Janis Kleperis

University of Latvia | LU · Institute of Solid State Physics

Photocatalytic degradation of pollutants have a high potential for sustainable and renewable uses. TiO2 is a widely studied photocatalyst due to its high chemical and photochemical stability and wide range of applications. However, the wide band gap and low capacity of photo-induced charge separation provide lower catalytic activity; thus, improvem...

Citation: Palmbahs, R.; Lesnicenoks, P.; Knoks, A.; Vitola, V.; Kleperis, J. Synthesis Method Comparison of N-Doped Carbons for Electrochemical Energy Storage. ChemEngineering 2024, 8, 80. https://doi.org/10.3390/ chemengineering8040080 Academic Editor:Ştefan-Ovidiu Dima Abstract: This study investigates nitrogen-doped carbon synthesis and electroc...

This study investigates the low-temperature hydrogen plasma treatment approach for the improvement of hydrogen generation through waste aluminum (Al) reactions with water and electricity generation via proton-exchange membrane fuel cell (PEM FC). Waste Al scraps were subjected to ball milling and treated using two different low-temperature plasma r...

Poster presented at the EMRS 2023 Fall meeting in Warsaw. To improve the photocatalytic activity of TiO₂, a stable and available catalyst, the optical absorption edge can be moved to longer wavelengths, or improve photoinduced charge carrier separation. Introducing additional materials to TiO₂ can do both. Notably, the added material should be a...

This work aims to explain aluminum hydrolysis reaction kinetics based on a properly chosen theoretical model with machined aluminum waste chips as well as alkali solutions up to 1M as a promoter and to estimate the overall reaction profit. The purpose of this work is to assess the optimal alkali concentration in the production of small-and medium-s...

It seems that we are on the brink of going all in on hydrogen and hydrogen energetics. Hydrogen has gained much traction and seems to be the new cool kid on the block. But is that really true? It has been "around" for a long time, but many production ways have not been environmentally friendly. There are alternative options, such as the use of wast...

The present work aims to explain the aluminum hydrolysis reaction kinetics based on properly chosen theoretical model with machined aluminum waste chips and alkali solutions up to 1M as a promoter, and to estimate overall reaction profit. In order to obtain results of better accuracy, we work with flat Al waste chips because a flat surface is prefe...

Solid state ionics is one of the key research topics of the Institute of Solid State Physics, University of Latvia since its establishment. The research direction included topics ranging from electrochromic phenomena in transition metal oxides through gas sensors and electronic nose to materials for rechargeable battery electrodes and materials for...

All three Baltic States have reached good figures regarding the change in total greenhouse gas emissions from transport during 1990-2017. Particularly successful is Lithuania, showing a negative value of -2.7%. Latvia considerably lags behind Estonia (+15.1% vs. +1.5%). Amid the achievement of Latvian scientists, engineers and merchants, the author...

Increasingly, aluminium is entering waste bins as lightweight packaging material in its pure form from seafoods, soft-drink cans, pet foods, and laminated and metalized packaging materials in combination with paper and plastics. As an amphoteric metal, aluminium can react with chemically acidic or caustic electrolytes. Research on using aluminium (...

1. The simulated flow of liquid is practically identical to real life. 2. Also, the simulation can predict particle settling location with good accuracy. 3. Additional simulations, with different sized meshes should be carried out for further data gathering and reactor design improvements. 4. The gained results can be used in future for more effici...

Renewable energy resources (wind, solar) are unpredictable, so it is wise to store the electricity they generate in an energy carrier X. Various PtX (power to useful energy-intensive raw material such as hydrogen, synthetic natural gas, fuel) applications have been proposed. At the heart of our work is widely used idea to convert residual CO2 from...

Single-layer graphene decorated with monodisperse copper nanoparticles can support the size and mass-dependent catalysis of the selective electrochemical reduction of CO2 to ethylene (C2H4). In this study, various active adsorption sites of nanostructured Cu-decorated graphene have been calculated by using density functional theory to provide insig...

Two different methods of synthesis of TiO2/WO3 heterostructures were carried out with the aim to increase photocatalytic activity. In this study, anodic TiO2 nanotube films were synthesized by electrochemical anodization of titanium foil. WO3 particles were applied to anodic Ti/TiO2 samples in two different ways – by electrophoretic deposition (EPD...

