Advances in Interfacial Engineering and Their Role in Heterostructure Formation for HER Applications in Wider pH

With 65% rise in the global demand, green hydrogen (H₂) as a clean energy carrier with high gravimetric energy density, has emerged as a premier candidate in the past decade. The production of sustainable and clean hydrogen through water electrolysis tends to majorly rely on electrocatalysts with the scope of achieving exceptional activity with low cost and excellent durability. The extensive use of high cost noble metal HER electrocatalysts in the industry diverts the attention to recent studies proposing that a proper design of non-noble metal heterostructure could show comparable electrocatalytic performance. Construction of interfaces appears as a solution to simultaneously address multiple challenges and, at the same time, take advantage of each component in constructing rich interfaces that could synergistically enhance the HER activity in acidic, alkaline, and neutral environments. This review describes the different forms of interfaces arising from different heterostructures at the structural and atomic level, underlining and correlating the principle mechanisms responsible for the performance enhancement in the HER electrocatalysts. The first part of the review recognizes the heterostructures at the micro/nano scale and at the scale focusing mainly of 2D materials. Further, the interfaces at the atomic level especially composed of chalcogenides, carbides, phosphides, and nitrides are analyzed comprehensively based on their electrochemical performance. Finally, the interfacial mechanisms arsing as a consequence of the heterostructure formation are briefly described and correlated to provide a better understanding in the future design of HER electrocatalysts.