Half-reaction Of Water Splitting Research Articles

Activating MoS2 for pH-Universal Hydrogen Evolution Catalysis.

MoS2 presents a promising catalyst for the hydrogen evolution reaction (HER) in water splitting, but its worse catalytic performance in neutral and alkaline media than in acidic environment may be problematic for practical application. This is because the other half reaction of water splitting, i.e., oxygen evolution reaction, often needs to be implemented in alkaline environment. Here we demonstrate a universal strategy that may be used to significantly improve the HER catalysis of MoS2 in all kinds of environments from acidic to alkaline, proton intercalation. Protons may be enabled to intercalate between monolayer MoS2 and underlying substrates or in the interlayer space of thicker MoS2 by two processes: electrochemically polarizing MoS2 at negative potentials (vs RHE) in acidic media or immersing MoS2 into certain acid solutions like TFSI. The improvement in catalytic performance is due to the activity enhancement of the active sites in MoS2 by the intercalated protons, which might be related with the effect of the intercalated protons on electrical conductance and the adsorption energy of hydrogen atoms. The enhancement in catalytic activity by the intercalated proton is very stable even in neutral and alkaline electrolytes.

Electrocatalytic Biomass Valorization Integrated with Hydrogen Production

Electrocatalytic water splitting has been widely considered as a promising approach to produce clean hydrogen (H2). The anodic half reaction of water splitting, O2 evolution reaction (OER), is the kinetic bottleneck of the overall water splitting process while its product O2 does not possess high market value. A novel strategy to replace OER with thermodynamically more favorable anodic reactions, such as the oxidative valorization of biomass-derived intermediates, represents an attractive approach, which not only reduces the overall voltage input but also produces two valuable products (H2 and biomass products) at both electrodes. This talk will present our recent work in electrocatalytic biomass valorization integrated with H2 production under ambient conditions. A series of biomass-derived intermediates, including 5-hdyroxymethylfurfural, furfural, furfuryl alcohol, and benzyl alcohol, were employed as representative organic substrates to be oxidized to value-added acids. 1st-row transition metal-based electrocatalysts were developed to catalyze biomass oxidation and H2 evolution. Results of long-term electrolysis demonstrated the bifunctionality of our electrocatalysts and nearly 100% Faradaic efficiencies for both H2 production and biomass oxidation reactions.

Electrocatalysis of Furfural Oxidation Coupled with H2 Evolution via Nickel‐Based Electrocatalysts in Water

AbstractElectrocatalytic water splitting has been widely considered as a promising approach to produce clean H2. The anodic half reaction of water splitting, the O2 evolution reaction (OER), is the kinetic bottleneck of the overall process and its product O2 is not of high value. Herein, we report a novel strategy to replace OER with a thermodynamically more favorable anodic reaction, furfural oxidation to 2‐furoic acid. Furfural is one of the dehydration products of biomass and its oxidation product 2‐furoic acid has many industrial applications. A bifunctional electrocatalyst of Ni2P‐derived arrays on nickel foam (Ni2P/Ni/NF) was developed for the integrated electrocatalysis of both furfural oxidation and H2 production. When Ni2P/Ni/NF acts as the electrocatalyst for both anode and cathode, nearly 100 % Faradaic efficiencies for H2 evolution and furfural oxidation were obtained. Such an integrated electrolysis catalyzed by Ni2P/Ni/NF required an applied voltage ≈110 mV smaller than that of pure water splitting to achieve the current density of 10 mA cm−2, together with robust stability. Overall, our novel electrolyzer produced valuable products at both electrodes (H2 at cathode and 2‐furoic acid at anode) and may extend to the coupling of H2 evolution with many other valuable organic oxidation reactions.

Binary and Ternary Earth-Abundant Transition Metal Phosphides As Electrocatalysts and Photocatalysts for Water Splitting

