Effective Hydrogen Production Research Articles

Enhancing hydrogen generation through advanced power conditioning in renewable energy integration

Producing hydrogen using renewable energy is a pivotal move towards cleaner and eco-friendlier energy generation, playing a vital role in safeguarding the environment. This method merges power electronic tools with electrolysers, which are key in enhancing hydrogen creation efficiency. Given that electrolysis operate on direct current (DC) voltage, there's a need for DC-DC or AC-DC converters to guarantee the right voltage and current for optimal electrolysis. This study aims to present a power regulation system tailored for hydrogen production powered by renewable resources. This system consists of two main stages: the matrix converter and the 12-pulse diode rectifier. The matrix converter ensures a controlled intake of current from the alternating current (AC) side, leading to a sinusoidal output with limited harmonic disruption. Additionally, it produces an AC voltage with a controlled magnitude and frequency, designed to suit the 12-pulse diode rectifier that follows. This meticulous voltage control is fundamental, granting enhanced operational adaptability and producing a high-quality waveform to support the electrolysis. Finally, the 12-pulse diode rectifier's task is to transform the AC from the matrix converter into a consistent DC voltage, crucial for effective hydrogen production.

Unlocking the potential of hematite photoanodes in acidic electrolytes: Boosting performance with ultra‐small IrOx nanoparticles for efficient water splitting

AbstractPhotoelectrochemical (PEC) water splitting offers a promising route for harnessing solar energy to produce clean hydrogen fuel sustainably. A major hurdle has been boosting the performance of photoanode materials within acidic electrolytes—a critical aspect for advancing PEC technology. In response to this challenge, we report a method to augment the efficacy of hematite photoanodes under acidic conditions by anchoring IrOx nanoparticles, replete with hydroxyl groups, onto their surface. A remarkable and steady photocurrent density of 1.71 mA cm−2 at 1.23 V versus RHE was achieved, marking a significant leap in PEC efficiency of hematite in acidic media. The introduction of the IrOx layer notably expanded the electrochemically active surface area for more active sites, fostering improved charge separation and transfer. It also served as an effective hole capture layer, drawing photogenerated holes from hematite to facilitate swift migration to the active sites for the water oxidation process. This advancement has the potential to fully harness the capabilities of hematite photoanodes in acidic environments, thereby smoothing the path toward more effective and sustainable hydrogen production through PEC water splitting.

A dual S-scheme heterojunction SrTiO3/SrCO3/C-doped TiO2 as H2 production photocatalyst and its charge transfer mechanism

Constructing an S-scheme heterojunction is a highly effective approach for enhancing photocatalytic performance. However, the impact of a single S-scheme heterojunction on charge transfer is limited. To overcome this constraint, a dual S-scheme heterojunction, SrTiO3/SrCO3/C-doped TiO2 (referred to as ST/SC/CT), is designed for UV-vis-driven hydrogen production. The mass-normalized and effective surface area-normalized hydrogen production activities of ST/SC/CT are higher than those of ST and CT, respectively. The enhancement in photocatalytic performance is primarily attributed to the improved separation and transfer of photogenerated charge carriers by the dual S-scheme heterojunction. Moreover, C-doping effectively extends the light absorption range from UV to visible and greatly improves the absorption intensity. The heterojunction and charge transfer mechanism are also investigated through microscopy and spectroscopic techniques, as well as density functional theory (DFT) calculations. This work offers valuable insights for the design of novel composites by combining surface modification with heterojunction engineering.

Increasing the capacity of pseudocapacitive WO3 auxiliary electrode for enhanced two-step decoupled acid water electrolysis

Decoupled water electrolysis has all the necessary properties to become an effective hydrogen production tool. Hydrogen evolution is decoupled from oxygen evolution using red-ox mediator electrodes in decoupled electrolysis. Therefore, oxygen and hydrogen are not produced simultaneously or in the same space. This simplifies the design of electrolysers and opens up the possibility of not using membranes and diaphragms for gas separation as conventional electrolysers do. Also, membrane-free technology improves the durability and efficiency of electrolysers. The reduction and oxidation of the red-ox mediator electrode must be reversible. Also, the electrode material should have a high charge capacity and be durable. In this work, we demonstrate WO3 as a red-ox mediator electrode in decoupled water electrolysis with acid electrolyte and investigate the effect of lyophilisation and annealing conditions on WO3 capacity. Indeed, the WO3 electrode can successfully act as a red-ox mediator through intercalation and deintercalation of H+ ions. Lyophilisation increases capacity more than two times than the air-dried sample, 495.55 and 201.41 F/g, respectively. Such high capacities as 837.43 F/g were reached when an inert annealing atmosphere was used. The electrolysis faradaic efficiency of 98–99 % was achieved in all prepared samples, with an energetical efficiency of 34–58 %.

