Rational fabrication of Ni2P-Ni12P5 heterostructure with built-in electric-field effects for high-performance urea oxidation reaction

Developing efficient electrocatalysts and investigating catalytic mechanisms are crucial in urea oxidation reaction (UOR) as a promising strategy to boost the energy efficiency of hybrid water electrolysis for H2 production. The present work rationally designed and fabricated Ni2P-Ni12P5 heterostructure with varying relative ratios embedded on the defective carbon-nitrogen-phosphorus substrate (Ni2P-Ni12P5/CNP) for high-performance UOR in alkaline conditions through a facile solution-combustion route without extra phosphorus sources. The developed synthesis method avoids the high cost, complicated routes, and extremely toxic emissions. Experimental and theoretical studies demonstrated that the Ni2P-Ni12P5 heterostructure regulated the interfacial electric field and promoted electron transfer. The abundantly defective CNP substrate improved the electrical conductivity and prevented Ni2P-Ni12P5 heterostructure from corrosion and detachment. The optimal electrocatalyst, with an approximately equal content of Ni2P and Ni12P5, exhibits a low potential of 1.32 V to deliver 100 mA cm-2, a small Tafel slope of 31.4 mV dec- 1, robust stability of 80 h in UOR, and a low voltage of 1.85 V to reach 100 mA cm-2 in HER||UOR. This work provides a facile route to design electrocatalysts for efficient electrochemical hydrogen production.