Hollow Fe-doped CoP with rich phosphorus defects as bifunctional electrocatalyst for overall water electrolysis

초록

Development of sustainable energy sources is becoming urgent issue due to the environmental problems and rapid depletion of fossil fuels. Hydrogen is considered as promising candidate to substitute fossil fuel owing to its high gravimetric energy density and environmental friendliness.[1] One of the promising technology to produce sustainable and ultra-pure hydrogen gas is electrochemical water splitting because of abundant water resources in the earth. Precious metal-based materials such as RuO2 and Pt/C have been used as efficient electrocatalysts for OER and HER, respectively, which have hampered the practical application of water electrolysis due to their scarcity, high expense, and inferior durability. Therefore, it is necessary to design novel catalysts which can substitute the precious metal-based materials, and many researchers have devoted to developing transition-metal based phosphide electrocatalysts because of their low expense and rich redox properties. Herein, we proposed facile synthetic procedur eof hollow structured Fe-doped CoP with abundant phosphorus vacancies (VP-Fe-CoP). Well-defined hollow structure of electrocatalysts can not only reduce the diffusion length for mass transport, but also maximize the exposure of abundant active sites. Additionally, the defect engineering strategy such as heteroatom doping and anion vacancy can adjust the electronic structure of the catalyst and provide additional active sites for electrocatalysis, thereby improving electrochemical performance for water electrolysis.[2,3]The obtained VP-Fe-CoP catalyst shows outstanding electrocatalytic performance with low ovepotentials of 300 and 143 mV to achieve a current density of 10 mA cm-2 and Tafel slope of 48.2 and 91.6 mV dec-1 for OER and HER, respectively. Also, the symmetric water electrolyzer assembled with the prepared VP-Fe-CoP as electrocatalyst for both OER and HER exhibits a low cell voltage of 1.63 V to afford a current density of 10 mA cm-2.