Microwave-assisted sumac based biocatalyst synthesis for effective hydrogen production

AbstractHydrogen (H2), a renewable energy source with a high energy density and a reputation for being environmentally benign, is being lauded for its potential in various future applications. In the present context, the catalytic methanolysis of sodium borohydride (NaBH4) is of considerable importance due to its provision of a pathway for the efficient production of hydrogen gas (H2). The main aim of this research attempt was to assess the viability of utilizing refuse defatted sumac seeds as an unusual precursor in microwave-assisted K2CO3 activation to produce a biocatalyst.The primary objective that motivated the synthesis of the biocatalyst was to facilitate the generation of hydrogen via the catalytic methanolysis of NaBH4. With the aim of developing a biocatalyst characterized by enhanced catalytic performance, we conducted an exhaustive investigation of a wide range of experimental parameters. The activation agent-to-sample ratio (IR), impregnation time, microwave power, and irradiation time were among these parameters.Significantly enhanced in catalytic activity, the biocatalyst produced under particular conditions achieved a peak hydrogen production efficiency of 10,941 mL min− 1 g.cat− 1. In particular, it was determined that the ideal conditions were as follows: 0.5 IR, 24 h of impregnation, 500 W of microwave power, and 10 min of irradiation. This novel strategy not only demonstrates the impressive potential of eco-friendly biocatalysts, but also positions them as a viable alternative material for the sustainable production of hydrogen via NaBH4 methanolysis.Three significant parameters contribute to the value and renewability of this study. The first is that waste is used as the primary material; the second is that the activator is less hazardous than other activators; and the third is that microwave activation is a green chemistry technique. Graphical Abstract

A brief review of hydrogen production technologies

As a result of the array of problems arising from the use of fossil fuels, it is necessary to develop and optimize alternative energy technologies. Despite hydrogen being an ideal form of energy, its primary source is still fossil fuels via conventional methods. Therefore, several hydrogen-production resources and techniques have been investigated, providing feasibility for clean and effective hydrogen production. This paper provided a mini-review of hydrogen production technologies, including renewable energy, chemical looping, water electrolysis, photocatalysis, and plasma.

Study on tritium permeation behavior in primary and second circuits of the hydrogen production system by methane steam reforming using HTGR

Hydrogen production by methane steam reforming (MSR) using the process heat from High-temperature gas-cooled reactor (HTGR) is one of the most promising technology for hydrogen production using nuclear energy in the near future. The permeation behavior of tritium produced by the reactor is extremely important when analyzing the safety of this hydrogen production system. There are two methods of connection between a nuclear reactor and a hydrogen production system. One is direct coupling that the steam reformer of the hydrogen production system is directly connected to the first circuit of the nuclear reactor. The other is indirect coupling via an intermediate heat exchanger (IHX) to connect nuclear reactor and hydrogen production system. Hence, this work proposed a model to analyze the difference in tritium permeation between these two coupling ways and to compare the tritium permeation behavior for different IHX alloys at various operating conditions. This model includes tritium's production rate, release fraction, and decay reduction in the system. The results show that the pre-exponential factor of the IHX alloy mainly limits the tritium permeation rate. In addition, the tritium permeation rate increases about two times when the temperature rises from 750 °C to 950 °C at a steady state. Further, the decrease of tritium permeation rate is seen from the calculation results for the system with IHX, e.g., for T = 750 °C, the mean permeation rate of tritium into the product gas is 9.31 × 10−12 mol/s at the whole year for indirect coupling with an IHX, compared to 3.86 × 10−12 mol/s for direct coupling, which reduced 58.54 % (This means that with IHX the permeation rate is lower than the system without IHX). These results will contribute to designing an effective and safe hydrogen production system by MSR using HTGR process heat.

