The newly published nature supplement "nature index - energy" focuses on research related to the United Nations sustainable development goal 7 "clean and affordable energy (sdg7)", and tracks and measures the scientific research output and cooperation in 82 leading natural science journals in this field. According to the natural index data, from 2015 to 2021, China's sdg7 related research output ranked first in the world, followed by the United States, Germany, South Korea and Japan. Last year, the sdg7 related research output tracked by the natural index soared, from 3345 articles in 2020 to 3889, the largest increase since 2015. According to "share", one of the main indicators of the natural index, China's sdg7 related research increased by 324.1% from 2015 to 2021, making it the fastest growing country in this field. Among the top 50 sdg7 related output institutions from 2015 to 2021, China is also in a dominant position, with 25 institutions on the list and 14 institutions in the United States. Among them, the top ten institutions are: Chinese Academy of Sciences, Tsinghua University, University of science and technology of China, Peking University, Stanford University, Suzhou University, Nanyang University of technology, Nanjing University, Massachusetts Institute of technology and University of Chinese Academy of Sciences. The supplement also focuses on scientific research cooperation in the field of clean and affordable energy from point to point. According to the natural index data, more than 80% of the articles published by France, Australia, Spain and the United Kingdom in this field involve co authors from other countries. In contrast, China is the only country among the top 30 countries that produces more non International Co authored articles than international co authored articles. Although China's international co authored articles account for less than half of its total output (46.3%), due to the high output of articles, China often appears in major scientific research cooperation. For example, the Chinese Academy of Sciences and the Georgia Institute of technology, Tsinghua University and Nanyang Technological University, and the University of California, Berkeley and the Chinese Academy of sciences are the top three bilateral cooperation among institutions; China and the United States, China and Australia, China and Singapore are the top three bilateral cooperation countries. In addition, Chinese institutions also dominate among the 30 institutions with the fastest growth in output related to the natural index sdg7. Among them, the only non Chinese institutions on the list are the Federal Institute of technology in Zurich, Switzerland, and the Indian Institute of science and technology, ranking 28th and 29th respectively. Simon Baker, editor in chief of the nature index, said that since 2015, with countries determined to shift from fossil fuels to greener energy to achieve decarbonization, research output related to clean and affordable energy has increased every year, with a clear trend. "From 2015 to 2021, China's natural index 'share' increased by more than 300%, showing its important position in this field. At the same time, many important international cooperation has also brought dividends to the competition for cleaner energy." (outlook new era)