Porous Cobalt–Nickel Binary Oxide Nanosheets for Electrochemical Glycerol Oxidation

Abstract

The substitution of the oxygen evolution reaction (OER) with more valuable anodic reactions (like the glycerol oxidation reaction; GOR) not only reduces the cell voltage for hydrogen production in the cathode but also provides more value-added products in the anode. The GOR provides an effective way to form value-added chemicals; for example, formic acid, glycolic acid, glyceraldehyde, glyceric acid, etc. Nevertheless, the current difficulty with catalysts are that they have low oxidation activity and low conversion ratio. In this regard, three-dimensional amorphous NiCoO_x/CN_x-300 nanosheets were synthesized for electrochemical glycerol oxidation. The catalyst exhibits greater activity toward electrochemical glycerol oxidation with a very low potential of 1.24 V (vs RHE) at 10 mA/cm² current density. It also shows a very high faradaic efficiency of ∼97% (formic acid of 87% and glycolic acid of 10%) at 1.5 V (RHE) potential along with a high selectivity of ∼89.7% towards formic acid production. The commercial Pt/C∥NiCoO_x/CN_x-300 (HER∥GOR) electrolyzer needs only 250 mV lower potential to reach 10 mA/cm² current density compared to conventional water splitting. Additionally, the electrolyzer is stable up to 48 h at 1.7 V cell potential, reducing 14.7% energy consumption compared to traditional water splitting. We also demonstrate that OH* adsorption on the catalytic surface plays an important role in glycerol oxidation. This work provides fascinating details to design cost-effective transition metal-based electrocatalysts for glycerol oxidation to form value-added products as well as low energy consumption for cathodic hydrogen production.