Hierarchical CoNiO 2 Microflowers Assembled by Mesoporous Nanosheets as Efficient Electrocatalysts for Hydrogen Evolution Reaction.

In order to alleviate the energy crisis and propel a low-carbon economy, hydrogen (H 2 ) plays an important role as a renewable cleaning resource. To break the hydrogen evolution reaction (HER) bottleneck, we need high-efficiency electrocatalysts. Based on the synergistic effect between bimetallic oxides, hierarchical mesoporous CoNiO 2 nanosheets can be fabricated. Combining physical representations with electrochemical measurements, the resultant CoNiO 2 catalysts present the hierarchical microflowers morphology assembled by mesoporous nanosheets. The ultrathin two-dimensional nanosheets and porous surface characteristics provide the vast channels for electrolyte injection, thus endowing CoNiO 2 the outstanding HER performance. The excellent performance with a fewer onset potential of 94 mV, a smaller overpotential at 10 mA cm -2 , a lower Tafel slope of 109 mV dec -1 and better stability after 1000 cycles makes CoNiO 2 better than that of metallic Co and metallic Ni.