Anion dependent CO/H₂ production ratio from CO₂ reduction on Au electro-catalyst

Hong, Sujik,Lee, Seunghwa,Kim, Sohaeng,Lee, Jae Kwang,Lee, Jaeyoung Elsevier 2017 CATALYSIS TODAY - Vol.295 No.-

<P><B>Abstract</B></P> <P>In this study, we first demonstrate that CO production selectivity from CO<SUB>2</SUB> on Au electro-catalyst depends on the type of electrolyte anion. Comparing the faradaic efficiencies of H<SUB>2</SUB>, HCOO<SUP>−</SUP> and CO in the presence of different anions such as Cl<SUP>−</SUP>, HPO<SUB>4</SUB> <SUP>2−</SUP>, SO<SUB>4</SUB> <SUP>2−</SUP> and HCO<SUB>3</SUB> <SUP>−</SUP> at constant potential of −0.7V (<I>vs.</I> RHE), we observe that the CO/H<SUB>2</SUB> ratio could be enhanced due to strongly adsorbed anion such as Cl<SUP>−</SUP>. Although HPO<SUB>4</SUB> <SUP>2−</SUP> is more strongly adsorbed than SO<SUB>4</SUB> <SUP>2−</SUP> and HCO<SUB>3</SUB> <SUP>−</SUP> on the surface of electrode, CO<SUB>2</SUB> reduction in HPO<SUB>4</SUB> <SUP>2−</SUP> containing solution exhibited a minimum faradaic efficiency of CO (11%) but a maximum faradaic efficiency of H<SUB>2</SUB> (70%). Based on physicochemical analytical tools (LSV, EIS, SEM, XPS and XRD) and according to previous studies, we conclude that the product distribution is associated with distinct properties caused by characteristic of each anion when adsorbed on the electrode surface such as specific adsorption strength and intrinsic characteristic of anions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The anion effect of 4 electrolytes for CO<SUB>2</SUB>RR on Au catalyst are investigated. </LI> <LI> The specific adsorption of anions could contribute to suppressing HER. </LI> <LI> Chloride anion plays a notable role as increasing CO/H<SUB>2</SUB> production ratio. </LI> <LI> Phosphate anion contributes to decrease CO/H<SUB>2</SUB> production ratio. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Depending on electrolytes containing different anions, CO/H<SUB>2</SUB> production ratio of CO<SUB>2</SUB> electroreduction on Au catalyst was differently observed. Usually, a specific adsorption strength of anions played a key role in determination of CO/H<SUB>2</SUB> ratio by a suppressing hydrogen evolution reaction. However, unlike that, certain anions such as chloride and phosphate differently contribute to increase CO/H<SUB>2</SUB> ratio due to their intrinsic characteristics.</P> <P>[DISPLAY OMISSION]</P>

Removal of hydrogen sulfide from a steam-hydrogasifier product gas by zinc oxide sorbent: Effect of non-steam gas components

김기석,Nokuk Park 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.6

Removal of H2S from a steam-hydrogasifier product gas was studied at 636 K and 1 atm using a commercially available zinc oxide sorbent in a packed-bed reactor. A mixture gas containing 22% CH4,18.7% H2, 8.8% CO and 5.5% CO2 (non-steam components subtotaling to 55%) balanced with steam was used to simulate the steam-hydrogasifier product gas. Sorbent particles of 150–250 mm size were used to eliminate the effect of intraparticle mass transfer limitation. Experiments were conducted to monitor H2S breakthrough of reactor effluent stream for operation parameters such as space velocity and inlet H2S concentration. With space velocity varied from 6000 to 8000 to 12,000 h1 for inlet H2S concentration in the range of 100–800 ppmv, sulfur capture capacity of the sorbent (Scap) for 2 ppmv H2S breakthrough did not change notably, indicating that, for each inlet H2S concentration tested, sorbent utilization for sulfur removal was not affected by the space velocity. Meanwhile, for each space velocity tested, Scap increased monotonically as the inlet H2S concentration increased from 100 to 500 to 800 ppmv,which is opposite to the result observed for the mixture gas devoid of CH4, H2, CO and CO2. As the overall content of these non-steam components of the simulation gas was halved for each inlet H2S concentration tested at 8000 h1 space velocity, Scap for non-steam gas components of 27.5% content corresponded approximately to themedian value of those for the non-steam gas components of 55% and 0% content, suggestive of linear dependency of Scap upon the content of the non-steam components for the inlet H2S concentration tested. 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Enhanced Photobiological H2 Production by the Addition of Carbon Monoxide and Hydrogen Cyanide in Two Unicellular N2-fixing Cyanobacterial Strains Isolated from Korean Coasts

