Fe@Fe 2 P Core‐Shell Nanorods Encapsulated in Nitrogen Doped Carbon Nanotubes as Robust and Stable Electrocatalyst Toward Hydrogen Evolution

Abstract Here, we report an efficient hydrogen evolution reaction (HER) electrocatalyst (Fe@Fe 2 P/NCNT) fabricated from the phosphorization of partially oxidized iron nanorod encapsulated in nitrogen doped carbon nanotubes (Fe@Fe 2 O 3 /NCNT) synthesized from iron trichloride and melamine, which only requires ∼0 mV and 78.2 mV overpotentials to achieve cathodic current densities of 1 mA cm −2 and 10 mA cm −2 with Tafel slope of 52.2 mV dec −1 in acidic media, which exhibits higher HER electrocatalytic activity compared to Fe/NCNT requiring a overpotential of 118.5 mV to attain 10 mA cm −2 with Tafel slope of 92.3 mV dec −1 . Due to the phosphorization process, additional active sites coming from Fe 2 P boost the electrocatalytic activity of Fe@Fe 2 P/NCNT resulting in decrement in overpotentials by 40.3 mV and 186 mV for 10 mA cm −2 and 50 mA cm −2 compared to Fe/NCNT electrocatalyst, respectively. Meanwhile, Fe@Fe 2 P/NCNT exhibits ignorable degradation in HER activity after 6000 potential cycles suggesting that the Fe@Fe 2 P/NCNT with superior HER activity and stability could potentially replace the benchmark Pt/C (overpotential@10 mA cm −2 : 31 mV) as efficient HER electrocatalyst for water splitting.