Maintaining an acceptable quality of life worldwide increasingly depends on the availability of clean and cost-effective energy, with power consumption expected to double by 2050. Therefore, the need for sustainable and affordable green energy has spurred innovative electrocatalysis research with the goal to develop materials and processes that are capable of producing environmentally friendly, carbon-neutral, clean, and green hydrogen fuel as an alternative to fossil fuel. In particular, heterostructured catalysts consisting of transition metal oxides and sulfides have emerged as a capable component of green energy technology. The dual functionality of these catalysts allows for water splitting, while the selectivity of the catalytic materials creates synergetic effects based on their electronic structure, surface composition, and electrochemical surface area. In this review, we examine the latest research and developments, synthesis methods, design strategies, reaction mechanisms, and performance outcomes for oxide/sulfide heterostructures. The review begins by introducing the current demand for hydrogen energy and electrocatalytic water-splitting and then describes the fundamental design principles for oxide/sulfide heterostructures and their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance. A large part of the review is then dedicated to a comprehensive discussion of the various transition metal oxide/sulfide heterostructures designed for the OER, the HER, and two-electrode electrolyzer applications. In addition, the use of in situ and operando techniques, which provide crucial information for the design of effective electrocatalysts, is described. We also discuss the present status of electrocatalysis technology, including the challenges it faces and its future prospects as a means to achieve carbon-neutral hydrogen production. Overall, this review delivers a summary of the latest developments in electrocatalysis based on oxide/sulfide heterostructures for use in green hydrogen production.