박종우,남승원,김형섭,윤석현,이원호 한국해양과학기술원 2014 Ocean science journal Vol.49 No.1

Photobiological H2 from marine cyanobacterial strains is widely accepted to be an ideal clean and renewable energy source. Using the two Korean N2-fixing unicellular cyanobacterial strains (Cyanothece sp. KNU CB MAL-031 and Cyanothece sp. KNU CBMAL-058) and the Synechococcus sp. Miami strain BG043511 we performed flask-scale experiments to measure the effect of CO and HCN addition on photobiological H2 production. For the test, 1, 5, 10 and 30% v/v of CO in the N2 atmosphere was applied. Enhancement of H2 production was remarkable at 1-5% concentration range of CO addition. At CO concentrations over 5% no further cost-effective enhancement of H2 production was detectable, which suggests to us that 1-5% CO addition should be adopted for practical photobiological H2 production by the cyanobacterial strains. Maximum enhancement of the photobiological H2 production by CO additions was 2-6 times over the control flasks without CO. When 3 ppm of HCN was injected into the cell suspension of BG043511, the enhancement of hydrogen production was 50-60% of that under 5% CO. Present result implies the possible recycling of waste CO and HCN for the enhancement of the photobiological H2 production using marine cyanobacterial strains.

Effects of addition of electrolysis products in methane-air diffusion flames

Park, J.,In Keel, S.,Han Yun, J.,Kwon Kim, T. Pergamon Press ; Elsevier Science Ltd 2007 International journal of hydrogen energy Vol.32 No.16

Evaluation of steam-added methane-hydrogen blends through the comparison of flame structures and pollutant emissions is numerically conducted with detailed chemistry. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuel of methane-hydrogen-steam through the molar addition of H<SUB>2</SUB>O. Flame structure is changed considerably for CH<SUB>4</SUB>-H<SUB>2</SUB> flames and CH<SUB>4</SUB>-H<SUB>2</SUB>-H<SUB>2</SUB>O flames in comparison to pure methane flame. The discernible differences in major flame structure are compared among a pure methane flame, CH<SUB>4</SUB>-H<SUB>2</SUB> flames and CH<SUB>4</SUB>-H<SUB>2</SUB>-H<SUB>2</SUB>O flames. Especially, emission indices of CO increase and then decrease after showing a maximum in the increase of methane mole fraction for CH<SUB>4</SUB>-H<SUB>2</SUB> flames and in the increase of H<SUB>2</SUB>O mole fraction for CH<SUB>4</SUB>-H<SUB>2</SUB>-H<SUB>2</SUB>O flames, while those of CO<SUB>2</SUB> increase monotonously. These behaviors are mainly caused by the competition of the production through the reaction step HCO+H<SUB>2</SUB>O->H+CO+H<SUB>2</SUB>O with the destruction of CO by the reaction step CO+OH->CO<SUB>2</SUB>+H. The changes of thermal NO and Fenimore NO are also analyzed for various combinations of the fuel composition. Importantly, contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, CH<SUB>4</SUB>-H<SUB>2</SUB> flames and CH<SUB>4</SUB>-H<SUB>2</SUB>-H<SUB>2</SUB>O flames.

한국 연안산 단세포성 수소생산 남세균 종주들의 분류계통, 색소함량 및 최적성장 환경

박종우,김주희,조애라,정연덕,김평중,김형섭,이원호,PARK, JONG-WOO,KIM, JU HEE,CHO, AE-RA,JUNG, YUN-DUK,KIM, PYOUNG JOONG,KIM, HYUNG-SEOP,YIH, WONHO 한국해양학회 2015 바다 Vol.20 No.3

