Abstract
Electrochemical water splitting has been considered one of the most promising methods of hydrogen production, which does not cause environmental pollution or greenhouse gas emissions. Oxygen evolution reaction (OER) is a significant step for highly efficient water splitting because OER involves the four electron transfer, overcoming the associated energy barrier that demands a potential greater than that required by hydrogen evolution reaction. Therefore, an OER electrocatalyst with large surface area and high conductivity is needed to increase the OER activity. In this work, we demonstrated an effective strategy to produce a highly active three-dimensional (3D)-printed NiFe-layered double hydroxide (LDH) pyramid electrode for OER using a three-step method, which involves direct-ink-writing of a graphene pyramid array and electrodeposition of a copper conducive layer and NiFe-LDH electrocatalyst layer on printed pyramids. The 3D pyramid structures with NiFe-LDH electrocatalyst layers increased the surface area and the active sites of the electrode and improved the OER activity. The overpotential (η) and exchange current density (i0) of the NiFe-LDH pyramid electrode were further improved compared to that of the NiFe-LDH deposited Cu (NiFe-LDH/Cu) foil electrode with the same base area. The 3D-printed NiFe-LDH electrode also exhibited excellent durability without potential decay for 60 h. Our 3D printing strategy provides an effective approach for the fabrication of highly active, stable, and low-cost OER electrocatalyst electrodes.
Highlights
Electrochemical water splitting has been considered one of the most promising methods of hydrogen production, which does not cause environmental pollution or greenhouse gas emissions
Graphene 3D pyramids were printed onto a flat square Cu foil with successive movements of the nozzle filled with a properly designed graphene ink (30 wt. % graphene microflakes, GMFs, and the 70 wt. % polymer solution)
For efficient deposition of the NiFe-layered double hydroxide (LDH) electrocatalyst on 3D electrodes, the Cu conductive layer was formed on the printed graphene pyramids through electrodeposition conducted at an applied potential of −0.4 V in the electrolyte (0.5 M CuSO4 5H2O) for 30 min
Summary
Electrochemical water splitting has been considered one of the most promising methods of hydrogen production, which does not cause environmental pollution or greenhouse gas emissions. The 3D pyramid structures with NiFe-LDH electrocatalyst layers increased the surface area and the active sites of the electrode and improved the OER activity. Our 3D printing strategy provides an effective approach for the fabrication of highly active, stable, and low-cost OER electrocatalyst electrodes. Several research groups have reported fabrication of effective 3D electrodes for water splitting applications using conventional 3D printing approaches such as a selective laser sintering (SLS) or a fused filament fabrication (FFF)[22,23,24,25,26]. It is possible to manipulate the surface area of the electrodes by producing 3D microstructures on the flat electrode surface
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