Lijing Ma

The poor interfacial stability between Pt coatings and Ti substrates, mainly caused by the unavoidable native TiOx layer, remains a challenge for stable porous transport layers in PEMWEs. Herein, a Ti interlayer-induced interface reconstruction strategy is proposed to regulate the Pt/TiOx interface and enhance the stability of ultrathin Pt coatings. A 4 nm Ti interlayer was introduced between Pt and TiOx to construct a Pt/Ti/TiOx heterostructure, increasing the pull-off adhesion strength from 5.29 to 9.26 MPa. Electrochemical measurements under simulated anodic conditions demonstrated that the Ti interlayer effectively suppressed coating degradation and preserved interfacial electrical transport. After 48 h polarization, the Pt/Ti/TiOx maintained an interfacial contact resistance of 9.36 mΩ·cm2, approximately 17-fold lower than that of Pt/TiOx. DFT calculations revealed favorable Pt-Ti and Ti-TiO2 interfacial interactions with work of adhesion values of 6.27 and 4.11 J·m-2, whereas the direct Pt-TiO2 interface exhibited a negative value of -3.38 J·m-2, confirming its weak interfacial bonding. Furthermore, the Ti interlayer-engineered coating enabled a PEMWE to achieve a 20 mV lower voltage and stable operation for 80 h with a degradation rate of 113.8 μV·h-1 at 2.0 A·cm-2. This work provides an effective strategy for developing durable coated porous transport layers through interface structure regulation.

Pt coating has been considered a promising strategy to protect the Ti porous transport layer substrate in a proton exchange membrane electrolyzer from corrosion. However, despite significant advancements in understanding the composition, process, and structure of Pt coatings, the underlying causes of coating failure remains unclear. Here, we systematically investigate the failure processes of magnetron-sputtered Pt coatings on Ti substrates through ex situ electrochemical tests that simulate anode operational conditions. Three different thicknesses of thin Pt coatings were prepared on Ti substrates by controlling the sputtering time. As the polarization time increases, the coating gradually fails and the failure time is directly related to the thickness of the coating. Experimental results indicate that Pt coatings approximately 6 nm thick begin to fail after 24 h of operation, with interfacial contact resistance reaching 220.61 mΩ cm² after 48 h, which is significantly higher than that of bare Ti at 28.39 mΩ cm². Further analysis reveals the role of oxygen in the coating failure: oxygen atoms generated from electrolyzed water first diffuse from the coating surface into the interface between the coating and the substrate, and eventually, the gradual buildup of oxygen pressure results in the detachment of the coating. A deeper understanding of the failure mechanism of coatings can enhance the efficiency and durability of water electrolysis for hydrogen production by guiding the design of more durable coatings.

Gas bubble formation and detachment during water electrolysis critically affect electrochemical performance, particularly at high current densities. Bubble dynamics at the electrode interface are strongly influenced by both current density and electrode geometry. These dynamics govern coalescence behavior and detachment efficiency, thereby influencing overall electrolytic efficiency. A deeper understanding of these mechanisms can enable the rational design of electrodes for improved bubble management and system performance. In this work, the evolution of oxygen bubbles on horizontal wire electrodes was investigated during acid electrolysis using synchronized high-speed imaging and electrochemical measurements. Bubble size distributions were quantified across current densities (0.05-1.0 A·cm^-2) and electrode diameters (100-500 μm). Coalescence dynamics were analyzed through energy and force balance considerations, while electrode performance was evaluated via polarization curves. The findings show that increasing the current density or electrode diameter leads to the formation of larger and more polydisperse bubbles. Coalescence events were predominantly concentrated at the apex of the electrode. Three distinct coalescence-driven dynamics emerged: the coalescence-induced movement mode, the coalescence-induced detachment mode, and the coalescence-induced jumping mode, with each mode governed by bubble radius ratios. Smaller diameter electrodes exhibited higher overpotentials at elevated current densities, underscoring their performance limitations. The results establish correlations between bubble behavior and electrode dimensions, offering valuable insights for designing optimized electrodes that enhance electrolysis efficiency via bubble control.

Regarding the rheological properties of fluids, certain nanoparticles can markedly modify the rheological behavior of low surface tension solutions by interacting with surfactant molecules. In this work, a low surface tension fluid with cetyltrimethylammonium chloride was prepared, and the silica nanoparticles were uniformly dispersed into it by ultrasonic dispersion. By adjusting the size, shape, and concentration of nanoparticles, the fluid behavior can be changed from Newtonian to non-Newtonian with finely tuned viscosity and characterized by a shear-thinning rheological behavior. In addition, this work explored how variations in environmental temperature and solution pH affect the rheological responses of the low surface tension suspension system. The experimental findings revealed that increasing the temperature substantially decreases the system’s viscosity and induces a shear-thickening behavior. It is particularly significant that, under extreme pH conditions (either strongly acidic or alkaline), the viscosity of the nanoparticle suspensions was markedly enhanced at a particle concentration of 10 000 ppm. This interesting result coincided with a notable reduction in the zeta potential and an increase in the average particle size, suggesting an intensified aggregation of particles within the suspension system. A mechanism detailing the interaction between silica nanoparticles and surfactant micelles was proposed. This work indicates that the incorporation of nanoparticles into surfactant solutions offers a powerful approach to modulating fluid rheology across various conditions.