Water Electrolysis using Flame-Annealed Pencil-Graphite Rods

Abstract

Inexpensive and sensitive graphite electrodes were fabricated by applying flame annealing to pencil-graphite rods (PGRs) as electrodes for water electrolysis cells. The resin (polymer, binder) on the surface of PGR was removed by flame annealing to make it porous, and the graphite electrodes with high activity and low cost were obtained. By flame annealing the PGR, although the PGR electrode became active upon water electrolysis, the PGR electrode became instable for long-time operation. The effects of flame annealing on PGR for water electrolysis were analyzed by SEM, FT-IR spectroscopy, Raman spectroscopy, NEXAFS, and electrochemical impedance spectroscopy (EIS).

Water Electrolysis Using Thin Pt and RuOx Catalysts Deposited by a Flame-Annealing Method on Pencil-Lead Graphite-Rod Electrodes

“…Hysteresis was observed between forward and reverse potential sweeping directions, which was considered to be the effect of the capacitance of the electrocatalyst on the PGR with a large specific surface area. 10 In addition, this capacitance effect did not change significantly before and after catalyst deposition. This suggested that the catalyst on the PGR surface did not have a porous structure, as observed by SEM (Figure 2).…”

“…In this study, a PGR (the hardness: 4B, uni exchangeable pencil graphite rod, φ2.0 mm × 130 mm, Mitsubishi Pencil Co., Ltd., Japan), which is low cost and useful as a base material for the catalyst-deposited electrode, was used as a base material for the catalyst-deposited electrode in water electrolysis. 10 Figure 1a shows the schematic illustration of the fabrication procedure of Pt and RuO x catalysts deposited on a PGR by flame-annealing. The PGR electrodes with Pt and RuO x catalysts were named Pt/PGR and RuO x /PGR, respectively.…”

“…In order to remove the coating polymer on the surface and to activate the graphite, the whole of the PGR was annealed for 1 min in a flame using liquefied petroleum gas until the PGR emitted red light by heat. 10 The PGR was aircooled to room temperature.…”

“…For Faraday efficiency measurement and stability test in the Hoffman electrolysis apparatus, the distance between electrodes were 60 mm. 10 For the Faraday efficiency measurement, the applied potential was set at 10 V, which is due to the significant solution resistance by the electrode distance (60 mm) in the Hoffman electrolysis apparatus, and the Faraday efficiency and hydrogen and oxygen evolution rates were measured until the hydrogen amount reached up to an apparatus limit of 50 mL. The stability test was performed with a constant voltage at 10 V, and the current variation was measured.…”

Pencil graphite rods decorated with nickel and nickel–iron as low-cost oxygen evolution reaction electrodes

“…'Previous data by SEM and BET showed that ame annealing treatment improves the porosity of PGRs'. 25 We tested FA@PGRs for the OER; however, they were not good catalysts for this reaction. For this reason, in order to improve the performance of PGRs, we developed new electrodes by the deposition of Ni and NiFe on the PGR (Fig.…”