Simultaneously high-rate furfural hydrogenation and oxidation upgrading on nanostructured transition metal phosphides through electrocatalytic conversion at ambient conditions

We successfully synthesize Cu3P nanosheets and granular Ni2P nanocrystals on the surface of commercial carbon fiber cloth (CFC) (Cu3P/CFC and Ni2P/CFC) respectively by a vapor-phase hydrothermal route. The as-synthesized Ni2P/CFC and Cu3P/CFC as electrodes all show the bifunctional electrocatalytic performances towards hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), simultaneously all demonstrating the electrocatalytic activities of the furfural hydrogenation reaction (FHR) and furfural oxidation reaction (FOR) in alkaline media. Comparatively, the Cu3P/CFC exhibits higher FHR activity with almost similar to 100% selectivity of the furfuryl alcohol (FAL) product and high Faradaic efficiency (FE) of 92.0%-98.0% over the applied potential range of -0.05 to -0.55 V (vs. RHE), while the Ni2P/CFC indicates higher FOR activity with almost similar to 100% selectivity of furoic acid (FA) product and FE of 90.0%-98.0% at the applied potential of 1.2-1.7 V (vs. RHE) in alkaline electrolyte containing 50 mM furfural. The DFT calculations results reveal that the (1-10) dominated Cu3P can obtain higher hydrogen coverage but restricted H-2 desorption compared to the (001) dominated Ni2P, therefore the adsorbed active hydrogen (H) atoms from water can be effectively used for the FHR process, resulting in high FE and current density. The superior FOR activity of the Ni2P/CFC is mainly stemmed from the formed high valence state Ni species during electrocatalysis. Thanks to the superior FHR performance of Cu3P/CFC and FOR activity of Ni2P/CFC, a two-electrode H-type electrocatalysis system assembled with the Cu3P/CFC as cathode and Ni2P/CFC as anode can be constructed for simultaneously electrocatalytic production of FAL and FA with almost similar to 100% selectivity in 1.0 M KOH electrolyte containing 50 mM furfural in each chamber under the given experimental conditions, demonstrating high FE of 97%-99%.