A Modular Design Concept for Photoelectrochemical Devices Toward Efficient Cathodic Metal Protection

Abstract Photocathodic protection (PCP) is a metal corrosion prevention technology that emerged in the past two decades with the merits of zero carbon emission, environmental benignancy, and low cost. In essence, a PCP system is like any photoelectrochemical (PEC) systems that convert solar energy to electrical energy and then to chemical energy, and thus the overall energy conversion efficiency of a PCP system is determined by three key steps, that is, light absorption, charge separation, and surface redox reaction. Despite the intensive studies devoted to improving charge separation via heterostructuring, there are barely any reports on the simultaneous optimization of PCP systems from all aspects, especially surface reactivity. Herein, we propose a “decentralization” strategy to build PCP systems, that is, multiple functional modules that act on the individual key steps and are assembled to a unified device for high‐efficiency metal protection. In this article, we outline the potential of PCP technology for protecting marine metal infrastructures, highlighting the importance of the synergy between anodic reaction and cathodic metal protection for the overall energy efficiency, summarize our latest research progress on a proof‐of‐concept PCP device with modular design, and discuss future upgrade options to meet the needs of diverse application scenarios.