5.1. Mechanism Analysis
In order to explore how the digital economy enhances the carbon emission reduction performance of energy-intensive manufacturing enterprises, this study conducted a regression test of Hypotheses 2–4 using the mediation effect model, and the results are shown in
Table 4.
Columns (1)–(2) of
Table 4 show partial mediating effects of digital economy on carbon emission reduction performance (
CERP) through total factor productivity (TFP). Specifically, TFP has a positive and statistically significant coefficient of 0.045 (
p < 0.01) on
CERP, while the coefficient of digital economy on TFP reaches 0.138 (
p < 0.01). These two results confirm Hypothesis 2: the digital economy enhances carbon reduction performance by systematically improving production efficiency.
These findings are also aligned with the results from Wang et al. [
77], that the digital economy drives innovation enhancement performance through TFP. While both studies identify total factor productivity (TFP) as a critical mediating pathway linking digital economy to enterprises performance, they diverge in the key reason. This paper illuminates the digital economy-driven environmental performance through TFP, whereas Wang et al. [
77] points to innovation-driven performance. Crucially, these findings collectively underscore the mediator of TFP under digital transformation, which simultaneously stimulates green transition and technological advancement.
Columns (3)–(4) of
Table 4 reveal a positive and statistically significant coefficient of R&D investment (β = 1.721,
p < 0.01) on carbon emission reduction performance (
CERP), demonstrating that targeted environmental R&D expenditures in energy-intensive manufacturing enterprises effectively drives decarbonization. This linear relationship contrasts with Li et al.’s [
59] inverted U-shaped relationship derived from a sample of all A-shares, highlighting industry specificity: R&D in carbon-intensive industries prioritizes emission reduction technologies, generating direct abatement returns that are absent in diversified samples. Furthermore, the regression coefficient of digital economy on R&D investment is also significantly positive. This indicates that the digital economy improves the technological level of enterprises and reduces energy waste by increasing R&D investment, thereby improving the carbon emission reduction performance, which verifies Hypothesis 3.
Whereas Ma et al. [
78] identified a moderating effect of R&D investment in the digital economy-carbon mitigation nexus at the provincial level, our enterprise-level analysis of energy-intensive manufacturers reveals a distinct mediating mechanism. This divergence stems from the industrial imperative that energy-intensive enterprises, confronted with stringent decarbonization requirements, strategically channel digital-driven R&D investments (β = 1.721) into evolving emissions mitigation technologies [
68], translating innovation inputs into direct carbon performance improvements rather than merely moderating existing relationships.
Column (6) reveals a statistically significant positive coefficient of technological innovation (p < 0.01) on carbon emission reduction performance (CERP). Furthermore, Column (5) demonstrates that the digital economy (DE) significantly enhances technological innovation (β = 8.681, p < 0.05). This dual-channel evidence confirms Hypothesis 4: digital transformation drives carbon mitigation by fostering innovation of resource and energy utilization efficiency, thereby systematically reducing carbon emissions.
While Li and Zhou [
12] identified the carbon mitigation effects of the digital economy through technological innovation at the city level, this enterprise-level analysis specifically validates the tripartite relationship within energy-intensive enterprise. This micro foundational perspective is theoretically grounded the primacy of enterprises as innovation agents [
69], which is further reinforced by China’s dual-carbon policy. Meanwhile, technological innovation of enterprises is prioritized to reduce carbon emissions [
46]. Digital transformation empowers enterprises to radically enhance information transmission efficiency (β = 8.681 innovation boost), which accelerates breakthroughs in low-carbon technologies and clean energy systems [
21]. This innovation catalysis effect provides empirical evidence for synchronizing digital progress with technological upgrading to achieve climate goals.
To further investigate the interaction of multiple mediating effects, this study incorporates the interaction term between total factor productivity (TFP) and R&D investment into the analysis as a mediating mechanism. Specifically, building upon the previously described mechanism, the term TFP * IIN is added as a mediator to demonstrate the partial mediating effects of the digital economy on carbon emission reduction performance (
CERP) through both TFP and R&D investment. The results are shown in
Table 5.
Columns (7)–(8) of
Table 5 confirm a positive and statistically significant coefficient of the interaction term of TFP and R&D investment (β = 0.363,
p < 0.01) on carbon emission reduction performance (
CERP), demonstrating that the improvement of total factor productivity and targeted environmental R&D expenditures in energy-intensive manufacturing enterprises significantly drives carbon emissions reduction.
