Metal DopedMulticomponent Copper-Based Arrays forFormaldehyde Oxidation Assisted Dual Hydrogen Production System

Green hydrogen production technology is an effective strategy for solving energy problems and environmental issues. In this paper, we report a bipolar hydrogen production system: Au–Cu_<i>x</i>O/CF∥Ru–Cu_<i>x</i>O/CF, in which the cathode produces hydrogen through the hydrogen evolution reaction (HER) process and the anode produces hydrogen through a formaldehyde oxidation reaction (FOR). It is found that when Au–Cu_<i>x</i>O/CF is used in FOR, the C–H bond of formaldehyde will be broken at low potential to produce reactive hydrogen H*. H* is recombined through the Tafel step (H* + H* ⇌ H₂) to produce H₂. At the same time, the formaldehyde is oxidized to a high-value-added product HCOOH. We found that the formation of grain boundary-rich structures on the Au–Cu_<i>x</i>O surface jointly promotes the oxidation of formaldehyde at low potentials. In addition, we introduced Ru elements into Cu_<i>x</i>O to enhance the cathodic HER. The FOR-HER system of Au–Cu_<i>x</i>O/CF∥Ru–Cu_<i>x</i>O/CF was tested in a flow cell. It produced a current density of 500 mA cm^–2 at a potential of only 0.38 V. This work provides system construction and catalyst design ideas for bipolar hydrogen production at low voltages.