To provide a sustainable carbon free energy system while moving away from fossil fuels and greenhouse gas (CO2) generating energy sources, an inexpensive and reliable process to produce hydrogen has to be implemented. Water splitting by electrolysis has been thought of as the ideal way to produce hydrogen but the current electrolysis of water requires energy or rare materials that make the process neither carbon independent or feasible due to the amount energy gained vs energy input. In this talk there are two methods to perform the electrolysis of water: a) electrocatalytic water-splitting and b) solar photo-electrochemical water-splitting. Recently, transition metal phosphides (TMP) have shown promising catalytic properties for the water splitting half reactions. Two key aspects to studying TMPs for the electrolysis of water are 1) to generate hydrogen with as little energy input as possible; meaning using materials that can harness solar energy or that have significantly low overpotentials for each water splitting half reactions and 2) to find competitive materials to rival the performance and stability of platinum and other noble metals so that industrial production and manufacturing may be achieved. This talk will focus on binary and ternary transition metal phosphides as electocatalysts and photocatalysts for the hydrogen and oxygen evolution reactions; transition metals of focus primarily include Nickel, Molybdenum, and Cobalt with Platinum and Titanium as reference metals. Phosphorus (P) atoms have been determined to stabilize the TMP surface structure and thus the concentration of surface P is a key factor in controlling the surface activity. To control size, shape and crystallinity, a colloidal synthesis method was used to synthesize the nano particles. MoxCo2-xP and Ni2-xMoxP ternary TMPs were synthesized owing to their synergistic effects towards electrocatalysis. These two specific ternary phosphides are being considered for the proposed work influenced by commercial hydrotreating ternary catalyst system (sulfided Co-Mo and Ni-Mo). Nickel phosphide is of primary interest resulting from its consistent performance over other TMPs as an electrocatalyst for water splitting. As electrocatalysts, TMPs show low overpotentials and good stability for the hydrogen-evolution reaction (HER) and oxygen-evolution reaction (OER) under relevant current densities (10 mA/cm2) without any sacrificial agent present. The particles show high stability under most conditions, specifically in acidic electrolytes. In our group, work has been done to synthesize, characterize and test TMP nanoparticles as electrocatalysts and photocatalysts using PEC methods for the HER and OER to understand the material’s electrochemical behavior. Electrode preparation methods may influence the behavior, stability and reproducibility of the electrode. Therefore, multiple preparation methods were conducted to determine the true performance of the material. FTO on glass and Titanium foil were used as substrates/current collectors for the catalytic nano-particles. The electrocatalytic performance of the binary and ternary TMPs have been evaluated as well as the photocatalytic performance. The photocatalytic testing was evaluated under 1 SUN (100mW/cm2) illumination from a 150 W Xe Lamp with and without an AM1.5 filter. The photocatalytic performance was evaluated for the materials tuned to have more semiconductor characteristics and that show signs of photovoltage. Various ratios of metal to phosphide and metal to metal alloys were examined to study the effect of the electrocatalytic and photocatalytic performance and the material’s stability.

Ni3(C3N3S3)2 coordination polymer as a novel broad spectrum-driven photocatalyst for water splitting into hydrogen

Sparked by the increasing energy crisis, much research has been focused on seeking board spectrum-driven photocatalysts for water splitting. Herein, the Ni3(C3N3S3)2 coordination polymer was firstly synthesized by a simple wet-chemical method, as a novel board spectrum-driven photocatalyst for water splitting. The as-prepared Ni3(C3N3S3)2 exhibited excellent photocatcalytic H2-producing activity from the half-reaction of water splitting without the help of any sacrificial agents or cocatalysts, and the amounts of H2 production are 65.3, 53.9 and 16.3μmol corresponding to UV (λ<400nm), visible (400≤λ≤760nm) and near-infrared (λ>760nm) irradiation after 24h, respectively. Another valuable finding is that after adding triethanolamine as a sacrificial donor, the average H2 evolution efficiencies on Ni3(C3N3S3)2 were efficaciously increased by around 2-fold with the H2 production value of 112.6, 93.3 and 30.1μmol for 24h under the UV light, visible light and near-infrared light exposure, respectively. More importantly, the stability of Ni3(C3N3S3)2 was effectively improved by means of triethanolamine. The results facilitate the increasing attention of narrow band gap non-noble metal coordination polymers treated as board spectrum-driven photocatalysts for expanding the utilization of solar light.

High-efficient and low-cost catalyst for hydrogen evolution reaction: Nickel phosphide nano-spheres

Catalysts have been a bottleneck in hydrogen evolution reaction (HER)—a half reaction of water splitting. Hitherto, the most efficient HER catalyst in terms of catalytic capacity remains to be platinum group metals, especially platinum; however, rare metals' exorbitant cost and scarcity inhibit their further application in industry, which therefore call for catalysts prepared from earth-abundant elements. Herein, we introduce nickel phosphide nano-spheres (NPNs) bearing excellent HER activity. Prepared via a facile, inexpensive, and eco-friendly preparation procedure, the as-synthesized NPNs have perfect over-potential to reach −100 mA/cm2 (η100), with η100 reaching 251 mV in 0.5 M H2SO4. A series of durability tests, including cyclic voltammetry and chronoamperometry, also indicate NPNs' favorable stability in both acidic and alkaline conditions. After taking into account a string of factors, including NPNs' mass density, handy preparation process, superior catalytic activity, and favorable durability, the NPNs bear probable potentiality of taking traditional noble metals' place as the HER catalyst and are worth studying further. At the request of the Editors-in-Chief and AIP Publishing this article is being retracted. The article had a high degree of overlap with an article published in the International Journal of Hydrogen Energy. The article is retracted from the scientific record effective 30 June 2017.

