Boosting formate production at high current density from CO2 electroreduction on defect-rich hierarchical mesoporous Bi/Bi2O3 junction nanosheets.

• Defect-rich mesoporous hierarchical nanostructure is in situ constructed. • A record mass-normalized formate production rate is achieved. • Broken local spatial symmetry brings about structural disorders and defects. • Improvement is due to componential and structural configuration of Bi/Bi 2 O 3. • Bi/Bi 2 O 3 junction contributes to CO 2 adsorption, activation and protonation. Electrocatalytic reduction of CO 2 to formate is believed as one of the most technologically and economically viable strategies for valuable fuels and chemical productions. Defect-rich Bi/Bi 2 O 3 nanosheets in situ grown on the carbon fiber papers (Bi/Bi 2 O 3 -CP) are directly used as an integrated cathode for CO 2 RR. Bi/Bi 2 O 3 -CP exhibits a high mass-normalized formate partial current density of 32.4 and 50.7 mA∙mg−1 cm−2 at −0.87 and −0.97 V, respectively, with high formate faradic efficiency of about 90 %. Incredibly, this cathode gives a record mass-normalized formate production rate of 1.12 mmol∙mg-1 cm-2 h-1 at −1.17 V, which exceeds drop-casted sample (0.41 mmol∙mg−1 cm−-2 h−1 at −1.17 V) and most state-of-the-art Bi based electrocatalysts. The boosted formation generation could be attributed to the unique mesoporous 3D hierarchical nanostructure with the integrated contributions of abundant defects and synergistic coordination of regionally disordered Bi/Bi 2 O 3 metal/oxide junction. [ABSTRACT FROM AUTHOR]