Encapsulated FeP nanoparticles with in-situ formed P-doped graphene layers: Boosting activity in oxygen reduction reaction

Ni, BX (Ni, Baoxia)^{[ 1 ]} ; Chen, R (Chen, Rui)^{[ 1 ]} ; Wu, LM (Wu, Luming)^{[ 1 ]} ; Sun, PC (Sun, Pingchuan)^{[ 2 ]} ; Chen, TH (Chen, Tiehong)^{[ 1 ]}

SCIENCE CHINA-MATERIALS, 2021, 64(5): 1159-1172

DOI: 10.1007/s40843-020-1525-7

摘要

Nonprecious metal-based oxygen reduction reaction (ORR) electrocatalysts with high efficiency in both alkaline and acidic media are being intensively studied for the purpose of replacing expensive Pt-based catalysts; however, it is still a challenge to achieve superior ORR performances, especially in acidic media. Herein, by pyrolysis of mixed precursors of diammonium phosphate, melamine and hemin, we prepared a nanocomposite catalyst (denoted as FeP@PGL) composed of nitrogen-doped carbon nanosheets with embedded FeP nanoparticles (NPs), which were encapsulated by in-situ formed phosphorus-doped graphene layers. It is found that phosphorous was preferentially doped in the coating layers on FeP NPs, instead of in the carbon nanosheets. The FeP@PGL catalyst exhibited excellent ORR performance, with the onset and half-wave potential up to 1.01 and 0.90 V vs. the reversible hydrogen electrode (RHE) in alkaline media, and 0.95 and 0.81 V vs. RHE in acidic media, respectively. By thorough microscopy and spectroscopy characterizations, the interfacial charge transfer between the encapsulated FeP NPs and P-doped graphene layers was identified, and the local work function of the catalyst surface was also reduced by the interfacial interaction. The interfacial synergy between the encapsulated FeP and phosphorus-doped graphene layers was essential to enhance the ORR performance. This study not only demonstrates the promising ORR properties of the encapsulated-FeP-based nanocomposite catalyst, but also provides direct evidence of the interfacial charge transfer effect and its role in ORR process.