Construction of hierarchically porous graphitized carbon-supported NiFe layered double hydroxides with a core-shell structure as an enhanced electrocatalyst for the oxygen evolution reaction.

The oxygen evolution reaction (OER) is a vital half-reaction in water splitting and metal-air batteries. Developing earth-abundant, highly efficient and durable OER catalysts has faced huge challenges until now, because OER is a strict kinetic sluggish process. Herein, we report the construction of hierarchically porous graphitized carbon (HPGC) supported NiFe layered double hydroxides (LDHs) with a core-shell structure (denoted as HPGC@NiFe) by a facile strategy. The HPGC was first obtained by pyrolysing phenolic resin nanospheres with FeCl3 and ZnCl2 as the catalyst and the activator, respectively. Then the NiFe LDH arrays were directly grown on the HPGC by a one-step hydrothermal method. The as-synthesized HPGC@NiFe reveals excellent OER properties with a low onset potential, a lower overpotential of 265 mV (corresponding to the current density at 10 mA cm-2) and a small Tafel slope (56 mV per decade). And its catalytic activity is even superior to that of the start-of-the-art noble-metal catalyst IrO2/C. Notably, the HPGC@NiFe electrode shows admirable stability measured by performing 2000 cycle CVs and long-term electrolysis for 50 h. The prominent performance can be attributed to the synergistic effect between the NiFe-LDHs and the hierarchically porous graphitized carbon, in which the former can increase the exposure of the active sites, while the latter can increase the charge transfer efficiency. Our research implies the possibility for the development of low-cost layered double hydroxides as a promising candidate in electrochemical energy storage and conversion equipment.

Nickel phosphide nanosphere: A high-performance and cost-effective catalyst for hydrogen evolution reaction

Catalyst has been a bottleneck in hydrogen evolution reaction (HER) – a half reaction of water splitting. Hitherto the most efficient HER catalyst in terms of catalytic capacity remains to be those platinum group metals, especially platinum; however, rare metals' exorbitant cost and scarcity inhibit their further application in industry, which therefore call for catalysts prepared from earth-abundant elements. Herein, we introduce nickel phosphide nanospheres (NPNs) bearing excellent HER activity. Prepared via a facile, inexpensive, and eco-friendly preparation procedure, the as-synthesized NPNs have perfect over-potential to reach −100 mA/cm2 (η100), with η100 reaching 251 mV in 0.5 M H2SO4. A series of durability tests, including cyclic voltammetry (CV) and chronoamperometry, also indicate NPNs' favorable stability under both acidic and alkaline conditions. After taking account of a string of factors, including NPNs' mass density, handy preparation process, superior catalytic activity as well as favorable durability, the NPNs bear probable potentiality of taking traditional noble metals' place as the HER catalyst and are worth studying further.

Spatial separation of photo-generated electron-hole pairs in BiOBr/BiOI bilayer to facilitate water splitting

The electronic structures and photocatalytic properties of bismuth oxyhalide bilayers (BiOX1/BiOX2, X1 and X2 are Cl, Br, I) are studied by density functional theory. Briefly, their compositionally tunable bandgaps range from 1.85 to 3.41 eV, suitable for sun-light absorption, and all bilayers have band-alignments good for photocatalytic water-splitting. Among them, heterogeneous BiOBr/BiOI bilayer is the best as it has the smallest bandgap. More importantly, photo-excitation of BiOBr/BiOI leads to electron supply to the conduction band minimum with localized states belonging mainly to bismuth of BiOBr where the H+/H2 half-reaction of water-splitting can be sustained. Meanwhile, holes generated by such photo-excitation are mainly derived from the iodine states of BiOI in the valence band maximum; thus, the O2/H2O half-reaction of water splitting is facilitated on BiOI. Detailed band-structure analysis also indicates that this intriguing spatial separation of photo-generated electron-hole pairs and the two half-reactions of water splitting are good for a wide photo-excitation spectrum from 2–5 eV; as such, BiOBr/BiOI bilayer can be an efficient photocatalyst for water-splitting, particularly with further optimization of its optical absorptivity.

