No abstract

Converting solar energy by photoelectrochemical water splitting has been regarded as a promising way to resolve the global energy crisis and alleviate environmental pollution. Silicon, which is earth-abundant and has a narrow band gap, is an attractive material for photoelectrochemical water splitting. However, Si-based photoelectrodes suffer from photocorrosion, which leads to instability in electrolytes and high overpotential. Herein, we have fabricated a metal–insulator–semiconductor structure of NiO x /Ni/n-Si photoanodes for highly efficient water splitting. NiO x /Ni nanoparticles, which act as well-known oxygen evolution catalysts, are deposited on the surface of silicon by facile pulsed electrodeposition. Light absorption and catalytic activity are greatly affected by the coverage of Ni nanoparticles, and the highly efficient NiO x /Ni catalyst structure is induced by simple annealing. The NiO x /Ni nanoparticles show highly enhanced charge separation and transport efficiency, which are vital factors for photoelectrochemical water splitting, leading to ∼100% Faradaic efficiency and incident photon-to-current efficiency. A low onset potential of 1.08 V versus a reversible hydrogen electrode for 1 mA/cm2 and a high photocurrent density of 14.7 mA/cm2 at 1.23 V are obtained.

Various noble metal-free electrocatalysts have been explored to enhance the overall water splitting efficiency. Ni-based compounds have attracted substantial attention for achieving efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. Here, we show superior electrocatalysts based on NiFe alloy electroformed by a roll-to-roll process. NiFe (oxy)hydroxide synthesized by an anodization method for the OER catalyst shows an overpotential of 250 mV at 10 mA cm −2 , which is dramatically smaller than that of bare NiFe alloy with an overpotential of 380 mV at 10 mA cm −2 . Electrodeposited NiMo films for the HER catalyst also exhibit a small overpotential of 100 mV at 10 mA cm −2 compared with that of bare NiFe alloy (550 mV at 10 mA cm −2 ). A combined spectroscopic and electrochemical analysis reveals a clear relationship between the surface chemistry of NiFe (oxy)hydroxide and the water splitting properties. These outstanding fully solution-processed catalysts facilitate superb overall water splitting properties due to enlarged active surfaces and highly active catalytic properties. We combined a solution-processed monolithic perovskite/Si tandem solar cell with MAPb(I 0.85 Br 0.15 ) 3 for the direct conversion of solar energy into hydrogen energy, leading to the high solar-to-hydrogen efficiency of 17.52%. Based on the cost-effective solution processes, our photovoltaic−electrocatalysis (PV-EC) system has advantages over latest high-performance solar water splitting systems.

No abstract

The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape-controlled Au NPs on bismuth vanadate (BiVO ) are studied, and a largely enhanced photoactivity of BiVO is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO achieves 2.4 mA cm at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO . It is the highest value among the previously reported plasmonic Au NPs/BiVO . Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells.

Tungsten oxide (WO 3 ) and bismuth vanadate (BiVO 4 ) are one of the most attractive combinations to construct an efficient heterojunction for photoelectrochemical (PEC) applications. Here, we report an all-solution-processed WO 3 /BiVO 4 heteronanostructure photoanode with highly enhanced photoactivity and stability for sustainable energy production. The vertically aligned WO 3 nanorods were synthesized on a fluorine-doped tin oxide/glass substrate by the hydrothermal method without a seed layer and BiVO 4 was deposited by pulsed electrodeposition for conformal coating. Owing to the long diffusion lengths of charge carriers in the WO 3 nanorods, the ability to absorb the wider range of wavelengths, and appropriate band-edge positions of the WO 3 /BiVO 4 heterojunction for spontaneous PEC reaction, the optimum WO 3 /BiVO 4 photoanode has a photocurrent density of 4.15 mA/cm 2 at 1.23 V versus RHE and an incident-photonto-current efficiency of 75.9% at 430 nm under front illumination, which are a double and quadruple those of pristine WO 3 nanorod arrays, respectively. Our work suggests an environment-friendly and low-cost all-solution process route to synthesize high-quality photoelectrodes.

The porous SnO2 nanorods/networked BiVO4 heterojunction is identified as apromising photoanode which exhibits high photocurrent under front illumination.The interplay of porous SnO2 NRs and optimum coverage of BiVO4 lead to high PEC performance.

No abstract