Carbon layer thickness manipulated polarized electric field on palladium for formic acid electrooxidation

To solve the severe problem of environmental pollution, the demand for commercial applications of direct formic acid fuel cell (DFAFC) has significantly increased. Designing electrocatalysts with high anti-poisoning ability and activity for formic acid electrooxidation (FAO) is the key for the development of DFAFC. Utilizing polarized electric field is a new attempt to improve catalytic performance as it can adjust the adsorption energy of reactants or intermediate species on the catalysts. In this work, pyroelectric material BaTiO3 (BTOH), which generate polarized electric field, was introduced for FAO for the first time. A series of core-shell structured Pd/ BTOHx@NCy catalysts was synthesized with BTOH as the core, nitrogen-doped carbon as the shell, and palladium nanoparticles as the active sites. Among all catalysts, Pd/BTOH1@NC0.5 with the optimal carbon shell thickness of 4.6 nm owns the highest FAO catalytic activity and anti-poisoning ability because the carbon layer regulates the electric field strength to optimize the palladium surface adsorption energy. The study excluded the influence of electronic effect and revealed the effect of polarized electric field strength on the FAO activity and antipoisoning ability through changing the thickness of carbon shell. In addition, the alternating cold-hot excitation experiments demonstrated that the polarized electric fields can effectively remove the poisoned substance on the surface of palladium. This study guides a new strategy to design electrocatalysts for FAO.