Tailor-designed bimetallic Co/Ni macroporous electrocatalyst for efficient glycerol oxidation and water electrolysis

Abstract

Water electrolysis is broadly considered one of the most promising technologies for green hydrogen production. However, the oxygen evolution reaction (OER) is thermodynamically unfavorable and requires large overpotentials to proceed with an adequate rate. Herein, we introduce key structural and compositional parameters controlling the hydrogen evolution reaction (HER) performance of a representative family of bimetallic CoNi porous electrocatalysts and highlight a simple strategy for replacing the OER with glycerol oxidation reaction (GOR) to reduce the input cell voltage. The structural, morphological, and electrochemical characterizations of a series of electrocatalysts, prepared by the dynamic hydrogen bubble template technique (DHBT), were fully studied which reveals that changing of Co: Ni ratio affects HER activity. Optimization of this ratio leads to enhancement in both intrinsic and mass activity besides the high density of accessible active sites. This, in turn, leads to an efficient electrocatalyst achieving a low overpotential of −67 mV at a current density of 10 mA/cm2 during HER. As a bifunctional electrocatalyst, it requires only 1.65 V to deliver the same current density with excellent stability for more than 20 h of continuous water electrolysis in alkaline medium. Moreover, the input cell voltage drops by at least 0.2 V during glycerol electrolysis with concurrent production of both hydrogen and value-added chemicals especially hydroxy pyruvate ion.