Photocatalytic Silicon Nanodisks Driven by Nonradiating Anapole Modes

Precisely nanofabricated dielectric platforms offer well-defined light–matter interactions that can be tailored to increase light absorption, with an emerging opportunity in photocatalytic studies. The anapole mode, a state with enhanced absorption and suppressed far-field scattering, is a promising optical state that can be leveraged for photocatalysis. Here, we demonstrate that the anapole mode in silicon nanodisk arrays directly influences photocatalytic activity. Finite-difference time-domain (FDTD) simulations were leveraged to design a silicon nanodisk array (Si ND) that exhibits an anapole resonance in the visible region. Large-area (>1 cm 2 ) Si ND arrays were fabricated by leveraging colloidal nanosphere lithography at the air/water interface. The fabricated Si ND arrays were combined with a platinum co-catalyst, and the impact of the anapole mode was studied through the oxidation of carbon monoxide as a model reaction. We report increased light-assisted rates when exciting the anapole mode compared to dark conditions. Moreover, wavelength-dependent studies were performed to further probe the impact of the anapole mode on surface photochemistry. Through FDTD simulations, we show that the anapole mode results in an 18-fold enhancement of the integrated photocurrent when on-resonance. Our results highlight the importance of balancing engineered optical properties and inherent semiconductor physics, and surface chemistry that governs reactivity and surface photochemistry.