Palladium Nanoparticles Hardwired in Carbon Nanoreactors Enable Continually Increasing Electrocatalytic Activity During the Hydrogen Evolution Reaction

Abstract

Catalysts typically lose effectiveness during operation, with much effort invested in stabilising active metal centres to prolong their functional lifetime for as long as possible. In this study palladium nanoparticles (PdNP) supported inside hollow graphitised carbon nanofibers (GNF), designated as PdNP@GNF, opposed this trend. PdNP@GNF exhibited continuously increasing activity over 30000 reaction cycles when used as an electrocatalyst in the hydrogen evolution reaction (HER). The activity of PdNP@GNF, expressed as the exchange current density, was always higher than activated carbon (Pd/C), and after 10000 cycles PdNP@GNF surpassed the activity of platinum on carbon (Pt/C). The extraordinary durability and self‐improving behaviour of PdNP@GNF was solely related the unique nature of the location of the palladium nanoparticles, that is, at the graphitic step‐edges within the GNF. Transmission electron microscopy imaging combined with spectroscopic analysis revealed an orchestrated series of reactions occurring at the graphitic step‐edges during electrocatalytic cycling, in which some of the curved graphitic surfaces opened up to form a stack of graphene layers bonding directly with Pd atoms through Pd−C bonds. This resulted in the active metal centres becoming effectively hardwired into the electrically conducting nanoreactors (GNF), enabling facile charge transport to/from the catalytic centres resulting in the dramatic self‐improving characteristics of the electrocatalyst.

Electrocatalytic activity for proton reduction by a covalent non-metal graphene–fullerene hybrid

“…4(D)). The self-improving electrocatalytic activity for materials has been reported in other works as well, 33,34 attributed to the activation of more catalytic sites in the hybrids during cycling.…”

Si regulation of hydrogen adsorption on nanoporous PdSi hybrids towards enhancing electrochemical hydrogen evolution activity

“…3,54 Meanwhile, the reduction peaks are formed at 41.4 and 51.3 mV for Pd 15 Si and Pd 3 Si, which indicate that OPD-H ads transfers to the underpotential deposition of H abs (UPD-H abs ). 22,37,42,52,53 This phenomenon of UPD of H is more likely to occur on electrocatalysts with high HER activity similar to Pt. At the same time, it is proved from the H ad that transferring H 2 gas on the surface Pd 15 Si and Pd 3 Si is easier than that of Pd.…”

“…These supports include CoS 2 , 26 MoS 2 , 27,28 VS 2 , 29 NiCo 2 S 4 , 30 Mo 3 N 2 , 31 MoO 3 , 32 TiO 2 , 33 FeOx (OH) 2 , 6 Co/CoO x , 34 graphene, 14,21,35,36 and graphitized carbon nanofibers. 37 Last, the most important way is to synthesize Pdbased alloys, and to change the hydrogen adsorption energy on their surfaces through the electronic effect between the alloys, which is the key parameter for HER. At present, Pdbased alloys such as PdFe, 24,38 PdAg, 9,39 PdNi, 11,40 Pd 3 Ru, 41 Pd@Ru, 16 PdIr, 42 Pd@Ir, 43 Ir-doped Pd, 12 PdNiCo, 35 PdBi 2 , 6 Pd/Bi/Cu, 13 PdMnCo, 44 PdCo@Pd, 45 and CuPd/Pd 17,46 have been developed, and their hydrogen evolution activities have been improved to varying degrees.…”

Electrochemistry of redox-active molecules confined within narrow carbon nanotubes

“…Future exploration of electrochemistry confined within SWCNTs and DWCNTs could help to discover new fundamental redox phenomena at the single-molecule level, as well as to advance many practical applications, including energy storage and conversion materials, 10 sensing devices and electrocatalysts. 61,62…”