Fabrication of an amorphous metal oxide/p-BiVO4 photocathode: understanding the role of entropy for reducing nitrate to ammonia

Abstract

The controllable design of chemical microenvironment with the expected thermodynamics and kinetics for boosting catalytic activity and selectivity presents a challenge. Herein, an amorphous metal oxide (A-M_xO_y) was employed to understand the polymetallic association of the effect of entropy, revealing the interplay between entropy and the NO₃⁻ reduction reaction (NITRR) in a photoelectrochemical (PEC) system. Based on ultrafast transient absorption spectroscopy, the signal recovery of an optimal heterostructure (CoFeMnO/BiVO₄) was 9.1 ps, confirming that amorphous CoFeMnO effectively promotes the kinetic factor of electrons. Thus, the NH₃ yield rate of the optimal heterostructure (CoFeMnO/BiVO₄) is up to 17.82 μg h⁻¹ cm⁻² (at −0.1 V vs. RHE), which is almost twice that of p-BiVO₄. Furthermore, isotope ¹H nuclear magnetic resonance spectroscopy was used to further demonstrate the exactitude of the NH₃ evolutionary process, using ¹⁵NO₃⁻ as the N resource. Therefore, desirable entropy regulation and NH₃ production make the herein A-M_xO_y/BiVO₄ heterostructure a promising NITRR catalyst for use in a future solar conversion system.