Photoelectrochemical dual hydrogen production via formaldehyde oxidation and neutral water reduction

Hydrogen production through water electrolysis is a crucial method for generating hydrogen; however, the oxygen evolution reaction (OER) requires high reaction potentials, leading to significant electrical energy consumption. In contrast, aldehyde oxidation at ultra-low potentials offers a promising alternative to OER. Coupling aldehyde oxidation with the hydrogen evolution reaction (HER) forms an ideal system for hydrogen production, simultaneously generating high value-added oxidation products and avoiding less economically valuable O 2 . This study employs a photoelectrocatalytic system to drive the oxidation of formalin solutions in a safe and sustainable manner. Utilizing water as the oxidant, the system provides a viable strategy for dual hydrogen production and organic synthesis in neutral media. Under an applied bias voltage of 0.6 V vs. Ag/AgCl and simulated sunlight of 100 mW cm −2 , the BiVO 4 photoanode achieved 83% selectivity for formic acid production. Furthermore, dual hydrogen production was realized at both the anode and cathode, with an apparent Faradaic efficiency of 35%. This work presents an energy-saving and environmentally friendly pathway for solar hydrogen storage and the production of high value-added chemicals, underscoring the potential application of the photoelectrochemical (PEC) method in coupled systems.