| Summary: | Hydrogen energy is considered as a promising alternative to fossil fuels to address the growing energy shortage and environmental pollution. Among various hydrogen production technologies, electrocatalytic hydrogen evolution reaction (HER) is an environmentally friendly, low-cost, and raw material-abundant method to produce high-purity hydrogen. Currently, Pt remains the state-of-the-art solid-state electrocatalyst to improve the energy utilization efficiency of this important electrochemical process. However, the low reserves, high cost, and suboptimal performance of Pt metal limit its large-scale application. Therefore, the research work in this dissertation is dedicated to optimizing the performance of Pt-based electrocatalysts and developing low-cost and efficient non-Pt-based materials for HER. This dissertation first addresses the role of heterointerfaces in optimizing the catalytic efficiency of most advanced Pt-based HER nanomaterials. Heterointerface-rich Pt/Pt5P2 nanocages were constructed via through hard template method and phosphating strategy. The Pt with optimized electronic structures as the active site at the interface between Pt and Pt5P2 contributes to the enhanced HER performance. In the second part of the research work, to explore lower cost non-Pt-based catalysts for HER, interstitial boron-doped osmium (B-Os) aerogels were synthesized by a sol-gel process. It shows the small overpotentials of 12, 19, and 33 mV at a current density of 10 mA cm−2 in acidic, alkaline, and neutral electrolytes, respectively, as well as excellent stability. The dynamic changes of the Os electronic structure during the reaction and the reaction mechanisms of HER in different electrolytes are revealed by theoretical calculations and operando X-ray absorption spectroscopies. Finally, the sub-nanometric PdRhMoFeMn high-entropy metallene was developed to gain insights into the multi-site synergistic effects for further increasing their HER performance. It shows better activity and stability than commercial Pt/C at all pH levels. Simulations combined with in situ characterizations identified true active sites and revealed reaction mechanisms in different electrolytes for HER. It is believed that these findings from this thesis work contribute to a deeper understanding of the structure-activity relationship of catalysts and their reaction mechanisms for HER, which is valuable for the rational design of future high-efficiency nanomaterials for other energy conversion applications and beyond.
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