Interface engineering via molecules/ions/groups for electrocatalytic water splitting

The electrochemical water splitting to produce hydrogen converts electric energy into clean hydrogen energy, which is a groundbreaking concept of energy optimization. To achieve high efficiency, numerous strategies have been developed to enhance the performance of electrocatalysts. Among these, interface engineering with molecules/ions/groups, serves as a versatile approach for optimizing the performance of electrocatalysts in water splitting. On the basis of numerous achievements in high-performance electrocatalysts engineered through molecules/ions/groups at interface, a comprehensive understanding of these advancements is crucial for guiding future progress. Herein, after providing a concise overview of the background, the interface engineering via molecules/ions/groups for electrocatalytic water splitting is demonstrated from three perspectives. Firstly, the engineering of electronic state of electrocatalysts by molecules/ions/groups at interface to reduce the Gibbs free energy of the corresponding reactions. Secondly, the modification of local microenvironment surrounding electrocatalysts via molecules/ions/groups at interface to enhance the transfer of reactants and products. Thirdly, the protection of electrocatalysts with molecule/ion/group fences improves their durability, including protecting active sites from leaching and defending them against harmful species. The fundamental principles of these three aspects are outlined for each, along with pertinent comments. Finally, several research directions and challenges are proposed.