Recent decoupling and coupling strategies for water splitting
Chenglin Zhong, Ming Song, Qingwen Zhou, Xuemei Li
Abstract
Abstract Using renewable energy to drive electrocatalytic or photocatalytic water splitting to produce H 2 is an effective and sustainable approach. In a traditional water-splitting electrolyzer, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) proceed simultaneously, which brings some challenges: a gas mixture of H 2 and O 2 , produces reactive oxygen species (ROS), using unstable renewable energy efficiently, the OER sluggish kinetics and system durability. Recently, to avoid these issues completely, much effort has been made to optimize conventional water electrolysis. Among them, a decoupling/coupling strategy has become a new type of water electrolysis technology. The decoupling strategy divides water splitting into two steps through the introduction of a redox mediator, which can completely separate the production of H 2 and O 2 in time. The coupling strategy refers to the formation of a redox coupling of the HER and other sacrificial additive oxidation reactions instead of the sluggish OER. This coupling strategy not only avoids the production of explosive hydrogen/oxygen mixtures and ROS, but reduces the voltage input, improves the energy conversion efficiency, and may produce valuable by-products. In this review, we will discuss these two water electrolysis strategies separately and provide comprehensive insight into and reference for the development of a novel water-splitting electrolyzer.