Operando Laser Scattering: Probing the Evolution of Local pH Changes on Complex Electrode Architectures

Understanding proton dynamics in the diffusion layers generated by metal electrodeposition processes is of prime importance from the point of view of knowledge-driven technology development. Here we introduce a simple, non-invasive pH-sensing approach that is based on the Tyndall effect enhancement modulated by pH-controlled agglomeration events. We employ a laser beam laterally aligned to an electrode surface where cobalt deposition and hydrogen evolution take place simultaneously. This configuration allows the visualization of pH changes that result in precipitate formation and that extend to greater distances over patterned surfaces compared to flat ones, demonstrating a pH-guiding effect in superconformal metal deposition. The method provides real-time visualization of the pH dynamics with high lateral spatial resolution (50 μm) without physically or chemically influencing the investigated system. We suggest that applicability of the method can be extended to other processes where nanoaggregation/decomplexation inherently occur, as part of the investigated phenomena, at light-addressable interfaces