Transparent Au Nanopatterned Catalysts: A Strategy for Improved Light Absorption in Photoelectrochemical CO₂-to-Syngas Conversion

Photoelectrochemical (PEC) catalysis is a promising approach for converting solar energy into chemical fuels, but a fundamental challenge lies in balancing catalytic activity with efficient light absorption. Catalyst surface coverage on light-harvesting supports often leads to a trade-off that limits overall performance. To address this issue, we developed a high-aspect-ratio (>20) gold (Au) nanopatterned catalyst designed to maximize both light harvesting and catalytic efficiency. Compared to conventional film-type catalysts, the nanopatterned catalyst exhibits a 3.6-fold increase in electrochemical surface area and a 2.5-fold improvement in transparency, enabling greater light transmission to the photoabsorber. In the reduction of CO₂ to syngas (H₂:CO = 1:1), the nanopatterned catalyst achieves a 240 mV lower onset potential and a 6.2-fold increase in syngas formation rates compared to its film counterpart. These enhancements are attributed to the unique structure of the nanopatterns, which feature smaller grain sizes, higher surface area, and improved light transmittance. This versatile nanopatterning approach is not limited to Au but can be extended to other catalytic materials, including metals, metal oxides, and transition metal dichalcogenides. The design offers a scalable solution to improve PEC performance for a wide range of applications, from CO₂ reduction to other catalytic processes. By overcoming the trade-offs associated with traditional catalysts, this study provides a pathway toward more efficient and sustainable PEC systems.