Triiodide Reduction Research Articles

Insight into electrocatalytic activity and mechanism of bimetal niobium-based oxides in situ embedded into biomass-derived porous carbon skeleton nanohybrids for photovoltaics and alkaline hydrogen evolution

Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm−2 and Tafel slope (54 mV dec−1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I3−/I− electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.

An integrated approach to construct tantalum derivatives for electrocatalysis beyond the triiodide reduction reaction

The counter electrode (CE) is an essential component in dye-sensitized solar cells (DSSCs) to transfer electrons and catalyze triiodide reduction. In this research, efficient and cost-effective tantalum derivatives (oxide, nitride, carbide, oxynitride, and corresponding hybrids) are synthesized and utilized as CEs in DSSCs toward the triiodide reduction. The DSSC with mixed-anionic TaON CE achieves a cell efficiency of 5.46%, surpassing that with pristine TaOx CE (5.20%) before nitriding treatment. Benefiting from the synergistic interaction between mesoporous carbon (MC) and TaC0.95, TaC0.95/MC hybrid CE-based DSSC possess superior cell efficiency of 7.23%, higher than that of respective TaC (6.24%) and MC (6.52%), especially standard Pt (6.34%). Furthermore, TaON and TaC0.95/MC CEs exhibit durably great catalytic activity for I3- reduction. This work raises an effective and generally accepted approach to construct transition metal derivatives, which could utilize as low-priced Pt-free electrocatalysts for new energy devices.

Surface active-site engineering in hierarchical PtNi nanocatalysts for efficient triiodide reduction reaction

Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis, but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature. We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer (PtNi@Pt-SL) towards efficient triiodide reduction reaction (TRR) via an acid-dealloying approach. The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys, and thus results in good catalytic performance towards TRR. Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites. The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.

Polyaniline/Ag2S–CdS Nanocomposites as Efficient Electrocatalysts for Triiodide Reduction in Dye-Sensitized Solar Cells

In this study, an Ag2S–CdS nanocomposite (AC11) was prepared through chemical co-precipitation of silver nitrate and cadmium acetate in an aqueous solution of thiourea. We then synthesized PACI, a nanocomposite of polyaniline (PANI) and AC11, through in situ polymerization of aniline in an AC11-containing solution, resulting in uniform embedding of the AC11 nanoparticles in the PANI fibers. Moreover, we synthesized the nanocomposite PACO through deposition of the AC11 nanoparticles on the surface of the PANI fibers. PANI, PACI, and PACO were then spin-coated onto conducting glasses to form PANI-S, PACI-S, and PACO-S counter electrodes, respectively, for dye-sensitized solar cells (DSSCs). Cyclic voltammetry revealed that the electrochemical catalytic activity of the PACI-S electrode was much higher than those of the PANI-S and PACO-S electrodes. Furthermore, the photovoltaic properties of the PACI-S-based DSSC were much better than those of the PANI-S- and PACO-S-based DSSCs. Indeed, the highest short-circuit current density (12.06 mA/cm2), open-circuit voltage (0.72 V), fill factor (0.58), and photoenergy conversion efficiency (5.04%) were those of the DSSC featuring PACI-S as the counter electrode.

Highly efficient MoS2/rGO electrocatalysts for triiodide reduction as Pt-free counter electrode for dye-sensitized solar cells

Developing large-scale and high-efficient electrocatalysts based on earth-abundant element is urgent to promote the development of dye-sensitized solar cells (DSSCs). As an attractive approach, ultrasonic spray pyrolysis (USP) could prepare large-scale micro-nano structured catalytic materials, whereas these spheroidal particles usually could not conduct electron well with each other, thus inhibits catalytic activity. Herein we introduce reduced graphene oxide (rGO) to improve the conductivity and catalytic performance of MoS2 synthesized by USP. The MoS2/rGO hybrids combines the abundant active sites of MoS2 and excellent conductivity of rGO, reduces the CE/electrolyte interfacial electron transfer resistance, increases the contact of film with substrate, thus exhibits decreased Rct (1.00 Ω), improved efficiency of 8.53% and enhanced stability. Due to the high yield and good reproducibility of USP method, the large-scale (10 cm × 10 cm) and flexible MoS2/rGO CE shows good consistency of catalytic activity and bending resistance. These results demonstrate that this synthetic approach and introducing of rGO offers a scalable and simple strategy for synthesizing efficient materials in various electrochemical applications.

