Does the coupling of digital and green technology innovation matter for carbon emissions?

The global situation of carbon reduction is very severe, and the coupling of digital and green technology innovation is one of the most significant approaches to promoting regional low-carbon transformation. A coupling evaluation model is employed to assess the coupling index between digital technology innovation and green technology innovation in China's 30 provinces from 2011 to 2021. The STIRPAT model is used to examine the impact of the increasing coupling index on carbon emissions, as well as its spatial effects, and heterogeneity. The results reveal that: (1) Recently, China has made remarkable strides in digital and green technology innovation. Nonetheless, there has been a decline trend in the average coupling level between these two, with slightly higher coupling levels observed in the central and western regions compared to the eastern coastal areas. (2) Green technology innovation has a significantl positive effect on carbon emissions, while digital innovation technology has an unstable negative impact on carbon emissions. (3) The increasing coupling index of green and digital technology innovation can substantially cut carbon emissions. The effects of different technological innovation levels and their coupling degree on carbon emissions show regional heterogeneity. (4) Coupling index and carbon emissions exhibit a notable spatial autocorrelation. Enhancing the local coupling index will result in a regional spillover effect on the carbon emission levels of surrounding regions. This study puts forward suggestions for increasing capital investment in digital and green technology innovation and optimizing the policy support environment for their integration and synergy, so as to lay the groundwork for advancing the national low-carbon transformation and hastening the attainment of "dual-carbon" goals.