Schreibersite-like engineered series of molybdenum phosphide-based compounds as a robust hydrogen production electrocatalyst

다국어 초록 (Multilingual Abstract)

To address the growing energy demand and imminent depletion of fossil fuels, it is urgent to develop clean and efficient new energy systems. Currently, new energy sources such as solar, tidal, and wind energy et al. have garnered widespread attention. However, these energy sources are heavily influenced by environmental and weather conditions, limiting their ability to provide stable energy for continuous industrialization. Given the potential utility of hydrogen energy, its higher calorific value and pollution-free properties during combustion can help convert the aforementioned electricity sources into easily stored and transported forms, addressing energy scarcity in various regions and potentially solving the problem of energy depletion fundamentally. Despite these advantages, the selection and application of catalytic materials for converting electrical energy into hydrogen through electrocatalytic water splitting reaction (WSR) remain challenging. Traditionally, platinum has been used as the cathode material in hydrogen evolution reactions (HER) due to its exceptional performance. However, platinum’s scarcity, high cost, and vulnerability to hydroxide poisoning under alkaline conditions have driven the search for alternative catalysts that can sustain large-scale industrial hydrogen production in alkaline media.
Molybdenum presents a potential substitute for platinum in catalysis due to its strong resistance to acids and alkalis, as well as its unique physicochemical properties that enable the formation of intermetallic compounds with non-metals like phosphorus, sulfur or carbon, etc. Meanwhile, the moderate atomic radius and electronegativity of molybdenum allow for precise tuning of the electronic structure through impurity substitution within specific crystal frameworks, thereby improving the catalytic activity, stability, and selectivity. These intrinsic advantages provide an effective strategy for enhancing the efficiency of Mo-based catalysts toward the HER. On this basis, molybdenum-based intermetallic compounds (IMCs) adopting the Schreibersite-type structure possess inherent advantages as electrocatalysts for HER. The metal-rich nature of Schreibersite-type Mo-based IMCs offers abundant sites for elemental substitution, which facilitates the rational design of novel catalysts with optimized electronic configurations and surface properties. Such tunability enriches the diversity of active sites while simultaneously promoting favorable adsorption–desorption energetics, ultimately leading to superior catalytic performance and stability.
In this dissertation, Schreibersite-type Mo3P was selected as the parent material to systematically design and investigate novel HER catalysts with high activity and durability. In accordance with the Sabatier principle, Mo-based catalysts usually exhibit relatively low catalytic activity toward the HER due to the strong binding interaction between Mo and hydrogen atoms within their lattice. To overcome this limitation, we propose a new strategy by incorporating Ru into Mo3P to modulate its electronic structure, yielding a novel water-splitting cathode material, Mo2RuP. Notably, Mo2RuP exhibits remarkable catalytic activity for alkaline HER, achieving ultralow overpotentials of 29 mV at current densities of 10 mA cm-2. This section primarily emphasizes the rational selection and design of the catalyst. To further extend the applicability of this system toward industrial-scale hydrogen production, a novel Mo2Fe0.8Ru0.2P catalyst with a structural transition from I̅42m to I̅4 symmetry was synthesized to explore the synergistic electronic modulation effects of multimetallic regulation on HER. This design successfully balances catalytic cost with performance, maintaining stable hydrogen evolution for over 1000 hours at ampere-level current densities. Furthermore, to address the industrial challenge of hydroxide over-adsorption–induced catalyst poisoning during alkaline HER, we introduced a Lewis acid site embedding strategy into Schreibersite-type IMCs, leading to the development of a highly active and durable catalyst, Mo1.6Ni0.4RuP. It is demonstrated that embedding Lewis acid sites effectively mitigates OH- poisoning under strong alkaline conditions, enabling continuous hydrogen production for over 3000 hours at stepped current densities. Remarkably, under industrial conditions (30 wt% KOH, 70 °C), Mo1.6Ni0.4RuP requires only 129 mV of overpotential to deliver 1 A cm-2, highlighting its substantial potential for practical large-scale hydrogen generation. Overall, this dissertation presents a comprehensive strategy to practical implementation for the development of highly efficient HER electrocatalysts suitable for industrial-scale applications.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1 Introductory Remarks . 1
• 1.2 Hydrogen Evolution Reaction. 5
• 1.3 Schreibersite-type Intermetallic Compounds 8
• 1.4 Structures and Properties of Mo-Based Electrocatalysts 11
• 1.5 Contents of This Dissertation 17
• Chapter 2. Enhanced Alkaline Hydrogen Evolution Performance through RuIncorporated Electronic Structure Modification: Transitioning from Mo3P to Mo2RuP 21
• 2.1 Introduction. 21
• 2.2 Experimental. 25
• 2.3 Results and Discussion . 29
• 2.4 Summary. 50
• Chapter 3. Multi-Metal Synergistic Integration for Electronic Structure Regulation in Schreibersite-Type Mo2Fe0.8Ru0.2P Electrocatalysts: Exceptional Enhancement of Activity and Stability for Alkaline Hydrogen Evolution Reaction 51
• 3.1 Introduction. 51
• 3.2 Experimental. 55
• 3.3 Results and Discussion . 59
• 3.4 Summary. 98
• Chapter 4. Lewis Acid SiteEnhanced Mo1.6Ni0.4RuP as Schreibersite-Type Intermetallic Electrocatalysts for High-Performance Alkaline Hydrogen Evolution Reaction 99
• 4.1 Introduction. 99
• 4.2 Experimental. 103
• 4.3 Results and Discussion . 108
• 4.4 Summary. 140
• Chapter 5. Conclusing Remarks. 141
• References. 143
• Korean Abstract. 159