Lattice Strain‐Modulated Trifunctional CoMoO 4 Polymorph‐Based Electrodes for Asymmetric Supercapacitors and Self‐Powered Water Splitting

Abstract Developing efficient, multifunctional electrodes for energy storage and conversion devices is crucial. Herein, lattice strains are reported in the β‐phase polymorph of CoMoO 4 within CoMoO 4 @Co 3 O 4 heterostructure via phosphorus doping (P‐CoMoO 4 @Co 3 O 4 ) and used as a high‐performance trifunctional electrode for supercapacitors (SCs), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) in alkaline electrolytes. A tensile strain of +2.42% on the β‐phase of CoMoO 4 in P‐CoMoO 4 @Co 3 O 4 results in superior electrochemical performance compared to CoMoO 4 @Co 3 O 4 . The optimized P‐CoMoO 4 @Co 3 O 4 achieves a high energy density of 118 Wh kg −1 in an asymmetric supercapacitor and low overpotentials of 189 mV for the HER and 365 mV for the OER at a current density of 500 mA cm −2 . This results in a low overall water splitting voltage of 1.71 V at the same current density making it an effective bifunctional electrode in a 1 m KOH freshwater electrolyte. Theoretical analysis shows that the excellent performance of P‐CoMoO 4 @Co 3 O 4 can be attributed to interfacial interactions between CoMoO 4 and Co 3 O 4 , and the β‐phase of CoMoO 4 , which lead to strong OH − adsorption and low energy barriers for reaction intermediates. Practical application is demonstrated by using P‐CoMoO 4 @Co 3 O 4 ‐based ASCs to self‐generate hydrogen (H 2 ) in a P‐CoMoO 4 @Co 3 O 4 ||P‐CoMoO 4 @Co 3 O 4 alkaline seawater electrolyzer, showcasing its potential for future energy technologies.