Substrate-activated autocatalytic in-situ fabrication of nano-structured titanium oxide/carbon hybrid gradient modified layers on titanium bipolar plates for proton exchange membrane fuel cells

Metallic bipolar plates (BPs) are critical components of proton exchange membrane fuel cells (PEMFCs), yet poor corrosion resistance and high interfacial contact resistance (ICR) hinder their commercialization. Conventional ex-situ coating methodologies suffer from instability, non-uniform coverage, complex preparation process and high cost. To overcome these challenges, a novel and facile substrate-activated autocatalytic in-situ growth strategy combining chemical etching, electroless plating, and heat treatment is proposed to fabricate a nano-structured titanium oxide/carbon hybrid gradient modified layer (NTOC) on Ti substrates. The NTOC with thickness 200 nm features a tripartite architecture comprising an amorphous carbon outer layer, an intermediate zone dominated by oxygen-vacancy-containing titanium oxide, and a Ti-O-C transition layer. This unique architecture enables atomic-level carbon/titanium oxide integration and strong interfacial metallurgical bonds, which shows high corrosion resistance (< 1 µA cm − 2 ) and quite low ICR (1.05 mΩ cm 2 ), far surpassing the Department of Energy 2025 targets for BPs. Moreover, NTOC modified Ti BPs in PEMFCs yield a peak power density up to 1200.6 mW cm − 2 , exceeding that of untreated Ti BPs by almost twofold (664.19 mW cm − 2 ) and the current study (1160.1 mW cm − 2 ). Therefore, this study offers a transformative solution for enhancing performance of BPs, accelerating the commercialization of PEMFCs.