Tandem Electrolysers for High‐Efficiency CO 2 ‐to‐Acetate Conversion Driven by Full‐Spectrum Solar Energy
Shangchun Su, Zongkang Wang, Jianhong Liu, Xiangyu Liu, Zhan Wu, Zhenyu Tian, Feifei Wang, Wenjia Li, Jian JinABSTRACT
Solar‐driven electrochemical conversion of CO 2 into multi‐carbon products offers a promising pathway for renewable energy storage, yet its efficiency is essentially constrained by the mismatch between the solar energy spectrum and the energy demands of CO 2 electrolysis. Here, a full‐spectrum solar photovoltaic–thermal tandem system is proposed for CO 2 ‐to‐acetate conversion: a high‐temperature solid oxide electrolysis cell (SOEC) first converts CO 2 to CO, followed by electrochemical reduction of CO to acetate. Short‐wavelength solar energy generates photovoltaic electricity to drive electrochemical reactions, while long‐wavelength solar energy is used for concentrated solar thermal collection to heat the high‐temperature SOEC device and preheat reactants. Two reference systems were also analyzed: one is direct electrocatalytic CO 2 reduction to acetate, and the other is water electrolysis to produce hydrogen, which then undergoes a thermochemical reaction with CO 2 to generate acetate. Under representative operating conditions (cutoff wavelength of 900 nm and concentration ratio of 5000), the proposed system achieves a solar‐to‐acetate efficiency of 15.8%, representing improvements of 11.2 and 8.3 percentage points compared with two reference systems, owing to effective matching between thermal and electrical energy supply and demand. These results underscore that a tandem system integrated with full‐spectrum solar energy is critical to overcoming efficiency limitations in solar‐driven CO 2 conversion.