Ce-doping induces rapid electron transfer in a bimetallic phosphide heterostructure to achieve efficient hydrogen production.

Using electrochemical water splitting to generate hydrogen is considered a desirable approach, which is greatly impeded by the sluggish dissociation of H2O and adsorption and desorption of H*. Effective hydrogen production can be achieved by speeding up the chemical process with a suitable electrocatalyst. In this work, we designed and synthesized a rare earth element cerium (Ce) regulated iron-nickel bimetallic phosphide Ce-NiFeP@NF (here NiFeP represents Fe2P/NiP2) nanoarray with nanoflowers. For the hydrogen evolution reaction (HER), Ce-NiFeP@NF only needs an overpotential of 106 mV to provide a current density of 10 mA cm-2, compared to NiFeP@NF (175 mV@10 mA cm-2). This self-supported electrocatalyst Ce-NiFeP@NF with a composite morphology exhibits excellent performance in the HER. Specifically, the introduction of Ce promotes the electron transfer process at the Fe2P/NiP2 heterojunction interface and the Ce-NiFeP@NF nanocomposite structure with nanoflowers has a larger electrochemically active specific surface area, which is more conducive to improving the intrinsic catalytic activity. Also, a dual-electrode alkaline electrolytic cell (Ce-NiFeP@NF functions as both the anode and the cathode) operates with a cell voltage of only 1.56 V to achieve a current density of 10 mA cm-2. The synergistic effect of rare earth element doping and heterojunction engineering can improve the morphology of intrinsic catalysts to achieve more efficient electrochemical water splitting for hydrogen production.

Investigation of the promotion effect of metal oxides on the water-gas shift reaction activity over Pt-MOx/CeO2 catalysts for aqueous phase reforming

Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO2 and a series of Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH3-TPD, CO2-TPD, etc. It was found that the addition of MOx weakened the Pt-CeO2 interaction and promoted the generation of Ptδ+ species with lower valence state, which contribute to the C–H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH4 selectivities were obtained over the Pt-MgO/CeO2, while the highest CH4 selectivity was obtained over the Pt-CrOx/CeO2 (2.21%). Over the Pt/CeO2 and Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts, CO2/CH4 ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H2O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.

Atomic layer deposited RuO2 with controlled crystallinity and thickness for oxygen evolution reaction catalysis

The effective production of hydrogen as an attractive alternative energy source requires efficient electrocatalysis of the oxygen evolution reaction (OER), the rate-determining step in water splitting. Ruthenium oxide has been investigated as a representative OER catalyst; however, additional research is required for practical applications because of its low stability and varied performance depending on the fabrication method. In this study, RuO2 was prepared via atomic layer deposition (ALD). The crystallinity of the film was controlled by adjusting the ALD growth temperature, and its influence on the OER performance was examined. In addition, ALD cycles were controlled to study the influence of film thickness on the OER performance, allowing for a comparative analysis. The RuO2 film was deposited onto carbon fiber paper (CFP) to enhance its active surface area for the OER. The as-obtained samples were analyzed using various techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the crystalline RuO2 grown at 400 °C performed better catalytic performance than amorphous RuO2 grown at 350 °C, and adjusting the film thickness enhanced the electrochemical performance and stability of the catalyst film.

An overview of hydrogen production from Al-based materials

Abstract A profound overview of the recent development for on-time, on-demand hydrogen production from light metal-based hydrolysis is presented. Hydrogen energy is one of the clean and renewable energy sources which has been recognized as an alternative to fossil fuels. In addition, aluminum is the most suitable light activity metal for hydrolysis materials attributed to its safety, environmental friendliness, high-energy density, inexpensive, and low density with high strength ratio. In general, dense oxide films formed act as a barrier on aluminum surfaces. Accordingly, effective removal of the oxide film is a key measure in solving the Al–water reaction. In this review, recent advances in addressing the main drawbacks including high-purity aluminum with acid–alkali solutions, nano-powders of aluminum or composite with acid–base solutions, ball-milled nano-powders, alloying blocks, and gas atomization powders are summarized. The characteristics of these three technologies and the current research progress are summarized in depth. Moreover, it is essential to promote low-cost aluminum-based materials based on effective hydrogen production efficiency and explore ways for practical large-scale applications.

