Interfacial Electronic Modulation of NiPd Alloy Nanoparticles on Boron-Doped Graphene for Bifunctional Methanol and Formic Acid Electrooxidation

Abstract

Improving the anodic electrocatalytic performance of direct methanol and direct formic acid fuel cells (DMFCs and DFAFCs) remains a key challenge for efficient liquid-fuel energy conversion. Although Pd-based catalysts have shown great potential for the methanol oxidation reaction (MOR) and formic acid oxidation reaction (FAOR), the synergistic regulation of Pd active sites through alloying and support engineering to enhance catalytic activity and durability is still being explored. In this study, B-doped graphene (BG)-loaded NiPd nanoparticle (NP) catalysts are synthesized via a facile chemical reduction strategy. Ni0.4Pd0.6/BG outperforms the other catalysts in both reactions, reaching mass activities of 3.24 A mgPd–1 toward MOR and 1.10 A mgPd–1 toward FAOR. These values are approximately 10.5 and 2.3 times those obtained with commercial Pd/C, respectively. Moreover, Ni0.4Pd0.6/BG exhibits the best long-term durability among all of the tested catalysts toward both MOR and FAOR. The superior bifunctional activity is mainly ascribed to the combined contributions of Ni–Pd alloying, the defect-rich BG support, and strong metal–support interactions (SMSI). These factors collaboratively modulate the electronic environment of Pd active centers, promote the uniform dispersion of NiPd NPs, and facilitate interfacial electron transfer, as further supported by DFT calculations. This study focuses on optimizing the Ni–Pd composition and boron-doping level to enhance bifunctional electrocatalytic activity, providing guidance for developing Pd-based catalysts for direct liquid fuel cells.