Proton Adsorption Research Articles

Three-Dimensional Graphene Networks with Abundant Sharp Edge Sites for Efficient Electrocatalytic Hydrogen Evolution.

To achieve sustainable production of hydrogen (H2 ) through water splitting, establishing efficient and earth-abundant electrocatalysts is of great necessity. Morphology engineering of graphene is now shown to modulate the electronic structure of carbon skeleton and in turn endow it with excellent ability of proton reduction. Three-dimensional (3D) graphene networks with a high density of sharp edge sites are synthesized. Electrocatalytic measurements indicate that the obtained 3D graphene networks can electrocatalyze H2 evolution with an extremely low onset potential of about 18 mV in 0.5 m H2 SO4 solution, together with good stability. A combination of control experiments and density functional theory (DFT) investigations indicates that the exceptional H2 evolution performance is attributed to the abundant sharp edge sites of the advanced frameworks, which are responsible for promoting the adsorption and reduction of protons.

Composition-Graded MoWSx Hybrids with Tailored Catalytic Activity by Bipolar Electrochemistry.

Among transition metal dichalcogenide (TMD)-based composites, TMD/graphene-related material and bichalcogen TMD composites have been widely studied for application toward energy production via the hydrogen evolution reaction (HER). However, scarcely any literature explored the possibility of bimetallic TMD hybrids as HER electrocatalysts. The use of harmful chemicals and harsh preparation conditions in conventional syntheses also detracts from the objective of sustainable energy production. Herein, we present the conservational alternative synthesis of MoWSx via one-step bipolar electrochemical deposition. Through bipolar electrochemistry, the simultaneous fabrication of composition-graded MoWSx hybrids, i.e., sulfur-deficient MoxW(1-x)S2 and MoxW(1-x)S3 (MoWSx/BPEcathodic and MoWSx/BPEanodic, respectively) under cathodic and anodic overpotentials, was achieved. The best-performing MoWSx/BPEcathodic and MoWSx/BPEanodic materials exhibited Tafel slopes of 45.7 and 50.5 mV dec-1, together with corresponding HER overpotentials of 315 and 278 mV at -10 mA cm-2. The remarkable HER activities of the composite materials were attributed to their small particle sizes, as well as the near-unity value of their surface Mo/W ratios, which resulted in increased exposed HER-active sites and differing active sites for the concurrent adsorption of protons and desorption of hydrogen gas. The excellent electrocatalytic performances achieved via the novel methodology adopted here encourage the empowerment of electrochemical deposition as the foremost fabrication approach toward functional electrocatalysts for sustainable energy generation.

Characterization of Platinum Electrode Surfaces by Electrochemical Surface Forces Measurement

The surface forces between platinum, Pt, electrodes and those between the Pt electrode and mica in aqueous HClO4 were measured at various potentials (E) applied to the electrodes using an electrochemical surface forces apparatus (EC-SFA). This apparatus uses the twin-path surface forces apparatus, recently developed for opaque samples. The influence of the proton adsorption on the surface interactions was studied. The Pt electrodes were prepared by the template-stripping procedure using glass templates. The electrode surfaces were smooth (RMS roughness: 0.26 nm for a 5 μm × 5 μm area) and polycrystalline based on the atomic force microscopy and cyclic voltammetry results, respectively. When the applied potential E was decreased from 0.5 to 0.2 V (vs Ag/AgCl), the electric double layer (EDL) repulsion between the Pt electrodes decreased. The absolute values of the surface potentials, |ψ0|, calculated using the EDL theory were 58 and 43 mV at E = 0.5 and 0.2 V, respectively. The EDL force at E = 0.2 V was t...

Development of hydrophilicity on the proton exchange using sulfonic acid on PEEK in the presence of water: a density functional theory study

The introduction of a protogenic group such as sulfonic acid enables the operation of polymer electrolyte membrane for fuel cells at intermediate temperatures (> 100 °C) and very low humidity. It has been reported that the addition of a strongly acidic sulfonic acid group to hydrophobic polyether ether ketone (PEEK) creates the water permeability and proton transfer. In order to understand how sulfonic acid develops hydrophilicity, we conducted density functional theory calculations to determine the adsorption affinity of water for sulfonated PEEK (SPEEK), which represents the binding energy and band gap between HOMO (highest occupied molecular orbital) of SPEEK and LUMO (lowest unoccupied molecular orbital) of water molecules. Moreover, we designed disulfonated PEEKs (DSPEEK) with cis- and trans-conformations and found that cis-DSPEEK exhibits higher adsorption affinity for water with strong hydrogen bonds. This is attributed to the narrow energy gap of water molecules on cis-DSPEEK. Furthermore, we investigated proton adsorption in the presence of water to determine the effect of hydrophilic environment on the proton exchange in SPEEK. We found that cis-DSPEEK shows high repulsion for hydrogen transfer and moderate adsorption affinity for protons. Theoretical findings confirm that sulfonation ultimately yields hydrophilicity and developed proton transfer ability for PEEK, leading to a suitable structure for preferable proton exchange membrane.

