The cobalt-based metal organic frameworks array derived CoFeNi-layered double hydroxides anode and CoP/FeNiP heterojunction cathode for ampere-level seawater overall splitting.

The seawater electrolysis technology powered by renewable energy is recognized as the promising "green hydrogen" production method to solve serious energy and environmental problems. The lack of low-cost and ampere-level current OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalysis limits their industrial application. In this work, a unique tri-metal (Co/Fe/Ni) layered double hydroxide hollow array anode catalyst (CFN-LDH/NF) and the CoP/FeNiP heterojunction hollow array cathode are successfully prepared via one in-situ growth of Co-MOF on nickel foam (Co-MOF/NF) precursor, which exhibits excellent catalytic performance. The η values of 352 and 392 mV are achieved for CFN-LDH/NF (OER catalyst) in 1.0 M KOH and alkaline seawater solution, respectively. The CFNP/NF with a low overpotential of 281 mV is required to reach 1000 mA cm current density for HER in 1.0 M KOH solution, while the η in alkaline seawater solution is 312 mV. The CFN-LDH/NF||CFNP/NF electrolyzer exhibits excellent long-term durability over 100 h, achieving current density of 500 mA cm at 1.825 V in 1.0 M KOH solution. The construction of hollow tri-metal LDH and phosphides heterostructures may open a new and relatively unexplored path for fabricating high performance seawater splitting catalysis.