Electrochemical Activation of Single-Walled Carbon Nanotubes with Pseudo-Atomic-Scale Platinum for the Hydrogen Evolution Reaction

Abstract

The development of effective and inexpensive hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. Platinum-based materials are the most active electrocatalysts for catalyzing HER, but reducing the use of Pt is required because of the high price and scarcity of Pt. Here, we achieve pseudo-atomic-scale dispersion of Pt, i.e. individual atoms or subnanometer clusters, on the sidewalls of single-walled carbon nanotubes (SWNTs) with a simple and readily upscalable electroplating deposition method. These SWNTs activated with an ultralow amount of Pt exhibit activity similar to that of commercial Pt/C with a notably higher (∼66–333-fold) Pt loading for catalyzing the HER under the acidic conditions required in proton exchange membrane technology. These catalysts resemble pseudo-atomic-scale Pt systems which are mainly composed of a few to tens of Pt atoms dispersed on the sidewalls of the SWNTs. The Pt loading is only 0.19–0.75 atom % at the electrode surface, and characteristic peaks for Pt cyclic voltammograms are undetectable. The atomic dispersion increases the portion of the surface active-atom sites, and therefore, notably lower Pt loading is needed to attain a high catalytic activity. Density functional theory (DFT) calculations suggest higher ability for SWNTs, in comparison to graphene, as a catalyst support for immobilizing Pt atoms, thus providing an atomic dispersion. Moreover, a high HER activity for the SWNTs activated with Pt atoms, similar to that of bulk Pt, is predicted.

The Multifaceted Reactivity of Single‐Atom Heterogeneous Catalysts

“…[5] These have mainly focused on Pt-based catalysts, [55,[114][115][116][117] because their established practical relevance,o ra lternatives based on earth-abundant metals (primarily Co or Fe). [5] These have mainly focused on Pt-based catalysts, [55,[114][115][116][117] because their established practical relevance,o ra lternatives based on earth-abundant metals (primarily Co or Fe).…”

“…[5] These have mainly focused on Pt-based catalysts, [55,[114][115][116][117] because their established practical relevance,o ra lternatives based on earth-abundant metals (primarily Co or Fe). Significantly enhanced activity has been reported in the hydrogen evolution reaction (HER) over pseudo-SACs based on N-doped graphene nanosheets (37 times) [55] or single-walled carbon nanotubes (up to 333 times) [114] in acidic media. In the majority of cases,t he performance of SACs has been evaluated with respect to the commercial Pt/C NP-based catalyst.…”

Densely Populated Single Atom Catalysts

“…Different from the transition metal atom, precious metal atoms usually have a weak interaction with the support; thus, it's much difficult to increase the loading of precious metal atoms in the SACs. To address this issue, Tavakkoli et al developed an electrodeposition method to achieve pseudo‐atomic‐scale dispersion of Pt on single‐walled carbon nanotubes. Briefly, Pt ions were dissolved in a sulfuric acid solution and electrochemically adsorbed on single wall carbon nanotubes (SWNTs) with atomically dispersed Pt loading from 2.94 to 10.22 wt%.…”

“…The Pt 1 /hNCNC‐2.92 catalyst showed an overpotential of 15 mV at a current density of 10 mA cm −2 , and mass activity of 7.6 A mg Pt −1 at the overpotential of 20 mV. Tavakkoli et al achieved pseudo‐atomic‐scale dispersion of Pt on single‐walled carbon nanotubes activated by 400 potential cycles (400‐SWNT/Pt) with atomically dispersed Pt loading from 2.94 to 10.22 wt%. The 400‐SWNT/Pt exhibited a low overpotential of 27 mV to achieve current densities of 10 mA cm −2 , which are similar to those of Pt/C.…”

Engineering the Coordination Environment of Single‐Atom Platinum Anchored on Graphdiyne for Optimizing Electrocatalytic Hydrogen Evolution

“…Therefore,g reat efforts have been devoted to increase the platinum utilization as well as to improve the HER activity of Pt-based catalysts. [14,15] ForSACs, the coordination environments of metal atoms will greatly influence their electronic structures,a nd subsequently affect their catalytic activity. [9][10][11][12][13] More recently,P tS ACsw ith individual Pt atoms anchored on the supports of carbon nanotube and CoP have also been developed as efficient HER electrocatalysts.…”