NSF-DFG Echem: Electrochemically enhanced low-temperature catalytic ammonia synthesis

随着国家和世界走向无碳能源经济，氨可能会作为氢的载体发挥重要作用。今天，基本上所有的氨都是在高压哈伯-博世工厂大规模生产的。人们对利用可再生资源进行规模较小、地理分布较广的氨合成的需求越来越大。然而，由于固有的热力学和动力学限制，典型的基于催化剂的热过程(如Haber-Bosch)在较小规模下并不经济。本项目寻求使用显著降低活化势垒的电化学相互作用来实现分布式氨合成。这项研究依赖于合作伙伴在材料合成、表征和工艺演示(KIT)以及电化学、电荷缺陷传输和催化(CSM)的物理模拟方面的综合、互补和独特的专业知识。这一联合项目解决了将氨生产作为能源载体和商品化学品向环境友好型生产过渡的重大科学挑战。该项目的目标是开发和展示能够实现低温低压氨合成的电化学增强技术。纳米Ru分散在质子导电的BCZY载体(BaCe1-x-yZrxYyO3-δ)上。用电场直接极化催化剂结构，降低了氮气活化的动力学限制势垒。尽管拟议的研究具有科学基础，但它在成本效益高的分布式氨生产方面具有极好的技术潜力。这项研究的重点是假设、建模和验证所提出的化学行为。电场有望通过两种协同机制降低限速的氮气解离势垒：1.电场影响质子传导的BCZY载体，使氢气解离形成质子，从而激活气相氮气，直接在BCZY载体上形成所需的表面吸附，如NH。分散的纳米Ru在0.1~1.0V/A范围内的电场也降低了氮活化势垒。氮活化能垒Ru在30-42kJ·mol-1之间变化。基于我们验证的Ba促进的Ru/YSZ的反应机理，模拟表明，将氮的离解能降低10kJ mol-1将使氨的生成速率增加一个数量级。这项研究是在NSF-DFG电合成和电催化领导机构活动(NSF-DFG eChem)机会NSF 20-578下资助的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

As the nation and the world move toward carbon-free energy economies, ammonia will likely play significant roles as a hydrogen carrier. Today, essentially all ammonia is produced in high pressure Haber-Bosch plants at very large scale. There is a growing need for smaller scale, geographically distributed, ammonia synthesis using renewable resources. However, because of inherent thermodynamic and kinetic limitations, typical catalyst-based thermal processes (e.g., Haber-Bosch) are not economic at smaller scale. The present project seeks to enable distributed ammonia synthesis using electrochemical interactions that significantly reduce activation barriers. The research relies on the combined, complementary, and unique expertise of the partners in the context of materials synthesis, characterization and process demonstration (KIT) and physically based modeling of the electrochemistry, charged-defect transport, and catalysis (CSM).This joint project addresses significant scientific challenges in transitioning to environmentally friendly ammonia production as an energy carrier and commodity chemical. The project’s objective is to develop and demonstrate electrochemical enhancement that enables low-temperature and low-pressure ammonia synthesis. Nanophase Ru is dispersed on a proton-conducting BCZY support (BaCe1-x-yZrxYyO3-δ). Directly polarizing the catalyst structure with an electric field decreases the kinetically limiting barrier for N2 activation. Although the proposed research is scientifically fundamental, it has excellent technology potential for cost-effective distributed production of ammonia. The research focuses on postulating, modeling, and validating proposed chemical behaviors. The electrical field is expected to reduce rate-limiting N2 dissociation barriers via two synergistic mechanisms:1. Electrical fields affect the proton-conducting BCZY support, enabling H2 dissociation to form protons that can activate gas-phase N2, directly forming desired surface adsorbates such as NH on the BCZY support.2. Fields in the range of 0.1 to1.0 V/Å on dispersed nano-Ru also reduce the nitrogen activation barrier. The energy barrier for nitrogen activation Ru varies between 30-42 kJ mol-1. Based on our validated reaction mechanisms for Ba-promoted Ru/YSZ, simulations show that reducing the N2 dissociation energy by 10 kJ mol-1 will increase the ammonia formation rate by an order of magnitude.This research was funded under the NSF-DFG Lead Agency Activity in Electrosynthesis and Electrocatalysis (NSF-DFG EChem) opportunity NSF 20-578.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.