Hydrogen production from solar water splitting has been considered as an ultimate solution to the energy and environmental issues. Over the past few years, graphene has made great contribution to improving the light-driven hydrogen generation performance. This article provides a comprehensive overview of the recent research progress on graphene-based materials for hydrogen evolution from light-driven water splitting. It begins with a brief introduction of the current status and basic principles of hydrogen generation from solar water splitting, and tailoring properties of graphene for application in this area. Then, the roles of graphene in hydrogen generation reaction, including an electron acceptor and transporter, a cocatalyst, a photocatalyst, and a photosensitizer, are elaborated respectively. After that, the comparison between graphene and other carbon materials in solar water splitting is made. Last, this review is concluded with remarks on some challenges and perspectives in this emerging field.
Designing high-quality interfaces is crucial for high-performance photoelectrochemical (PEC) water-splitting devices. Here, we demonstrate a facile integration between polycrystalline np-Si and NiFe-layered double hydroxide (LDH) nanosheet array by a partially activated Ni (Ni/NiO) bridging layer for the excellent PEC water oxidation. In this model system, the thermally deposited Ni interlayer protects Si against corrosion and makes good contact with Si, and NiO has a high capacity of hole accumulation and strong bonding with the electrodeposited NiFe-LDH due to the similarity in material composition and structure, facilitating transfer of accumulated holes to the catalyst. In addition, the back illumination configuration makes NiFe-LDH sufficiently thick for more catalytically active sites without compromising Si light absorption. This earth-abundant multicomponent photoanode affords the PEC performance with an onset potential of ∼0.78 V versus reversible hydrogen electrode (RHE), a photocurrent density of ∼37 mA cm at 1.23 V versus RHE, and retains good stability in 1.0 M KOH, the highest water oxidation activity so far reported for the crystalline Si-based photoanodes. This bridging layer strategy is efficient and simple to smooth charge transfer and make robust contact at the semiconductor/electrocatalyst interface in the solar water-splitting systems.
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