Fuel cells, batteries and supercapacitors are critical to meet the rising global demand for clean, sustainable energy. Biomass-derived activated carbon can be obtained with tailored properties to fulfil the extensive need for low-cost, high-performance, catalyst and electrode materials. To investigate the possibility of nanoporous nitrogen-doped ca...

GDE development as well as Catalyst investigations are driving force for electrochemical CO2 reduction reactions and new electrochemical systems. In this work, we provide our observations during experiments that catalyze CO2 into more complex products.

ICE remains the leader in transportation sector, however emission are a problem which must be mitigated or preferably eliminated . by modification of combustion process or modification of fuel using hydrogen additive it is possible to increase combustion temperatures, as well as to decrease needed fuel. There are multiple companies in Baltics tryin...

As EU is steadily moving in the direction of emission reduction, each country must develop plans to decarbonise the transport and energy sectors. In Latvia, transport sector is one of the biggest emission sources. The heating applications come next. Both require carbon containing fuels and a transfer to carbon neutral fuel is necessary; therefore,...

Graphene was discovered in the early 21st century, but has already proven itself in many applications – energy, medicine, electronics, food and sports, and more. Functionalization of nanostructured carbon materials with both non-metallic and metallic atoms is possible in various ways, imparting enhanced or new properties to the starting material, e...

Background This work studied how the exposure to an unusual substrate forced a change in microbial populations during anaerobic fermentation of crude glycerol, a by-product of biodiesel production, with freshwater sediment used as an inoculum. Results The microbial associations almost completely (99.9%) utilized the glycerol contained in crude gly...

By means of the CRYSTAL computer program package, first-principles calculations of polar ZrO-, Ca- and O-terminated CaZrO3 (011) surfaces were performed. Our calculation results for polar CaZrO3 (011) surfaces are compared with the previous ab initio calculation results for ABO3 perovskite (011) and (001) surfaces. From the results of our hybrid B3...

We investigated photoelectronic properties of composite films based on semiconducting polymer poly(indacenodithiophene-co-benzothiadiazole) (PIDT-BT) and single-walled carbon nanotubes (SWCNTs). It was found that the absorbance spectra of PIDT-BT and PIDT-BT/SWCNT (1:0.3) films were in the spectral region from 200 to 800 nm, with an absorbance edge...

A promising method for reduction of pollution is photocatalytic degradation with widely available TiO2 nanostructures. A convenient method to improve the photocatalytic activity of TiO2 is to dope it. Traditionally dopants are applied after synthesis of TiO2 i.e. by deposition on it, but in this research in situ doping of TiO₂ nanotubes with graphe...

The main emphasis of this research was to describe air pollution level and dispersion in a typical street canyon (Valdemara Street in Riga (Latvia) city centre), afterward to postulate potential development scenarios and perform modelling in order to understand the influence on air pollution level. For this purpose special mathematical model was us...

LiFePO4/C/reduced graphene oxide (rGO) composites with different morphologies were synthesized, allowing evaluation of the electrochemical performance as a function of the sample morphology. LiFePO4 particles anchored on rGO sheets and rGO sheets wrapping LiFePO4 agglomerations were two of the most pronounced features observed. The structure with L...

Energy harvesting with lowest environmental impact is one of key elements for cleaner future. Photocatalytic as well as electrocatalytic CO2 reformation processes are considered as prominent methods. Thus, extensive research of CO2 reformation is being done to find the right materials that holds crucial qualities. For photocatalysis that includes p...

Reduction of CO2 into valuable synthetic materials and/or fuels is possible, but catalyst is necessary to lower necessary energy and promote not just reduction but also reformation into valuable materials such as methane. Catalyst material should hold such properties as high electrochemical stability and abundance. TiO2 is such material, but for su...

LatvijasUniversitātesCietvielufizikasinstitūts Viens no katalizatoriem CO 2 elektroķīmiskasreducēšanasparetilēnureakcijaiirvarš, kura kristāliskā forma būtiski ietekmē reakcijas galaproduktus. Zināmas vairākas metodes,kāšometālakatalizatorustrukturēt,unvienanotāmirelektroķīmiskavara izgulsnēšana. Darba gaitā varš tiek elektroķīmiski izgulsnēts uz g...

