Photo-induced self-catalysis of nano-Bi₂MoO₆ for solar energy harvesting and charge storage

Efficient, sustainable, and integrated energy systems require the development of novel multifunctional materials to simultaneously achieve solar energy harvesting and charge storage. Bi-based oxysalt aurivillius phase materials are potential candidates due to their typical photovoltaic effect and their pseudo-capacitance charge storage behavior. Herein, we synthesized nano-Bi₂MoO₆ as a material for both solar energy harvesting and charge storage due to its suitable band gap for absorption of visible light and its well-defined faradaic redox reaction from Bi metal to Bi³⁺. The irradiation of visible light significantly affected the electrochemical processes and the dynamics of the Bi₂MoO₆ electrode. The photo-induced self-catalytic redox mechanism was carefully explored by adding sacrificial agents in photocatalysis reaction. In accordance with the rule of energy matching, the photo-generated holes oxidized the Bi metal to Bi³⁺, and the corresponding peak current increased by 79.5% at a scanning rate of 50 mV s^-1. More importantly, the peak current retention rate remained higher than 92.5% during the entire 200 cycles. The photo-generated electrons facilitated a decrease of 184 mV in the overpotential of the reduction process. Furthermore, the irradiation of visible light also accelerated the ionic diffusion of the electrolyte. These investigations provide a unique perspective for the design and development of new multifunctional materials to synergistically realize solar energy harvesting and charge storage.