR GLOBAL CO_2 RECYCLING

我们提出了一个二氧化碳循环系统，以防止由二氧化碳排放引起的全球变暖，并与人类活动的发展相结合。该系统包括二氧化碳的甲烷化，这些二氧化碳在燃料消费场所(如发电厂)回收。甲烷化需要高活性的催化剂和氢气，而利用太阳能从海水电解中可以获得氢气。为了在全球范围内证实这一体系，我们需要开发低成本、高效率的催化剂和电极用于海水电解的析氢和析氧反应。本研究的目的是开发这类新型催化剂和电极材料。我们发现，由非晶态镍-锆合金制备的甲烷化催化剂具有较高的甲烷化活性。我们还利用非晶态的Ni-Zr-Sm合金作为催化剂的前驱体，成功地开发出了活性更高的催化剂。结果表明，Sm稳定了Ni-p-…弥散在其上的四方氧化锆相更多的文章也得到了增强。气雾化Ni-Zr-Sm合金制备的催化剂也具有较高的活性，溅射沉积制备的Ni-Mo和Co-Al-Mo合金电极表现出较高的析氢反应活性。采用电弧离子镀的方法，不仅提高了镍钼合金电极与基材的结合力，而且提高了析氢效率，最有效的成分为Ni-(10-20)at%Mo-(5-10)at%O，在电流密度为4×103A/m2时析氢过电位低于100 mV。制备的电极结构为化学均一的纳米氧化锰，其结构为γ-MnO2结构，其中含有固溶的六价钨。研究还发现，在海水电解过程中，Mo和W的联合添加对选择性析氧更有效，并成功地降低了电解电压。较少

We are proposing a CO_2 recycling system for preventing global warming caused by CO_2 emissions in conjunctions with development of human activities. The system contsists of methanation of CO_2 which are recovered at fuel consumers sites such as power plants. Methanation needs highly active catalysts and hydrogen which can be obtained from seawater electrolysis using solar energy. To substantiate this system global scale, we need to develop low cost catalysts and electrode with high efficiency for hydrogen evolution and oxygen evolution reactions at seawater electrolysis. The objectives of this investigation are to develop such new catalysts and electrode substances.We have found methanation catalysts prepared from amorphous Ni-Zr alloys have high activity for methanation. We have also succeeded in develop more active catalyst using amorphous Ni-Zr-Sm alloys as precursors of the catalysts. It was clarified that samarium stabilize tetragonal phase of zirconia on which dispersion of Ni p … More articles are also enhanced. Catalysts prepared from gas-atomized Ni-Zr-Sm alloys also had high activity.Ni-Mo and Co-Al-Mo alloy electrode fabricated by sputter-deposition showed high activity for hydrogen evolution reaction. By using arc-ion-plating method, not only adhesiveness to the substrate but also hydrogen evolution efficiency of Ni-Mo alloy electrode was improved ; the most effective composition was Ni-(10-20)at%Mo-(5-10)at%O with the overpotential for hydrogen evolution lower than 100 mV at the cuurent density of 4×10^3A/m^2.It was succeeded to prepare an electrode with 100% oxygen evolution efficiency for seawater electrolysis using MnO_2 type oxide electrode installed on titanium stubstrate. The structure of the prepared electrode consisted of chemically homogeneous nanocrystalline manganese oxide with γ-MnO_2 structure containing solid-solved hexavalent tungsten. It was also found combined addition of Mo and W is more effective for selective oxygen evolution at seawater electrolysis and we were able to reduce electrolysis voltage successfully. Less