Configuring Nanostructured and High-Entropy Liquid Metal based Electrocatalysts for Nitrate Reduction to Ammonia

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Chinese explanation / 中文解读

中文解读待补充：本站会优先为光伏效率、钙钛矿太阳能电池、储能技术、太阳能热利用、BIPV、并网技术等高价值论文补充中文说明。

Original abstract

Ammonia, as both a hydrogen carrier and a vital chemical feedstock, represents a promising route for sustainable energy storage and decarbonisation. This thesis focuses on developing advanced catalysts for electrochemical ammonia synthesis via nitrate reduction, combining experimental innovation with computational modelling. The background and foundational principles of the work are introduced based on a comprehensive literature review. The materials, characterisation techniques, and experimental methods used throughout the research are also outlined. Three interconnected projects are presented. First, a liquid metal-based strategy is employed to fabricate bismuth (Bi) nano-electrocatalysts by electrochemically expelling Bi from a Ga–Bi alloy. Through controlled cooling and interfacial perturbations, Bi nanostructures—including nanosheets, nanotubes, and nanoparticles—are formed, with nanoparticles exhibiting the highest current density due to superior surface area and conductivity. These nanostructures are integrated into graphene oxide liquid crystals, creating a hierarchical conductor–catalyst framework. The electrodes, produced via 3D printing, enable precise architecture, enhancing mass transport, electron transfer, and catalyst stability. This system achieves a high ammonia production rate (400 nmol s⁻¹ cm⁻²), over 90% Faradaic efficiency, and current densities exceeding 350 mA cm⁻², surpassing industrial benchmarks. Next, the design of a high-entropy liquid metal alloy (HELMA) catalyst composed of Ga–Fe–Zn–Sn–Bi–Ni is explored. The catalyst is developed using ab initio molecular dynamics (AIMD) and Design of Experiments (DoE), which reduce the candidate pool to 28 targeted compositions. The liquid state facilitates atomic-level dispersion and dynamic surface reconfiguration. The optimised HELMA achieves a sevenfold improvement in ammonia production (320 nmol s⁻¹ cm⁻²) with 90% Faradaic efficiency over binary systems. This is followed by Density Functional Theory (DFT) calculations to investigate nitrate reduction (NO₃RR) mechanisms on HELMA, considering minimal endothermic energy and reaction energy. Zn initiates nitrate adsorption, Bi and Sn assist in deoxygenation, Ni promotes nitrogen hydrogenation, and Fe serves as a hydrogen reservoir. This hydrogen shuttling mechanism accelerates kinetics and prevents surface poisoning. Finally, the key outcomes are summarised, highlighting the untapped potential of liquid alloys and computational modelling in catalyst development, and outlining directions for future research.

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