High-Performance Cu6Sn5 Alloy Electrocatalysts for Formaldehyde Oxidative Dehydrogenation and Bipolar Hydrogen Production.

Aldehyde-assisted water electrolysis offers an attractive pathway for energy-saving bipolar hydrogen production with combined faradaic efficiency (FE) of 200% while converting formaldehyde into value-added formate. Herein we report the design and synthesis of noble metal-free Cu6Sn5 alloy as a highly effective electrocatalyst for formaldehyde electro-oxidative dehydrogenation, demonstrating a geometric current density of 915 ± 46 mA cm-2 at 0.4 V versus reversible hydrogen electrode, outperforming many noble metal electrocatalysts reported previously. The formaldehyde-assisted water electrolyzer delivers 100 mA cm-2 at a low cell voltage of 0.124 V, and a current density of 486 ± 20 mA cm-2 at a cell voltage of 0.6 V without any iR compensation and exhibits nearly 200% faradaic efficiency for bipolar hydrogen production at 100 mA cm-2 in 88 h long-term operation. Density functional theory calculations further confirm the notably lowered barriers for dehydrogenation and Tafel steps on the Cu₆Sn₅ surface compared to Cu, underscoring its potential as a highly active catalyst.