Overcoming hydrogen loss in single-chamber microbial electrolysis cells by urine amendment

The effective hydrogen production in single-chamber microbial electrolysis cells (MECs) has been seriously challenged by various hydrogen consumers resulting in substantial hydrogen loss. In previous studies, the total ammonia nitrogen (TAN) has been used to inhibit certain hydrogen-consuming microorganisms to enhance hydrogen production in fermentation. In this study, we explored the feasibility of using source-separated urine to overcome hydrogen loss in the MEC, with the primary component responsible being TAN generated via urea hydrolysis. Experimental results revealed that the optimal TAN concentration ranged from 1.17 g N/L to 1.75 g N/L. Within this range, the hydrogen production rate substantially improved from less than 100 L/(m3·d) up to 520 L/(m3·d), and cathode recovery efficiency and energy recovery efficiency were greatly enhanced, with the hydrogen percentage achieved over 95 % of the total gas volume, while maintaining uninterrupted electroactivity in the anode. Compared to using chemically added TAN, using source separated urine as the source of ammonia also showed the effect of overcoming hydrogen loss but with lower Coulombic efficiency due to the complex organic components. Pre-adaptation of the reactor with urea enhanced hydrogen production by nearly 60 %. This study demonstrated the effectiveness of TAN and urine in suppressing hydrogen loss, and the results are highly relevant to MECs treating real wastewater with high TAN concentrations, particularly human fecal and urine wastewater.

Triggering the high catalytic activity of Ni-based catalyst for urea and urine electrolysis by adding Fe and constructing the CoFeP@Ni3S2 heterostructure

For effective hydrogen production, urea oxidation reaction (UOR) with much lower potential has been used to replace the water oxidation reaction (OER), while fulfilling the wastewater treatment. Development of bifunctional electrocatalysts is the crucial link in urea-assistant water electrolysis. Here, a novel composite consisting of the bimetallic phosphide nanosheets and porous Ni3S2 nanospheres was prepared by a hydrothermal-electrodeposition method. It proves that the NF/CoFeP@Ni3S2 electrode exhibits an outstanding performance for HER/UOR (HER overpotential is 173 mV and EUOR is 1.358 V, 100 mA cm−2). As for a two-electrode system taking NF/CoFeP@Ni3S2 as cathode and anode in urea medium, the voltage at 100 mA cm−2 is just 1.454 V. Even in human urine electrolyte, just only a slight current decrease is observed. Both in urea and urine, the voltage of NF/CoFeP@Ni3S2 remain stable during a 50-hour continuous operation. The formation of heterostructures between the bimetallic phosphides and Ni3S2, and Fe addition realize the gradual improvement in activity from the pristine CoP to CoFeP and then to the CoFeP@Ni3S2. This strategy provides a practical hetero-structured catalyst design form considering the structure properties of urea molecule for the efficient water-hydrogen conversion synchronous sewage treatment.

Numerical and experimental investigation of irradiance profiles on suspended particles in a flat disk photoreactor for hydrogen generation

Regarding sustainable energy alternatives, the present work evaluates hydrogen production using suspended particles exposed to an irradiance of 247 W/m2. A 1.0 L flat disk photoreactor (FDP) was designed for evaluating agitation speeds of 100, 175, and 250 RPM, and particle concentrations of 0.5, 1.0, and 2.0 g/L. Through CFD-assisted, a non-conformal meshing of 551,000 polyhedral elements was created, coupling Volume of Fluids, Discrete Particle Modelling, and Discrete Ordinates Model methods. Transient simulation shows a maximum particle homogenization of 84 % at 0.5 g/L and 250 RPM, and a maximum average exposure profile of 140 W/m2 for 27% of the particles with an initial loading of 1.0 g/L at 250 RPM.Effective concentration in the FDP was measured, determining an accuracy of 84.35% and 71.32%, respectively, concerning the model used in the simulation. It is concluded that the FDP developed provides good semiconductor behavior for an effective hydrogen production process.

