Electrolytic splitting of water into hydrogen (H₂) and oxygen (O₂) provides a promising approach for the storage of renewable energy resources such as solar and wind in the form of chemicals, therefore caters the demand of a continuous usage as well as facile distributions of these intermittent and diffusive energy sources.^1,2 To be commercially viable, highly active hydrogen evolution reaction (HER) electrocatalysts are required. Currently, platinum (Pt) and its alloys are the state-of-the-art catalysts for HER, showing excellent activity as well as stability in both acidic and alkaline media. However, a large-scale implementation of these catalysts has been severely restrained by the cost and scarcity of Pt. As a result, non-precious materials based hydrogen electrodes that exhibit comparable HER catalytic activity to the Pt based catalysts are urgently required.  

Herein, we report the superior HER performances obtained with a series of hierarchically structured binder-free electrodes that comprise transitional metal (Co, Ni and Mn) nanostructures (nanosheets, nanoflakes and nanopyramids) on a three-dimensional Ni foam (Ni-F) current collector. The nanostructures were directly grown on the surface of Ni-F via industrially well-established methods (electrodeposition and hydrothermal treatments), which can avoid the usage of polymeric binders therefore minimize the resistance arisen from the contact between the catalysts and Ni-F current collector, and results in high electrical conductivity and improved catalytic activity.³ Moreover, hierarchical structures are established between the transitional metal nanostructures and the macroporous Ni-F substrate, which will exhibit several apparent advantages, including (i) large accessible surface area for HER to take place, (ii) facile bubbles removal under intensive gas/bubble evolution conditions, thereby avoiding the accumulation of bubbles on the electrode surface that will lead to the blockage of active sites and the prohibition of ionic transportation.⁴ As a result, the as-prepared electrodes exhibit HER catalytic activities close to the benchmark Pt/C catalysts in alkaline media, together with prominent stability, and have the potential to be scaled up for practical applications.   

Reference 

(1) Cook, T. R.; Dogutan, D. K.; Reece, S. Y.; Surendranath, Y.; Teets, T. S.; Nocera, D. G. Chem. Rev. 2010, 110, 6474.

(2) Lu, X. Y.; Yim, W. L.; Suryanto, B. H. R.; Zhao, C. J. Am. Chem. Soc. 2015, 137, 2901.

(3) Xiao, C. L.; Li, Y. B.; Lu, X. Y.; Zhao, C. Adv. Funct. Mater. 2016, 26, 3515.

(4) Lu, X. Y.; Zhao, C. Nat. Commun. 2015, 6, 6616.