Boost reactivity of tri-iodide reduction electrode by highly faceted octahedral PtNi nanocrystals

PtNi octahedra were utilized as the counter electrodes (CEs) of N719-dye based DSSCs and well characterized via high-resolution transmission electron microscopy, powder x-ray pattern scan, and on-axis transmission Kikuchi Diffraction technique, rendering the crystallographic orientation of individual particle. The photovoltaic results show that the power conversion efficiency (PCE) of devices with different CEs is in the following sequence: Pt thin film < Pt7Ni3 octahedra < Pt5Ni5 octahedra < Pt4Ni6 octahedra. The device of Pt4Ni6 octahedra reveal the PCE over 10%. The electrochemical measurements show the tri-iodide reduction activity is in a sequence of Pt4Ni6 octahedra > Pt5Ni5 octahedra > Pt7Ni3 octahedra > Pt thin film. This study provides fundamental understanding of the exposed surface of PtNi octahedra, for which the coverage of {111} facets plays a key role in the tri-iodide reduction and thereby leads to the increase of device PCE with significant decrease of the Pt component in CEs.

Atomic Evolution of Metal–Organic Frameworks into Co–N3 Coupling Vacancies by Cooperative Cascade Protection Strategy for Promoting Triiodide Reduction

Precisely controlled synthesis is one of the key issues for single-atom catalysts (SACs) due to isolated atoms have high surface-free-energy toward aggregation. Here, we propose a facile cooperativ...

Nickel-Based Single-Atom Catalyst toward Triiodide Reduction Reaction in Hybrid Photovoltaics

It is very significant to obtain highly efficient, cost-effective, and durable electrocatalysts toward triiodide reduction reaction (TRR) in hybrid photovoltaics. In this study, a nickel-based single-atom catalyst (SAC) (Ni-SAC) was prepared by the facile carbonization of NiPc@ZIF-8 and explored as a highly efficient Pt-free catalyst for TRR. During the carbonization process, the Ni species were separated by coordinate nitrogen atoms and distributed homogeneously within the porous carbon matrix, with the formation of the atomically dispersed Ni–N₄ active sites, revealed by the X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy. Compared to the reference porous nitrogen-doped carbon, Ni-SAC exhibited superior catalytic activity toward TRR. More importantly, Ni-SAC possessed better stability over the triiodide/iodide redox couple than the Pt counterpart during the stability test. The resultant solar cell presented an efficiency of 7.42%, comparable to that of the Pt-based device (7.69%). Additionally, the Kelvin probe force microscopy measurement revealed that the enhanced catalytic activity of Ni-SAC originated from the moderate energy level matching with the triiodide/iodide redox couple. The formation of Ni–N₄ active sites within the carbon matrix promoted the electron transferring at the interfaces of the catalyst/electrolyte. All results demonstrated that the SAC could be one of the Pt-free catalysts toward efficient TRR in hybrid photovoltaics.

