Supported transition metal phosphides: Activity survey for HER, ORR, OER and corrosion resistance in acid and alkaline electrolytes
File(s)
Supporting information
Accepted version
Author(s)
Type
Journal Article
Abstract
Carbon supported MxPy (M = Ni, Co, W, Cr and Mo) were prepared via pyrolysis using a very simple and scalable method utilizing non-toxic metal and phosphorous precursors. The electrochemical hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER) reactions and corrosion resistance under both acid and alkaline conditions were examined for all these catalysts and compared to the benchmark catalysts Pt/C (HER/ORR) and IrO2(OER). The highest activities were found in alkaline solutions for Co2P for HER and ORR and Ni2P for OER. Good activity for these was also found in acid for some of these reactions, although the catalysts suffered from susceptibility to corrosion. Co2P was further studied in an alkaline environment as it shows high catalytic activity towards the oxygen reduction reaction (ORR) without significant hysteresis. The onset potential (at 0.5 mA cm-2) obtained was 0.8 V and a Tafel slope value of 38 mV dec-1 with a maximum kinetic mass activity of 2870 A gCo-1 at 0.7 V (RHE). Utilising high resolution transmission electron microscopy (HRTEM) it is possible to observe high-surface area needle-like single crystal cobalt oxide structures on the surfaces of the Co2P particles at the beginning of the ORR. Hence the high rates of initial corrosion of the Co2P identified appear to be associated with the dissolution and precipitation of Cobalt oxide on the particle surface. The as-synthesised Co2P/C also shows good performance in an 8-hour stability test for the Oxygen Evolution Reaction (OER), carried out at 1.6 V vs. RHE in alkaline conditions, with negligible drop in current density over time. Interestingly, in an acidic environment the catalyst is very active towards 2-electron- oxygen reduction leading to H2O2 with high selectivity (85%). It is intriguing that the pH dependence on this catalyst towards the ORR is similar to that seen for gold.
Date Issued
2019-12-06
Date Acceptance
2019-10-01
Citation
ACS Catalysis, 2019, 9 (12), pp.11515-11529
ISSN
2155-5435
Publisher
American Chemical Society (ACS)
Start Page
11515
End Page
11529
Journal / Book Title
ACS Catalysis
Volume
9
Issue
12
Copyright Statement
© 2019 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.9b03359
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Grant Number
EP/M023508/1
EP/J016454/1
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Chemistry
metal phosphides
transition metals
hydrogen peroxide
oxygen reactions
single crystal
OXYGEN REDUCTION REACTION
EFFICIENT BIFUNCTIONAL ELECTROCATALYSTS
COBALT-PHOSPHIDE
EVOLUTION ACTIVITY
FACILE SYNTHESIS
DOPED GRAPHENE
CO2P
NANOPARTICLES
NANOCRYSTALS
CATALYST
0302 Inorganic Chemistry
0305 Organic Chemistry
Publication Status
Published
Date Publish Online
2019-10-31