To ensure the robustness of the estimated mediating effects of total factor productivity (TFP), R&D investment, and technological innovation, this study conducts a bootstrap test with 1000 replications at the 95% confidence level. The results are presented in
Table 6.
The bootstrap test validates the hypothesized multiple mediation model. It reveals that the influence of the digital economy on CERP is partially transmitted through the individual channels of TFP R&D investment and technology innovation with the strongest effect occurring through the interaction and mutual reinforcement of these three factors.
Specifically, the bootstrap results confirm the significant mediating roles of TFP IIN and TEI individually. The indirect effects are positive and statistically significant (β = 0.059, p < 0.01 for TFP; β = 0.078, p < 0.01 for IIN;β = 0.022, p < 0.01 for TEI), as their 95% confidence intervals do not contain zero. These findings support Hypothesis 2 to Hypothesis 4, indicating partial mediation.
Crucially, the interaction term TFP*IIN demonstrates a highly significant and substantial indirect effect (β = 0.104, p < 0.01; 95% CI [0.078, 0.129]). This finding strongly suggests that the digital economy enhances CERP not only through TFP and IIN individually but, more importantly, through their synergistic interaction. The effect size of this interactive pathway is the largest among all mediators, underscoring its importance.
5.2. Heterogeneity Analysis
Industrial characteristics and geographic disparities significantly moderate the carbon mitigation performance of energy-intensive manufacturing enterprises in the context of the digital economy. This study employs a meticulous classification of enterprises according to industry categories and geographic disparities, followed by a comparative analysis of the carbon emission reduction performance of different enterprise groups.
5.2.1. Sub-Industry Analysis
To dissect the heterogeneous impact of the digital economy (
DE) on Carbon Emission Reduction Performance (
CERP), this study conducts a sub-industry analysis based on the official classification of the six major energy-intensive industries in China [
25]. The regression results, systematically presented in
Table 7, reveal significant disparities in the digital economic influence across these sectors.
The empirical findings indicate that the effectiveness of the digital economy in promoting CERP is not uniform across industries. Specifically, the digital economy coefficients for the petroleum processing, coking, and nuclear fuel processing industry (C25), as well as the production and supply of electric and heat power (D44), are statistically insignificant. This lack of significant effect can be explained from two primary perspectives. First, from a resource-based view, the prohibitively high capital investment required for digital equipment upgrades in these capital-intensive sectors creates a substantial barrier, discouraging enterprises from undertaking deep digital transformation. Second, from an organizational inertia perspective, the complex and entrenched production processes in these industries may generate greater resistance to change, resulting in slower and less effective adoption of digital technologies.
In stark contrast, the digital economy exhibits statistically significant and substantially larger positive coefficients in the Chemical Raw Materials and Chemical Products Manufacturing (C26), Smelting and Rolling of Non-Ferrous Metals (C32), and D44 industries compared to the baseline regression. The particularly strong effect observed in C32 (coefficient = 0.360) indicates a more pronounced promotional impact. This heterogeneity can be explained through the technology-organization-environment framework and innovation diffusion theory. The relative affordability and compatibility of digital solutions in these sectors likely lower the adoption threshold, thereby increasing enterprises’ willingness to implement technological improvements. The digital economy acts as a catalyst by enhancing energy efficiency through smart process control and optimizing internal production logistics, ultimately leading to more substantial carbon reduction gains.
A noteworthy example is the ferrous metal smelting and rolling processing industry (C31), where the DE coefficient is positive and consistent with the baseline results, although it is not the largest. This suggests that despite facing high equipment replacement costs similar to those in C25, regulatory pressure and the strategic imperative for sustainability may motivate firms in this highly polluting sector to continue incremental technological optimization efforts. This observation aligns with institutional theory, which posits that firms undertake environmental innovations, including digital ones, to gain legitimacy and comply with stringent regulatory requirements, even when the direct economic returns are not immediately evident.
In conclusion, this sub-industry analysis demonstrates that disparities in digital technology adoption and assimilation capabilities among the six energy-intensive industries are key determinants of their varying carbon emission reduction performances. The findings move beyond a monolithic view of the digital economy’s impact, highlighting how industry-specific structural factors, resource endowments, and institutional pressures interact to shape the pathways and effectiveness of digital decarbonization.
