N-doped MoSi2 with tuned electronic structure for highly selective photocatalytic CO2 reduction

Solar-driven CO 2 reduction is often limited by slow surface reactions and large thermodynamic barriers. In this work, we activated the hidden reactivity of molybdenum disilicide (MoSi 2 ) through controlled nitrogen (N) doping. Instead of simple physical mixing, nitrogen incorporation triggers a clear rearrangement of the crystal structure, leading to the preferred exposure of the active (110) facets and an improvement in the porous framework. Comprehensive spectroscopic analyses combined with density functional theory (DFT) calculations reveal a synergistic electronic modulation mechanism. Crucially, the formation of electron-rich Mo centers significantly lowers the work function and establishes a robust electron reservoir. This configuration thermodynamically drives the rapid injection of photogenerated electrons into surface-adsorbed species, effectively reversing the rate-determining protonation step of CO 2 * to COOH* from an endergonic barrier to a spontaneous process. As a result, the optimized catalyst achieves a striking 34-fold increase in the CO production rate and reaches a CO to CH 4 selectivity of about 134. This study not only explains how activity is improved in non-oxide systems from several different aspects but also provides a clear and practical approach for designing future intermetallic photocatalysts by carefully tuning their energy bands and defect states.