광생물학적 수소생산 잠재력을 가진 한국산 단세포성 남세균 단종배양체를 확립하기 위하여, 2005부터 4년 동안 우리나라 연근해역의 68개 정점에서 반복적으로 시료를 채집하였다. 확보된 77개 종주의 단종배양체 가운데 6개 종주(KNU CB-MAL002, 026, 031, 054, 055, 058)는 일반적인 수소생산 조건에서 0.15 mL $H_2\;mL^{-1}$ 이상의 수소 누적량을 나타내었고, 60시간 이상의 수소 지속생산을 기록하였다. 6개 실험 종주의 수소생산을 더욱 높여주는 최적의 공정을 규명하기 위한 연구의 일환으로, 각 종주의 수온 및 염분 등급 별 성장도를 측정하여, 종주 간의 차이(interstrain difference)를 비교 하였다. 실험 종주 6개의 일일 최대 성장률은 1.78~2.08 범위로 높았고, 모든 실험 종주가 질소고정능을 나타내어, 광생물학적 수소생산 잠재력이 높은 것으로 예상되었다. 16S rRNA 분석결과, 실험 종주 들은 Cyanothece sp. ATCC51142와 높은 유사도(99%)를 보였으나, 6개의 종주 모두가 분자계통도에서는 ATCC51142와 서로 다른 clade에 별도로 나뉘어져, 본 실험 종주의 일부는 신종일 가능성이 있다. 엽록소-a는 건중량 대비 함유량이 3.4~7.8%의 범위로 나타났으며, 보조색소인 홍조소와 남조소의 함유량은 대서양산 남세균 Synechococcus sp. Miami BG03511의 절반 수준이었다. 최적 성장온도로 확인된 $30{\sim}35^{\circ}C$ 구간 밖의 온도에서는 성장이 크게 제한되었으며, $40^{\circ}C$의 고온에서는 모든 실험종주의 성장이 거의 정지됨을 확인하였다. 실험 종주들은 30 psu의 염분에서 성장이 우세하였다. 이 가운데 CB055 종주는 15 psu까지의 상대적 저염 구간에서도 높은 성장을 유지하여, 염분의 변동에 대한 내성이 높은 종주로 확인되었다. 이와 같은 광염 특성의 종주는 연안수의 계절적인 염분변화가 상대적으로 큰 온대 연안역에서 이 종주를 생물공학적으로 응용하게 될 경우, 기반해수의 계절적인 염분 변화에도 불구하고 배양 공정상의 높은 유연성을 나타내게 될 것이다. 본 연구 결과 규명된 각 종주 별 생리적 특성 자료는 향후 광생물학적 수소생산 최적공정을 확립하기 위한 모델연구에 긴요할 것이다. To set up unicellular cyanobacterial strains with photo-biological $H_2$ production potential, live samples were repeatedly collected from 68 stations in the coastal zone of Korea for the four years since 2005. Among 77 cyanobacterial strains established six (KNU strains, CB-MAL002, 026, 031, 054, 055 and 058) were finally chosen as the excellent strains for $H_2$ production with $H_2$ accumulation over 0.15 mL $H_2\;mL^{-1}$ under general basic $H_2$ production conditions as well as positive $H_2$ production for more than 60 hr. To explore optimum procedures for higher $H_2$ production efficiency of the six cyanobacterial strains, the inter-strain differences in the growth rate under the gradients of water temperature and salinity were investigated. The maximum daily growth rates of the six strains ranged from 1.78 to 2.08, and all of them exhibited $N_2-fixation$ ability. Based on the similarity of the 16S rRNA sequences, all the test strains were quite close to Cyanothece sp. ATCC51142 (99%). The six strains, however, were grouped into separate clades from strain ATCC51142 in the molecular phylogeny diagram. Chlorophyll- a content was 3.4~7.8% of the total dried weight, and the phycoerythrin and phycocyanin contents were half of those in the Atlantic strain, Synechococcus sp. Miami BG03511. The growth of the six strains was significantly suppressed at temperatures above the optimal range, $30{\sim}35^{\circ}C$, to be nearly stopped at $40^{\circ}C$. The growth was not inhibited by high salinities of 30 psu salinity in all the strains while strain CB055 maintained its high growth rate at low salinities down to 15 psu. The euryhaline strains like CB055 might support massive biotechnological cultivation systems using natural basal seawater in temperate latitudes. base seawater. The biological and ecophysiological characteristics of the test strains may contribute to designing the optimal procedures for photo-biological $H_2$ production by unicellular cyanobacteria.

