2.1 Studies on driving factors of carbon emission reduction
(1) Research perspective: ①Analyze the driving factors of carbon emissions from the perspective of economic development mode. Most existing studies analyze the economic driving force of carbon emissions from the aspects of industrial structure, innovation-driven, and new urbanization(Huang and Yi 2023; Xiao et al. 2023).Lin and Wang (2023), based on empirical analysis, believed that the transfer of high energy consumption and high emission industries was accompanied by a large amount of carbon dioxide transfer, and the industrial transfer of different structures would form different degrees of carbon emission spillover effects. However, Li et al. (2022a) believed that although the path of industrial structure transfer and carbon emissions transfer was similar, the industrial structure transfer and carbon emissions transfer did not produce complete synergy. Zhao et al. (2023) analyzed the data of 252 cities in China and concluded that cooperative green innovation is more effective in reducing carbon emissions than independent green innovation. Xiaomin and Chuanglin (2023) confirmed that the development of urbanization significantly promoted carbon emissions, and the faster the urbanization development, the faster the growth of carbon emissions in provinces. ②It is emphasized to influence carbon emissions through environmental regulation. There are disputes in academic circles about the role of environmental regulation on carbon emission reduction. On the one hand, the "Porter Hypothesis" believes that reasonable environmental regulation can reduce carbon emissions by stimulating technological R&D innovation of enterprises and compensating the cost increase of environmental regulation with innovation(Danish et al. 2020). On the other hand, the "green paradox hypothesis" believes that China's fiscal decentralization governance model will weaken the inhibitory effect of environmental policies on carbon emissions(Zhang et al. 2017). Some scholars also believe that under different degrees of environmental regulation, environmental regulation has different impacts on carbon emission reduction, such as U-shaped (Huang and Tian 2023). ③Dai et al. (2022) test the effect of a series of policies or actions on carbon emission reduction. It can not only reduce the carbon emissions of the region, but also promote the carbon emission reduction effect of the surrounding areas. Meng and Yu (2023) believed that the renewable energy portfolio standard and carbon tax policy promote the carbon emission reduction of China's power industry. Sun and Li (2021) and Zeng et al. (2023) tested the policy effect of low-carbon pilot city construction and high-speed rail construction on carbon emission reduction. (2) Research methods: Most of the existing literatures use spatial econometric model(Li and Li 2020), quantile model(Razzaq et al. 2023), threshold model(Wu et al. 2020), and policy evaluation model(Pan et al. 2020) to study the spatial spillover effect, heterogeneity, interval effect, and policy effect of carbon emissions.
2.2 Studies on the influences brought by UR
The existing research has carried out extensive and in-depth research on the economic, social, and natural environment impacts brought by the application of robots. The development of robots has added new impetus to economic growth. Industrial automation improves the resource allocation efficiency of innovation factors (Chu et al., 2022). Robots may improve productivity growth, but they may have a complex impact on the labor force. Robotic technology has brought positive economic impacts, such as improving productivity, quality, flexibility of multiple industries and breeding new business models, which are expected to have a huge pull on global economic growth(Hubinská 2020). UR could benefit the green economic growth and green technology innovation(Qian et al. 2022; Yin et al. 2022). However, some studies have shown that the development of robot technology will have a negative effect on the labor market. Acemoglu and Restrepo (2020) found that robots may reduce employment and wages by studying the impact of industrial robots on the U.S. labor market (Xie et al., 2022). And the use of industrial robots significantly widened the income gap of urban residents (Zhou et al., 2022). This is mainly reflected in the substitution effect of robots on the labor force in the area. However, Wang et al., (2022) thought robot application has a positive impact on manufacturing employment in the medium and long term.
In addition, some scholars also pay attention to the impact of robot applications on the natural environment, including pollutant emissions, carbon emissions, etc.(Sheng et al., 2022; jiang et al., 2022). Figliozzi and Jennings (2020)found that automatic delivery robots can significantly reduce energy consumption and carbon dioxide emissions in urban areas(Liu et al. 2022). The empirical results show that the use of robot technology significantly reduces the carbon intensity. However, Lange et al., (2020)studied the impact of UR on energy consumption, and found that UR did not save energy, but brought additional energy consumption. In addition, Z. Li & Wang (2022)found that the relationship between digital economy and carbon emissions is inverse-u.
Furthermore, existing studies have also discussed the regional heterogeneity and industry heterogeneity of the effect of UR on carbon emissions. In addition, Z. Li & Wang (2022) believe that there is regional heterogeneity in the impact of the digital economy on carbon emissions. The impact of the digital economy on carbon emissions faces significant resource endowment thresholds, city size thresholds, and innovation capability thresholds. Y. Li et al., (2022) concluded that the emission reduction effect of industrial robots in developed countries is better than that in developing countries. In addition, compared with capital-intensive industries, UR significantly reduces carbon intensity in labor-intensive and technology-intensive industries (Liu et al., 2022). E.-Z. Wang et al. (2022) and Lee et al. (2022) also got similar conclusions. The use of robots has not reached a consensus on the impact of environmental factors such as carbon emissions.
Regarding the specific mechanism of UR affecting carbon emissions, some studies have discussed it from the perspectives of industrial organization, technological innovation, green production efficiency, and energy intensity. Increasing the proportion of non-fossil energy use and optimizing industrial structure are effective mechanisms for digital technology innovation to reduce carbon emission intensity (Wang et al. 2021). Y. Li et al. (2022) found that the application of industrial robots improves productivity, optimizes factor structure, promotes production technology innovation, improves energy efficiency, and reduces carbon intensity. Furthermore, R&D investments curb emission levels and mediate between digitalization and CO2 emissions. Technological innovation has similar direct and moderating effects (Ma et al., 2022). Additionally, UR can promote the marketization of the market and product market. Specifically, the development of technologies such as big data, and the internet has promoted the cross-regional flow of production factors such as talents, capital, and technology, broken down administrative barriers and improved the marketization of production factors. Configurations have a positive impact on carbon reduction. Secondly, robots are widely used in various industries, which significantly promotes the innovation of products and services in various industries, improves the industry's production efficiency, eliminates many backward production capacities, and further upgrades the market structure, thereby reducing carbon emissions. However, the existing research ignores the mediating effect of the marketization.
In general, scholars have conducted a more in-depth discussion on the impact of the application of information technology on carbon emissions, providing theoretical support and experience for subsequent research, but there is still room for further expansion: Firstly, this paper further focuses on the carbon emission reduction effect of UR, and decomposes the carbon emission reduction effect into direct effect part and space spillover effect part with the help of SDM. Secondly, there is little research on the intermediary effect of the degree of marketization on the relationship between the UR and carbon emissions. This paper further establishes an analytical framework through theory and demonstration to explore the carbon emission reduction effect of UR and the intermediary role of marketization in it, which fills the gap of existing research and enriches the existing theoretical mechanisms. This is of great significance to how the government can achieve better carbon emission control through UR in the context of the digital economy. It has important implications for how governments can achieve better carbon emission control through UR in the context of the digital economy.