Hollow sphere h-Ni-NC@CuO tandem catalysts through control over morphology, Cu+/Cu0 interface and intermediate retention to facilitate CO2RR to ethylene

Efficient conversion of CO2 into ethylene is highly desirable through electrochemical carbon dioxide reduction reaction (CO2RR) but it yet remains challenging. In this work, we design hollow sphere h-Ni-NC@CuO tandem catalysts to facilitate CO2RR to ethylene, which is conveniently built by in-situ hydrolysis of copper salt in the presence of h-Ni-NC. During CO2RR, h-Ni-NC has been shown to provide sufficient active area for continuous and efficient generation of *CO intermediate. Meanwhile, the hollow sphere structure with h-Ni-NC has the capability to store the surplus CO intermediate, thus enhancing the retention time of *CO over the interface between h-NiNC and CuO. Furthermore, it has been demonstrated that h-Ni-NC can transfer electrons to the CuO shell to stabilize the Cu+/Cu0 interface, effecting a substantial enhancement in the selectivity and yield rate of ethylene. Finally, the morphology of h-Ni-NC@CuO catalysts also has an important impact on their ethylene performance which can be adjusted by the amount of copper salt. At-1.1 V (vs. RHE), the ethylene Faraday efficiency of the optimal h-Ni-NC@CuO catalyst reaches a maximum of 32 %, and the ethylene partial current density attains to 36.26 mA cm-2. Our work provides a guidance to design tandem catalyst to boost C2+ product production through simultaneous control over morphology, Cu+/Cu0 interface and *CO intermediate retention.