Free‐standing Stanene for High Selectivity of Formate in Electrocatalytic Carbon Dioxide Reduction Reaction

As well‐known electrocatalysts with good catalytic efficiency for carbon dioxide reduction reaction (CO2RR) towards the production of formate, tin (Sn)‐based catalysts have aroused broad concern. Here, free‐standing porous stanene is synthesized for the first time by a facile wet chemical method, and its excellent electrocatalytic performance for formate (HCOO−) formation in CO2RR is demonstrated. High Faradaic efficiency (F.E., 93% at −930 mV versus reversible hydrogen electrode (RHE)) can be achieved in the CO2RR catalyzed by stanene in 0.5 m KHCO3 aqueous solution. The in situ Mössbauer spectra reveal that zero‐valent Sn aids in improving the selectivity of formate production. Furthermore, density functional theory calculations suggest that the high selectivity of HCOO− of CO2RR on stanene mainly originates from the edge sites on Sn (100). To further explore the practicability of the stanene‐based catalysts for CO2RR, stanene decorated by 3 wt% BP‐2000 is prepared, showing an excellent F.E. of 98% at −930 mV versus RHE due to the higher exposure of catalytic active sites. These new findings of the activity origination and reaction mechanism of stanene contribute to the deeper understanding of Sn‐based catalysts for CO2RR, which is beneficial for the future designation of highly efficient CO2RR catalysts. A bottom‐up approach without substrate is achieved to synthesize free‐standing stanene as the catalyst for CO2RR. In situ Mössbauer spectroscopy is used to investigate stanene in CO2RR for the first time, revealing that zero‐valent tin (Sn) aids in improving the formate selectivity. Density functional theory calculations suggest that the selectivity mainly originates from the edge sites on Sn (100).