Electrochemical reforming of ethanol with acetate Co-Production on nickel cobalt selenide nanoparticles

• Ni x Co y Se 2 nanoparticles with controlled Ni/Co ratio are produced. • They were used for ethanol conversion into a valuable chemical and hydrogen. • Optimized electrocatalysts deliver 0.34 mmol cm -2 h −1 of acetate from ethanol oxidation. • Co enhances ethanol adsorption and decreases the dehydrogenation energy barrier. The energy efficiency of water electrolysis is limited by the sluggish reaction kinetics of the anodic oxygen evolution reaction (OER). To overcome this limitation, OER can be replaced by a less demanding oxidation reaction, which in the ideal scenario could be even used to generate additional valuable chemicals. Herein, we focus on the electrochemical reforming of ethanol in alkaline media to generate hydrogen at a Pt cathode and acetate as a co-product at a Ni 1-x Co x Se 2 anode. We first detail the solution synthesis of a series of Ni 1-x Co x Se 2 electrocatalysts. By adjusting the Ni/Co ratio, the electrocatalytic activity and selectivity for the production of acetate from ethanol are optimized. Best performances are obtained at low substitutions of Ni by Co in the cubic NiSe 2 phase. Density function theory reveals that the Co substitution can effectively enhance the ethanol adsorption and decrease the energy barrier for its first step dehydrogenation during its conversion to acetate. However, we experimentally observe that too large amounts of Co decrease the ethanol-to-acetate Faradaic efficiency from values above 90% to just 50 %. At the optimized composition, the Ni 0.75 Co 0.25 Se 2 electrode delivers a stable chronoamperometry current density of up to 45 mA cm −2 , corresponding to 1.2 A g −1 , in a 1 M KOH + 1 M ethanol solution, with a high ethanol-to-acetate Faradaic efficiency of 82.2% at a relatively low potential, 1.50 V vs. RHE, and with an acetate production rate of 0.34 mmol cm −2 h −1 .