Designing a Pt-alternative cocatalyst capable of dissociating HO–H bonds is of great significance yet challenging for the development of high-efficiency and cost-effective water splitting photocatalytic systems. In this study, we designed and constructed a 0D ultrafine ruthenium (U-Ru) quantum dot decorated 3D porous g-C3N4 (3DpCN) nanohybrid (U-Ru/3DpCN) for photocatalytic hydrogen evolution, in which the U-Ru quantum dots act as cocatalysts accelerating the surface proton reduction reaction, and the 3D porous architecture assembled by 2D ultrathin nanosheets inherits a short charge diffusion distance and has a large specific surface area. Owing to these structural and physicochemical merits, the optimal photocatalyst U-1Ru/3DpCN achieves a superior hydrogen evolution performance of 2945.47 μmol g−1 h−1 under visible light with a high apparent quantum efficiency (AQE) of 9.5% at 420 nm, which is close to Pt-cocatalyst/3DpCN and better than most reported co-catalysts/g-C3N4 photocatalytic systems. Experimental results indicate that the formed Schottky junction between U-Ru and 3DpCN contributes to efficient charge separation, and DFT calculations show that the Ru-cocatalyst/g-C3N4 system has an appropriate hydrogen adsorption Gibbs free energy (ΔGH*) of 0.24 eV, which are both responsible to improve the photocatalytic performance. This study provides a new way to develop excellent photocatalysts for hydrogen evolution by the integration of cost-effective Ru quantum dot cocatalysts with nanostructured semiconductors.
The hydrogen evolution reaction (HER) is a key step for producing hydrogen by water electrolysis , and an economical, facile and environment friendly method of fabricating catalysts for HER is urgent and essential. In this work, we design a high efficient and stable HER catalyst though a simple adsorption and pyrolysis method. The fabricated catalyst presents ruthenium (Ru) quantum dots (QDs) uniformly distributes on the carbon nanofibers (CNF) with a three dimensional (3D) networks structure (Ru@CNF). By means of quantum size effect of Ru QDs and the 3D networks structure of the carbon nanofibers, the former is beneficial to provide more catalytic active sites and the latter is in favour of electron transport . The sample Ru@CNF exhibits a low overpotential of 20 mV at a current density of 10 mA cm −2 and Tafel slope of 31 mV dec −1 in 1 M KOH, which is better than that of Pt/C (28 mV and 36 mV dec −1 ), and most of reported Ru-based and transition metal catalysts . Furthermore, it exhibits robust stability when testing at an overpotential of 75 mV for 24 h. Therefore, this work provides a low-cost, simple and feasible method for fabricating HER catalyst, which possesses commercial application prospect in the field of producing hydrogen by water electrolysis.
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