Selective electrooxidation of 2-hydroxybenzyl alcohol coupled with H2 production promoted by surface reconstruction of β-Ni(OH)2 nanosheets

2-Hydroxybenzaldehyde (SALD) exhibits special reactivity in various chemical reactions due to the existence of aldehyde and hydroxyl groups, which also make it a challenge to achieve high conversion and selectivity for SALD production. Herein, β-Ni(OH)2 nanosheets over nickel foam (NF) at different hydrothermal temperatures were synthesized for electrocatalytic oxidation (ECO) of 2-hydroxybenzyl alcohol (SAL) into SALD. The β-Ni(OH)2 electrode obtained at 160 °C achieves the best ECO performance in 2.5 M KOH at the applied potential of 1.45 V (RHE), showing the SALD selectivity of 78.90% and the Faradaic efficiency of 87.94% at the SAL conversion of 69.76%. ECO of SAL reduces the cell voltage and boosts the hydrogen productivity by 2.74 times. It is of great importance to find that potential-driven surface reconstruction of β-Ni(OH)2 enables selective conversion of SAL into SALD. Side reactions including OER as well as oxidation of phenolic group can be effectively controlled via regulating applied potentials on β-Ni(OH)2. This work is the first report on direct electrochemical oxidation of SAL with high SALD selectivity, and offers a green and clean strategy for highly selective production of SALD under mild conditions.