Effective Hydrogen Production from Alkaline and Natural Seawater using WO3-x@CdS1-x Nanocomposite-Based Electrocatalysts.

Offshore hydrogen production through water electrolysis presents significant technical and economic challenges. Achieving an efficient hydrogen evolution reaction (HER) in alkaline and natural seawater environments remains daunting due to the sluggish kinetics of water dissociation. To address this issue, we synthesized electrocatalytic WO3-x@CdS1-x nanocomposites (WCSNCs) using ultrasonic-assisted laser irradiation. The synthesized WCSNCs with varying CdS contents were thoroughly characterized to investigate their structural, morphological, and electrochemical properties. Among the samples tested, the WCSNCs with 20 wt % CdS1-x in WO3-x (Wx@Sx-20%) exhibited superior electrocatalytic performance for hydrogen evolution in a 1 M KOH solution. Specifically, the Wx@Sx-20% catalyst demonstrated an overpotential of 0.191 V at a current density of -10 mA/cm2 and a Tafel slope of 61.9 mV/dec. The Wx@Sx-20% catalysts demonstrated outstanding stability and durability, maintaining their performance after 24 h and up to 1000 CV cycles. Notably, when subjected to natural seawater electrolysis, the Wx@Sx-20% catalysts outperformed in terms of electrocatalytic HER activity and stability. The remarkable performance enhancement of the prepared electrocatalyst can be attributed to the combined effect of sulfur vacancies in CdS1-x and oxygen vacancies in WO3-x. These vacancies promote the electrochemically active surface area, enhance the rate of charge separation and transfer, increase the number of electrocatalytic active sites, and accelerate the HER process in alkaline and natural seawater environments.

Interfacial and Electronic Modulation of W Bridging Heterostructure Between WS2 and Cobalt-Based Compounds for Efficient Overall Water Splitting.

The development of high performance electrocatalysts for effective hydrogen production is urgently needed. Herein, three hybrid catalysts formed by WS2 and Co-based metal-organic frameworks (MOFs) derivatives are constructed, in which the small amount of W in the MOFs derivatives acts as a bridge to provide the charge transfer channel and enhance the stability. In addition, the effects of the surface charge distribution on the catalytic performance are fully investigated. Due to the optimal interfacial electron coupling and rearrangement as well as its unique porous morphology, WS2 @W-CoPx exhibits superior bifunctional performance in alkaline media with low overpotentials in hydrogen evolution reaction (HER) (62mV at 10mA cm-2 ) and oxygen evolution reaction (OER) (278mV at 100mA cm-2 ). For overall water splitting (OWS), WS2 @W-CoPx only requires a cell voltage of 1.78V at 50mA cm-2 and maintains good stability within 72 h. Density functional theory calculations verify that the combination of W-CoPx with WS2 can effectively enhance the activity of OER and HER with weakened OH (or O) adsorption and enhanced H atom adsorption. This work provides a feasible idea for the design and practical application of WS2 or phosphide-based catalysts in OWS.

Phosphorous-doped cadmium sulfide hollow octahedrons for enhanced visible-light photocatalytic H2 evolution

Currently, promoting solar absorption ability and photoexcited charge separation and transfer of semiconductors is of significance for enhancing their solar-to-hydrogen (STH) efficiency. Hollow-structured design and element doping strategy have proven to be effective in strengthening solar absorption and manipulating the charge dynamics. Herein, an ingenious design of doping phosphors (P) into hollow-structured CdS octahedrons is applied for achieving effective photocatalytic hydrogen production. The P-doped CdS semiconductor has a hollow interior for enhancing the photon absorbance and a narrow bandgap with upshift of valence band for facilitating photoinduced charge separation and transport, all of which contribute to their improved photocatalytic performance. Consequently, the synergistic effect in the designed archicture leads to an enhanced hydrogen production rate of up to 9.58 mmol·g−1 h−1, being about 11.7 fold higher than the reported CdS nanorods. Our work offers a new way for developing other types of sulfur-based semiconductors towards effective solar-to-hydrogen conversion.

