Layered bismuth oxide/bismuth sulfide supported on carrageenan derived carbon for efficient carbon dioxide electroreduction to formate

Electrochemical reduction of carbon dioxide (CO2ER) into formate plays a crucial role in CO2 conversion and utilization. However, it still faces the problems of high overpotential and poor catalytic stability. Herein, we report a hybrid CO2ER electrocatalyst composed of layered bismuth sulfide (Bi2S3) and bismuth oxide (Bi2O3) supported on carrageenan derived carbon (Bi-CDC) prepared by a combined pyrolysis with hydrothermal treatment. In such 3D hybrid, layered Bi2O3 and Bi2S3 are uniformly grown on nanocarbon supports. Benefiting from strong synergistic effect between Bi2O3/Bi2S3 and nanocarbon, Bi-CDC-1:2 displays a high Faradic efficiency (FE) of >80% for formate production in the range of −0.9 V to −1.1 V with the maximum formate FE of 85.6% and current density of 14.1 mA·cm−2 at −1.0 V. Further, a positive onset potential of −0.5 V, a low Tafel slope of 112.38 mV·dec−1, and a slight performance loss during long-term CO2ER tests are observed on Bi-CDC-1:2. Experimental results shows that the better CO2ER performance of Bi-CDC-1:2 than that of Bi2O3 can be attributed to the strong interfacial interactions between nanocarbons and Bi2O3/Bi2S3. In situ ATR-FTIR measurements reveal that the rate-determining step in the CO2ER is the formation of HCOO* intermediated. Compared with carbon support, Bi-CDC-1:2 can promote the production of HCOO* intermediate and thus promoting CO2ER kinetic.