A tremella-like Ni76Co24 layered double hydroxides nanosheets as an efficient catalyst for oxygen evolution reaction

The oxygen evolution reaction (OER), as a key half-reaction in water splitting for clean hydrogen energy, is kinetically sluggish and usually requires efficient electrocatalysts to reduce the overpotential. Herein, we report a simple method to synthesize novel two-dimensional Ni76Co24 layered double hydroxides (Ni76Co24–LDHs) nanosheets as an effective OER catalyst. The obtained Ni76Co24–LDHs display a low onset overpotential of 242 mV, along with an excellent cycling stability. The Tafel slope of Ni76Co24–LDHs is only 57 mV dec−1 which demonstrates an active kinetics for OER. The high catalytic activity of Ni76Co24–LDHs may be attributed to the porous tremella-like structure with large surface area, synergistic effect of Ni and Co, and a pinning of the Co3+/4+ and Ni3+/4+. More importantly, the high catalytic property and simple synthetic method of Ni76Co24–LDHs may have a promising potential for practical application.

CoMn Layered Double Hydroxides/Carbon Nanotubes Architectures as High‐Performance Electrocatalysts for the Oxygen Evolution Reaction

AbstractHigh‐efficiency, earth‐abundant oxygen evolution reaction (OER) catalysts are highly desired and required for the half reaction of water splitting. Herein, an integrated system composed of CoMn layered double hydroxides (CoMn‐LDH) and carbon nanotubes (CNTs) were configured for the OER. Ultrathin CoMn‐LDH nanoplates can grow and assemble in situ on conducting CNT frameworks to form the CoMn‐LDH/CNT nanoarchitectures. The CNT frameworks provide conducting channels for fast charge transfer, whereas CoMn‐LDH features highly active sites and is capable of catalyzing the OER process. Benefiting from functional integration of the highly active CoMn‐LDH nanoplates and the strong coupling effects between ultrathin nanoplates and conducting CNT frameworks, the as‐made CoMn‐LDH/CNT nanohybrids achieve excellent OER performance with a small overpotential (355 mV at 10 mA cm−2), low Tafel slope (45 mV dec−1), and prominent electrochemical durability.

Abrupt Mechanistic Variation of Hydrogen Evolution Reaction on Metal Electrode Surfaces in the Potential-pH Space

Understanding the mechanisms of multi-electron and multi-proton electrochemical reactions, particularly in the context of renewable electrochemical energy conversion, is an outstanding challenge. The electrocatalytic hydrogen evolution (2H+ + 2e-...> H2) is the half reaction of water splitting and is heavily studied. However, the kinetic variation of this reaction under various pH conditions has not been fully understood. In this work, we studied hydrogen evolution reaction on different electrodes (Pt, Cu, FeS2, Ni, and Ti) over a wide range of neutral (pH=6.5) to acidic (pH=1.5) solutions. Despite variations in the properties of these electrodes, we observe a discontinuous change in the onset potential as a function of current in the pH range of 2.5 to 3.5 in all the electrodes. We also represent two fundamental kinetic parameters, empirical electron transfer coefficient α and the reaction order with respect to proton ρ, as a function of pH and potential. An important observation is that α is constant (α≈0.2) at pH values higher than the discontinuous jump, while at lower pH values alpha increases with decreasing pH. The maximum value of alpha varies for different electrodes and is increasing from Ti < Ni< Cu < FeS2 < Pt. The proton reaction order is non-zero in the acidic side, whereas it is zero in the neutral limit and this trend is common for all the electrodes. To our knowledge, for the first time, we are presenting the kinetic parameters in two-dimensional plots as a function of both pH and potential. This representation allows us to clearly see global trends in the kinetics of the reaction. We will propose possible explanations for such common behavior based on a kinetic model that accounts for both concerted and step-wise electron and proton transfer. We hope that this study sheds light on the fundamentals of electron-proton transfer during hydrogen evolution. Figure 1

A mini review on nickel-based electrocatalysts for alkaline hydrogen evolution reaction

