PEFC 用カーボンフリーカソード担体としてのニオブドープ酸化チタンの表面積と導電率の最適化

概要

Energy has become the key to the development of human society and the progress of civilization. Woods, hays, and other combustibles which are easily accessible from nature were used for cooking, heating, and other essential purposes by primitive humans. With advances in geology and mining technology, coal has a much higher energy density than traditional animal and plant fuels.

Generally, Karl Marx recognized positive feedback between advanced productivity and technological progress.[1,2] In 1776, James Watt improved on the Newcomen steam engine with his Watt steam engine, marking the Industrial Revolution’s arrival. Until the 1830s, one worker’s output was increased around 500 times in mechanized cotton spinning [3]; the needed fuel decreased to 1/5 -1/10 due to the efficiency of steam energy. [4, 5] In the 1780s, the first transformation was that coal became the largest share of primary energy instead of the woods. [6] In 1876, Nicolaus Otto invented the Neuer Otto-Motor which used gas as fuel and made the efficiency improvements to 12%, this cycle named as Otto cycle. Then, in 1885, Gottlieb Wilhelm Daimler invented the first gasoline engine. It was one of the features of the Second Industrial Revolution. The second industrial revolution saw another leap forward in manufacturing, such as die construction of railways, large-scale steel production, the widespread use of machinery, the general use of the telegraph, oil, and the beginning of electrification. [7] The second transformation was that the share of petroleum and gas in the primary energy mix improved rapidly, and instead, coal was the most prominent part in 1965. [6] Herein, in the second transformation, the primary energy source is transferred from coal to oil and natural gas.

With the development of the social economy and further improvement of efficiency the production mode of human society is bound to undergo the third transformation: from traditional fossil fuel to non-fossil new energy is becoming inevitable. Specifically, with the development of information technology, people’s demand for electricity is gradually increasing. The total power generation in 1985 was 9826 TWh, of which the proportion of oil, gas, and coal were 1108.76,1422.36, and 3748.31 TWh, respectively; in 2021, the power generation was 27520.52 TWh, of which the proportion of oil, gas, and coal were 851.7, 10042.2 and 6098.08 TWh, respectively. [8, 9] A lot of interesting facts could be found in those data. First, in die past 36 years, the power generation increased 2.8 times. This is in line with the global economic development over the past century. Then, in the part of primary energy, oil is decreasing, the position of natural gas is increasing rapidly, and the increment of coal is less than the increment of total power generation, which is related to the reduction of harmful NOx, SOx emissions as well as international energy prices, market supply stability. Finally, although the increment of total power generation is enormous, the primary part is decreased. It benefits from renewable energy development and the efficiency improvement of traditional power generation methods, like ultra-supercritical. The importance of non-primary energy is steadily increasing.

With industrialization, various greenhouse or harmful gas emissions increased very quickly and massive, such as NOK, SOX, CO2, CH4, HFCs, etc. Since the Industrial Revolution, within the unreasonable time of 300 years, greenhouse gas / harmful gas emissions have been several times higher than before. Even worse, the emission still increases with a high growth rate. For example: the CO2 emission from fossil fuels was 27869 Mt in 2007 and expanded to 30127 Mt in 2017 [8, 10,11].The growth rate in 10 years is 8.1%, which is obviously a dangerous acceleration. On the other hand, based on the IPCC-AR5 report, it could be easily found that the CO2 emission is more about 5682 Mt than the natural absorption amount of 24445 Mt, which means that the carbon cycle balance has been broken.

In Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC-AR5), they reported the Representative Concentration Pathways (RCPs) model, which is predicted the impact of different conditions of greenhouse gas emissions on the global environment by the radiative forcing value in 2100 (1.9, 2.6, 3.4,4.5, 6, 7 and 8.5, W/m2, respectively. In the model, several possible scenarios for greenhouse gas emissions are assumed. From RCP 1.9 to RCP 8.5, the number represents their atmospheric concentrations. Herein, the RCP 3.4 was considered the most reasonable prediction[12], although it is still a strict emission target. In addition, according to the emission reduction plans announced by major countries, RCP 4.5 is also a possible model. The emissions peak would be reached around 2040, which would cause the temperature to rise 2-3 Celsius, and many plants and animals will be hard to survive at RCP 4.5 or higher RCPs [11]. The deterioration of the environment is affecting the earth’s atmosphere. Sea levels are rising. extreme climates are increasing, and the living environment of humans and other species is deteriorating· It is increasingly necessary and urgent to reduce greenhouse gas emissions. According to NASA's speculative data [13], if the RCP 4.5 forecast model can be strictly implemented, the global sea level rise will be controlled within two meters, which is still a grim situation for some regions. Meantime if emissions cannot be effectively controlled, the average sea level rise will exceed two meters around 2180 and about 4.7 meters in 2300. This will lead to extremely serious consequences. For example, the area near Yokohama Station with an average altitude of about two meters will disappear, and the coastal industrial area near Isogo will also be seriously threatened or even submerged.

Meanwhile, from the perspective of energy security and stability, renewable energy development is becoming more and more necessary. From the 1973 oil crisis, 1979 oil crisis, 1990 oil price shock, etc., to the 2022 Russo-Ukrainian War, which is still ongoing, international energy prices are prone to significant fluctuations due to external Actors such as wars. Since the 2022 Russo- Ukrainian War, the global crude oil price has remained above 100 dollars per barrel for a long time; it increases the cost of production and living in many countries and even threatens the security of the energy simply chain.

Not only the environment but energy security problems. To defend the development of human civilization, developing renewable energy is necessary and urgent.

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