Single‐Atom to Single‐Atom Grafting of Pt1 onto FeN4 Center: Pt1@FeNC Multifunctional Electrocatalyst with Significantly Enhanced Properties

AbstractNonprecious metal catalysts (NPMCs) FeNC are promising alternatives to noble metal Pt as the oxygen reduction reaction (ORR) catalysts for proton‐exchange‐membrane fuel cells. Herein, a new modulation strategy is reported to the active moiety FeN4 via a precise “single‐atom to single‐atom” grafting of a Pt atom onto the Fe center through a bridging oxygen molecule, creating a new active moiety of Pt1O2Fe1N4. The modulated FeNC exhibits remarkably improved ORR stabilities in acidic media. Moreover, it shows unexpectedly high catalytic activities toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), with overpotentials of 310 mV for OER in alkaline solution and 60 mV for HER in acidic media at a current density of 10 mA cm−2, outperforming the benchmark RuO2 and comparable with Pt/C(20%), respectively. The enhanced multifunctional electrocatalytic properties are associated with the newly constructed active moiety Pt1O2Fe1N4, which protects Fe sites from harmful species. Density functional theory calculations reveal the synergy in the new active moiety, which promotes the proton adsorption and reduction kinetics. In addition, the grafted Pt1O2 dangling bonds may boost the OER activity. This study paves a new way to improve and extend NPMCs electrocatalytic properties through a precisely single‐atom to single‐atom grafting strategy.

Time-of-day-dependent global distribution of lunar surficial water/hydroxyl.

A new set of time-of-day-dependent global maps of the lunar near-infrared water/hydroxyl (H2O/OH) absorption band strength near 2.8 to 3.0 μm constructed on the basis of Moon Mineralogy Mapper (M3) data is presented. The analyzed absorption band near 2.8 to 3.0 μm indicates the presence of surficial H2O/OH. To remove the thermal emission component from the M3 reflectance spectra, a reliable and physically realistic mapping method has been developed. Our maps show that lunar highlands at high latitudes show a stronger H2O/OH absorption band in the lunar morning and evening than at midday. The amplitude of these time-of-day-dependent variations decreases with decreasing latitude of the highland regions, where below about 30°, absorption strength becomes nearly constant during the lunar day at a similar level as in the high-latitude highlands at midday. The lunar maria exhibit weaker H2O/OH absorption than the highlands at all, but showing a smaller difference from highlands absorption levels in the morning and evening than at midday. The level around midday is generally higher for low-Ti than for high-Ti mare surfaces, where it reaches near-zero values. Our observations contrast with previous studies that indicate a significant concentration of surficial H2O/OH at high latitudes only. Furthermore, although our results generally support the commonly accepted mechanism of H2O/OH formation by adsorption of solar wind protons, they suggest the presence of a more strongly bounded surficial H2O/OH component in the lunar highlands and parts of the mare regions, which is not removed by processes such as diffusion/thermal evaporation and photolysis in the course of the lunar day.

Synthesis and characterization of carboxylic cation exchange bio-resin for heavy metal remediation

A new carboxylic bio-resin was synthesized from raw arecanut husk through mercerization and ethylenediaminetetraacetic dianhydride (EDTAD) carboxylation. The synthesized bio-resin was characterized using thermogravimetric analysis, field emission scanning electron microscopy, proximate & ultimate analyses, mass percent gain/loss, potentiometric titrations, and Fourier transform infrared spectroscopy. Mercerization extracted lignin from the vesicles on the husk and EDTAD was ridged in to, through an acylation reaction in dimethylformamide media. The reaction induced carboxylic groups as high as 0.735mM/g and a cation exchange capacity of 2.01meq/g functionalized mercerized husk (FMH). Potentiometric titration data were fitted to a newly developed single-site proton adsorption model (PAM) that gave pKa of 3.29 and carboxylic groups concentration of 0.741mM/g. FMH showed 99% efficiency in Pb(II) removal from synthetic wastewater (initial concentration 0.157mM), for which the Pb(II) binding constant was 1.73×103L/mol as estimated from modified PAM. The exhaustion capacity was estimated to be 18.7mg/g of FMH. Desorption efficiency of Pb(II) from exhausted FMH was found to be about 97% with 0.1N HCl. The FMH simultaneously removed lead and cadmium below detection limit from a real lead acid battery wastewater along with the removal of Fe, Mg, Ni, and Co.

