Unitized regenerative proton exchange membrane fuel cell (UR-PEMFC) technology has progressed in the recent past and has started appearing towards few applications. However, the UR-PEMFC viability is limited by its lower round-trip efficiency mainly due to several reasons such as sluggish air electrode reactions, lower performance/stability, higher materials cost etc. In this context, many approaches are being implemented for efficiency enhancement including design and development of effective bifunctional air electrodes (oxygen reduction and evolution reactions) materials both for fuel cell and electrolyzer modes as well as for optimization of operating condition for performance stability in real life applications. This review focusses on the recent developments of air electrode active materials design/development for performance improvement in UR-PEMFC. Among all developed electrode materials, the catalysts with Pt- and Ir-based metals still provided the maximum round-trip efficiency of about 50% at 500 mA cm⁻² in the unit cell.

单元式再生质子交换膜燃料电池（UR-PEMFC）技术在最近已经取得了进步，并开始出现在很少的应用领域。但是，UR-PEMFC的可行性受其往返效率较低的限制，这主要是由于以下几个原因，例如空气电极反应缓慢，性能/稳定性较低，材料成本较高等。在这种情况下，正在实施许多方法来提高效率包括设计和开发有效的双功能空气电极（氧还原和放出反应）材料，用于燃料电池和电解槽模式，以及优化操作条件以实现实际应用中的性能稳定性。这篇综述集中在空气电极活性材料设计/开发方面的最新进展，以提高UR-PEMFC的性能。在所有已开发的电极材料中，含Pt和Ir的金属的催化剂在500 mA cm时仍可提供约50％的最大往返效率单位^晶格中的^-2。