The variation in the volume of published literature serves as a pivotal metric for gauging the research activity within a particular domain (Schjønning et al., 1999; Xiao et al., 2017). This study utilized the “Web of Science Core Collection” as the platform for literature retrieval, encompassing a time span from 2009 to 2022 (with statistical data up to 20 January 2023, which does not represent the full-year data; hence, one published document from 2023 was excluded from the analysis). The findings revealed a continuous increase in the volume of publications in the field of international carbon neutrality (Figure 1), indicating widespread scholarly interest and robust potential for development in this area.

As can be seen from Figure 1, there were three breakthroughs in the number of articles in the field of carbon neutrality from 2009 to 2022. The first was in 2014, when the number of articles published exceeded 100 for the first time. The number of published papers grew very slowly before, but began to steadily increase after 2009, and the research results gradually increased. The second was in 2019, when the number of published articles exceeded 300 for the first time, and increased rapidly thereafter. The third was in 2022, when the number of published articles exceeded 500 for the first time, and the number is expected to continue to increase.

By analyzing the top 10 journals in the international carbon neutral research field in terms of co-citation frequency and intermediate centrality (Table 1), it can be found that these journals share the common characteristics of a wide range of research fields and a high concentration of articles.

As can be seen from Table 1, the top 3 journals in total cited frequency are the Journal of Cleaner Production, Energy Policy, and Applied Energy, which lead the international research frontier of carbon neutrality. The top 3 journals with high mediating centrality are the Journal of Cleaner Production, Energy Economics, and Ecological Economics, and the highest mediating centrality is 0.07. These are the three journals in which research in the field of carbon neutrality is generally published. At the same time, it shows that the journals with a high number of publications and citations are not exactly corresponding.

The number of publications, total citations, and average citations of the top 10 regions in the international carbon neutral field are shown in Table 2.

As can be seen from Table 2, in terms of the number of articles published, only the top three regions have more than 100 articles published. China topped the list with 1,520 articles. The US, with 247 articles, was second only to China. In terms of total citations, the top three regions are China, the United States, and the United Kingdom. In terms of average citations, among the top 10 regions, the United States had the highest average citations, reaching 31.49, followed by Pakistan (31.09) and Canada (30.40). It can also be seen that China ranked third from the bottom in terms of average citations (17.32), although the number of published articles was the largest among the 10 regions.

The color of the outer circle of the node formed in Figure 3 represents the number of published documents by December 2022. It can be seen from Figure 3 that the research results are consistent with those in Table 2, namely, that the carbon neutral research is mainly conducted in 10 regions: China, the United States, the United Kingdom, Australia, India, Canada, South Korea, Japan, Pakistan, and Taiwan. Five of the top 10 are from Asia: China, India, Japan, South Korea, and Taiwan.

The number of publications, total citations, and average citations of the top 10 international research institutions in the field of carbon neutrality are shown in Table 3.

As can be seen from Table 3, the average number of papers published by the top 10 research institutions in the world is 54, but there are only 3 research institutions with more than the average number of papers published, and they are all in China, namely, the Chinese Academy of Sciences, North China Electric Power University, and Tsinghua University. In terms of the number of publications, the Chinese Academy of Sciences topped the list with 99. In terms of total citations, the Chinese Academy of Sciences, Tsinghua University, and Chongqing University ranked in the top 3. In terms of average citation amount, among the top 10 scientific research institutions, Tsinghua University of China has the highest average citation amount of 40.98 times, followed by Chongqing University of China with 47.94 times, and the Chinese Academy of Sciences with 30.25 times.

It can be seen that no matter the number of articles published, the total number of citations, or the average number of citations, China’s scientific research institutions are among the top in the world and very influential in the field of carbon neutrality research. At the same time, it should be emphasized that although the number of articles published by the School of Aeronautics and Astronautics of Nanjing University is only 37, the total number of citations and the average number of citations are both very high, whose influence cannot be underestimated.

