Modulating Carrier Kinetics in BiVO<sub>4</sub> Photoanodes through Molecular Co<sub>4</sub>O<sub>4</sub> Cubane Layers
Hang Chen, Jingguo Li, Lingshen Meng, Sanghyun Bae, Rolf Erni, Daniel F. Abbott, Shangkun Li, Carlos A. Triana, Victor Mougel, Greta R. Patzke
Abstract
Abstract Understanding the role and immobilization of molecular catalysts on photoelectrodes is essential to use their full potential for efficient solar fuel generation. Here, a Co II 4 O 4 cubane with proven catalytic performance and an active H 2 O─Co 2 (OR) 2 ─OH 2 edge‐site moiety is immobilized on BiVO 4 photoanodes through a versatile layer‐by‐layer assembly strategy. This delivers a photocurrent of 3.3 mA cm −2 at 1.23 V RHE and prolonged stability. Tuning the thickness of the Co 4 O 4 layer has remarkable effects on photocurrents, dynamic open circuit potentials, and charge carrier behavior. Comprehensive‐time and frequency‐dependent perturbation techniques are employed to investigate carrier kinetics in transient and pseudo‐steady‐state operando conditions. It is revealed that the Co 4 O 4 layer can prolong carrier lifetime, unblock kinetic limitations at the interface by suppressing recombination, and enhance charge transfer. Additionally, its flexible roles are identified as passivation/hole trapping/catalytic layer at respective lower/moderate/higher potentials. These competing functions are under dynamic equilibrium, which fundamentally defines the observed photocurrent trends.