NiCu mixed metal oxide catalyst for alkaline hydrogen evolution in anion exchange membrane water electrolysis

Alejandro Oyarce Barnett,Alaa Y. Faid,Svein Sunde,Frode Seland

doi:10.1016/j.electacta.2021.137837

Alejandro Oyarce Barnett, Alaa Y. Faid + Show 2 more

Open Access

https://doi.org/10.1016/j.electacta.2021.137837

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Abstract

We report on the optimization of nickel-copper catalysts for superior performance as a cathode catalyst in anion exchange membrane (AEM) water electrolysis. The bifunctional system of NiCu mixed metal oxide (MMO) nanosheets includes Ni metallic, NiO, and CuO oxides provide rapid kinetics for the hydrogen-evolution reaction (HER) of the Volmer step. In-situ Raman spectroscopy for NiCu MMO proved that nickel hydroxide was sustained under HER conditions for at least 30,000 s, which may explain why the exceptional activity of NiCu MMO as compared to other nickel-copper catalysts is maintained over time. The activity of the NiCu MMO for the HER activity in alkaline electrolytes increased as KOH concentration raised from 0.1 M to 1 M. The NiCu MMO nanosheets showed superior stability under alkaline HER conditions for 30 h. The use of Nafion ionomer in the ink resulted in a higher HER current density as compared to inks with a Fumion anion ionomer. The maximum HER performance was achieved at a Nafion ionomer to catalyst weight ratio of 0.5. Using Ir black as the anode, the NiCu MMO cathode gave an AEM electrolyzer performance of 1.85 A/cm2 at 2 V in 1 M KOH at 50 °C. The NiCu MMO catalyst developed here delivers AEM performance comparable to PEM water electrolysis.

Highlights

Efficient and cheap renewable hydrogen production from water electrolysis is a crucial challenge for a sustainable society [1,2]
We investigated another nickel-copper catalyst without the addition of Na2CO3 and annealed the resulted powder in the air (NiCu oxide) and 5% H2/Ar (NiCu alloy) and they exhibited an agglomerated nanosheets morphology similar to NiCu mixed metal oxide (MMO) as seen in (Fig. S1)
NiCu mixed metal oxide (MMO) nanosheets synthesized by chemical reduction showed an exceptional activity for the hydrogen evolution reaction (HER) compared to NiCu alloy and NiCu oxide catalysts, with higher performance in 1 M KOH than 0.1 M KOH

Summary

Introduction

Efficient and cheap renewable hydrogen production from water electrolysis is a crucial challenge for a sustainable society [1,2]. Nickel is the most active and cheapest non-noble metal catalyst reported for hydrogen evolution reaction (HER) in alkaline electrolysis [5,6]. We suggest NiCu mixed metal oxide (MMO) to catalyze the HER so that the catalyst contains both Ni (which has an affinity for Had) and NiO (which has an affinity for OHad), the simultaneous presence of these being stabilized by CuO under HER conditions. Its activity and stability and the interaction of NiCu metal mixed oxide catalyst with ionomers and effects of an aqueous electrolyte, is important if this catalyst is to play a role in upscaling to AEM water electrolyzer devices, preferably including experiments in aqueous cells and electrolyzer testing. The NiCu MMO/Ir MEA shows comparable performance to Pt/Ir MEA which indicates that it could replace scarce and expensive Pt catalyst

Catalyst synthesis

Structural and electrochemical characterization

In situ Raman measurements

Structural characterization

Electrochemical characterization

Conclusions