High efficiency coupled electrocatalytic CO 2 reduction to C 2 H 4 with 5-hydroxymethylfurfural oxidation over Cu-based nanoflower electrocatalysts

To improve the total value of the redox products and energy conversion efficiency in CO 2 electroreduction (CO 2 RR) and 5-hydroxymethylfurfural electrooxidation (HMFOR), commercial Cu foam was chemically oxidized into nanoflower CuO on its surface and used as an electrocatalyst in both CO 2 RR and HMFOR. In CO 2 RR, the prepared CuO nanoflower on Cu foam (CuO-NF@Cu) was quickly reduced to hybrid Cu 2 O/Cu nanoflower (Cu 2 O/Cu-NF@Cu). At a reduction potential of −0.95 V ( vs. RHE), a high C 2 H 4 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, CO 2 RR and HMFOR can be coupled together with CuO-NF@Cu as the anode electrocatalyst and Cu 2 O/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 C 2 H 4 up to 96.6%/74.5%, respectively, were achieved in coupled CO 2 RR-HMFOR within 5 h. This work makes it easy to simultaneously efficiently convert CO 2 to high-value C 2 H 4 and upgrade a renewable biomass platform compound.