High gravimetric energy density, earth-abundance, and environmental friendliness of hydrogen sources have inspired the utilization of hydrogen fuel as a clean alternative to fossil fuels. Hydrogen evolution reaction (HER), a half reaction of water splitting, is crucial to the low-cost production of pure H2 fuels but necessitates the use of electrocatalysts to expedite reaction kinetics. Owing to the availability of low-cost oxygen evolution reaction (OER) catalysts for the counter electrode in alkaline media and the lack of low-cost OER catalysts in acidic media, researchers have focused on developing HER catalysts in alkaline media with high activity and stability. Nickel is well-known as an HER catalyst and continuous efforts have been undertaken to improve Ni-based catalysts as alkaline electrolyzers. In this review, we summarize earlier studies of HER activity and mechanism on Ni surfaces, along with recent progress in the optimization of the Ni-based catalysts using various modern techniques. Recently developed Ni-based HER catalysts are categorized according to their chemical nature, and the advantages as well as limitations of each category are discussed. Among all Ni-based catalysts, Ni-based alloys and Ni-based hetero-structure exhibit the most promising electrocatalytic activity and stability owing to the fine-tuning of their surface adsorption properties via a synergistic nearby element or domain. Finally, selected applications of the developed Ni-based HER catalysts are highlighted, such as water splitting, the chloralkali process, and microbial electrolysis cell.

Comprehensive Study of an Earth-Abundant Bifunctional 3D Electrode for Efficient Water Electrolysis in Alkaline Medium.

We report efficient electrolysis of both water-splitting half reactions in the same medium by a bifunctional 3D electrode comprising Co3O4 nanospheres nucleated on the surface of nitrogen-doped carbon nanotubes (NCNTs) that in turn are grown on conductive carbon paper (CP). The resulting electrode exhibits high stability and large electrochemical activity for both oxygen and hydrogen evolution reactions (OER and HER). We obtain a current density of 10 mA/cm(2) in 0.1 M KOH solution at overpotentials of only 0.47 and 0.38 V for OER and HER, respectively. Additionally, the experimental observations are understood and supported by analyzing the Co3O4:NCNT and NCNT:CP interfaces by ab initio calculations. Both the experimental and the theoretical studies indicate that firm and well-established interfaces along the electrode play a crucial role on the stability and electrochemical activity for both OER and HER.

Constructing Ru/TiO2 Heteronanostructures Toward Enhanced Photocatalytic Water Splitting via a RuO2/TiO2 Heterojunction and Ru/TiO2 Schottky Junction

Photocatalysts based on metallic Ru and RuO2 dual co‐catalysts modified TiO2 nanobelts (NBs) are constructed through a wet‐impregnation reduction method with post thermal oxidation. The samples are characterized carefully and their photocatalytic activities for the half reactions of water splitting as well as full water splitting are evaluated systematically under solar light irradiation. The detailed characterizations and analyses clearly reveal the formation of a Schottky junction at the Ru‐TiO2 interface and of RuO2/TiO2 heterojunctions. The results of the photocatalytic tests show that both Ru and RuO2 can improve the photocatalytic activity for H2/O2 evolution and water splitting. Moreover, the photocatalytic activity of the TiO2 NBs can be further enhanced by co‐modification with dual Ru and RuO2 co‐catalysts. The RuO2/TiO2 heterojunction improves the transfer of the photogenerated holes from the TiO2 to the RuO2, where water can be oxidized by the holes to evolve O2, and the Ru/TiO2 Schottky junction promotes the transfer of photogenerated electrons from the TiO2 NBs to the metallic Ru for proton reduction into H2. These two processes are involved in the overall water splitting. This work provides an important reference for designing highly efficient photocatalysts for water splitting through loading of dual co‐catalysts containing the same element but with different valence structures.

Plasmon-enhanced light energy conversion using gold nanostructured oxide semiconductor photoelectrodes

Abstract We have successfully demonstrated plasmon-enhanced photocurrent generation using gold nanoparticle-loaded titanium dioxide single-crystal (TiO2) photoelectrodes with visible-light irradiation. Water molecules serve as an electron source in photocurrent generation, and oxygen evolution occurs due to water oxidation from a gold nanostructured TiO2 photoelectrode as a half reaction of water splitting. On the basis of this property, the photocurrent generation system was applied to the plasmon-induced water-splitting system using both sides of the same strontium titanate (SrTiO3) single-crystal substrate without an electrochemical apparatus. The chamber on the side of the gold nanoparticles was the anode side, whereas the chamber on the side of the platinum plate was the cathode side. Platinum was used as a co-catalyst for hydrogen evolution. Hydrogen and oxygen were separately evolved from the anode and cathode chambers, respectively. Water splitting was induced with a relatively low chemical bias of 0.23 V due to plasmonic effects based on efficient water oxidation. Similar to the artificial photosynthesis system, we have also demonstrated ammonia formation via nitrogen fixation using ruthenium as a co-catalyst via an analogous setup of the water-splitting system.