Selective charge transfer to dioxygen on KPF₆-modified carbon nitride for photocatalytic synthesis of H₂O₂ under visible light

Kim, Sujeong,Moon, Gun-hee,Kim, Hyejin,Mun, Yeongdong,Zhang, Peng,Lee, Jinwoo,Choi, Wonyong Academic Press 2018 Journal of catalysis Vol.357 No.-

<P><B>Abstract</B></P> <P>Photochemical production of H<SUB>2</SUB>O<SUB>2</SUB> through O<SUB>2</SUB> reduction has been proposed as an alternative method of solar energy storage. A carbon nitride (CN) photocatalyst was selected for this purpose. The incorporation of KPF<SUB>6</SUB> into the CN structure greatly enhanced the apparent quantum yield (AQY) of H<SUB>2</SUB>O<SUB>2</SUB> production in the UV and visible light region. The AQY of KPF<SUB>6</SUB>-modified CN was measured to be 35.9% and 24.3% under monochromatic irradiation at 370 and 420 nm, respectively, which are 8.3 and 26.1 times higher than for bare CN. The KPF<SUB>6</SUB>-enhanced activity is ascribed to several factors including (i) enhanced absorption of UV and visible light, (ii) higher charge carrier density, (iii) retarded radiative recombination of charge pairs, (iv) highly selective two-electron transfer to O<SUB>2</SUB>, and (v) hindered photodecomposition of in-situ generated H<SUB>2</SUB>O<SUB>2</SUB>. The markedly high selectivity of KPF<SUB>6</SUB>-modified CN toward the two-electron reduction of O<SUB>2</SUB> (leading to H<SUB>2</SUB>O<SUB>2</SUB>) was demonstrated in comparision with other photoreductive conversions such as the reduction of polyoxometalate (POM → POM<SUP>−</SUP>), hexavalent chromium (Cr<SUP>VI</SUP> → Cr<SUP>III</SUP>), CCl<SUB>4</SUB> (dechlorination), and protons (H<SUB>2</SUB> production). This study developed a simple method of efficient production of H<SUB>2</SUB>O<SUB>2</SUB> using visible light, which could be utilized for a variety of applications that employ H<SUB>2</SUB>O<SUB>2</SUB> as a solar fuel or a green oxidant.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The photocatalytic production of H<SUB>2</SUB>O<SUB>2</SUB> was markedly enhanced by the incorporation of KPF<SUB>6</SUB> into the carbon nitride (CN) structure. </LI> <LI> The highest quantum yields of the production of H<SUB>2</SUB>O<SUB>2</SUB> were achieved using KPF<SUB>6</SUB>-modified CN (35.9% and 24.3% at 370 and 420 nm, respectively). </LI> <LI> KPF<SUB>6</SUB>-modified CN exhibited markedly high selectivity for two-electron reduction of O<SUB>2</SUB> to produce H<SUB>2</SUB>O<SUB>2</SUB>. </LI> <LI> The present catalytic system consisting of earth-abundant elements utilizes only visible light and dioxygen without using any noble metal catalysts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Surface synergism of Pd/H₂Ti₃O₇ composite nanowires for catalytic and photocatalytic hydrogen production from ammonia borane

Lai, Shiau-Wu,Park, Ji-Won,Yoo, Sung-Ho,Ha, Jum-Mok,Song, Er-Hong,Cho, Sung-Oh Elsevier 2016 International journal of hydrogen energy Vol.41 No.5

<P><B>Abstract</B></P> <P>Pd-incorporated H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires are synthesized using a facile one-step procedure. H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires are prepared using a modified alkaline hydrothermal method and Pd is incorporated into the H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires using a photodeposition technique. The prepared Pd-incorporated H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires are characterized using XRD, TEM, XPS, ultraviolet–visible spectroscopy, and photoluminescence spectroscopy. The results show that Pd-incorporated H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires are formed and that the photocatalytic properties of the H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanowires are improved by the doping and deposition processes. Furthermore, 1 wt% Pd/H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> composite nanowires show a high hydrogen production rate (up to 0.31 mol min<SUP>−1</SUP>) under visible light illumination at 20 °C, and the efficiency of 0.25 wt% Pd/H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> composite nanowires is enhanced by 20% under visible light illumination. The detailed mechanism of hydrogen production through hydrolysis of ammonia borane by using Pd/H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> composite nanowires is discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pd/H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> was synthesized by one-step procedure. </LI> <LI> The band gap was shifted through Pd-doped, leading to the visible light response. </LI> <LI> Pd/H<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> revealed good visible light-driven photocatalytic activity. </LI> <LI> The enhancement of H<SUB>2</SUB> production rate could be assigned to the surface synergism. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Degradation mechanism of anatoxin-a in UV-C/H₂O₂ reaction

