MOF-Derived Co(Fe)OOH\nSlab and Co/MoN Nanosheet-Covered\nHollow-Slab for Efficient Overall Water Splitting

The development of economical, efficient, and stable\nnonprecious\nmetal electrocatalysts presents a crucial approach to achieving alkaline\noverall water splitting and generating renewable hydrogen. This work\npresents a simple method for the synthesis of transition metal oxyhydroxides\nand nitrides derived from the MOF template with different morphological\nstructures for efficient overall water splitting. Co(Fe)OOH slab array\nis obtained by the electro-activation of Fe-doped Co-MOF precursor,\nwhich is usually regarded as the real active substance in the alkaline\nOER process. Doping the Co(Fe)OOH with Fe alters the local electronic\nstructure of the Co sites, leading to a notable improvement in OER\nperformance, which shows an overpotential of 209 mV at 10 mA cm<sup>–2</sup> and demonstrates excellent stability. On the other\nhand, Co/MoN nanosheet-covered hollow-slab heterostructure is prepared\nby the nitrogenization of Na<sub>2</sub>MoO<sub>4</sub>-etched Co-MOF\ntemplate, which displays superior HER performance due to its abundant\nelectrochemical active sites and rapid interfacial electron transfer,\nachieving an overpotential of 37 mV at 10 mA cm<sup>–2</sup> while sustaining good stability. Notably, utilizing Co(Fe)OOH as\nthe anode and Co/MoN as the cathode in the alkaline electrolyzer results\nin a cell voltage of 1.49 V at 10 mA cm<sup>–2</sup>, while\ndemonstrating a remarkable long-term stability of 100 h. This work\nprovides a facile way to construct an efficient alkaline electrolyzer\nfor overall water splitting by controlling the structures of MOF derivatives.