Hydrogen Evolution Reaction Current Density Research Articles

Enhancement of hydrogen evolution reaction by Pt nanopillar-array electrode in alkaline media and the effect of nanopillar length on the electrode efficiency

Pt nanopillar-array 3D electrodes with nanopillar length of 150, 450 and 900 nm and nanopillar density of ~109 cm−2 were fabricated. Their catalytic activity for hydrogen evolution reaction (HER) was evaluated by linear sweep voltammetry and electrochemical impedance spectroscopy. In comparison with straightly electrodeposited black Pt film and forged Pt sheet electrodes, the HER current density has been significantly improved by the nanopillar-array architecture. The overpotential of HER at current density of 10 mA cm-2 at 26 °C is as low as 78 mV, lower than the black Pt film of 107 mV and the Pt sheet of 174 mV. The improvement of HER is ascribed to the low charge transfer resistance of the 3D electrode and the high desorption capability of hydrogen bubbles at the nanotips. Interestingly, the nanopillar-array 3D electrode has an optimal nanopillar length for HER. The mechanisms for the optimal nanopillar length were investigated here.

A MoS2-Co9S8-NC heterostructure as an efficient bifunctional electrocatalyst towards hydrogen and oxygen evolution reaction

Development of economical, stable and high-efficient electrocatalysts gives vital incentives to promote the large-scale implementation of clean energy devices. Transition metal sulfides and carbon materials provide broad platforms for design of highly active electrocatalysts thanks to their flexibility, high electrical conductivity, and possessing various catalytically active sites towards different reaction systems. Herein, a ternary-component MoS2–Co9S8-NC nanohybrid is synthesized, in which Co9S8, MoS2, and N-doped carbon (NC) are integrated with each other. Owing to forming abundant varied active centers including Co9S8–MoS2 heterojunctions, and Co–N, Mo–N coupling centers locating at the contact interfaces between transition metal sulfides and N-doped carbon, the hybrid demonstrates greatly enhanced performances towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Such hybrid represents low overpotentials of 95 mV and 230 mV to achieve 10 mA cm−2 current density for HER and OER in 1.0 M KOH, respectively, and demonstrates favorable prospects for large-scale applications in overall water splitting.

Cobalt‐Embedded N‐Doped Carbon Arrays Derived In Situ as Trifunctional Catalyst Toward Hydrogen and Oxygen Evolution, and Oxygen Reduction

AbstractThe carbons containing metals coordinated with nitrogen are emerging as the most promising catalysts toward various heterogeneous catalyses. In this paper, such a carbon catalyst is prepared through a chemical vapor deposition (CVD)‐supported precursor pyrolysis. Compared with the direct pyrolysis of polypyrrole@cobalt salt precursor, the incorporation of dicyanodiamide as the CVD source facilitates the diversification and hierarchization of carbon morphology, the reduction of Co particle size, and the increase of the proportion of interfacial Co−N−C and pyridinic‐N. The catalyst is composed of in‐situ‐grown multiple‐morphology carbons (MMCs) with metallic Co particles embedded, where the MMCs are a combination of nano‐particles, ‐rods, and ‐wires, all comprised by small N‐doped carbon nanoflakes. Owing to the combined modulation on morphology configurations and defect states, the Co/MMCs catalyst demonstrates excellent activities toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). A half‐wave potential of 0.84 V and low overpotentials of 86 and 180 mV at 10 mA cm−2 current density for HER and OER are achieved, respectively. Additionally, the catalyst also demonstrates favorable prospects for large‐scale applications in overall water splitting and Zn‐air battery.

Hydrothermal synthesis of spherical Ru with high efficiency hydrogen evolution activity

