Highly efficient counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) were developed using thin films of scalable and high-quality, nitrogen-doped graphene nanoplatelets (NGnP), which was synthesized by a simple two-step reaction sequence. The resultant NGnP was deposited on fluorine-doped SnO2 (FTO)/glass substrates by using electrospray (e-spray) coating, and their electrocatalytic activities were systematically evaluated for Co(bpy)3(3+/2+) redox couple in DSSCs with an organic sensitizer. The e-sprayed NGnP thin films exhibited outstanding performances as CEs for DSSCs. The optimized NGnP electrode showed better electrochemical stability under prolonged cycling potential, and its Rct at the interface of the CE/electrolyte decreased down to 1.73 Ω cm(2), a value much lower than that of the Pt electrode (3.15 Ω cm(2)). The DSSC with the optimized NGnP-CE had a higher fill factor (FF, 74.2%) and a cell efficiency (9.05%), whereas those of the DSSC using Pt-CE were only 70.6% and 8.43%, respectively. To the best of our knowledge, the extraordinarily better current-voltage characteristics of the DSSC-NGnP outperforming the DSSC-Pt for the Co(bpy)3(3+/2+) redox couple (in paticular, FF and short circuit current, Jsc) is highlighted for the first time.

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The electrodeposition of aluminum on the atomically smooth nitrogen-incorporated tetrahedral amorphous carbon (taC:N) electrode in ambient temperature AlCl 3 /EMIC chloroaluminate melts has been interpreted using a prior model of three-dimensional diffusion controlled nucleation and growth. Aluminum requires an unusually high overpotential for nucleation on taC:N because of the low density of intrinsic active sites, which act as critical nuclei during the initial stage of deposition. The current-time characteristics of nucleation on taC:N show a strong dependency on overpotential. Generation of additional, overpotential-induced active sites imposes a partial progressive nature on the overall nucleation process, resulting in a slight deviation from the limiting behavior of an ideal instantaneous nucleation model.

Visible-light-driven organic oxidations carried out under mild conditions offer a sustainable approach to performing chemical transformations important to the chemical industry. This work reports an efficient photocatalytic benzyl alcohol oxidation process using one-dimensional (1D) TiO2 nanorod (NR)-based photoanodes with surface-adsorbed ruthenium polypyridyl photocatalysts at room temperature. The photocatalyst bis­(2,2′-bipyridine)­(4,4′-dicarboxy-2,2′-bipyridine)­Ru­(II) (RuC) was covalently anchored onto TiO2 nanorod arrays grown on fluorine-doped tin oxide (FTO) electrode surfaces (FTO|t-TiO2|RuC, t = the thickness of TiO2 NR). Under aerobic conditions, the photophysical and photocatalytic properties of FTO|t-TiO2|RuC (t = 1, 2, or 3.5 μm) photoanodes were investigated in a solution containing a hydrogen atom transfer mediator (4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl, ACT) as cocatalyst. Dye-sensitized photoelectrochemical cells (DSPECs) using the FTO|t-TiO2|RuC (t = 1, 2, or 3.5 μm) photoanodes and ACT-containing electrolyte were investigated for carrying out photocatalytic oxidation of a lignin model compound containing a benzylic alcohol functional group. The best-performing anode surface, FTO|1-TiO2|RuC (shortest NR length), oxidized the 2° alcohol of the lignin model compound to the Cα-ketone form with a > 99% yield over a 4 h photocatalytic experiment with a Faradaic efficiency of 88%. The length of TiO2 NR arrays (TiO2 NRAs) on the FTO substrate influenced the photocatalytic performance with longer NRAs underperforming compared to the shorter arrays. The influence of the NR length is hypothesized to affect the homogeneity of the RuC coating and accessibility of the ACT mediator to the RuC-coated TiO2 surface. The efficient photocatalytic alcohol oxidation with visible light at room temperature as demonstrated in this study is important to the development of sustainable approaches for lignin depolymerization and biomass conversion.

Reducing the cost of dye-sensitized solar cells (DSSCs) by replacing the expensive platinum (Pt) counter electrode (CE) with low-cost and earth-abundant materials without sacrificing their power conversion efficiency (PCE) is a topic of high interest. Herein, we prepared graphene nanoplatelets/nickel nanoparticles (GnPs/NiNPs) hybrid as a CE for DSSCs by electrochemical deposition of NiNPs onto fluorine-doped tin oxide (FTO) followed by spin coating of GnPs onto NiNPs/FTO electrodes. The optimal GnPs/NiNPs-CE with homogeneously distributed NiNPs with well-defined crystallinity exhibited excellent catalytic activity toward the I−/I3 − redox mediator with low charge transfer resistance at the electrode∣electrolyte interface. The DSSCs with an optimized GnPs/NiNPs-CE electrode exhibited a substantial improvement in efficiency to 7.24%, which is similar to the PCE of the cells with Pt-CE (ca. 7.99%). The GnPs/NiNPs-CE is a promising replacement for the expensive Pt used in DSSCs.