As a sustainable and clean energy source, hydrogen can be generated by electrolytic water splitting (i.e., a hydrogen evolution reaction, HER). Compared with conventional noble metal catalysts (e.g., Pt), Mo based materials have been deemed as a promising alternative, with a relatively low cost and comparable catalytic performances. In this review, we demonstrate a comprehensive summary of various Mo based materials, such as MoO₂, MoS₂ and Mo₂C. Moreover, state of the art designs of the catalyst structures are presented, to improve the activity and stability for hydrogen evolution, including Mo based carbon composites, heteroatom doping and heterostructure construction. The structure–performance relationships relating to the number of active sites, electron/ion conductivity, H/H₂O binding and activation energy, as well as hydrophilicity, are discussed in depth. Finally, conclusive remarks and future works are proposed.

A Yb³⁺-doped BiOI 3D nanosheet array composite was successfully fabricated through a solvothermal deposition strategy on flexible carbon cloth (CC). This composite was subsequently integrated with high-chlorine fly ash (FA) blocks to form the Yb-BiOI/CC/FA hybrid material. Comprehensive characterization was performed using multiple analytical techniques for crystalline phase identification, morphological analysis, valence state, band structure evaluation, and charge carrier separation assessment. Electrochemical measurements were conducted to evaluate the material’s electronic properties. Experimental results demonstrated superior photocatalytic performance under visible light irradiation, with the Yb-BiOI/CC/FA composite achieving 52.87% methylene blue degradation efficiency. The reaction rate constant of this modified nanomaterial was approximately 2.1 times higher than that of pristine BiOI/CC/FA. Radical trapping experiments revealed that superoxide radicals (·O₂⁻) served as the predominant oxidative species. This study presents a dual-benefit strategy for environmental remediation by simultaneously achieving sustainable waste valorization of industrial byproducts (FA) and developing high-efficiency photocatalytic materials. The successful integration of rare-earth metal modification with substrate engineering provides valuable insights for designing advanced photocatalytic systems for pollutant degradation.