Sorption of copper, nickel and cadmium on bone char

The sorption capacity of bone char was tested on the removal of copper, nickel and cadmium ions, from aqueous solutions. The Freundlich and Langmuir models were applied to the adsorption isotherms. The equilibrium data fitted well with the Langmuir model and the maximum loading capacities showed the following affinity order: Cu2+ (1.093 mmol g–1 at pH i 3, and 0.884 mmol g–1 at pH i 4) > Cd2+ (0.760 mmol g–1 at pH i 3, and 0.690 mmol g–1 at pH i 4) > Ni2+ (0.453 mmol g–1 at pH i 3, and 0.225 mmol g–1 at pH i 4). The kinetic data follow a diffusion model in the film and inside particles. A sorption mechanism based on ion exchange, attack by protons of the carbonate and hydroxide positions in the apatite lattice, and also on the adsorption of protons on the basic active sites of carbon, is proposed to explain the heavy metals removal and the pH decreasing in solution.

Determination of the specific surface area of layered silicates by methylene blue adsorption: The role of structure, pH and layer charge

The specific surface area of three layered silicates was determined by three independent methods; it was estimated from the average dimensions of individual silicate layers, determined by nitrogen adsorption using the BET model and calculated from the adsorption of methylene blue on their surface in aqueous sol. The BET model gave smaller surface areas than expected, because nitrogen molecules cannot penetrate freely into the interlayer space of the silicates. Geometric calculations and the methylene blue approach yielded very similar values for two different types of Laponite when the pH of the dispersion was adjusted to 6.5 or the edges of the silicate were modified with tetrasodium pyrophosphate dispersing agent. The measurement of surface area in water without the control of pH yielded smaller surface area, because methylene blue decreased the pH of the solution resulting in the competitive adsorption of methylene blue cations and protons at the basal surface. The methylene blue approach resulted in larger surface area than expected for the silicate with large ion exchange capacity, because of the tilted orientation of the adsorbed methylene blue molecules. All these factors must be considered during the use of the methylene blue method for the determination of the specific surface area of smectites.

Modeling the adsorption of hydrogen, sodium, chloride and phthalate on goethite using a strict charge-neutral ion-exchange theory.

Simultaneous adsorption modeling of four ions was predicted with a strict net charge-neutral ion-exchange theory and its corresponding equilibrium and mass balance equations. An important key to the success of this approach was the proper collection of all the data, particularly the proton adsorption data, and the inclusion of variable concentrations of conjugate ions from the experimental pH adjustments. Using IExFit software, the ion-exchange model used here predicted the competitive retention of several ions on goethite by assuming that the co-adsorption or desorption of all ions occurred in the correct stoichiometries needed to maintain electroneutrality. This approach also revealed that the retention strength of Cl− ions on goethite increases in the presence of phthalate ions. That is, an anion-anion enhancement effect was observed. The retention of Cl− ions was much weaker than phthalate ions, and this also resulted in a higher sensitivity of the Cl− ions toward minor variations in the surface reactivity. The proposed model uses four goethite surface sites. The drop in retention of phthalate ions at low pH was fully described here as resulting from competitive Cl− reactions, which were introduced in increasing concentrations into the matrix as the conjugate base to the acid added to lower the pH.

Proton-Promoted Electron Transfer in Photocatalysis: Key Step for Photocatalytic Hydrogen Evolution on Metal/Titania Composites

Metal cocatalysts are widely utilized for enhancing photocatalytic conversion. In TiO2-based photocatalysts, a wide range of metals dispersed on TiO2 surfaces were observed to be effective for photocatalytic hydrogen production. To clarify the metal/oxide synergistic effect in photocatalysis and the insensitivity of photoactivity on metal types, here we investigate the mechanism of electron transfer from semiconductor to the cocatalyst by using ab initio molecular dynamics and hybrid density functional theory calculations. By determining the optimal geometry of a Pt13 subnano cluster on anatase TiO2(101) and quantifying the electron transfer energetics, we find that the electron transfer from oxide to the metal cluster is significantly boosted (exothermic by more than 0.3 eV) by the adsorption of proton on the metal cluster, which is otherwise endothermic without the presence of proton. This cooperative effect between oxide, subnano metal cluster, and adsorbed proton is rationalized from electronic struct...

