01874nas a2200157 4500008004100000245008400041210006900125260000800194300002500202490000600227520128900233100002801522700002301550700003001573856011301603 2017 eng d00aPossibly scalable solar hydrogen generation with quasi-artificial leaf approach0 aPossibly scalable solar hydrogen generation with quasiartificial cJUL aArticle Number: 65150 v73 aAny solar energy harvesting technology must provide a net positive energy balance, and artificial leaf concept provided a platform for solar water splitting (SWS) towards that. However, device stability, high photocurrent generation, and scalability are the major challenges. A wireless device based on quasi-artificial leaf concept (QuAL), comprising Au on porous TiO2 electrode sensitized by PbS and CdS quantum dots (QD), was demonstrated to show sustainable solar hydrogen (490 +/- 25 mu mol/h (corresponds to 12 ml H-2 h(-1)) from similar to 2mg of photoanode material coated over 1 cm(2) area with aqueous hole (S2-/SO32-) scavenger. A linear extrapolation of the above results could lead to hydrogen production of 6 L/h.g over an area of similar to 23 x 23 cm(2). Under one sun conditions, 4.3 mA/cm(2) photocurrent generation, 5.6% power conversion efficiency, and spontaneous H-2 generation were observed at no applied potential (see S1). A direct coupling of all components within themselves enhances the light absorption in the entire visible and NIR region and charge utilization. Thin film approach, as in DSSC, combined with porous titania enables networking of all the components of the device, and efficiently converts solar to chemical energy in a sustainable manner.1 aPatra, Kshirodra, Kumar1 aBhuskute, Bela, D.1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/possibly-scalable-solar-hydrogen-generation-quasi-artificial-leaf-approach01970nas a2200157 4500008004100000022001400041245010800055210006900163260000900232300001400241490000800255520136400263100002801627700003001655856012701685 2018 eng d a1932-744700aHarnessing visible-light and limited near-IR photons through plasmon effect of gold nanorod with AgTiO20 aHarnessing visiblelight and limited nearIR photons through plasm cJAN  a1206-12140 v1223 a

The utilization of the red-green-blue (RGB) and limited near-IR photons for solar hydrogen evolution (SHE) has been reported in a single plasmonic nanocomposite. Present study describes the use of AgTiO2 (AgT) decorated with Au nanorods (AgT-AuNR) to enhance the absorption of entire visible-light and limited near-IR wavelength range in the sunlight for SHE from photocatalytic water splitting reaction. It is demonstrated that the longitudinal plasmon resonance of AuNR in AgT-AuNR induces SHE between 550 and 800 nm, whereas TiO2-AuNR or AgT shows no activity in this wavelength range. The key aspect of achieving the high photocatalytic activity of AgT-AuNR in the solar spectrum is the electronic integration among metal NPs as well as with TiO2, and the heterojunctions among them. Presence of such heterojunctions has been supported by different characterization studies. However, gold nanorod exhibits field effect and further enhances light harvesting. Although the absolute amount of energy harvested only from near-IR photons is low, when combined with high-energy visible-light photons within one sun conditions, it shows a multiplier effect rather than a simple additive effect. Likely, this is the first report, where SHE has been achieved with significant amount of light absorption at lambda >= 550 nm with a plasmonic nanocomposite.

1 aPatra, Kshirodra, Kumar1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/harnessing-visible-light-and-limited-near-ir-photons-through-plasmon-effect-gold-nanorod02228nas a2200181 4500008004100000022001400041245011500055210006900170260000800239300001400247490000600261520154900267100002801816700002901844700001901873700003001892856012401922 2019 eng d a2050-748800aDirect solar-to-hydrogen generation by quasi-artificial leaf approach: possibly scalable and economical device0 aDirect solartohydrogen generation by quasiartificial leaf approa cFEB a3179-31890 v73 a

