Synergistic effect of carbon-decorated hollow TiN architecture for boosting oxygen reduction reaction activity and durability

The development of low-cost and high-efficient electrocatalysts for oxygen reduction reaction (ORR) is a severe challenge for the commercial application of fuel cells. Herein, a durable acidic ORR electrocatalyst composed of carbon nanoparticles decorated on a mesoporous structure of TiN hollow spheres (H-TiN/NC-x) is fabricated for the first time through a hydrothermal-calcination strategy. By moderately adjusting carbon content, the H-TiN/NC-1.00 catalyst exhibits remarkable ORR performance in 0.1 M HClO4 electrolyte with a half-wave potential of 0.80 V, which is close to commercial Pt/C catalyst (0.83 V). Meanwhile, the catalyst reveals a high selectivity for the four-electron pathway with lower H2O2 yield (7 %) and superior tolerance ability to methanol crossover. More importantly, the H-TiN/NC-1.00 catalyst exhibits a higher stability with negligible activity decay than Pt/C catalyst (ΔE1/2 = −80 mV) after 10,000 potential cycles. This outstanding ORR performance for H-TiN/NC-1.00 is attributed to the synergistic effect of unique hollow nanostructure and multiple active sites, which can improve electron transfer and ion diffusion/penetration, maintain the structural stability of hollow spheres for exposing more active sites (H-TiN and NC). Our work demonstrates that manipulating surface state and composition of TiN material is a superior method for optimizing ORR performance in fuel cells applications.