Tak, So-Yeon,Kim, Moon-Kyung,Lee, Jung-Eun,Lee, Young-Min,Zoh, Kyung-Duk Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.334 No.-

<P><B>Abstract</B></P> <P>In this study, the kinetics and removal mechanism of anatoxin-a (C<SUB>10</SUB>H<SUB>15</SUB>NO) during a UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction were investigated. The removal of anatoxin-a was more effective during a UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction than with either UV photolysis or H<SUB>2</SUB>O<SUB>2</SUB> alone, due to the effective production of hydroxyl (OH) radicals. The UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction of anatoxin-a resulted in an approximately 60% decrease in total organic carbon (TOC) within 420 min, while 45% of the carbon in anatoxin-a was converted into acetate, and most of the nitrogen in anatoxin-a was converted into NH<SUB>4</SUB> <SUP>+</SUP>, NO<SUB>2</SUB> <SUP>−</SUP>, and NO<SUB>3</SUB> <SUP>−</SUP> ions. More than 50% of the nitrogen in anatoxin-a was mineralized, mainly into NO<SUB>3</SUB> <SUP>−</SUP> ions, and complete nitrogen recovery was achieved after 120 min of the UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction. Using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), we identified six degradation by-products in the UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction ([M+H]<SUP>+</SUP> = 142, 127, 113, 132, 117, and 124, respectively), which were further degraded as the reaction continued. Using these by-products, we proposed a degradation pathway for anatoxin-a during the UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction. Our results indicate that anatoxin-a can be effectively removed by a UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction during water treatment processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Removal of anatoxin-a was effective during UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction. </LI> <LI> NH<SUB>4</SUB> <SUP>+</SUP>, NO<SUB>2</SUB> <SUP>−</SUP>, and NO<SUB>3</SUB> <SUP>−</SUP> ions were produced as nitrogen byproducts in UV/H<SUB>2</SUB>O<SUB>2</SUB> reaction. </LI> <LI> Acetate was produced as a carbon short chain byproduct from anatoxin-a. </LI> <LI> Six degradation byproducts during UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction were newly identified. </LI> <LI> The degradation pathway of anatoxin-a during UV-C/H<SUB>2</SUB>O<SUB>2</SUB> reaction was proposed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Integrated techno-economic analysis under uncertainty of glycerol steam reforming for H₂ production at distributed H₂ refueling stations

Lee, Boreum,Heo, Juheon,Kim, Sehwa,Kim, Chang-Hyun,Ryi, Shin-Kun,Lim, Hankwon Elsevier 2019 Energy conversion and management Vol.180 No.-

<P><B>Abstract</B></P> <P>In this paper, we report an integrated techno-economic analysis of glycerol steam reforming (GSR) targeting distributed H<SUB>2</SUB> refueling stations for a H<SUB>2</SUB> production capacity of 700 m<SUP>3</SUP> h<SUP>−1</SUP>. A process simulation based on mass and energy balances was performed to identify the product yield at effect of temperature and water/glycerol ratio. The results show that temperature of 900 K and a water/glycerol ratio of 9 are optimal to techno-economically operate a GSR process. An economic analysis using itemized cost estimation, sensitivity analysis (SA), and profitability analysis (PA) was carried out to investigate the economic feasibility of GSR for distributed H<SUB>2</SUB> refueling stations. The unit H<SUB>2</SUB> production cost was 4.46 $ kgH<SUB>2</SUB> <SUP>−1</SUP> at the optimum conditions identified in the process simulation, and the most influential economic key factor was the reactant from the SA. Meaningful economic indicators such as net present value, discounted payback period, present value ratio, and rate of return on investment were obtained from the PA through a discounted cash flow diagram. Moreover, a cumulative probability analysis based on an uncertainty analysis using a Monte-Carlo simulation method was applied to unit H<SUB>2</SUB> production cost and B/C ratio calculations to quantify the risk of a proposed GSR process as premature technology providing crucial guidelines to decision-makers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Performing integrated analysis of glycerol steam reforming for H<SUB>2</SUB> production. </LI> <LI> Obtaining ranges of unit H<SUB>2</SUB> production cost and B/C ratio from uncertainty analysis. </LI> <LI> Economic viability for glycerol steam reforming in distributed H<SUB>2</SUB> refueling station. </LI> </UL> </P>

