3D printing of combustive inks for hierarchically porous electrochemical electrodes

Monolithic porous metals have attracted great interest due to their excellent material properties such as high specific surface area, low density and good electrical conductivity. Herein, a novel 3D printing approach is proposed to construct self-supporting nickel electrodes with digitally programmable macropores and combustion-induced nanopores through a facile "direct ink writing and combustion synthesis" strategy. The pore size distribution and composition of the electrodes can be adjusted by carefully designing the combustive ink composition and controlling the parameters of the combustion process. Chain-like nickel microstructures generated by combustion act as "bridges" to give the electrodes robust mechanical and electrical properties and simultaneously increase electrochemical active sites. In addition, the hierarchical porosity promotes charge transfer and mass transfer at the NiFe nanosheet electrode, with overpotentials of similar to 289 mV and 131 mV for oxygen and hydrogen evolution reactions, respectively, at 30 mA center dot cm(-2). This work highlights a new 3D printing strategy for fabricating hierarchically porous structures, which can be applied to energy storage and conversion, catalysis, adsorption, gas sensing, and separation.