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• Photocatalyst Water splitting as clear energy for hydrogen evolution reaction. • Silicon earth-abound material as substrate photoabsorber absorbs wide range solar light. • Carbon material low cost, high chemical stability for water splitting. • Graphene synthesis by different methods, next though to transferred to silicon by polymer substrate as a catalyst layer. In the present report, graphene-based catalysts on silicon substrate have been examined as the photocathode for solar hydrogen evolution reaction (HER). Mono-layered graphene has been synthesized through low-pressure chemical vapor deposition (LPCVD), whereas multi-layered graphene has been synthesized by atmospheric pressure chemical vapor deposition (APCVD). Copper foil is used as the substrate. The graphene layer on Cu foil subsequently transferred on to silicon photoabsorber using poly(methyl-2-methylpropenoate) (PMMA). At the initial linear sweep voltammetry (LSV) scan, LPCVD-synthesized graphene-Si (LPCVD-Si) electrode showed an onset potential of −0.65 V and photocurrent of −4.31 mA cm−2 (at −0.385 V). On the contrary, the onset potential and photocurrent of APCVD-prepared graphene-Si (APCVD-Si) photocathode are −0.36 V and −28.28 mA cm−2 (at −0.385 V), respectively. After the 130th LSV scan, the onset potential and photocurrent of LPCVD-Si improved to −0.39 V and −13.28 mA cm−2 (at −0.385 V), respectively. In addition, the onset potential and photocurrent of APCVD-Si photocathode at the LSV 130th scan are enhanced to −0.36 V and −28.28 mA cm−2 (at −0.385 V), respectively. The graphene sample grown via LPCVD-Si show stable performance whereas, the graphene obtained via APCVD-Si have higher photocurrent poor stability. [ABSTRACT FROM AUTHOR]

Development of a solar water splitting device requires design of a low-cost, efficient, and non-noble metal compound as alternative to noble metals. For the first time, we showed that CoSe2 can function as co-catalyst in phototoelectrochemical hydrogen production. We designed a heterostructure of p-Si and marcasite-type CoSe2 for solar-driven hydrogen production. CoSe2 successively coupled with p-Si can act as a superior photocathode in the solar-driven water splitting reaction. Photocurrents up to 9 mA cm−2 were achieved at 0 V vs. reversible hydrogen electrode. Electrochemical impedance spectroscopy showed that the high photocurrents can be attributed to low charge transfer resistance between the Si and CoSe2 interfaces and that between the CoSe2 and electrolyte interfaces. Our results suggest that this CoSe2 is a promising alternative co-catalyst for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Development of a solar water splitting device requires design of a low-cost, efficient, and non-noble metal compound as alternative to noble metals. For the first time, we showed that CoSe2 can function as co-catalyst in phototoelectrochemical hydrogen production. We designed a heterostructure of p-Si and marcasite-type CoSe2 for solar-driven hydrogen production. CoSe2 successively coupled with p-Si can act as a superior photocathode in the solar-driven water splitting reaction. Photocurrents up to 9 mA cm−2 were achieved at 0 V vs. reversible hydrogen electrode. Electrochemical impedance spectroscopy showed that the high photocurrents can be attributed to low charge transfer resistance between the Si and CoSe2 interfaces and that between the CoSe2 and electrolyte interfaces. Our results suggest that this CoSe2 is a promising alternative co-catalyst for hydrogen evolution. [ABSTRACT FROM AUTHOR]

• P-doped MoS 2 was integrated on Si pyramids as photocathode for hydrogen evolution. • The Efficiency was enhanced by exposing edges and activating basal planes of MoS 2. • MoS 1.75 P 0.25 /Si pyramids showed the optimal current density of −23.8 mA cm−2. • MoS 1.75 P 0.25 /2 nm TiO 2 /Si electrode presented the current retention of 84.0%. Herein, molybdenum disulfide (MoS 2) integrated on Si pyramids was used as a co-catalyst to improve charge separation efficiency. Various quantities of phosphorus (P) heteroatoms were doped into MoS 2 materials to boost catalytic performance. Raman and extended X-ray absorption fine structure spectra showed that the introduction of P dopants increased the number of exposed edges and sulfur vacancies that acted as hydrogen evolution reaction (HER) active sites on MoS 2 and enhanced photoelectrochemical activity. Density functional theory calculations revealed that the HER inert basal plane of MoS 2 became catalytically active after P atoms doping. MoS 1.75 P 0.25 /Si pyramids presented the optimal onset potential of +0.29 V (vs. RHE) and current density −23.8 mA cm−2. A titanium dioxide (TiO 2) layer was prepared through atomic layer deposition and served as a passivation layer that improved photocathode stability. The photocurrent retention of MoS 1.75 P 0.25 /10 nm TiO 2 /Si pyramids was 84.0% after 2 h of chronoamperometric measurement. [ABSTRACT FROM AUTHOR]