Value-Added Formate Production from Selective Methanol Oxidation as Anodic Reaction to Enhance Electrochemical Hydrogen Cogeneration.

Electrolytic overall water splitting is a promising approach to produce H2 , but its efficiency is severely limited by the sluggish kinetics of the oxygen evolution reaction (OER) and the low activity of current electrocatalysts. To solve these problems, in addition to the development of efficient precious-metal catalysts, an effective strategy is proposed to replace the OER by the selective methanol oxidation reaction. Ni-Co hydroxide [Nix Co1-x (OH)2 ] nanoarrays were obtained through a facile hydrothermal treatment as the bifunctional electrocatalysts for the co-electrolysis of methanol/water to produce H2 and value-added formate simultaneously. The electrocatalyst could catalyze selective methanol oxidation (≈1.32 V) with a significantly lower energy consumption (≈0.2 V less) than OER. Importantly, methanol was transformed exclusively to value-added formate with a high Faradaic efficiency (selectivity) close to 100 %. Specifically, a cell voltage of only approximately 1.5 V was required to generate a current density of 10 mA cm-2 . Furthermore, the Ni0.33 Co0.67 (OH)2 /Ni foam nanoneedle arrays presented an outstanding stability for overall co-electrolysis.