A series of s-dialkynyl ruthenium complexes showing a D-p-[M]-p-A structure (where [M] ¼ [Ru(dppe) 2 ], dppe ¼ bisdiphenylphosphinoethane) were designed and synthesized for dye-sensitized solar cell (DSSC)applications. The molecular structure of these highly modular organometallic complexes was fine-tuned through the introduction of a bithiophene, rhodanine or benzothiadiazole unit. This original molecular engineering approach combined with convergent synthetic pathways thus afforded efficient photosensitizers with tunable colors across the visible spectrum, ranging from red to purple, blue and blue-green dyes. The optoelectronic properties of the new complexes were fully assessed and the dyes were tested in standard single-dye devices as well as in co-sensitized DSSCs, yielding 7.5% power conversion efficiency in the presence of an iodine-based liquid electrolyte. ; Tel: +33 5 40 00 24 25 † Electronic supplementary information (ESI) available: Materials and methods, synthetic procedures, compound characterization, and theoretical calculation details. See a DE ge ¼ main transition energy. b l ge ¼ calculated l max . c f ge ¼ oscillator strength. d Only the transitions with coefficients higher than 0.15 are given. e L ¼ spatial overlap. f q CT ¼ quantity of transferred charge. g D CT ¼ distance between the barycentres of the density depletion and density increment zones related to the CT excitation. J. Mater. Chem. AThis journal is

Oxygen evolution reaction (OER) plays a key role in many renewable energy technologies such as water splitting and metal-air batteries. Metal-organic frameworks (MOFs) are appealing to design efficient OER electrocatalysts, however, their intrinsic poor conductivity strongly hinders the activity. Here, we show a strategy to boost the OER activity of poor-conductive MOFs by confining them between graphene multilayers. The resultant NiFe-MOF//G gives a record-low overpotential of 106 mV to reach 10 mA cm−2 and retains the activity over 150 h, which is in significant contrast to 399 mV of the pristine NiFe-MOF. We use X-ray absorption spectroscopy (XAS) and computations to demonstrate that the nanoconfinement from graphene multilayers not only forms highly reactive NiO6-FeO5 distorted octahedral species in MOF structure but also lowers limiting potential for water oxidation reaction. We also demonstrate that the strategy is applicable to other MOFs of different structures to largely enhance their electrocatalytic activities.

Development of cost-effective and highly efficient oxygen evolution reaction (OER) electrocatalysts has become a vital project of renewable energy technologies. The OER is critical for a variety of electrochemical energy devices such as water electrolyzers, metal-air batteries, CO 2 reduction, and electrosynthesis of ammonia. Compared to extensively studied metal oxide catalysts, graphitized carbon catalysts have been newly emerged as promising OER catalysts especially in less corrosive alkaline media, due to their low cost, high electrical conductivity, unique physicochemical properties, and excellent electrocatalytic performances. In this review, we discussed recent advances in nanostructured carbon electrocatalysts. At first, metal-free OER carbon electrocatalysts including single-and multi-heteroatom doping and edge-and defect-rich defects are introduced. Then, transition metal and heteroatom co-doped nanocarbons are summarized including CoÀ NÀ C, NiÀ NÀ C, and Fe-NÀ C. In addition, carbon based hybrid electrocatalysts are highlighted, which include carbon based transition metal nitrides (TMN x ), sulfides (TMS x ), and selenides (TMSe x ), and phosphides (TMP x ). Finally, current challenges and perspective for future research on carbon-based OER catalysts are outlined.