Alkaline Earth Element Adsorption onto PAA-Coated Magnetic Nanoparticles

In this paper, we present a study on the adsorption of calcium (Ca2+) onto polyacrylic acid-functionalized iron-oxide magnetic nanoparticles (PAA-MNPs) to gain an insight into the adsorption behavior of alkaline earth elements at conditions typical of produced water from hydraulic fracturing. An aqueous co-precipitation method was employed to fabricate iron oxide magnetic nanoparticles, whose surface was first coated with amine and then by PAA. To evaluate the Ca2+ adsorption capacity by PAA-MNPs, the Ca2+ adsorption isotherm was measured in batch as a function of pH and sodium chlorite (electrolyte) concentration. A surface complexation model accounting for the coulombic forces in the diffuse double layer was developed to describe the competitive adsorption of protons (H+) and Ca2+ onto the anionic carboxyl ligands of the PAA-MNPs. Measurements show that Ca2+ adsorption is significant above pH 5 and decreases with the electrolyte concentration. Upon adsorption, the nanoparticle suspension destabilizes and creates large clusters, which favor an efficient magnetic separation of the PAA-MNPs, therefore, helping their recovery and recycle. The model agrees well with the experiments and predicts that the maximum adsorption capacity can be achieved within the pH range of the produced water, although that maximum declines with the electrolyte concentration.

Surface state and proton adsorption phenomena on CoRu-based materials during hydrogen evolution reaction in acid conditions

The electrocatalytic activity for hydrogen evolution reaction (HER) of cobalt-ruthenium based nanomaterials (Co80Ru20 and Co80Ru15Pt5) synthesized by high energy mechanical milling was studied in acid medium. The synthesized materials were immersed in a carbon paste electrode matrix (20 wt.%). X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the synthesized powders. The composition of the nanomaterials was established by means of energy dispersive spectroscopy (EDS). SEM and TEM analysis showed the formation of agglomerates of 1–5 μm, constituted by particles of ca. 20 nm. The electrocatalytic activity of the prepared materials was evaluated in 0.5 M H2SO4 at 25 °C using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS) techniques. EIS diagrams were obtained in a frequency range from 100 kHz to 10 mHz at selected potentials. Nyquist diagrams showed the presence of two semicircles. The kinetic parameters for HER obtained from analysis of polarization and impedance data showed that both materials exhibit good performance toward HER. According to the electrochemical parameters, the material with the best performance was Co80Ru15Pt5.

Magic angle spinning 31P NMR spectroscopy reveals two essentially identical ionization states for the cardiolipin phosphates in phospholipid liposomes

Specific membrane lipid composition is crucial for optimized structural and functional organization of biological membranes. Cardiolipin is a unique phospholipid and important component of the inner mitochondrial membrane. It is involved in energy metabolism, inner mitochondrial membrane transport, regulation of multiple metabolic reactions and apoptotic cell death. The physico-chemical properties of cardiolipin have been studied extensively but despite all these efforts there is still lingering controversy regarding the ionization of the two phosphate groups of cardiolipin. Results obtained in the 1990s and early 2000s suggested that cardiolipin has two disparate pKa values where one of the protons was proposed to be stabilized by an intramolecular hydrogen bond. This has led to extensive speculations on the roles of these two putative ionization states of cardiolipin in mitochondria. More recently the notion of two pKa values has been challenged and rejected by several groups. These studies relied on external measurements of proton adsorption or electrophoretic mobility of membranes but did not take into account the low pH phase behavior and chemical stability of cardiolipin. Here we used 31P NMR to show that in the physiologically relevant membrane phospholipid environment, cardiolipin carries two negative charges at physiological pH. We additionally demonstrate the pH dependent phase behavior and chemical stability of cardiolipin containing membranes.

Silver- and copper-modified decahedral anatase titania particles as visible light-responsive plasmonic photocatalyst

Decahedral anatase particles (DAPs) with eight equivalent (101) facets and two (001) facets were prepared by the gas-phase process. Monometallic and bimetallic photocatalysts were prepared by photodeposition of silver and copper on DAP. It was found that the method of metal deposition (sequential/simultaneous) is crucial for resultant properties and thus for photocatalytic performance. The fastest hydrogen evolution during metal deposition was observed for copper deposited on premodified DAP with silver (DAP/Ag/Cu), probably due to partial coverage of silver with fine clusters of Cu and thus facilitation of proton adsorption and reduction on well-dispersed Cu nanoclusters. Although DAP/Ag/Cu exhibited the fastest rate of hydrogen evolution, single-modified DAP with silver exhibited the best performance for oxidative decomposition of organic compounds under vis irradiation.