The collaborative network map is also used to further explore the number of publications of various scientific research institutions in the field of carbon neutrality, as shown in Figure 4.

It can be seen in Figure 4 that universities are the major carbon-neutral research institutions, accounting for a relatively high proportion. Nine of the top 10 scientific research institutions are universities: North China Electric Power University, Tsinghua University, Chongqing University, Tianjin University, Beijing Normal University, Beijing Institute of Technology, University of Chinese Academy of Sciences, School of Aeronautics and Astronautics of Nanjing University, and the University of Science and Technology of China.

The main characteristics of the top 10 international authors and their research teams in the field of carbon neutrality are shown in Table 4 and Figure 5.

As illustrated in Table 4, the top 10 authors in the field of carbon neutrality are all from China. Two authors, ZHANG Y and LI Y, both had more than 70 articles at most, occupying the dominant position. In terms of international carbon neutral research teams, three research teams with outstanding research achievements and significant team collaboration effects have been initially formed. The following figure shows the collaboration network of authors in the field of international carbon neutrality research (Figure 5). Each node in the figure represents an author; the larger the node is, the more the author has published in the field of carbon neutrality research; the thicker the line between the nodes, the closer the cooperation.

The author collaboration network in Figure 5 is composed of 524 authors and 859 collaboration links, indicating that there are a large number of researchers in the field of international carbon neutrality research and a wide range of collaborative relationships among them. The collaborators and research areas of the three main research teams are as follows:

1) The research team with ZHANG Y as the core (in the black box) published the most papers, up to 80. ZHANG Y cooperates with Chen, Xi, and other authors the most frequently and has the closest connection. According to the color of the connection between nodes, it can be seen that the cooperation between the three mainly occurs in 2019, 2020, and 2021. Zhang Y’s research team is mainly engaged in crude oil price forecasting (Zhang and Li, 2020), carbon trading policy (Zhang and Liu, 2021; Liu and Zhang, 2021), energy investment (Zhang et al., 2021a; Zhang et al., 2021b; Zhang and Pan, 2021), and carbon emissions (Zhang et al., 2020). The peak of the number of publications by Zhang Y’s team in the field of carbon neutrality was 15 in 2019. It can also be seen in the author collaboration network map that the color of the outer ring of the nodes formed is orange, indicating that the ZHANG Y research team has been active in recent years, which is consistent with the number of published papers from 2019 to 2021. It also indicates that Zhang Y’s research team will continue to explore the field of carbon neutrality in the future.

Keywords will reflect the author’s research direction and interests (Sun, 2012; Li et al., 2015), which is a high condensation and manifestation of the main research content of the paper. With the help of this, others can quickly browse the keywords of the paper to obtain effective information such as research objectives, research content, research methods, and views held by the author (Yin, 2009; Feng, 2010). Therefore, the analysis of the occurrence frequency of keywords in literature is the key to exploring the hot spots and changes in development in a certain research field (Pan and Wang, 2011; Yang, 2015).

This paper uses the keyword co-occurrence analysis function of CiteSpace software to draw the keyword co-occurrence network diagram of carbon neutrality research and measure the main research hotspots in this field (Figure 7). In order to more accurately reflect the main keywords in the field of carbon neutrality research, by setting the functional threshold for software co-occurrence analysis, Figure 7 only shows the keywords whose occurrence frequency is greater than or equal to 178 times. Each node in the figure represents a keyword, and the larger node indicates a higher frequency of keyword occurrence. Similarly, the width of the line represents the frequency of keyword co-occurrence, and the thicker line represents the higher frequency of occurrence between two keywords.

According to Figure 7, the keywords with frequency greater than or equal to 178 times, that is, the top 10, are CO₂ emission (532 times), carbon emission (478 times), impact (328 times), energy consumption (262 times), dioxide emission (227 times), energy (225 times), model (209 times), China (205 times), economic growth (186 times), and performance (178 times). These keywords become important nodes in the network because of their high frequency.

