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。越来越需要使用可再生资源进行小规模、地理分布的氨合成。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（例如，Haber-Bosch）在较小规模上并不经济。目前的项目旨在利用电化学相互作用来实现分布式氨合成，从而显著降低活化障碍。该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，带电缺陷传输和催化（CSM）的物理建模方面的组合，互补和独特的专业知识。这个联合项目解决了向作为能源载体和商品化学品的环境友好型氨生产过渡的重大科学挑战。该项目的目标是开发和演示电化学增强，使低温低压氨合成成为可能。纳米相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N2活化的动力学限制势垒。虽然提出的研究是科学基础，但它具有极好的技术潜力，具有成本效益的分布式生产氨。研究的重点是假设，建模和验证提出的化学行为。电场有望通过两种协同机制降低限速N2解离障碍：1。电场影响质子导电的BCZY载体，使H2解离形成可以激活气相N2的质子，直接在BCZY载体上形成所需的表面吸附物，如NH 2。在分散纳米ru上0.1 ~ 1.0 V/Å范围内的电场也降低了氮的活化势垒。氮活化Ru的能垒在30 ~ 42 kJ mol-1之间。基于我们验证的ba促进Ru/YSZ的反应机制，模拟表明，将N2解离能降低10 kJ mol-1将使氨的生成速率提高一个数量级。这项研究是由NSF- dfg牵头机构在电合成和电催化活动（NSF- dfg化学）机会NSF 20-578资助的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.