New Material Design of Electron-Proton Mixed Conductor Ru-Doped BaCe0.90Y0.10O3- d Thin Film As Fuel Cell Anode Electrode

Perovskite oxide Y3+-doped BaCeO3 (BaCe1-x Y x O3- d: BCY) is a promising material as an electrolyte of solid oxide fuel cells (SOFCs) that operate in the intermediate- temperature (IMT) region. The electrical conductivity of the bulk crystal exhibits a high proton conductivity of ~7.0×10-2 S·cm-1 at 800 ºC and ~1.0×10-2 S·cm-1at 400 ºC in a wet atmosphere. The proton adsorption and conduction mechanisms have been extensively studied by theoretical and experimental approaches. In order to realize hydrogen separation membranes for hydrogen production in the high-temperature region, Matsumoto and co-workers have developed a Ru5+-doped BCY (BCRY) ceramic that exhibits the electron-proton mixed conduction in moist reducing atmosphere at approximately 800 ºC. When the Ru5+ concentration is in the range of 5~10 mol%, BCRY ceramics exhibit the mixed conduction of 3.0~6.0×10-3 S·cm-1. Although such a mixed conductor can be used as an anode electrode of SOFCs, BCRY thin films have not been realized thus far. Therefore, understanding of the detailed electrical and structural properties of BCRY thin films is most important for the material design of SOFC electrodes. In this study, we present the structural and electrical properties at the surface and bulk regions of BCRY thin films and discuss the role of Ru5+substitution in terms of electron structure. The BCRY thin film was deposited on Al2O3 and Nb-doped SrTiO3 (Nb-STO) substrates by RF magnetron sputtering. The flow rate of Ar gas, the deposition pressure, and substrate temperature were set at 20 sccm, 5.0×10-3 Torr and 600 ºC, respectively. The film thicknesses were changed between ~100 and ~477 nm. The structural property of the BCRY thin films were characterized as a function of film thickness by powder X-ray diffraction (XRD) analysis. The electrical conductivity was measured by the AC impedance method in dry atmosphere in a temperature region from 200 to 600 ºC. The measurement frequency region was from 0.1 Hz to 32 MHz. In order to probe conducting carriers, the conductivity was measured by changing oxygen gas partial pressure (P O2). The electronic structure was characterized by photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The energy resolutions of PES and XAS were 100 and 60 meV, respectively, at h n= 700 eV. The a- and c-axes-oriented BaCe0.85Ru0.05Y0.10O3- d thin films have been deposited by RF magnetron sputtering. The thin films have mixed valence states of Ce4+ and Ce3+. The activation energy for the conductivity of film thicker than 200 nm at the surface region and bulk region are 0.26 eV and 0.60 eV, respectively. The thin films exhibit ion conduction at the bulk region and electron-ion mixed conduction at the surface region. Proton conductions are also observed in the surface state and bulk state. The Fermi levels (E F) locate at the middle position in the band gap region, although E F of the BaCe0.90Y0.10O3- d thin films locates on the valence band side. These results indicate that the Ru5+ions and protons act as donor ions in BCRY thin films.

Surface modification and electrophoretic deposition of materials using carboxyalkylphosphonic acids

Bipolar carboxyalkylphosphonic acid molecules were investigated for dispersion and charging of inorganic particles in ethanol and film formation by electrophoretic deposition (EPD). The analysis of deposition yield for different molecules and FTIR data provided an insight into the influence of interactions of the molecules with different surface metal atoms on adsorption of the molecules, particle dispersion and charge. The dispersant molecules showed strong adsorption on MnO2 and allowed for anodic EPD of MnO2 for electrodes of electrochemical supercapacitors. In contrast, huntite particles showed preferred adsorption of protons and cathodic huntite films were obtained by EPD for applications based on flame retardant properties of this material.