Often, a disadvantage in one area of science may become an advantage in another area. In contrast, a successful concept in one area could work for a complementary area of research too. These two philosophies have been successfully used for solar hydrogen generation and they underscore the necessity to connect relevant concepts. We, herein, report a quasi-artificial leaf (QuAL) device in a wireless configuration with a TiO2/Mn-CdS composite and NiCu as a co-catalyst for possibly scalable as well as commercially viable solar hydrogen production under one sun conditions. The device works at no applied potential and generates 10.5 mL h(-1) (16 mL h(-1)) H-2 with Ni5Cu2.5 alloy (Pt) as a co-catalyst, which corresponds to a power conversion efficiency (PCE) of 4.8% (7.3%). The significant resemblance of NiCu alloy to Pt in terms of its electrochemical activity and electronic structure makes the device more economical. While the millisecond lifetime of electrons in Mn-CdS is known to help for white light emission, the same factor helps to greatly improve charge utilization for H-2 production in the QuAL device. In contrast, the reabsorption of emitted light is a vexing problem in emission applications; however in the present work, reabsorption is successfully utilized to enhance hydrogen yield. Spectroscopy techniques combined with electrocatalytic studies were employed and the results correlated with solar hydrogen generation, demonstrating this as a new pathway to design better solar-light-harvesting architectures.

1 aPatra, Kshirodra, Kumar1 aBharad, Pradnya, Arunrao1 aJain, Vanshika1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/direct-solar-hydrogen-generation-quasi-artificial-leaf-approach-possibly-scalable-and03435nas a2200181 4500008004100000245019300041210006900234260000800303300001700311490000800328520267900336100002803015700002703043700002103070700001603091700003003107856011603137 2019 eng d00aOxidative disproportionation of MoS2/GO to MoS2/MoO3-x/RGO : integrated and plasmonic 2D-multifunctional nanocomposites for solar hydrogen generation from near-infrared and visible regions0 aOxidative disproportionation of MoS2GO to MoS2MoO3xRGO integrate cSEP a 21685-216930 v1233 a

Two dimensional (2D) semiconductor materials have been recently demonstrated to be effective plasmonic materials and alternatives to costly noble metals. However, tuning the plasmon resonance of 2D semiconductors and integrating with another material or semiconductor for various applications, such as solar light harvesting, remains a challenge. Herein, we designed a simple and attractive method, which facilitates the diffusion of oxygen from the graphene oxide (GO) layers of the MoS2/GO (MG) composite to oxidize the MoS2 layers significantly due to thermal treatment under inert atmosphere. This is the key step in the formation of MoS2/MoO3-x/RGO (MMR) (x = 0, 0.5, and 1, and all stoichiometries co-exist), due to disproportionation of MoS2/GO, with bulk heterojunctions among the components. The observed behavior is attributed to the oxidation of Mo4+ cations (of MoS2) to higher oxidation states in MMR (Mo(5+ )and Mo6+ of MoO3-x), which also alters the valence-band electronic structure and work function of the resulting composite. The 2D MoO3-x layers with a large amount of Mo5+ oxidation states enables facile charge carrier generation due to plasmonic effect, whereas MoS2 provides active sites for catalysis. The solar H-2 generation was demonstrated in the visible and near-infrared region by combining both the plasmonic and catalytic effects in one composite. These results demonstrate the important role of RGO to provide energy-level alignment, charge carrier diffusion, and help to generate plasmonic effect in the composite.

1 aPatra, Kshirodra, Kumar1 aGhosalya, Manoj, Kumar1 aBajpai, Himanshu1 aRaj, Sreeya1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/oxidative-disproportionation-mos2go-mos2moo3-xrgo-integrated-and-plasmonic-2d01946nas a2200181 4500008004100000022001400041245014500055210006900200260000800269300001400277490000600291520123600297100002101533700002801554700002401582700003001606856012801636 2019 eng d a2046-206900aWhy the thin film form of a photocatalyst is better than the particulate form for direct solar-to-hydrogen conversion: a poor man's approach0 aWhy the thin film form of a photocatalyst is better than the par cFEB a6094-61000 v93 a

We demonstrated an easy method to improve the efficiency of photocatalysts by an order of magnitude by maximizing light absorption and charge carrier diffusion. Degussa titania (P25) and Pd/P25 composite photocatalyst thin films coated over regular glass plates were prepared and evaluated for solar hydrogen production in direct sunlight with aqueous methanol. It is worth noting that only UV light present in direct sunlight (similar to 4%) was absorbed by the catalysts. The hydrogen production activities of catalysts were compared for thin film and particulate forms at 1 and 25 mg levels. The hydrogen yield values suggested that 1 mg thin film form of Pd/P25 provided 11-12 times higher activity than 25 mg powder form. Comparable light absorption throughout the entire thickness of photocatalyst device and better contact of nanostructures that enabled the charge diffusion and charge utilization at redox sites are the reasons for high efficiency. While solar cells require charge carriers to diffuse through long distances of microns, they are utilized locally in an ensemble of particles (of nanometres) for hydrogen generation in photocatalyst thin films; this concept was used effectively in the present work.

