Cascade electrocatalysis via Cu-O-C interfaces for ultralow-Pd formate oxidation

Direct formate fuel cells (DFFCs) are promising clean-energy devices, yet the efficiency of Pd-based anodes is limited by the strong adsorption of reaction intermediates, particularly adsorbed hydrogen (H ad ). This blockage of active sites raises the overpotential and slows reaction kinetics, while compensating with high Pd loading further increases cost. Here, we design a Pd-lean catalyst featuring a dual-function interface that simultaneously mitigates intermediate poisoning and enhances precious-metal utilization. The catalyst consists of Cu-rich Pd-Cu nanoparticles (∼2-3 nm) anchored on carbon nanotubes coated with a tannic-acid-derived, oxygen-doped carbon layer. The engineered Cu-O-C interface promotes water dissociation at low potentials, supplying interfacial hydroxyl species (OH ad ), while Cu alloying downshifts the Pd d-band center, significantly weakening the Pd-H binding energy (HBE) and facilitating H ad desorption. This cascade electrocatalysis accelerates the H ad -OH ad coupling step, which is the rate-determining step in formate oxidation, thereby enabling rapid regeneration of active sites. As a result, the catalyst achieves a peak mass activity of 5.59 A mgPd -1 at -0.31 V (vs. Hg/HgO), which is 4.9 times higher than that of commercial Pd/C. Remarkably, this performance is obtained with an ultralow Pd loading of only 1.54 wt %, demonstrating exceptional precious-metal utilization efficiency. • Developed a Cu-rich PdCu alloy catalyst with an ultralow Pd loading of 1.54 wt%, substantially reducing the precious-metal cost for efficient formate oxidation. • Unveiled a cascade electrocatalysis mechanism for the FOR through a spatially organized interface, where a Cu-O-C structure supplies OHad adjacent to Cu-rich PdCu alloy sites that favor Had/COad desorption. • Achieved a superior FOR mass activity of 5.59 A mg Pd -1 (4.86 times that of commercial Pd/C), which compellingly demonstrates its exceptional anti-poisoning capability.