Figure S1. Cross-sectional view of nanoporous Fe 2 O 3 grown on Fe. This is synthesized in 6 min by applying 50V DC . The electrolyte used is ethylene glycol + (3 v%) H O + 0.5 wt %NH 4 F.

The production of energy from renewable and waste materials is an attractive alternative to the conventional agricultural feed stocks such as corn and soybean. This paper describes an approach to extract oil from spent coffee grounds and to further transesterify the processed oil to convert it into biodiesel. This process yields 10-15% oil depending on the coffee species (Arabica or Robusta). The biodiesel derived from the coffee grounds (100% conversion of oil to biodiesel) was found to be stable for more than 1 month under ambient conditions. It is projected that 340 million gallons of biodiesel can be produced from the waste coffee grounds around the world. The coffee grounds after oil extraction are ideal materials for garden fertilizer, feedstock for ethanol, and as fuel pellets.

This paper describes the design of a photoelectrochemical (PEC) cell using carbon-doped titanium dioxide (TiO2 - x C x ) nanotube arrays as the photoanode and platinum, Pt nanoparticles incorporated in TiO2 (titania) nanotube arrays, as the cathode. The PEC cell is found to be highly efficient (i.e., gives good photocurrent at a low external bias, j p = 2.5−2.8 mA/cm2 at −0.4 VAg/AgCl), inexpensive (only 0.4 wt % Pt on TiO2), and robust (continuously run for 80 h without affecting the photocurrent) for hydrogen generation by water splitting under the illumination of simulated one sun intensity. The synthesis of the photoanode is carried out by the sonoelectrochemical anodization technique using aqueous ethylene glycol and ammonium fluoride solution. This anodization process gives self-organized hexagonally ordered TiO2 nanotube arrays with a wide range of nanotube structure, which possess good uniformity and conformability. As-synthesized titania nanotubes are annealed under reducing atmosphere (H2), which converts the amorphous nanotube arrays to photoactive anatase phase as well as it helps in doping of the carbon (from the reduction of ethylene glycol) to give the TiO2- x C x type photoanode. The cathode material is prepared by synthesizing Pt nanoparticles (by reduction of a Pt salt to Pt(0)) into the titania nanotubular arrays by the incipient wetness method. Various characterization techniques, viz., field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, electron diffraction, and glancing angle X-ray diffraction, etc., are used to study the morphology, phase, band gap, and doping of the nanotubes.

A coupled semiconductor material is prepared by filling one-dimensional (1D) titania (TiO2) nanotubes (NTs) with cadmium sulfide (CdS) nanoparticles (NPs). Self-assembled TiO2 NTs (length = 550 nm, diameter = 80 nm) are prepared by the sonoelectrochemical anodization method. These NTs are functionalized with CdS NPs by a single-step electrodeposition method. This material harvests solar light in UV as well as visible light (up to 510 nm) region. An eight to 9-fold enhancement in photoactivity is observed using CdS functionalized TiO2 NTs compared to pure TiO2 NTs and commercial P25 NPs. This methodology will be useful in designing multijunction semiconductor materials confined inside 1D nanochannels.

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