Metallic ruthenium-based nanomaterials for electrocatalytic and photocatalytic hydrogen evolution
Developing a sustainable technology to produce hydrogen efficiently is crucial to realize the “hydrogen economy”, which may address the growing energy crisis and environmental pollution nowadays. Electrocatalytic and photocatalytic hydrogen evolution reactions have received great attention during the past few decades since they can realize hydrogen production from the water splitting reaction directly. Although platinum has been widely used as a catalyst for the electrocatalytic and photocatalytic hydrogen evolution reaction (HER), its high cost and limited supply make it imperative to develop alternative high-performance catalysts. Ruthenium (Ru), the cheapest one among platinum-group metals, has been emerging as a promising candidate recently. Until now, tremendous efforts have been devoted to improving the HER performance of metallic Ru-based catalysts through the rational design and synthesis of Ru nanomaterials, in which the size, morphology, chemical composition and crystal phase could be controlled. In this review, we summarized the synthesis of various metallic Ru-based nanomaterials as catalysts for the HER, including pure Ru nanocrystals, Ru-based bimetallic nanomaterials and Ru/non-metal nanocomposites. Then, we covered the recent progress in the utilization of metallic Ru-based nanomaterials as catalysts for the electro- and photo-catalytic HER; meanwhile, the mechanisms and fundamental science behind morphology/composition/crystal structure–performance relationships were discussed in detail. Finally, the challenges and outlook are provided for guiding the development of metallic Ru-based electro- and photo-catalysts for further fundamental research and practical applications in renewable energy-related areas.