These important nodes basically cover several major aspects of international carbon neutrality research: First, scholars mainly focus on “carbon dioxide emissions”, “carbon emissions”, and the “impact” of emissions as the starting point for carbon neutrality research; second, the main research directions are “energy consumption”, “low carbon consumption”, “energy,” and “economic growth”; third, the emergence of the keyword “performance” shows that scholars pay more attention to the performance of carbon neutrality.

In order to explore the close relationship between keywords, a cluster analysis of keywords in the research field of carbon neutrality is now carried out, as shown in Figure 8.

As can be seen from Figure 8, the keywords in the field of carbon neutrality are clustered into 10 categories, numbered 0 through 9. The smaller the number, the more keywords contained in the clustering. The 10 categories are carbon emission efficiency, energy consumption, game theory, impact, carbon emission trading, carbon emission and spatial spillover effects, scenario analysis, climate change, and abatement cost. Each cluster is composed of several closely related keywords. The specific keywords can be obtained by exporting the detailed information about clustering from the report (Table 6). In this network, attention should be paid to the average contour value of clustering, which represents the quality of clustering results. It is generally believed that when the average contour value of clustering is >0.5, the clustering is reasonable; when the average contour value is >0.7, the clustering is convincing.

As described in Table 6, the average contour values of the top 10 clusters in the research field of carbon neutrality are all greater than 0.7, indicating that the clustering results presented have certain convincing power, which also confirms the correctness of selecting carbon neutrality as the title of the paper. For example, in clustering #5, Research topics related to carbon neutrality include carbon neutrality, carbon emissions, embodied energy, and input-output analysis, which can be seen as related to topics such as carbon neutrality, carbon emissions, and energy. Similarly, the topics under the other nine categories of clustering labels are basically the same.

CiteSpace software provides a burst detection function, which is mainly used to detect the large changes in the reference amount of keywords in a certain period (Shi et al., 2022; Shi et al., 2020). Burst detection is considered an indicator of highly active research fields. It can explore emerging research trends and ephemeral trends, which provides a clear visual analysis of the duration of research hotspots in domestic and foreign academic circles. The higher the intensity of the burst, the more obvious the research orientation (Li, 2022; Dai et al., 2022)—which is the node that research needs to focus on—becomes. In this study, the burst intensity changes of a total of 20 keywords from 2009 to 2022 were plotted using CiteSpace’s burst detection function (Figure 9), where Strength represents the burst strength, Begin represents the beginning year of the burst, End represents the end year of the burst, and the red part is the year of the keyword burst.

Three main conclusions can be drawn from Figure 9. Firstly, from 2009 to 2022, the keyword with the highest burst intensity was “climate change”, with a strength value of 11.84. The burst began in 2009 and ended in 2017, which may be mainly related to the UN climate change conference in Copenhagen in 2009, which was held to prevent man-made interference in the climate system and stabilize the concentration of greenhouse gases in the atmosphere, but only a few developed countries made commitments to reduce emissions. In 2015, after learning the lessons of the Copenhagen Conference in 2009, all parties conducted rational and pragmatic negotiations on the expectations of each country’s emission reduction targets and finally reached the Paris Agreement, which ushered in a new stage of global climate governance. All these undoubtedly promoted the academic research on climate change tracking.

Secondly, the keywords “sequestration”, “bioma”, “storage”, “industry”, “regional allocation”, “model”, “system,” and so on also attracted great attention for a time, with the burst intensity greater than 5. However, with the continuous refinement and maturity of carbon neutral research, the attention given to other keywords has declined except for “plant” and “regional allocation”

Finally, since 2018, the three keywords “manufacturer”, “network design,” and “supply chain management” have always maintained a high degree of attention. In the context of global climate change, carbon emission reduction, carbon neutrality, and green energy application are entrusted with important tasks and heavy responsibilities, requiring improvements in industrial manufacturing, energy consumption structure, supply chain management, and other aspects.