B doped cobalt-nickel bimetallic phosphide as bifunctional catalyst for ethanol oxidation reaction and hydrogen evolution reaction

Abstract

The ethanol oxidation reaction (EOR) is an ideal alternative to the oxygen evolution reaction (OER) towards energy efficient hydrogen production. Here, the chrysanthemum-shaped B doped cobalt-nickel bimetallic phosphide with heterogeneous structure grown on nickel foam (B-Ni2P/CoP/NF) are synthesized and can act as a high activity bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and EOR. In 1.0 M KOH, the obtained catalyst shows good activity and excellent long-term stability (no decay after 108 h) for HER, with an overpotential of only 33 mV (vs. RHE) to reach a current density of 10 mA cm−2. The calculation of turnover frequency (TOF) and transfer coefficient (β) prove that the catalyst has good intrinsic catalytic activity, For EOR, in 1.0 M KOH+1.0 M C2H5OH solution, the B-Ni2P/CoP/NF catalyst requires only 1.45 V (vs. RHE) oxidation potential to reach the current density of 50 mA cm−2, which is 270 mV less than OER. Using B-Ni2P/CoP/NF as a bifunctional catalyst, the current density of 20 mA cm−2 can be achieved with only 1.48 V cell voltage in 1.0 M KOH+ 1.0 M C2H5OH solution, which is remarkably lower than the required cell voltage of water electrolysis (1.63 V) to achieve the same current density. This study demonstrates an efficient bimetallic phosphide as earth-abundant bifunctional electrocatalysts for green hydrogen production coupled with electrolysis of ethanol.