Solar-driven photoelectrochemical (PEC) water splitting systems are highly promising for converting solar energy into clean and sustainable chemical energy. In such PEC systems, an integrated photoelectrode incorporates a light harvester for absorbing solar energy, an interlayer for transporting photogenerated charge carriers, and a co-catalyst for triggering redox reactions. Thus, understanding the correlations between the intrinsic structural properties and functions of the photoelectrodes is crucial. Here we critically examine various 2D layered photoanodes/photocathodes, including graphitic carbon nitrides, transition metal dichalcogenides, layered double hydroxides, layered bismuth oxyhalide nanosheets, and MXenes, combined with advanced nanocarbons (carbon dots, carbon nanotubes, graphene, and graphdiyne) as co-catalysts to assemble integrated photoelectrodes for oxygen evolution/hydrogen evolution reactions. The fundamental principles of PEC water splitting and physicochemical properties of photoelectrodes and the associated catalytic reactions are analyzed. Elaborate strategies for the assembly of 2D photoelectrodes with nanocarbons to enhance the PEC performances are introduced. The mechanisms of interplay of 2D photoelectrodes and nanocarbon co-catalysts are further discussed. The challenges and opportunities in the field are identified to guide future research for maximizing the conversion efficiency of PEC water splitting.

A couple of novel donor–π–acceptor dyes based on organometallic ruthenium diacetylide complexes (SL1 and SL2) have been designed and synthesized for use in NiO-based p-type dye-sensitized solar cells (p-DSCs).

The development of NiO-based molecular photocathodes is attracting growing interest in the field of dye-sensitized photoelectrochemical cells (DS-PEC) for efficient conversion of sunlight into fuel. For this purpose different strategies are developed to assemble the molecular components together in order to build functional devices. Here, an original dye-catalyst supramolecular assembly was designed and obtained via axial coordination of a cobalt-based H2-evolving catalyst, i.e. a cobaloxime complex, to a pyridyl-functionalized rutheniumdiacetylide photosensitizer. The new supramolecular assembly was successfully employed for the construction of efficient NiO-based photocathodes for solar hydrogen production. We report a joint experimental and theoretical study of the new photocatalytic system, including electrochemical and XPS analyses. Photo-electrochemical generation of H2 under pertinent aqueous conditions eventually led to a faradaic efficiency of 27 %.

Developing highly efficient transition metal dichalcogenide electrocatalysts would be significantly beneficial for the electrocatalytic hydrogen evolution reaction (HER) from water splitting. Herein, we reported novel ultrathin tantalum disulfide nanosheets (TaS2 NSs) prepared by electrochemically exfoliating bulk TaS2 with an alternating voltage in an acidic electrolyte. The obtained TaS2 NS electrocatalyst possessed an ultrathin structure with a lateral size of 2 μm and a thickness of ∼3 nm. Owing to the unique 2D structure, the achieved TaS2 NSs displayed remarkable electrocatalytic activity toward the HER by a small overpotential of 197 mV at 10 mA cm–2 and a small Tafel slope of 100 mV dec–1 in acidic solution, much lower than those of TaS2 (>547 mV and 216 mV dec–1, respectively) and other reported TaS2-based HER electrocatalysts. Furthermore, highly efficient full water splitting could be realized with two electrodes in which TaS2 NSs acted as the cathode while Ir/C served as the anode, with help of two AA size batteries or solar cells. By replacing the oxygen evolution reaction with the urea oxidation reaction (UOR), bifunctional TaS2 NSs enabled an energy-effective HER process in the cathode and UOR process in the anode with decreased applied potential.

Noble metal materials are widely employed as benchmark electrocatalysts to achieve electrochemical water splitting which comprises of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, the high cost and scarcity limit the wide ranging commercial applications of noble metal-based catalysts. Development of noble metal-free two dimensional (2D) carbon-based materials can not only reduce the consumption of noble metals, but also create materials with the characteristics of high active surface area, abundance, easy functionalization, and chemical stability, which may carve a way to promising electrochemical water splitting. In this review, noble metalfree 2D carbon-based electrocatalysts, including heteroatom (B, S, N, P, F, and O) doped graphene, 2D porous carbons modified with heteroatoms and/or transition metals, and 2D carbon-based hybrids are introduced as cost-effective alternatives to the noble metal-based electrocatalysts with comparable efficiencies to conduct HER, OER, and overall water splitting. This review emphasizes on current development in synthetic strategies and structure-property relationships of noble metal-free 2D carbon-based electrocatalysts, together with major challenges and perspectives of noble metal-free 2D carbon-based electrocatalysts for further electrochemical applications.