Green Innovation, Export Synergy, and Total Factor Productivity: Evidence from China's Marine Enterprises

In the context of China's "dual carbon" goals and rising green trade barriers, green transformation is key to improving total factor productivity (TFP) and competitiveness in marine industries. This study uses panel data of Chinese listed marine enterprises (2014-2023) and a multidimensional fixed-effects model to examine how green innovation, export, and R&D investment jointly affect TFP. Results show that (1) green innovation has an inverted "S"-shaped nonlinear effect on TFP, with marginal returns rising, then accelerating, and finally declining; (2) positive synergies exist between green innovation and both exports and R&D, while the export-R&D interaction negatively affects TFP, indicating coordination challenges.; and (3) ownership heterogeneity matters, as state-owned enterprises benefit from stronger institutional support, mitigating negative effects, while private firms are more vulnerable due to weaker green technology mechanisms. This study emphasizes green innovation as a driver for sustainable productivity growth in marine enterprises and suggests policies that improve institutional frameworks, incentives, and resource allocation to support high-quality green innovation.