Manipulating Interfacial Charge Distribution for Water Reduction

Heterogeneous electrocatalysis often involves a complex interplay of the non-Faradaic process and the Faradaic process at the electrode/electrolyte interface, with the reaction kinetics typically exhibiting an exponential dependence on applied bias. However, the indivisible nature of bias hinders independent understanding and fine-tuning of each process. Synergistically regulating these two processes containing multiple reaction steps via one single, yet unified mediator remains a formidable challenge. Here, precise manipulation of the interfacial charge distribution is proposed to tackle this critical challenge. Through lattice strain engineering in NiCo2S4, the optimal amount matching between non-Faradaic charges and Faradaic charges is yielded during alkaline hydrogen evolution reaction (HER). As a result, the restriction of electrostatic potential on the water molecule reorganization process is alleviated, and the positive contribution of chemical potential to the water molecule dissociation process is concurrently strengthened. Furthermore, the moderate eg orbital filling is evidenced as the essential origin of a substantial increase in Faraday charges, the relationship between which is in the volcanic form. This interfacial charge redistribution enabled a synergistic optimization route of kinetic multisteps that can be further extended to other heterogeneous electrocatalytic reactions beyond HER.