Self-templating synthesis of Pd₄S hollow nanospheres as electrocatalysts for oxygen reduction reaction

Hollow nanostructures with structural advantages have been widely exploited as catalysts in electrochemical reactions. However, there are only limited strategies for constructing hollow Pd-based nanostructures. In this work, Pd₄S hollow nanospheres (Pd₄S HNSs) are synthesized with a facile wet-chemical method via a self-templating process. Intermediate Pd-L-cysteine solid nanospheres (SNSs) were firstly obtained by the coordination of L-cysteine with Pd²⁺, and then in situ converted to hollow nanospheres in the following reduction process. The formation mechanism of the Pd₄S HNSs was studied, and the size of the Pd₄S HNSs can be readily adjusted by tuning the size of the SNSs. The hollow morphology would help the exposure of active sites and the prevention of aggregation during the catalytic reactions. As a result, the Pd₄S HNSs exhibit improved catalytic performances in the oxygen reduction reactions, with a half-wave potential of 0.913 V vs. reversible hydrogen electrode (RHE) and impressive stability in the accelerated durability test.