Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co₃O₄ Interfaces

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co₃O₄ interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co₃O₄ precursors. Nano-sized Ag particles are uniformly dispersed on Co₃O₄ nanosheets, and electron-deficient Ag^δ+ are formed by the SMSI between Ag and Co₃O_4. Ag/Co₃O₄ demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32 V versus RHE and 0.65 V versus RHE, achieving current densities of 10 and 100 mA cm^-2, respectively. The electrolyzer "Ag/Co₃O₄||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.