Crystalline metal phosphide-coated amorphous iron oxide-hydroxide (FeOOH) with oxygen vacancies as highly active and stable oxygen evolution catalyst in alkaline seawater at high current density

In this study, we employed a straightforward phosphorylation approach to achieve a dual objective: constructing c-a heterostructures consisting of crystalline Ni 12 P 5 and amorphous FeOOH, while simultaneously enhancing oxygen vacancies . The resulting oxygen evolution reaction (OER) catalyst, Ni 12 P 5 /FeOOH/NF, exhibited remarkable performance with current densities of 500 mA cm −2 in both 1 M KOH and 1 M KOH +  seawater , requiring low overpotentials of only 288 and 365 mV, respectively. Furthermore, Ni 12 P 5 /FeOOH/NF exhibited only a slight increase in overpotential, with increments of 18 mV and 70 mV in 1 M KOH after 15 and 150 h, and 32 mV and 108 mV in 1 M KOH + seawater at 500 mA cm −2 after 15 and 150 h, respectively. This minimal change can be attributed to the stabilized c-a structure, the protective coating of Ni 12 P 5 , and superhydrophilic. Through in-situ Raman and ex-situ XPS analysis, we discovered that Ni 12 P 5 /FeOOH/NF can undergo a reconfiguration into an oxygen vacancy-rich (Fe/Ni)OOH phase during OER process. The elevated OER activity is mainly due to the contribution of the oxygen vacancy-rich (Fe/Ni)OOH phase from the reconfigure of the Ni 12 P 5 /FeOOH/NF. This finding emphasizes the critical role of oxygen vacancies in facilitating the production of O O species and overcoming the limitations associated with OOH formation, ultimately enhancing the kinetics of the OER.