Raw sugarcane juice assisted hybrid electrolysis for formic acid and hydrogen production based on reversible redox cycle of CoNi LDH

Abstract

The major bottleneck in self-powered water splitting devices by renewable energy lies in the kinetically sluggish oxygen evolution reaction (OER), which only produces low-value oxygen. Herein, we explore sucrose electrooxidation as an alternative anodic reaction for production of valuable chemicals at a reduced electricity consumption. By developing a reversible redox cycle of Ni2+/Ni3+ and Co2+/Co3+ in the CoNi layered double hydroxide (LDH), the required voltage of sucrose oxidation for 100 mA cm−2 is reduced by 240 mV compared to oxygen evolution. The sucrose electrooxidation by CoNi LDH is a two-step reaction including the electrooxidation of Ni2+/Co2+ to Ni3+/Co3+ and the spontaneous reaction between Ni3+/Co3+ and sucrose. By feeding with natural sugarcane juice, a solar-driven electrolyser is assembled for the co-production of value-added formic acid and hydrogen. Our work demonstrates a sustainable route for integrating hydrogen production and biomass electrooxidation for energy applications.