Three-Dimensional N-Doped Carbon Nanotube Frameworks on Ni Foam Derived from a Metal-Organic Framework as a Bifunctional Electrocatalyst for Overall Water Splitting

Rational design of bifunctional, high-performance, and stable non-noble metal-based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great importance and challenging for the realization of overall water splitting. Metal-organic frameworks (MOFs) have been intensively studied as pyrolyzing precursors to prepare electrocatalysts. However, the aggregation of powder and the low conductivity of polymer binders have limited the applications of powder electrocatalysts. Therefore, the direct growth of MOFs on conductive and porous substrates will be a favorable way to prepare efficient electrocatalysts for electrocatalytic water splitting. Herein, we report a facile strategy for constructing three-dimensional N-doped carbon nanotube frameworks derived from metal-organic framework on Ni foam as a bifunctional electrocatalyst for overall water splitting. The resulting electrocatalyst exhibits excellent stability and high OER and HER activity with rather low overpotentials of 230 and 141 mV at 10 mA/cm² in 1.0 M KOH, respectively. Specifically, the as-synthesized electrodes were used as both the cathode and anode for overall water splitting with 10 mA/cm² at a cell voltage of only 1.62 V. The outstanding electrocatalytic performance is mainly attributed to a large number of accessible active sites of Co nanoparticles dispersed by the N-doped carbon nanotubes (CNTs) and the ultra-high surface area of CNT frameworks. The presented strategy offers a novel approach for developing MOF-derived nanocarbon materials on Ni foam for electrocatalysis and electrochemical energy devices.