Carbon Nitride Materials as Efficient Catalyst Supports for Proton Exchange Membrane Water Electrolyzers.

Ana Jorge,Thomas Miller,Ishanka Dedigama,Paul Mcmillan,Daniel Brett,Paul Shearing

doi:10.3390/nano8060432

Abstract

Carbon nitride materials with graphitic to polymeric structures (gCNH) were investigated as catalyst supports for the proton exchange membrane (PEM) water electrolyzers using IrO2 nanoparticles as oxygen evolution electrocatalyst. Here, the performance of IrO2 nanoparticles formed and deposited in situ onto carbon nitride support for PEM water electrolysis was explored based on previous preliminary studies conducted in related systems. The results revealed that this preparation route catalyzed the decomposition of the carbon nitride to form a material with much lower N content. This resulted in a significant enhancement of the performance of the gCNH-IrO2 (or N-doped C-IrO2) electrocatalyst that was likely attributed to higher electrical conductivity of the N-doped carbon support.

Highlights

Among the different ways to produce high-purity hydrogen, proton-exchange water electrolysis currently constitutes the most promising and efficient solution
Our result shows that the presence and formation of Ir/IrO2 NPs in the system can catalyze the decomposition of the carbon nitride support, resulting in a material that corresponds more closely to an electrically conducting N-doped graphite rather than the expected gCNH semiconductor
Conclusions gCNH materials were investigated as catalyst supports for proton-exchange membrane (PEM) water electrolyzers, as support for IrO2, catalyzing the water oxidation reaction taking place at the anode

Summary

Introduction

Among the different ways to produce high-purity hydrogen, proton-exchange water electrolysis currently constitutes the most promising and efficient solution. Preliminary results using IrO2 supported on polymeric gCNH in a PEMWE cell revealed an enhancement in the charge-transfer resistance as the current density increases when compared to unsupported IrO2 This was attributed to a higher active surface area of the catalyst nanoparticles (NP) on the carbon nitride support [38,42]. At 900 ◦C, the appearance of IrO2 could be detected by XRD, while some Ir metal remained present This behavior is completely different from the sample studied without the presence of gCNH, indicating that the carbon nitride material is an essential participant in the redox reactions. Nanomaterials 20p1o8t,e8n,ti4a3l2of the gCNH-IrO2 at 400 °C MEA increased, giving a final cell potential of 1.93 V at 1 A cm−2, the highest current density tested in these experiments This value was slightly higher than that obtained for the commercial MEA (1.90 V). FTuarbthleer1.dEeItSafiiltsteodf pthareasmyenttehrsesoifsthaenddacthaasrhaocwtenriinzaFtiigounreof8.this material are given elsewhere [45]

Synthesis of IrO2 Nanoparticles

Synthesis of gCNH-IrO2

Structural and Compositional Characterization

Electrochemical Performance Evaluation

Findings

Conclusions