Daudzslāņugrafēns(GSS)irmateriālsarlabuelektrisko vadītspēju,pielietojamsgāzu sensoros, superkondensatoru elektrodos, elektrovadošās tintēs. Tā īpašības ietekmē sintēzes apstākļi, kā arī struktūras defektu un piemaisījumu sastāvs. Priekšapstrādē iespējamsveikt grafēnareducēšanu,aizvadotsintēzesblakusproduktus, kāarī sintēzes nākamajos soļos ievadīt...

Membrānas-elektrodu sistēma (MES) ir centrālā daļa protonu apmaiņas membrānu elektrolīzeros (PAME) un degvielas šūnās (PAMDŠ). Katalizatora slānis ir MES sastāvdaļa, kas pilda vairākas funkcijas: savieno membrānu un elektrodus, ar katalizatoru kontrolē reakcijas procesus, nodrošina izejvielu un reakcijas produktu transportu, elektronuunjonupārnesi,...

Mūsdienu pilsētās viens no kaitīgākajiem piesārņojumiem gaisā, kas rodas no fosilā kurināmā, piemēram, transporta izplūdes gāzēm, ir NO 2 , kas spēj cilvēkam izraisīt veselības problēmas jau pie 4 ppm lielas koncentrācijas. Lai ierobežotu šīs gāzes saskari ariedzīvotājiem, tiekmeklēti pietiekamijutīgiun lēti gāzu sensora materiāli brīdināšanassistē...

LU CFI piedalās Valsts pētījumu programmas "Enerģētika" projekta "Latvijas dabasgāzesinfrastruktūrasattīstībastendences,izaicinājumiunrisinājumi(LAGAS)" (vadošais partneris-RTU EI) īstenošanā, izvērtējot ūdeņraža iespējas atjaunojamo energoresursu saražotās enerģijas transportēšanā un uzglabāšanā. Ūdeņradis ir tāds pats enerģijasnesējs kāelektrība-...

Ierīcesuntehnoloģijas, 20. februāris METODIKASIZSTRĀDESPEKTROSKOPISKAI CO 2 Viensnoceļiemzemaoglekļaekonomikasattīstībāpasaulēirsamazinātogļūdeņražu un CO 2 emisijas tautsaimniecībā gan rūpniecības, gan enerģētikas, gan transporta sektoros. To var veikt, gan samazinot oglekli saturošu fosilo degvielu izmantošanu, ganattīrotizplūdesgāzesnoogļūdeņraž...

Mathematical models are intensively used in environmental science for various reasons – status quo assessment, statistical modeling, forecasting, and planning, scenario analysis. Traffic flow and related atmospheric pollution modeling is one of the most complex challenges because of various aspects, - wide versa of affecting factors, daily, diurnal...

Substitution of fossil-based chemical processes by the combination of electrochemical reactions driven by sources of renewable energy and parallel use of H 2 O and CO 2 to produce carbon and hydrogen, respectively, can serve as direct synthesis of bulk chemicals and fuels. We plan to design and develop a prototype of electrochemical reactor combini...

Overview of CO2 reduction pathways and technologies

Two nanostructured oxides, α-Fe 2 O 3 and TiO 2 with a particle diameters 50 nm and 21 nm, were mixed with graphene oxide (GO). Composite thin films on a stainless steel substrate were obtained by electrophoretic de-position (EPD) procedure from water suspensions: α-Fe 2 O 3 /GO, TiO 2 /GO and α-Fe 2 O 3 /TiO 2 /GO. Subsequently reduction of as-pre...

Solid-state narrow band gap semiconductor heterostructures with a Z-scheme charge-transfer mechanism are the most promising photocatalytic systems for water splitting and environmental remediation under visible light. Herein, we construct all-solid Z-scheme photocatalytic systems from earth abundant elements (Ca and Fe) using an aqueous synthesis p...

We investigate yttrium-doped hematite thin-film photoelectrochemical properties and find yttrium incorporation to amply improve the performance as a photoanode for water splitting under visible light. We used the spray pyrolysis method to prepare a set of yttrium doped Fe2-xYxO3 (x = 0, 0.05, 0.10, 0.15, 0.2) thin films (thickness below 500 nm) on...