5.2.2. Sub-Regional Analysis
Due to regional differences in population, economic development, and other factors across China’s eastern, central, and western regions, enterprises in different areas have different sizes, development trajectories, business types, and levels of digital transformation [
79].
Table 8 presents empirical results on the impact of the digital economy on the carbon emission reduction performance of energy-intensive manufacturing enterprises in these regions.
The estimated coefficient for DE is 0.117 (p < 0.01) in the eastern region, compared to 0.108 (p < 0.01) in the central-western region. Crucially, the test confirms that the difference between these coefficients is statistically significant at the 1% level. This validates that the regional disparity is not due to random chance, allowing for a meaningful theoretical interpretation of why the effect is more pronounced in the central and western regions.
This finding can be explained by combining regional development and technology diffusion theories. The concepts of the “Latecomer Advantage” and technology leapfrogging are particularly relevant: firms in the central and western regions are not burdened by legacy systems or sunk costs associated with older, carbon-intensive technologies that are more common in the industrialized eastern region. This freedom enables them to adopt the latest and most efficient digital and green technologies directly. Furthermore, from a knowledge spillover perspective, these regions can readily absorb and implement advanced production and management knowledge developed and refined in the eastern region, thereby accelerating their CERP improvements and narrowing the regional development gap.
Institutional Pressure and Legitimacy-Driven Change: The findings align with institutional theory. Enterprises in the central and western regions, which often depend on resource-intensive and heavily polluting industries, face increasing regulatory and social pressures to enhance their environmental legitimacy. The digital economy offers a viable and measurable pathway to achieve this compliance. Consequently, adopting digital technologies in these regions is not merely an efficiency-driven activity but also a strategic response to institutional demands, thereby amplifying its perceived impact on carbon reduction.
Resource Reallocation and the “Sailing Ship Effect” in Inland Development: The stronger effect observed inland reflects a strategic geographic shift in digital infrastructure and policy support, as noted in prior research [
3]. This shift fosters a regional innovation system that increasingly facilitates digital transformation. For local firms, this external “push” alleviates traditional resource constraints. The significant coefficient indicates that, for these firms, marginal investments in digitalization yield higher returns in
CERP by effectively addressing fundamental inefficiencies in their production processes. This phenomenon resembles the “sailing ship effect,” where late-stage entrants leverage new technologies to overcome core disadvantages.
In conclusion, the regional heterogeneity analysis reveals that the digital economy acts as a powerful equalizing force in China’s green development landscape. While it benefits all regions, its impact is most pronounced in the less developed central and western areas due to a combination of latecomer advantages, stronger institutional pressures for environmental legitimacy, and targeted regional digitalization policies. This underscores the importance of considering regional contextual factors when designing and implementing national digital decarbonization strategies.
5.2.3. Sub-Enterprise Size Analysis
To further investigate the differential impact of the digital economy (
DE) on Carbon Emission Reduction Performance (
CERP) across firms with varying resource endowments and capacities, this study stratifies the sample into small, medium, and large enterprises according to the classification standards of the National Bureau of Statistics [
80]. The regression results, presented in
Table 9, reveal a striking and non-monotonic relationship between firm size and the efficacy of the digital economy in promoting carbon reduction.
The heterogeneity analysis reveals a nonlinear relationship between the digital economy and carbon emission reduction performance (CERP). The results indicate that the digital economy’s positive effect on CERP is strongest and most significant for small enterprises (β = 0.224, p < 0.01), significant but weaker for large enterprises (β = 0.108, p < 0.05), and statistically insignificant for medium-sized enterprises (β = 0.019).
This divergence can be theoretically explained by differences in firms’ resource endowments and organizational characteristics. Small enterprises leverage their organizational agility to rapidly adopt digital technologies, enabling “technological leapfrogging” and yielding higher marginal returns in emission reduction. Medium-sized enterprises may encounter a trap, where their resources are insufficient for comprehensive digital transformation, yet they have lost the flexibility characteristic of smaller firms [
81]. Although large enterprises possess substantial resources, their structural inertia leads to a more incremental approach to digital transformation, thereby limiting the marginal effects.
These findings highlight the differential impact of the digital economy on enabling carbon reduction across firms of varying sizes, offering a theoretical foundation for developing tailored, size-specific policy measures.