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[Display omitted] Cocatalysts play a key role in improving photocatalytic performance by enhancing conductivity and providing an enormous number of active sites simultaneously. However, cocatalysts are usually made of noble metals such as Pt, which are expensive and rare. Therefore, cocatalysts derived from cheap and abundant elements are highly desirable. Here, for the first time, we demonstrate that NiCS 3 , which is made from nickel that is abundant and costs less than 0.04 % of Pt, is an effective substitute for Pt cocatalysts for the photocatalytic activity of CdS nanorods in hydrogen evolution reaction (HER). Under visible light, the NiCS 3 /CdS composite with NiCS 3 as the cocatalyst achieved an astonishing H 2 production of 61.9 mmol·g−1·h−1 while maintaining high stability, which is 14 times higher than that observed when using CdS alone and nearly 2 times higher than that of Pt/CdS. We also established that the metallicity of NiCS 3 results in good carrier conductivity, which promotes the electron transfer and the separation of photo-induced carriers. Due to the appropriate adsorption energy ΔG H* , NiCS 3 more readily adsorbs hydrogen protons and desorbs molecular hydrogen during the photocatalytic process compared with Pt. Additionally, NiCS 3 can effectively inhibit the photo-corrosion effect of CdS itself, ensuring a good stability of HER. These results suggest that NiCS 3 is a promising substitute for Pt cocatalysts. [ABSTRACT FROM AUTHOR]

• Superior peroxidase mimetic performance towards H 2 O 2 is founded in the typical Weyl semimetal WTe 2 , which is derived from the two-step electron pathway. • The robust topological surface states (TSSs) on WTe 2 which serve as effective electron bath are directly involved in the electron transfer process during the enzyme-like reaction. • The TSSs can efficiently deliver electrons and thus tune the peroxidase-like activity of WTe 2 , leading to faster reaction kinectics. [Display omitted] Nanozymes, as promising alternatives that integrate the advantage of natural enzymes and nanomaterials are attracted enormous interest due to their low cost, environmental tolerance, high stability, as well as significant catalytic activity. Two-dimensional materials, transition metal dichalcogenides (TMDs) harbor the potential as peroxidase mimic which is attributed to the active edge sites and surface electron transfer capability. However, a challenge faced in peroxidase mimetic of TMDs is the low catalytic activity which originates from the inert structures. Here, we, for the first time, report that the typical Weyl semimetal WTe 2 possesses the superior peroxidase-like performance toward H 2 O 2 , which derives from the two-step electron-pathway. We demonstrate a novel functionality of the Weyl semimetal through introducing topologically protected surface states (TSSs) for regulating the electron transfer processes. The underlying mechanism for TSSs promoting enzyme mimetic catalysis is attributed to the effective electron bath provided by the robust TSSs. Experiments and the first-principles calculations show that TSSs of WTe 2 which serve as effective electron baths are directly involved in the two-step electron transfer process. In the first step, TSSs accept the electrons donated by the substrate which further enhances the substrate's absorption. Upon H 2 O 2 adsorption, the electrons are transferred out of TSSs and injected into the absorbed H 2 O 2 orbitals. These findings offer a new linkage between the topological matters with TSSs and nanomaterials for enzyme mimicking. [ABSTRACT FROM AUTHOR]