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

Mehtap Aygün,Melanie Guillen‐Soler,Andrei N Khlobystov,Maria Del Carmen Gimenez‐Lopez,Abdullah Kurtoglu,Thomas W Chamberlain,Jose M Vila‐Fungueiriño

doi:10.1002/cssc.202102197

Abstract

Invited for this month's cover is the group of Maria Gimenez-Lopez at the University of Santiago de Compostela. The image shows the self-improving electrochemical activity of palladium nanoparticles hardwired into a graphitic step-edge for hydrogen production. The Full Paper itself is available at 10.1002/cssc.202101236.

Highlights

HRTEM confirmed the metallic nature of the palladium nanoparticles (PdNP) in PdNP@graphitised carbon nanofibers (GNF) with the spacing of the lattice fringes (0.22 nm) corresponding to the (111) planes of the face-centred cubic packing of Pd metal (Supplementary Figure 1b), in agreement with the diffraction peak centred at 39.5° (2q) in the powder X-ray diffraction (XRD) measurements (Figure 2c)
thermogravimetric analysis (TGA) studies of PdNP@GNF showed that there was a small weight loss (~ 2%) at ~ 200 °C, which could be due to the presence of a small amount of residual dibenzylideneacetone ligand left adsorbed in the sample
Over 30000 cycles of the hydrogen evolution reaction, the activity of palladium nanoparticles confined within the carbon nanoreactor continually increases, surpassing other palladium catalysts and matching that of platinum

Summary

Introduction

In the last two decades there has been an increasing demand for clean and renewable energy sources as alternatives to fossil fuels.[1,2,3,4] For instance, the water-splitting reaction, which consists of the hydrogen and oxygen evolution half-reactions (HER and OER, respectively), has attracted a great deal of attention as a sustainable source of hydrogen (H2).[5,6,7] Hydrogen gas has been identified as a key energy carrier that can be used to produce clean electricity in fuel cells, where the hydrogen oxidation and oxygen reduction reactions (HOR and ORR, respectively) convert chemical energy into electrical energy.[7,8] driving the HER with renewable sources of energy can lead to a sustainable source of hydrogen fuel that can be used in a zeroemission fuel cell. The hydrogen evolution reaction (2H+ + 2e− → H2) - the cathodic reaction in electrochemical water splitting, is a classic example of a two-electron transfer reaction with one catalytic intermediate, H* (where * indicates a site on the electrode surface) and may occur through either the Volmer-Heyrovsky or the Volmer-Tafel mechanism: Volmer step: H+ + e– + * → H* Equation (1). The electron transfer increased after supporting Pd-MoS2 on multiwalled carbon nanotubes (MWNT) These studies demonstrate an excellent HER activity for Pd-MoS2/MWNT compared to that observed for free standing Pd-MoS2 and MoS2/MWNT, as well as notable stability in acid media after 500 potential cycles.[18]

Methods

Results

Conclusion