1 aNalajala, Naresh1 aPatra, Kshirodra, Kumar1 aBharad, Pradnya, A.1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/why-thin-film-form-photocatalyst-better-particulate-form-direct-solar-hydrogen-conversion01968nas a2200265 4500008004100000022001400041245014300055210006900198260000900267300001600276490000700292520103800299653002001337653001801357653001901375653001301394653001901407100002101426700002801447700001701475700002101492700002901513700003001542856013001572 2020 eng d a1944-824400aCan half-a-monolayer of pt simulate activity like that of bulk pt? solar hydrogen activity demonstration with quasi-artificial leaf device0 aCan halfamonolayer of pt simulate activity like that of bulk pt  cJUL  a30420-304300 v123 a

Pt is the best cocatalyst for hydrogen production. It is also well-known that the surface atomic layer is critical for catalysis. To minimize the Pt content as cocatalyst, herein we report on half-a-monolayer of Pt (0.5 theta(Pt)) decorated on earth-abundant Ni-Cu cocatalyst, which is integrated with a quasiartificial leaf (QuAL) device (TiO2/ZnS/CdS) and demonstrated for efficient solar hydrogen production. For the QuAL, TiO2 is sensitized with ZnS and CdS quantum dots by the SILAR method. The 0.5 theta(Pt)-decorated Ni-Cu shows an onset potential of 0.05 V vs reversible hydrogen electrode for the hydrogen evolution reaction, which is almost similar to that of commercial Pt/C. Photoactivity of the present QuAL device with either bulk Pt or 0.5 theta(Pt)-coated Ni-Cu cocatalyst is, surprisingly, equal. Our findings underscore that a fraction of a monolayer of Pt can enhance the activity of the cocatalyst, and it is worth exploring further for the high activity associated with atomic Pt and other noble metals.

10aartificial leaf10anickel-copper10aPhotocatalysis10aplatinum10aSolar hydrogen1 aBajpai, Himanshu1 aPatra, Kshirodra, Kumar1 aRanjan, Ravi1 aNalajala, Naresh1 aReddy, Kasala, Prabhakar1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/can-half-monolayer-pt-simulate-activity-bulk-pt-solar-hydrogen-activity-demonstration-quasi02212nas a2200313 4500008004100000022001400041245014500055210006900200260000800269300001600277490000700293520116000300653001701460653003401477653001901511653002801530653002301558653001901581100002801600700001301628700001701641700001901658700001901677700002501696700002001721700001801741700001401759856012501773 2022 eng d a2155-543500aBoosting electrochemical CO2 reduction to methane via tuning oxygen vacancy concentration and surface termination on a copper/ceria catalyst0 aBoosting electrochemical CO2 reduction to methane via tuning oxy cSEP a10973-109830 v123 a

Metal oxides are a promising material for designing highly active and selective catalysts for the electrochemical reduction of carbon dioxide (CO2RR). Here, we designed a Cu/ceria catalyst with high selectivity of methane production at single-atomic Cu active sites. Using this, we report favorable design concepts that push the product selectivity of methane formation by combining detailed structural analysis, density functional theory (DFT), in situ Raman spectroscopy, and electrochemical measurements. We demonstrate that a higher concentration of oxygen vacancies on the catalyst surface, resulting from more available Cu+ sites, enables high selectivity for methane formation during CO2RR and can be controlled by the calcination temperature. The DFT calculation and in situ Raman studies indicate that pH controls the surface termination; a more alkaline pH generates hydroxylated surface motifs with more active sites for the hydrogen evolution reaction. These findings provide insights into designing an efficient metal oxide electrocatalyst by controlling the atomic structure via the reaction environment and synthesis conditions.

