Designing nanoporous Pd catalyst with dual enhancement of thermodynamics and kinetics for formic acid oxidation reaction

Abstract

Conventional strategies for developing highly efficient electrocatalysts involve enhancing thermodynamics to minimize overpotential and improving kinetics to maximize reaction current. However, current research on Pd-based catalysts for formic acid oxidation reaction (FAOR) mainly focuses on accelerating its kinetics to increase the peak current. This study proposes a catalyst design that can simultaneously improve the kinetics and thermodynamics of FAOR. Specifically, the home-made catalyst (NPG-Pt1-Pd1) is obtained by sequentially depositing monolayer Pt and Pd shells on the surface of nanoporous gold (NPG) substrate. Compared with commercial Pd/C, this electrocatalyst exhibits a noticeable negative shift in onset potential (∼100 mV) and a significantly improved peak current (∼6 times). Experimental data and theoretical calculations demonstrate that NPG-Pt1-Pd1 exhibits a comparatively suitable adsorption energy for small molecules, not only reducing the overpotential but also accelerating the reaction rate of FAOR. Moreover, when applied in direct formic acid fuel cells (DFAFC), the NPG-Pt1-Pd1 anode with an exceptionally low Pd loading of 8.5 μg cm−2, achieves a remarkable power density of 141 mW cm−2. The power efficiency of Pd is 230 times that of Pd/C (1 mg cm−2, 73 mW cm−2). Therefore, this work provides a new methodology for developing efficient Pd-based FAOR electrocatalysts.