How do H₂ oxidation molecular catalysts assemble onto carbon nanotube electrodes? A crosstalk between electrochemical and multi-physical characterization techniques

Abstract

How do efficient hydrogen-oxidation molecular electrocatalysts connect onto their carbon nanotube conductive support? A coupled neutron scattering SANS and STEM electron microscopy study to observe soft active matter organizing on 3D nanosurfaces.

Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

“…An all-organometallic fuel cell was also demonstrated by physisorption of [Ni­(P Py 2 N tolyl 2 ) 2 ] 2+ to the anode and cathode . Further studies of [Ni­(P Cy 2 N Arg 2 ) 2 ] 2+ focused on the use of carboxylic acid substituted graphene (graphene acid) for electrostatic absorption and to control loading density, as well as the use of a combination of advanced characterization methods to understand immobilization and the corresponding loading on acid substituted multiwalled carbon nanotubes . This series of studies demonstrated the promise of the [Ni­(P 2 N 2 ) 2 ] 2+ complexes in practical systems, which need further improvements to be competitive in a functioning PEM fuel cell.…”

“…203 Further studies of [Ni(P Cy 2 N Arg 2 ) 2 ] 2+ focused on the use of carboxylic acid substituted graphene (graphene acid) for electrostatic absorption and to control loading density, 204 as well as the use of a combination of advanced characterization methods to understand immobilization and the corresponding loading on acid substituted multiwalled carbon nanotubes. 205 With the use of a related approach, multiwalled carbon nanotubes were modified by using a pyrene butyric acid derivative to create the negatively charged substituents at the electrode surface. 206 These substituents were then equivalently used to electrostatically attract the protonated form of [Ni(P Cy 2 N Arg 2 ) 2 ] 2+ , yielding a catalytic current of 0.21 A cm −2 with an overpotential of 0.4 V for this anode at 25 °C.…”

Non‐Covalent Integration of a [FeFe]‐Hydrogenase Mimic to Multiwalled Carbon Nanotubes for Electrocatalytic Hydrogen Evolution

“…In parallel, the immobilization of various related [FeFe]‐H 2 ase mimics on multi‐walled carbon nanotube (MWNT) functionalized electrodes has been shown to provide remarkable stability and activity under acidic aqueous condition [54,55] . Among the previously reported grafting strategies, immobilization relying on nonspecific physisorption often results in poor electron transfer rates combined with limited stability of the anchoring over long term electrolysis, [56] while covalent coupling typically leads to lower surface loadings, [47,53] inhomogeneous catalyst distribution and possible degradation of the MWNT support [57] . In recent years, non‐covalent integration of metal complexes modified with pyrene units onto π ‐conjugated supports, using π‐π interactions, has been shown to improve catalyst loading and the electronic communication between the complex and the electrode, while providing stable grafting in aqueous catalytic conditions [46,58–65] .…”

“…[ 54 , 55 ] Among the previously reported grafting strategies, immobilization relying on nonspecific physisorption often results in poor electron transfer rates combined with limited stability of the anchoring over long term electrolysis, [56] while covalent coupling typically leads to lower surface loadings,[ 47 , 53 ] inhomogeneous catalyst distribution and possible degradation of the MWNT support. [57] In recent years, non‐covalent integration of metal complexes modified with pyrene units onto π ‐conjugated supports, using π‐π interactions, has been shown to improve catalyst loading and the electronic communication between the complex and the electrode, while providing stable grafting in aqueous catalytic conditions. [ 46 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ] To date, this mild surface functionalization strategy has not yet been reported for the anchoring of {(μ‐S 2 )Fe 2 (CO) 6 } derivatives.…”