Enerģētika, 21.februāris 33 GRAFĒNUINTERKALĀCIJAARCUDEFEKTUZONĀS UN UZ PLĀKSNĒMCO 2 REĢENERĀCIJAI JānisKleperis, PēterisLesničenoks LatvijasUniversitātesCietvielufizikasinstitūts Grafēna plākšņu aglomerātu (GSS) elektrodu materiāla sintēze izmantojot elektroķīmiskās eksfoliācijas metodi dod iespēju ātri un lēti sintezēt lielus tilpumus pulvera. Tā...

Globālu klimata pārmaiņu mazināšanai ir nepieciešams samazināt gāzveida izmešu daudzumu. Avotu samazināšana ne vienmēr ir iespējama, bet to emisijas var samazinātardažādāmmetodēm.CO 2 emisijas ir netikaidūmeņoskrāsnīm,kurāstiek dedzināti fosilie vai bioloģiskie energoresursi, bet arī pārtikas rūpniecībā dažādos pārtikas ražošanas procesos, piemēram...

Stendareferāti, 21.februāris 64 REDUCĒTAGRAFĒNA-NITROCELULOZESKĀRTIŅUIZVEIDE, IZMANTOJOTŠĶĪDINĀTĀJAIZTVAIKOŠANASMETODI IngarsLukoševičs,PēterisLesničenoks,JānisKleperis LatvijasUniversitātesCietvielufizikasinstitūts Viensnoreducētadažu-slāņugrafēna(rFLG)nanodaļiņupielietojumiemirrFLGun polimērukompozītmateriāluizveide.Irnovērots,kašādiemsintezētiem...

The increasing pollution due to intensive industrial growth brings the question of sustainable Solar energy transformation into fuel more pressing. TiO2 has brought wide interest as a stable, accessible and possible photocatalytic material, but the limited only to UV excitation lowers how effective it can be. Lower band gap and simple synthesis met...

Investigation of Ti/TiO2/WO3 systems was performed.

Photoactivity was determined using three electrode cell, sample as working electrode, auxiliary electrode Pt and as the reference electrode calumel electrode (SCE) was used. In photoactivity measurements 150 W xenon lamp with 10 mW/cm 2 was used, esperimental setup can be seen in Fig. 2. Photocatalytic activity is investigated by measuring open cir...

Graphene sheet stacks were obtained using electrochemical exfoliation method. The morphology, distribution of elements and structure of the obtained samples were investigated using scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy and Brunauer-Emmett-Teller methods. The graphene sheet stacks mostly have been formed wi...

Biological hydrogen production by anaerobic fermentation of widely available renewable resources is a promising and advantageous area. By microbiological hydrogen production from crude glycerol we obtain renewable energy carrier and utilize biodiesel-derived waste. We studied biogas and hydrogen production by Enterobacter aerogenes MSCL 758 and by...

Describes the development of a universal technology that can be used to provide continuous capacity for small and medium-sized autonomous objects or their micro-grids using alternative energy sources and energy storage systems. It is shown that the technology utilizes the advanced development of hydrogen electrolyzers and fuel cells for the efficie...

Energy storage becomes more important as mankind switch to renewable energy, away from fossil resources. Traditional way – batteries - offer a limited number of cycles, require regular maintenance; nevertheless gravitational storage, flywheels, compressed air are mainly large scale and expensive methods. The hydrogen as energy carrier and hydrogen...

In our fast growing world, the energy consumption and it caused environmental pollution is constantly rising. That requires transition to renewable energy sources which are clean and sustainable; the hydrogen economy with photocatalytically produced hydrogen would be one of the right answers. That requires photocatalytically active materials. Titan...

Air intake Vortex camera • Water and air electrolysis Ionization camera Enriched air exhoust Large cities not only in Europe but also worldwide suffer from air pollution, which is created on the spot by internal combustion engines. Vehicles in streets of the cities are largest sources of pollution-the fuel combustion process produces a lot of harmf...

Gas containment and absorption in intercalated carbon nanomaterial is investigated – through experimental work, gathering data – regarding cleaner air and more efficient sorb