Synergistic intensification of palladium-based membrane reactors for hydrogen production: A review

Hydrogen is a clean, zero-carbon energy carrier that is critical in the transition to a renewable energy system. Hydrogen production membrane reactors are based on membrane technology for process intensification, allowing simultaneous reaction enhancement and hydrogen purification. However, concentration polarization creates mismatch between reaction and separation processes, limiting the performance. To further develop and increase the hydrogen production efficiency in membrane reactors, this review first provides advances in membrane reactor research from several perspectives, including membrane materials, performance metrics, and evaluation tools. Subsequently, the effects of operating conditions and structural design on the performance enhancement of membrane reactors are organized and analyzed. The review focuses on summarizing the mechanisms for improving membrane reactor design performance, proposing four methods: shortening distance, increasing routes, smoothing paths, and multi-product removal. Additionally, it is suggested to draw on membrane surface pattern designs to guide the disruption of concentration boundary layers. The review finds that enhancement ways primarily revolve around mitigating concentration polarization. Various ways have the potential to achieve low-cost and higher performance by complementing each other's strengths, such as minimizing the use of precious metals and employing low-cost multi-product separation. Moreover, there is a lack of corresponding evaluation standards for membrane reactors, which hinders the subsequent commercialization development. Finally, this review combines existing challenges and research progress to provide perspectives for the future development of membrane reactors. The major goal is to introduce new research methods to further promote the application of membrane reactors in greater depth.