Synergistic effect of iron diselenide decorated multi-walled carbon nanotubes for enhanced heterogeneous electron transfer and electrochemical hydrogen evolution

Abstract Iron diselenide (FeSe 2 ) has been of recent interest as a potentially useful electrode material. Here we demonstrate, for the first time, the synergistic effect between multi-walled carbon nanotubes (MWCNT) and FeSe 2 in a form of MWCNT/FeSe 2 composite, for the heterogeneous electron transfer (HET) reaction with the [Ru(NH 3 ) 6 ] 3+/2+ redox probe and the electrochemical hydrogen evolution reaction (HER) in acidic media. Plain FeSe 2 and the MWCNT/FeSe 2 composite were synthesized using a one-pot hydrothermal method. Although all electrode materials (pristine MWCNT, FeSe 2 , and MWCNT/FeSe 2 ) show a quasi-reversible electrode behavior, MWCNT/FeSe 2 has a smaller peak separation potential and exhibits an enhanced HET rate constant, k 0  = 5.4 × 10 −3  cm/s, which is 3.2 and 1.6 times higher than that of FeSe 2 and MWCNT, respectively. Similarly, the HER performance of the composite demonstrates a smaller Tafel slope of 70 mV/dec and a reduced overpotential. We anticipate that such promising outcome can be further improved by employing different morphologies of FeSe 2 and engineered interaction with other conductive supports suitable for their applications in electrochemical sensing and energy conversion.