A combined experimental and model analysis on the effect of pH and O₂(aq) on γ-radiolytically produced H₂ and H₂O₂

Joseph, J.M.,Seon Choi, B.,Yakabuskie, P.,Clara Wren, J. Pergamon 2008 Radiation physics and chemistry Vol.77 No.9

The effects of pH and dissolved O<SUB>2</SUB> on the γ-radiolysis of water were studied at an absorbed dose rate of 2.5Gys<SUP>-1</SUP>. Argon- or air-saturated water with no headspace was irradiated and the aqueous samples were analyzed for molecular radiolysis products (H<SUB>2</SUB> and H<SUB>2</SUB>O<SUB>2</SUB>) as a function of irradiation time. The experimental results were compared with computer simulation results using a comprehensive water-radiolysis kinetic model, consisting of the primary radiolysis production, subsequent reactions and related acid-base equilibria. Both the experimental and computer model results were discussed based on the steady-state kinetic analysis of smaller reaction sets consisting of key production and removal reactions. While the main production path for a water decomposition product is the primary radiolysis, the main removal path varies. For H<SUB>2</SUB>O<SUB>2</SUB> the main removal path is the reactions with <SUP>?</SUP>e<SUB>aq</SUB><SUP>-</SUP> and <SUP>?</SUP>OH, whereas for H<SUB>2</SUB> it is the reaction with <SUP>?</SUP>OH. As a result, the presence of a dissolved species, or a change in chemical environment, affects the concentrations of H<SUB>2</SUB>O<SUB>2</SUB> and H<SUB>2</SUB> through interaction with radicals <SUP>?</SUP>e<SUB>aq</SUB><SUP>-</SUP> and <SUP>?</SUP>OH. Over a wide range of conditions, there exist quantitative but simple relationships between the radical and the molecular product concentrations. The experimental and model analyses show that dissolved oxygen increases the steady-state concentrations of H<SUB>2</SUB>O<SUB>2</SUB> and H<SUB>2</SUB> by reacting with <SUP>?</SUP>OH and <SUP>?</SUP>e<SUB>aq</SUB><SUP>-</SUP>, and the impact of oxygen is more noticeable at pH below 8. The steady-state concentrations of water decomposition products are nearly independent of pH in the range 5-8. However, raising pH above the pKa value of the acid-base equilibrium of <SUP>?</SUP>H (⇆<SUP>?</SUP>e<SUB>aq</SUB><SUP>-</SUP>+H<SUP>+</SUP>) significantly increases [H<SUB>2</SUB>O<SUB>2</SUB>] and [H<SUB>2</SUB>] at the expenses of [<SUP>?</SUP>OH] and [<SUP>?</SUP>e<SUB>aq</SUB><SUP>-</SUP>]. At pH >10, the radiolytical production of O<SUB>2</SUB> becomes significant, but at a finite rate. This considerably increases the time for the irradiated system to reach a steady state, and is responsible for different impacts on [H<SUB>2</SUB>O<SUB>2</SUB>] and [H<SUB>2</SUB>] due to radically produced O<SUB>2</SUB>, compared to impacts due to initially dissolved O<SUB>2</SUB>. Model sensitivity analysis has shown that at higher pHs (pH >10) transient species such as <SUP>?</SUP>O<SUB>2</SUB><SUP>-</SUP> and <SUP>?</SUP>O<SUB>3</SUB><SUP>-</SUP> play a major role in determining the steady-state concentration of molecular products H<SUB>2</SUB> and H<SUB>2</SUB>O<SUB>2</SUB>. Further validation of the water radiolysis model, particularly at higher pHs, is also discussed.