Value-added methanol electroreforming coupled with green hydrogen production at the edge interface of 2D boron nanosheets

Abstract

Electrocatalytic water splitting has been regarded as a promising technology for the production of ultrapure hydrogen (H₂) in this decade. Nonetheless, the efficiency of the water splitting is severely hampered by the sluggish anodic oxygen evolution reaction (OER). The coupling of thermodynamically favourable anodic oxidation reactions (small molecule oxidations) is an innovative strategy to overcome these critical challenges in conventional technology. Herein, we demonstrate the use of liquid phase exfoliated 2D boron nanosheets (eBNSs) as an efficient non-noble electrocatalyst for a traditional/hybrid water electrolyzer. The physico-chemical studies revealed that the exfoliation of boron sheets leads to a decrease in lateral size, layer numbers and an increase in surface area without affecting their crystallinity. Benefitting from the increased surface and edge interfaces, the eBNSs showed enhanced electrocatalytic activity towards the hydrogen evolution reaction (HER) (146 mV), OER (291 mV) and methanol oxidation reaction (MOR) (190 mV) to meet 10 mA cm⁻² which is better than that of bulk boron. The eBNS/NF-4 hybrid electrolyzer (HER + MOR) requires 1.55 V (@10 mA cm⁻²) to electrosynthesis value added formate and hydrogen with a 160 mV lower voltage compared to a conventional electrolyzer (HER + OER). Furthermore, the real time hybrid water electrolyzer (in a H-type cell) delivers superior H₂ production with 93% faradaic efficiency. Overall, this work demonstrates the use of non-noble 2D eBNSs as a potential candidate for next generation energy-efficient green H₂ production systems.