High efficiency coupled electrocatalytic CO2 reduction to C2H4 with 5-hydroxymethylfurfural oxidation over Cu-based nanoflower electrocatalysts

To improve the total value of the redox products and energy conversion efficiency in CO2 electroreduction (CO2RR) and 5-hydroxymethylfurfural electrooxidation (HMFOR), commercial Cu foam was chemically oxidized into nanoflower CuO on its surface and used as an electrocatalyst in both CO2RR and HMFOR. In CO2RR, the prepared CuO nanoflower on Cu foam (CuO-NF@Cu) was quickly reduced to hybrid Cu2O/Cu nanoflower (Cu2O/Cu-NF@Cu). At a reduction potential of -0.95 V (vs. RHE), a high C2H4 faradaic efficiency (FE) up to 70% with a current density of 104.5 mA cm(-2) can be obtained within 45 h of testing. In HMFOR, CuO-NF@Cu gave a 99.3% FDCA FE at a potential of 1.62 V (vs. RHE). Moreover, CO2RR and HMFOR can be coupled together with CuO-NF@Cu as the anode electrocatalyst and Cu2O/Cu-NF@GDL as the cathode electrocatalyst. A current density up to 188.8 mA cm(-2) at a cell voltage of 2.75 V can be obtained. FEs of FDCA and C2H4 up to 96.6%/74.5%, respectively, were achieved in coupled CO2RR-HMFOR within 5 h. This work makes it easy to simultaneously efficiently convert CO2 to high-value C2H4 and upgrade a renewable biomass platform compound.