In situ intergrown chromium nitride‐oxide heterophase systems were synthesized through controlled ambient annealing of chromium nitride (Cr 2 N) at temperatures ranging from 450 to 1050°C. This thermally induced phase evolution enables the formation of biphasic (Cr 2 N/CrN) and triphasic (Cr 2 N/CrN/Cr 2 O 3 ) architectures with intimately coupled interfaces, allowing systematic modulation of their structural and electronic properties. Among the samples, the triphasic CN950 system exhibits remarkable photocatalytic activity, achieving hydrogen evolution and ammonia synthesis rates of 349.5 and 152.4 μmol g −1 h −1 , respectively, under solar irradiation. The enhanced performance is attributed to efficient interfacial charge separation and Schottky‐barrier‐assisted cascade electron transfer within this in situ intergrown heterophase structure. In this configuration, semiconducting Cr 2 O 3 functions as the primary light‐absorber, while metallic CrN and Cr 2 N act as conductive electron‐sinks and reduction‐active sites for H 2 generation and N 2 fixation. The spatial separation of photogenerated charge carriers significantly suppresses recombination, as evidenced by quenched photoluminescence intensity and prolonged carrier lifetimes (~4.36 ns). Comprehensive structural, optical, and electronic analyses reveal that controlled‐oxidation induces favorable band alignment, enhances visible‐light absorption, and establishes functional heterophase interfaces within the system. These findings highlight the potential of in situ intergrown chromium nitride‐oxide heterophase materials as efficient and multifunctional photocatalysts for solar‐driven applications.
Ravikumar et al. (Fri,) studied this question.