10acopper-ceria10aelectrochemical CO2 reduction10aelectrolyte pH10agas diffusion electrode10amethane production10aOxygen vacancy1 aPatra, Kshirodra, Kumar1 aLiu, Zhu1 aLee, Hojeong1 aHong, Seungwon1 aSong, Hakhyeon1 aAbbas, Hafiz, Ghulam1 aKwon, Youngkook1 aRinge, Stefan1 aOh, Jihun uhttp://library.ncl.res.in/content/boosting-electrochemical-co2-reduction-methane-tuning-oxygen-vacancy-concentration-and01641nas a2200157 4500008004100000022001400041245011700055210006900172260000800241300001400249490000700263520102900270100002801299700003001327856012601357 2023 eng d a1359-734500aCO2 electrolysis towards large scale operation: rational catalyst and electrolyte design for efficient flow-cell0 aCO2 electrolysis towards large scale operation rational catalyst cJUN a6774-67950 v593 a

The electrochemical CO2 reduction reaction (CO2RR) to renewable fuels/chemicals is a potential approach towards addressing the carbon neutral economy. To date, a comprehensive analysis of key performance indicators, such as an intrinsic property of catalyst, reaction environment and technological advancement in the flow cell, is limited. In this study, we discuss how the design of catalyst material, electrolyte and engineering gas diffusion electrode (GDE) could affect the CO2RR in a gas-fed flow cell. Significant emphasis is given to scale-up requirements, such as promising catalysts with a partial current density of >= 100 mA cm(-2) and high faradaic efficiency. Additional experimental hurdles and their potential solutions, as well as the best available protocols for data acquisition for catalyst activity evaluation, are listed. We believe this manuscript provides some insights into the making of catalysts and electrolytes in a rational manner along with the engineering of GDEs towards CO2RR.

1 aPatra, Kshirodra, Kumar1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/co2-electrolysis-towards-large-scale-operation-rational-catalyst-and-electrolyte-design02216nas a2200205 4500008004100000022001400041245012900055210006900184260000800253300001400261490000700275520145200282100002301734700002801757700002101785700002301806700002701829700003001856856012401886 2023 eng d a1477-922600aNanostructured Co-doped BiVO4 for efficient and sustainable photoelectrochemical chlorine evolution from simulated sea-water0 aNanostructured Codoped BiVO4 for efficient and sustainable photo cFEB a2051-20610 v523 a

The co-production of hydrogen and chlorine from sea-water splitting could be a potential, sustainable and attractive route by any method. However, challenges to overcome are many, and critically, the sustainability and operating potential of the electrocatalyst are important. In this work, we report on Co-doping in the BiVO4 (Co-BV) crystal lattice and employed the same as the photoanode; Co-BV exhibits a photocurrent of 190 mu A cm(-2) at 1.1 V vs. RHE (the reversible hydrogen electrode) in the acidic sodium chloride solution (pH 2.3) under one sun illumination. The best-performing photoanode, with 0.05 mol% of Co doping (0.05 Co-BV), selectively produced active chlorine with 92% faradaic efficiency at 1.1 V vs. RHE by successfully suppressing the kinetically sluggish oxygen evolution reaction (OER) and the stability of the catalyst was demonstrated for up to 20 h. This is the lowest operating potential reported for the chlorine evolution reaction (CER), thus far. The overpotential required for CER with 0.05 Co-BV is lower than that of OER, which leads to selective CER at 1.1 V (vs. RHE). Co-doping into the BiVO4 lattice decreases the charge transfer resistance and enhances the CER kinetics due to its structural and electronic integration with the BV lattice. We demonstrate that Co-doping also improves the lifetime of the charge carrier and enhances the current density of CER and sustainability of the catalyst.

1 aChauhan, Inderjeet1 aPatra, Kshirodra, Kumar1 aBajpai, Himanshu1 aMhamane, Nitin, B.1 aSalgaonkar, Kranti, N.1 aGopinath, Chinnakonda, S. uhttp://library.ncl.res.in/content/nanostructured-co-doped-bivo4-efficient-and-sustainable-photoelectrochemical-chlorine