High loading accessible active sites: Via designable 3D-printed metal architecture towards promoting electrocatalytic performance

The design and development of highly efficient three-dimensional (3D) supports for electrocatalytic reactions at the boundary of gas-liquid-solid phases are vital in lowering their energy losses. However, 3D supports with geometrically complex designs are very difficult to prepare directly by conventional methods. Here we have demonstrated that high performance catalyst supports with customized three-dimensional metal architectures can be achieved through a direct 3D printing technique, which allows investigating the relationship between 3D support structures and OER performance. Such 3D supports, optimized with control over the design, can possess good electrical conductivity, high mechanical strength and large surface areas, with tunable porous and hollow structures and large holes for effective electrolyte circulation and quick removal of bubbles, all contributing to the enhanced electrocatalytic performance. Because of the large increase in the electrochemically active surface area achieved by 3D printing, when high catalytic activity NiCo₂S₄ nanoneedles are grown in situ on the optimized 3D support, dramatic improvements in electrochemical performance can be obtained with a low Tafel slope (38.7 mV dec^-1) and overpotential (226 mV) at 10 mA cm^-2. Surprisingly, at a high current density of 100 mA cm^-2, the overpotential of the designed electrode is as low as 277 mV. Importantly, the NiCo₂S₄ coating also plays a key role in corrosion protection for the 3D-printed metal support in alkaline media. 3D printing and catalyst coating provide a flexible and versatile approach for the design and fabrication of novel support structures for electrocatalytic applications.