Composition-Dependent Catalytic Activities of Noble-Metal-Free NiS/Ni3S4 for Hydrogen Evolution Reaction

The development of efficient noble-metal-free hydrogen evolution catalysts is quite appealing with the aim of providing cost-competitive hydrogen. Herein, nickel sulfides (NiSx) with tunable NiS/Ni3S4 molar ratios were synthesized via a simple hydrothermal method. Detailed electrochemical studies under neutral conditions indicated that the electrocatalytic property of NiSx catalysts was determined by the composition. Notably, the NiSx sample with the NiS/Ni3S4 molar ratio of 1.0 exhibited the lowest overpotential and charge-transfer resistance. As analyzed from the Tafel plots, the rate-determining step of NiSx catalysts for hydrogen generation was the Volmer step, in which the proton adsorption played a key role. Theoretical calculation revealed that NiS and Ni3S4 exhibited the metallic behaviors with different work functions. Consequently, the NiSx sample with the NiS/Ni3S4 molar ratio of 1.0 owned the most adsorbed protons, which led to the highest electrocatalytic property. Meanwhile, NiSx was demonst...

Highly active nonprecious metal hydrogen evolution electrocatalyst: ultrafine molybdenum carbide nanoparticles embedded into a 3D nitrogen-implanted carbon matrix

The generation of clean and sustainable hydrogen fuel through water splitting demands efficient and robust earth-abundant catalysts for the hydrogen evolution reaction (HER). A new hybrid, which was fabricated by incorporating molybdenum carbide (MoxC) nanoparticles into a nitrogen-implanted three-dimensional carbon matrix (MoCN-3D), was developed as a highly active and durable nonprecious metal electrocatalyst for HER. The porous architecture of MoCN-3D can provide continuous mass transportation with a minimal diffusion resistance and thus produce effective electrocatalytic kinetics in both acidic and alkaline media. Experimental observations in combination with density functional theory calculations reveal that the effective coupling between molybdenum carbide nanoparticles and the carbon matrix, as well as N hybrid coordination, can modify the electronic Fermi level of the final hybrid, which synergistically reduces the proton adsorption and the reduction barrier during electrocatalytic HER. A three-dimensional, porous catalytic framework makes it easier to flow water past active sites that turn this molecule into hydrogen. The hunt for cheaper alternatives to platinum catalysts for water splitting led Jinhua Ye from Tianjin University in China and co-workers to investigate molybdenum carbide (Mo2C). These catalysts show significant hydrogen evolution when confined to nanoscale shapes. The researchers enhanced this behaviour by replacing imidazole-zinc units in a zeolite-type metal organic framework with molybdenum. Heating at high temperature turned the sieve-like template into a new composite containing ultrafine Mo2C nanoparticles and a three-dimensional matrix of graphitic carbon implanted with nitrogen atoms. The physical structure of this material improves mass transport of reagents to and from catalytic surface sites, while favorable interactions between Mo2C and the carbon matrix lower energy barriers needed to slice water apart. A new hybrid, fabricated by incorporating molybdenum carbide (Mo2C) nanoparticles into nitrogen-implanted three-dimensional carbon matrix (MoCN-3D), has been developed as a highly active and durable nonprecious metal electrocatalyst for HER. The porous architecture of the developed catalyst MoCN-3D can provide continuous mass transportation with a minimal diffusion resistance and thus produce effective electrocatalytic kinetics in both acidic and alkaline media.

Amorphous transitional metal borides as substitutes for Pt cocatalysts for photocatalytic water splitting

Cocatalysts for H2 production are often made from noble metals, which are expensive and rare. Cocatalysts made from cheap and abundant elements are therefore highly desirable for economically viable H2 production. Here, we demonstrate that amorphous transitional metal borides (TMBs)—made from abundant materials and costing less than 0.1% of the price of Pt cocatalysts—are effective substitutes for Pt-based cocatalysts and result in superior H2 production via water-splitting under visible light irradiation. Under visible-light driven photocatalytic water-splitting, using TMBs as cocatalysts for nanostructured NiCoB/CdS composites achieved an extraordinary H2 production of 144.8mmolh−1g−1, up to 36 times greater than that observed when using CdS alone. The apparent quantum efficiency was measured as 97.42% at 500nm, which is the highest value reported for CdS photocatalysts. The hydrogen atom adsorption energy (ΔE(H)) and hydrogen molecule adsorption energy (ΔE(H2)) of NiB, NiCoB and Pt have been calculated for the first time. Compared with Pt cocatalyst, amorphous TMBs cocatalysts more readily adsorb hydrogen protons and desorb molecular hydrogen during the photocatalytic process. Superior performance of TMBs as cocatalyst, much better than Pt, can be attributed to its powerful trapping electrons ability and highly adsorption of protons. These findings provide a straightforward and effective route to produce cheap and efficient cocatalysts for large-scale water splitting.