Versatile Synthesis of Pd−M (M=Cr, Mo, W) Alloy Nanosheets Flower-like Superstructures for Efficient Oxygen Reduction Electrocatalysis

Pd-based nanoalloys are promising electrocatalysts for replacing Pt-based ones toward oxygen reduction reaction. Despite that great progress has been achieved, universally synthesizing Pd-based alloy nanosheets and further integrating them into porous or hierarchical superstructures remain a challenge, and their ORR performances are not systematically investigated. Herein, novel ultrathin and highly wrinkled Pd−M (M=Cr, Mo, W) alloy nanosheets flower-like superstructures (NSFSs) are universally fabricated via a polyether and small molecules/ions ligand assisted solvothermal method. Such Pd−M NSFSs possess mesoporous structures and co-exist single-atom-like and cluster-like M species on their surfaces. Compared with pure Pd NSFSs, those Pd−M NSFSs show greatly enhanced ORR activity in alkaline media. Due to the unique microstructure feature, proper alloy constituent and stronger interatomic polarization or electronic coupling, the Pd−W NSFSs show the highest ORR activity with the half-wave potential of 0.89 V (vs. RHE) and mass activity of 0.46 A mg_Pd ⁻¹ at 0.90 V (vs. RHE), outperforming commercial Pt/C, and most of reported Pd(or Pt)-based catalysts. Moreover, the Pd−W NSFSs manifest outstanding durability and anti-CO poisoning ability yet. This work may spur the development of 2D Pd-based nanoalloy superstructures and promote their applications in fuel cells or other clean energy fields.