High-pressure vapor-solid transformation of 2D template to derive 2D Co-N-C electrocatalysts for oxygen reduction reaction.

Two-dimensional (2D) cobalt zeolitic imidazolate frameworks (ZIF-67) have attracted significant research interests to synthesize cobalt and nitrogen co-doped carbon-based (Co-N-C) catalyst for oxygen reduction reaction (ORR). However, most of the current synthetic approaches of 2D ZIF-67 are energy-intensive, environmentally hazardous and low-yield. Herein, a feasible and efficient "morphology-retaining method via a high-pressure vapor-solid reaction" are reported to synthesize 2D ZIF-67 nanosheets by using 2D cobalt carbonate hydroxide template. In the strategy, the high-pressure vapor caused by sublimation of 2-Melm and the pores formed from effusion of CO2 during transformation ensure the complete transformation from 2D template to 2D ZIF-67. The corresponding 2D Co-N-C catalyst exhibits comparable ORR electrocatalytic activity and better stability than Pt/C in alkaline media. The present method is expected to offer a feasible and universal way to efficiently synthesize 2D M-N-C catalysts.