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Microfabrication of the Ammonia Plasma-Activated Nickel Nitride–Nickel Thin Film for Overall Water Splitting in the Microfluidic Membraneless Electrolyzer

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posted on 2021-09-02, 18:08 authored by Biswajit S. De, Pawan Kumar, Neeraj Khare, Jing-Li Luo, Anastasia Elias, Suddhasatwa Basu
Hydrogen production in the microfluidic alkaline membraneless electrolyzer (μAME) marks a new paradigm in sustainable energy technology. One challenge in this field is implementing a bifunctional catalyst to catalyze hydrogen evolution reaction and oxygen evolution reaction using methods compatible with microfabrication techniques. Herein, the scalable synthesis, micropatterning, and performance of a nickel nitride (Ni3N/Ni) bifunctional catalyst are demonstrated. Microfabrication is used to pattern Ni microelectrodes, and nitridation and N–H grafting of the electrodeswhich also act as the catalystsare achieved by ammonia plasma. These electrodes are incorporated into the μAME device, and the electrolyte flow rate is optimized to maximize gas product separation. The μAME is operated in a two-electrode configuration exhibiting a current density of 263.73 mA cm–2 at 2.5 V and a stable 6 h operation for overall water splitting. The μAME performance efficiency is 99.86%, with a current density of 150 mA cm–2. Gas chromatography of the electrolysis products revealed no gas cross-over across the electrodes. Volumetric collection efficiencies of 97.72% for H2 and 96.14% for O2 are obtained. The performance of the μAME is comparable to a membrane-based electrolyzer operating under stringent conditions of high temperature (60–80 °C) and extreme electrolyte pH (30–40 wt % KOH).

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