Frontispiece: A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

Frontispiece: A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

Frontispiz: A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

Frontispiz: A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

Photoelectrochemical applications of electrochemical deposition of Ni2+-doped FeS2 thin films

Different concentration (1–5 mol%) of Ni2+-doped FeS2 thin films were deposited by facile ECD technique. XRD pattern Ni2+ ion-doped FeS2 thin films were cubic structure with the high intensity plane (2 0 0). HRSEM images show that the undoped with 1–2 mol% Ni2+-doped FeS2 thin films were spherical-like morphology with aggregated grains. 3 mol% Ni2+-doped FeS2 thin film was aggregated with smaller size grains. Electrochemical impedance analysis reveals that the minimum charge transfer resistance (69 Ω) is obtained for 3 mol% Ni2+ ion-doped FeS2 thin films with exceptional conductivity character compared to other samples. Photoelectrochemical test indicates that 3 mol% Ni2+ ion-doped FeS2 thin film generates enhanced photocurrent response and faster immigration of photoinduced charge carriers compared to the other samples. It has been observed from CV analysis; the optimized 3 mol% Ni2+-doped FeS2 thin film delivers superior electrocatalytic performance of triiodide reduction.

A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

AbstractAn efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)‐doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C‐S‐C linkage‐triggered confined‐pyrolysis strategy for the high‐efficiency in situ N‐doping into carbon matrix and an ultrahigh doping level up to 13.5 at %, which is close to the theoretical upper limit (15.2 at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3− reduction as an example, the resultant NCM‐5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site‐dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron‐withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2.

A C‐S‐C Linkage‐Triggered Ultrahigh Nitrogen‐Doped Carbon and the Identification of Active Site in Triiodide Reduction

An efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)-doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C-S-C linkage-triggered confined-pyrolysis strategy for the high-efficiency in situ N-doping into carbon matrix and an ultrahigh doping level up to 13.5 at %, which is close to the theoretical upper limit (15.2 at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3 - reduction as an example, the resultant NCM-5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site-dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron-withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2 .

Ultralong NiSe nanowire anchored on graphene nanosheets for enhanced electrocatalytic performance of triiodide reduction.

Like their higher-dimensional counterparts, nanowire structures possess desirable features for electrocatalysis applications. In this study, ultralong NiSe nanowires (of diameters 50–150 nm and length 20 μm) were successfully anchored onto graphene nanosheets (NiSe NW/RGO). The NiSe nanowires were coated with a thick (∼10 nm) disordered surface replete with active sites. Benefiting from the fast charge-transfer channels and plentiful electroactive sites on the NiSe nanowires, in synergy with the high electroactive surface and electrical conductivity of the graphene nanosheets, the optimized NiSe NW/RGO exhibited a remarkably higher electrocatalytic activity than NiSe nanowires and typical Pt counter-electrodes (CEs). NiSe NW/RGO also exhibited the low charge-transfer resistance of 1.64 Ω cm2 and delivered a higher power conversion efficiency (PCE = 7.99%) than Pt CEs (PCE = 7.76%).

High electron transfer of TiO2nanorod@carbon layer supported flower-like WS2nanosheets for triiodide electrocatalytic reduction

1D–2D multidimensional nanostructured TNRs@C@WS2has been prepared and introduced as an effective catalyst for the triiodide reduction reaction.

Dual-phase zinc selenide in situ encapsulated into size-reduced ZIF-8 derived selenium and nitrogen co-doped porous carbon for efficient triiodide reduction reaction

A ZIF-derived Se/N-doped carbon-supported dual-phase ZnSe hybrid as a robust CE catalyst for DSSCs provides a high PCE of 8.48%.

Highly efficient & economic synthesis of CoS1.097/nitrogen-doped carbon for enhanced triiodide reduction

The rational design and feasible synthesis of the metal organic frameworks (MOFs)-derived carbon-based materials with excellent triiodide reduction (IRR) performance still remains challenging. Generally, for the present synthesis methods, the MOFs-derived bulk or big-sized metallic particles imbedded into the carbon matrix are directly removed and discarded without considering to be further utilized, which can not meet the requirements of green chemical engineering techniques. Herein, we report a green & atomic economic synthesis route for the in situ utilization and conversion of these metallic source to highly active CoS1.097 species constructed on the nitrogen-doped carbon (denoted as CoS1.097/ZNCA) by using zeolitic imidazolate framework (ZIF-67) as the precursor. Notably, the CoS1.097/ZNCA CE exhibits an excellent power conversion efficiency of 8.54%, surpassing that of the noble Pt CE. This significantly improved electrocatalytic activity towards the IRR is contributed to the synergistic effects between the highly electroactive CoS1.097 species and the carbon framework acting as the conductive substrate.

