Integrated Catalyst‐Substrate Electrodes for Electrochemical Water Splitting: A Review on Dimensional Engineering Strategy

Abstract Water splitting (or, water electrolysis) is considered as a promising approach to produce green hydrogen and relieve the ever‐increasing energy consumption as well as the accompanied environmental impact. Development of high‐efficiency, low‐cost practical water‐splitting systems demands elegant design and fabrication of catalyst‐loaded electrodes with both high activity and long‐life time. To this end, dimensional engineering strategies, which effectively tune the microstructure and activity of electrodes as well as the electrochemical kinetics, play an important role and have been extensively reported over the past years. Here, a type of most investigated electrode configurations is reviewed, combining particulate catalysts with 3D porous substrates (aerogels, metal foams, hydrogels, etc.), which offer special advantages in the field of water splitting. It is analyzed the design principles, structural and interfacial characteristics, and performance of particle‐3D substrate electrode systems including overpotential, cycle life, and the underlying mechanism toward improved catalytic properties. In particular, it is also categorized the catalysts as different dimensional particles, and show the importance of building hybrid composite electrodes by dimensional control and engineering. Finally, present challenges and possible research directions toward low‐cost high‐efficiency water splitting and hydrogen production is discussed.