Unlocking the catalytic potential of nickel sulfide for sugar electrolysis: green hydrogen generation from kitchen feedstock

Abstract

Amongst the various food ingredients available in our kitchen, table sugar is commonly associated with satisfying our sweet cravings and serving as a fundamental source of energy in the form of glucose for powering cellular activities and various biological processes. Interestingly, sugar can be electrolyzed in an aqueous solution, oxidizing into value-added chemicals at the anode while producing hydrogen at the cathode. However, developing cost-effective and highly active electrocatalysts for sugar and/or glucose electrolysis remains a significant challenge. This work presents solution-processed nickel sulfide nanowires on a nickel foam substrate (Ni7S6/NF) as a promising electrocatalyst for the glucose oxidation reaction (GOR), achieving electrolysis currents of 10, 100, and 400 mA cm-2 at anodic potentials of 1.30, 1.41 and 1.45 V vs. RHE, respectively. These anodic potentials, compared to the conventional OER potentials, are lowered by 140, 190 and 230 mV, respectively. Additionally, table sugar and orange juice are also electrolyzed to realize competitive hydrogen generation. By assembling a two-electrode (Ni7S6/NF parallel to Ni7S6/NF)-based electrolyzer and feeding table sugar as the key electrolyte in 1.0 M KOH aqueous solution, a remarkable result exhibiting a cell voltage lowered by 170 mV compared to that required for conventional alkaline water (1.0 M KOH aqueous solution) splitting to achieve an electrolysis current density of 100 mA cm-2 is obtained. In addition, the Ni7S6/NF catalyst exhibits outstanding stability for 24 h during sugar electrolysis. The first-ever demonstration of Ni7S6/NF-based electrolyzer with sugar or orange-juice as active electrolyte for an alternative anodic oxidation reaction in water-electrolysis and achieving a higher rate of green-hydrogen at a lower cell voltage.