In situ synthesis of ZnFe2O4 rough nanospheres on carbon nanofibers as an efficient titanium mesh substrate counter electrode for triiodide reduction in dye-sensitized solar cells

There is no doubt that counter electrode (CE) plays a vital role in dye-sensitized solar cells (DSSCs). Herein, Zinc Ferrite/carbon nanofibers (ZnFe2O4/CNFs) composite is successfully fabricated by electrospinning and hydrothermal method and coated on titanium (Ti) mesh as an efficient CE material, which is further applied to DSSCs. The Ti mesh has been done as conductive substrate to make the DSSCs have smaller transmission resistance, great stability and sustainable utilization. Via repeated measurements, the ZnFe2O4/CNFs CE which is prepared on Ti mesh exhibits good power conversion efficiency (PCE) of 9.05%, which is higher than commercial Platinum (Pt) fluorine-doped tin oxide (FTO) CE (7.21%) and CNFs Ti mesh CE (7.80%) under the same conditions. Most interestingly, the CNFs CE that prepared on Ti mesh has higher PCE than Pt CE, this is mainly due to the use of Ti mesh which is more conducive to the interface transport of iodine ion and electron transfer rate. All of these results indicate that ZnFe2O4/CNFs composite Ti mesh CE has high electrochemical performance and can be favorable for low-cost efficient DSSCs application.

Electrochemical Reduction of Samarium Triiodide into Samarium Diiodide

Electrochemical reduction of samarium triiodide (SmI3) into samarium diiodide (SmI2) is investigated as a model reaction to reuse samarium compounds in catalytic ammonia production under ambient re...

Dye sensitized solar cell (DSC) based on reduced graphene oxide (rGO)-TiO2 nanocomposite photoelectrode and polyaniline (PANI) counter electrode

We report the successful application of reduced graphene oxide–titania (rGO–TiO2) nanocomposite as an efficient photoelectrode and an inexpensive polyaniline (PANI) synthesized by in-situ polymerization on graphite foam as a platinum substitute for tri-iodide reduction for dye‐sensitized solar cell (DSC). The bulk carrier concentration and conductivity of the PANI was measured to be 3.02x1017cm-3 and 4.89x10-1 W-1cm-1 respectively. Subsequently, three DSCs were assembled with rGO–TiO2 nanocomposite photoelectrode and PANI as counter electrode for one and the other two assembled using unmodified TiO2 photoelectrode with PANI and platinum as counter electrodes, respectively. The rGO loading allows more dye to be adsorbed due its large surface area thus improving the light harvesting efficiency (LHE). This improvement in LHE increases the short circuit current density (JSC). The JSC increase is more substantial compared to the reduction in VOC; thus, the increase in the efficiency of the cell with rGO-TiO2 nanocomposite electrode. The short circuit current density for the rGO-TiO2 DSC with PANI counter electrode is 0.45mAcm-2 while that for the unmodified TiO2 DSCs with PANI counter electrode and platinum counter electrode are 0.11mAcm-2 and 0.10 mAcm-2 respectively. This corresponds to 76% increase in the current density and it increases collection rate at the photoelectrode leading to enhanced power conversion efficiency of 0.13% compared with 0.04% and 0.02% for the DSCs assembled with unmodified TiO2 under full sunlight illumination (100 mW/cm2, AM 1.5G) as a result of the better charge collection efficiency of rGO, which reduces the back electron transfer process. This represent 69% enhancement of energy conversion efficiency in the DSC consisting of rGO modified TiO2