Boron and Nitrogen Co-doped Molybdenum Carbide Nanostructures for Oxygen Reduction Electrocatalysis

Molybdenum carbide (Mo2C) with unique Pt-like electronic structure displays promising electrocatalysis for oxygen reduction reaction (ORR). However, the oxygen adsorption of Mo2C is overly strong for boosted catalytic activity. Herein, this work developed a bidirectional electronegative heteroatom doping strategy to tune the electronic cloud density of Mo2C. Boron and nitrogen, which have different electronegativities compared to Mo, co-doped nano-Mo2C moieties embedded in a nanoporous nitrogen-doped carbon frame (B,N-Mo2C/NPNC) were synthesized via a cross-linking-pyrolysis process. The introduced B not only tailored the electronic structure of Mo2C but also created additional electron-deficient B active sites for ORR. Additionally, the unique nanoporous carbon structure with dominant nanochannels benefits the exposure of specific surface areas and fast mass transfer. As a result, compared to N-Mo2C/NPNC without B tuning, B,N-Mo2C/NPNC exhibited superior ORR catalytic activity comparable to commercial Pt/C catalysts, making it outstanding among the Mo-based ORR catalysts. Moreover, B,N-Mo2C/NPNC showed robust catalytic stability for ORR with little shift in half-wave potential even after 10,000 cycles. As a cathode catalyst, a B,NMo2C/NPNC-driven zinc-air battery displayed discharge performance superior to the Pt/C-driven one, heralding promising application prospects. This work provided a feasible strategy for boosting the ORR catalytic activity of molybdenum carbide by simultaneously tuning the electronic structure, creating auxiliary active site, and constructing three-dimensional opening nanoporous carbon structures, which can be extended to other metal catalysts for energy conversion.

Automated summary

This study developed a bidirectional electronegative heteroatom doping strategy to tune the electronic cloud density of Mo2C, creating additional electron-deficient B active sites for improved ORR catalytic activity. The B,N-Mo2C/NPNC exhibited superior ORR catalytic performance compared to Pt/C catalysts and demonstrated robust catalytic stability for long-term cycling. The construction of a three-dimensional nanoporous carbon structure also contributed to the enhanced ORR performance, showing promising prospects for energy conversion applications.