Perovskite-Hematite Tandem Cells for Efficient Overall Solar Driven Water Splitting.

Photoelectrochemical water splitting half reactions on semiconducting photoelectrodes have received much attention but efficient overall water splitting driven by a single photoelectrode has remained elusive due to stringent electronic and thermodynamic property requirements. Utilizing a tandem configuration wherein the total photovoltage is generated by complementary optical absorption across different semiconducting electrodes is a possible pathway to unassisted overall light-induced water splitting. Because of the low photovoltages generated by conventional photovoltaic materials (e.g., Si, CIGS), such systems typically consist of triple junction design that increases the complexity due to optoelectrical trade-offs and are also not cost-effective. Here, we show that a single solution processed organic-inorganic halide perovskite (CH3NH3PbI3) solar cell in tandem with a Fe2O3 photoanode can achieve overall unassisted water splitting with a solar-to-hydrogen conversion efficiency of 2.4%. Systematic electro-optical studies were performed to investigate the performance of tandem device. It was found that the overall efficiency was limited by the hematite's photocurrent and onset potential. To understand these limitations, we have estimated the intrinsic solar to chemical conversion efficiency of the doped and undoped Fe2O3 photoanodes. The total photopotential generated by our tandem system (1.87 V) exceeds both the thermodynamic and kinetic requirements (1.6 V), resulting in overall water splitting without the assistance of an electrical bias.

Understanding the Influence of Structure on Activity and Stability in the Catalysis of the Oxygen Evolution Reaction (OER) Using Crystalline Oxides As a Platform

Oxides of manganese and cobalt have proved to be effective (electro)catalysts for the water oxidation half-reaction in water splitting. Recently, the research focus has mostly been on developing high surface area morphologies of catalysts with high specific activity that are potentially easily adaptable to photoelectrochemical cells for water splitting. However, it is still not completely understood why these catalysts show such high intrinsic activity, and many have amorphous structures, making it difficult to elucidate structure-function relationships. Using crystalline oxides as an experimental framework, we have elucidated the effects of structure on the activity and stability of cobalt and manganese oxides for the oxygen evolution reaction (OER). For instance, in two distinct polymorphs of lithium cobalt oxide (LiCoO2), we have found the cubic structure (Fd-3m, spinel-like), with a Co4O4 oxo-metallic cube motif, is highly active for water oxidation, whereas the layered polymorph (R-3m) with slabs of CoO2 (used for rechargeable Li ion batteries) is not. In fact, upon electrochemical processing, the layered polymorph undergoes a surface restructuring that we can monitor using high-resolution transmission electron microscopy (HRTEM). This has been shown to occur in both aqueous and non-aqueous electrolyte. After the transformation occurs, which can also be monitored by the electrochemical profile and corrosion of lithium, the OER activity of the layered material mirrors that of the cubic LiCoO2. However, it is unstable and eventually diminishes with repeated electrochemical cycling or prolonged electrolysis. In this way, we show that the underlying bulk crystal structure has influence over not just activity, but also stability, both equally important for commercial applications. Parallel to this work, we isolated discrete Co2O2, Co3O3, and Co4O4 molecular clusters in the same ligand sets, and found only the complete Co4O4 cubanes were catalytically active for water oxidation. This difference in activity correlates to the accessibility of a formal Co4+ oxidation state, which occurs at modest potentials only for the cubane, which compensates by delocalizing the hole across all cobalt and bridging oxos. The singly oxidized cubane is sufficient to produce O2 just in reaction with hydroxide. We believe this phenomenon relates back to the solid-state, and is in part the reason for the high activity in the cubic LiCoO2.

A nanotubular framework with customized conductivity and porosity for efficient oxidation and reduction of water

A quaternary inorganic nanotube framework delivering efficient electrocatalytic activities towards the two half reactions of water splitting was designed.

Logic gates operated by bipolar photoelectrochemical water splitting.

A new approach for the design of logic gates that do not involve chemical inputs is presented here. This concept is based on the polarization of a light-sensitive interface. AND and OR logic gates, working with cheap reactants, which locally triggered water splitting half reactions, were designed and operated.