Efficient oxygen reduction using a polymorphic tungsten catalyst

The oxygen reduction reaction (ORR) constitutes an important transformation process in fuel cells. Here we report a polymorphic tungsten catalyst with a concerted tungsten single-atom site (W-SAC) and tungsten nitride nanoclusters (WN-NPs) for mediating the ORR processes. The catalyst is prepared via pyrolysis of phthalocyanine-typed material (WPc) with g-C3N4. Synergy of the W-SAC and WN-NP sites over the designed 2D g-C3N4 layer is responsible for the competitive ORR performance of the catalysts. Consequently, the WNPc/gC3N4-700 sample gives a half-wave potential of 0.835 V, a Tafel slope of 40.47mV dec−1, and a mass diffusion-limited current of 0.596 mA/cm2; such results are comparable with and even better than that of 20% Pt/C. Furthermore, WNPc/gC3N4-700 also outperforms 20% Pt/C in terms of stability and durability. Our work may point toward a design strategy for active, stable, non-noble-metal ORR catalysts.