Electrochemistry lies at the interface of chemistry and energy materials and represents one of the most promising approaches for enhancing energy efficiency, mitigating environmental impacts and carbon emissions, and enabling renewable energy technologies. Our research focuses on the fundamental understanding of electrochemical mechanisms at interfaces with an emphasis on CO2 reduction, clean H2 production and rechargeable batteries. The central scheme of the Yang group lies in developing operando methods, based on advanced electron microscopy at Cornell Center for Materials Research (CCMR) and synchrotron based X-ray methods at Cornell High Energy Synchrotron Source (CHESS), to investigate fundamental aspects of solid-liquid interfaces related to renewable energy technologies.