Boosting photocatalytic hydrogen evolution through efficient charge separation in NiSe2 nanooctahedra-TiO2 heterostructures.

The transition to clean energy has recently become the primary focus of researchers. Photocatalytic hydrogen evolution from aqueous sacrificial solutions using TiO2 as the photocatalyst has emerged as a viable approach. However, TiO2 is limited by its large band gap and rapid charge recombination. To overcome these limitations, we investigate the non-noble metal nickel diselenide (NiSe2), synthesized by a simple hydrothermal method, and a series of NiSe2/TiO2 (P25) composites prepared by a wet impregnation method. The intrinsic structural, morphological, optical, and electronic properties of the as-prepared NiSe2/TiO2 composites were investigated using a variety of characterization techniques. The introduction of nanooctahedral NiSe2 led to a 258-fold enhancement in hydrogen evolution compared to pristine TiO2 under UV irradiation. The optimized catalyst exhibited a hydrogen evolution rate of ≈129.4 µmol h-1 and an apparent quantum efficiency (AQE) of ≈4% at 365 nm. This enhancement is attributed to improved charge separation and transfer arising from the morphology, high conductivity, and promising catalytic activity of NiSe2, enabling efficient hydrogen production. Furthermore, the comparison of sacrificial agents shows that for methanol, CO2 was the only detected carbon-containing gaseous product under the applied conditions, whereas glycerol reforming resulted in the formation of both CO and CO2. During glycerol reforming, post-reaction 1H NMR analysis did not reveal major detectable liquid-phase intermediates within the sensitivity limits of the measurement. To further investigate the effect of NiSe2 on the photocatalytic hydrogen evolution of TiO2, a reaction mechanism is proposed. This study demonstrates the potential of nanooctahedral NiSe2 as a cost-effective, stable, and efficient non-noble metal co-catalyst for hydrogen evolution.