Dual Hydrogen Production System: Synergistic Effect of Ru and Ce Over Cu 2 O Nanotubes Drives Hydrogen Evolution and Formaldehyde Oxidation.

Water splitting for hydrogen production is limited by high cell voltage and low energy conversion efficiencies due to the slow kinetic process of the oxygen evolution reaction (OER). Here, an electrolytic system is constructed in which the cathode and anode co-release H 2 at ultra-low input voltage using formaldehyde oxidation reaction (FOR) instead of OER. The prepared RuCe co-doped Cu 2 O nanotubes on copper foam (RuCe-Cu 2 O/CF) are used as electrode materials for the HER-FOR system. A current density of 0.8 A cm -2 is achieved at 0.55 V, and a stable hydrogen production process is realized at both the cathode and anode. Density functional theory (DFT) studies show that the synergistic effect of Ru and Ce drives: i) the d-band center of RuCe-Cu 2 O/CF away from the Fermi energy level; ii) the energy barrier for the C─H cracking of the H 2 C(OH)O * intermediate in FOR is lowered, which promotes the formation of H 2 from H * , and iii) ΔG H* tends to 0 (-0.1 eV), optimizing the reaction kinetics of HER. This work provides a new design for an efficient catalyst for dual hydrogen production systems from water splitting.