Enhanced photoactivity towards bismuth vanadate water splitting through tantalum doping: An experimental and density functional theory study

The activation of hole trap states in bismuth vanadate (BiVO4) is considered an effective strategy to enhance the photoelectrochemical (PEC) water-splitting activity. Herein, we propose a theoretical and experimental study of tantalum (Ta) doping to BiVO4 leading to the introduction of hole trap states for the enhanced PEC activity. The doping of Ta is found to alter the structural and chemical surroundings via displacement of vanadium (V) atoms that cause distortions in the lattice via the formation of hole trap states. A significant enhancement of photocurrent to ∼4.2 mA cm−2 was recorded attributing to the effective charge separation of efficiency of ∼96.7 %. Furthermore, the doping of Ta in the BiVO4 lattice offers improved charge transport in bulk and decreased charge transfer resistance at the electrolyte interface. The Ta-doped BiVO4 displays the effective production of hydrogen (H2) and oxygen (O2) under AM 1.5 G illumination with a faradaic efficiency of 90 %. Moreover, the density functional theory (DFT) study confirms the decrease in optical band gap and the activation of hole trap states below the conduction band (CB) with a contribution of Ta towards both valence and CB that increases the charge separation and majority charge carrier density, respectively. The findings of this work propose that the displacement of V sites with Ta atoms in BiVO4 photoanodes is an efficient approach for enhanced PEC activity.

Production of HHO gas in the water-electrolysis unit and the influences of its introduction to CI engine along with diesel-biodiesel blends at varying injection pressures

Hydrogen has been identified as a clean and renewable energy source that has a significant potential to replace fossil fuels. The effective production of hydrogen on a commercial scale, however, presents a vital obstacle in today's world. Water splitting electrolysis, which offers high energy conversion and storage capabilities, has emerged as a promising approach for achieving the efficient hydrogen production to address this issue. This experimental research focuses on the production of hydrogen-oxygen gas through the electrolysis process. HHO gas provides promising benefits in terms of better combustion and lower emissions. Therefore, it also focuses on how best HHO gas can be utilized in diesel engines to improve the performance and to reduce the emissions. HHO gas produced at 60 L per hour through electrolysis process is mixed with air in a mixing chamber. Also, Palm munja methyl ester of 10% and diesel fuel of 90% was volumetrically blended to get B10 biodiesel. Therefore, totally four test fuels (Diesel, Diesel + HHO, B10, and B10 + HHO) were tested on a single-cylinder Kirloskar water-cooled direct injection diesel engine under different engine speeds ranging from 1447 to 1550 rpm. The engine injector pressure was varied from 200, 220, and 240 bar during the experiments with an interval of 20 bar. The engine has been modified for hydrogen and oxygen inlet at the entrance manifold 6 cm away at an angle of 30°. The results shows that at 200 bar injection pressure with B10 + HHO blend exhibits better performance and released lower emissions. The performance results also show that the brake thermal efficiency was improved up to 14.16%, and the brake power was increased by 3.22%, while the brake-specific fuel consumption is reduced by 11.53%. The emission results show that CO, HC, NOx, and CO2 emissions were reduced by 20.87%, 11.47%, 1.96%, and 5.22%, respectively. Therefore, it can be concluded that B10 + HHO provides better performance and the lowest emissions compared with other blends.

Cobalt incorporation-induced photocatalytic reactivity enhancement in ZnIn2S4 nanosheets for effective hydrogen production

Heteroatom incorporation is commonly used resorts to construct highly active centers in photocatalysis. Especially, cobalt with tunable spin orbitals is a desirable dopant for photocatalytic hydrogen production. However, the charge and adsorption properties associated with cobalt-incorporated sites have not been elucidated. In this work, the cobalt with the spin state (e4t23) was successfully incorporated into ZnIn2S4 nanosheets. Experimental and calculated results show that the cobalt-induced electron occupancy displays an obvious interaction with oxygen-containing intermediates, which promotes water dissociation. Meanwhile, the enhanced covalency of CoS bonds effectively balances the hydrogen adsorption/desorption ability, which is favorable for H2 production. Nevertheless, the weakened water adsorption restricts the improvement of H2 production as the amount of Co doping increases. Under the balance of these factors, optimum doping of cobalt in ZnIn2S4 is achieved and it shows a significantly enhanced H2-evolution rate of 72.1 μmol h−1, which is 5.5 times higher than that of ZnIn2S4.