Hydrogen is an important renewable energy source. Electrochemical decomposition of water for hydrogen production has attracted more and more attention as an appealing hydrogen production strategy. Previous studies have proved that controlling the morphology of Ru can improve hydrogen evolution reaction (HER) activity. Therefore, the preparation of ordered spherical ruthenium nanocatalysts by hydrothermal method (Ru-HT) is described in this paper. The morphology, crystal structure and electronic state of Ru-HT were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). At the same time, the electrochemical properties and surface charge were studied and analyzed by cyclic voltammetry (CV) characterization and electrochemical impedance spectroscopy (EIS). The experimental results have demonstrated that the HER activity of Ru-HT is obviously better than that of Ru by liquid phase reduction method (Ru-LR). When HER current density reaches 10 mA cm−2, the overpotential of Ru-LR electrocatalyst is 88.8 mV, while the overpotential of Ru-HT electrocatalyst is reduced to 55.7 mV in acidic medium. The Tafel slope of Ru-HT is only 36.5 mV dec−1 and the exchange current density is 0.44 mA cm−2, which indicates the rate determining step of the HER process should be the electrochemical desorption step (Heyrovsky step). By adjusting hydrothermal time and hydrothermal temperature, HER activity was further optimized. During the optimization process, the preparation conditions would change the hydrogen adsorption intensity on Ru surface to some extent. The adsorption strength of RuH, together with the electrochemical surface area, will affect the HER activity of Ru.

Enhanced activity and stability of Co-Ni-P-B catalyst for the hydrogen evolution reaction via predeposition of Co-Ni on a Cu substrate

In this work, the effect of a predeposited Co-Ni layer on the catalytic activity and long-term durability of the quaternary Co-Ni-P-B catalyst for the hydrogen evolution reaction (HER) is investigated. To study the effect of predeposition of the Co-Ni layer for the Co-Ni-P-B catalyst, both Co-Ni-P-B/Co-Ni/Cu and Co-Ni-P-B/Cu catalysts are prepared. The current density for HER of the Co-Ni-P-B/Co-Ni/Cu catalyst at −0.5 VRHE is 36.1% higher than that of Co-Ni-P-B/Cu in 0.5 M H2SO4 solution at 18 °C. This is because the porous morphology of the Co-Ni-P-B/Co-Ni/Cu catalyst leads to a 10.6% larger electrochemical surface area and higher atomic ratio for both the P and B contents, which act as a proton acceptor and a supplier of electrons to the d orbital of the transition metals, respectively, compared to Co-Ni-P-B/Cu on the catalytic surface. Furthermore, the Co-Ni-P-B/Co-Ni/Cu catalyst retains 94.5% of the catalytic activity during durability test of 1 h owing to its higher adhesion strength between the substrate and catalyst and rougher morphology, whereas the Co-Ni-P-B/Cu catalyst shows a retention of only 64.4%.

Synthesis of Tri‐functional Core‐shell CuO@carbon Quantum Dots@carbon Hollow Nanospheres Heterostructure for Non‐enzymatic H2O2 Sensing and Overall Water Splitting Applications

AbstractA core‐shell structure with CuO core and carbon quantum dots (CQDs) and carbon hollow nanospheres (CHNS) shell was prepared through facile in‐situ hydrothermal process. The composite was used for non‐enzymatic hydrogen peroxide sensing and electrochemical overall water splitting. The core‐shell structure was established from the transmission electron microscopy image analysis. Raman and UV‐Vis spectroscopy analysis confirmed the interaction between CuO and CQDs. The electrochemical studies showed the limit of detection and sensitivity of the prepared composite as 2.4 nM and 56.72 μA μM−1 cm−2, respectively. The core‐shell structure facilitated better charge transportation which in turn exhibited elevated electro‐catalysis towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting. The overpotential of 159 mV was required to achieve 10 mA cm−2 current density for HER and an overpotential of 322 mV was required to achieve 10 mA cm−2 current density for OER in 1.0 M KOH. A two‐electrode system was constructed for overall water splitting reaction, which showed 10 and 50 mA cm−2 current density at 1.83 and 1.96 V, respectively. The prepared CuO@CQDs@CHNS catalyst demonstrated excellent robustness in HER and OER catalyzing condition along with overall water splitting reaction. Therefore, the CuO@CQDs@CHNS could be considered as promising electro‐catalyst for H2O2 sensing, HER, OER and overall water splitting.

Electrocatalytic properties of porous Ni-Co-WC composite electrode toward hydrogen evolution reaction in acid medium

Porous Ni-Co-(WC)x ternary composite electrodes were fabricated by means of electrodeposition on a foam Ni substrate. The surface morphology and microstructure of the electrodes were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrocatalytic properties of porous Ni-Co-(WC)x electrodes for hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution at temperatures from 25 to 50 °C were conducted by means of cathodic polarization, electrochemical impedance spectroscopy (EIS), cyclic voltammetry and chronoamperometry (CA). These Ni-Co-WC electrodes are efficient electrocatalysts for HER. Compared with the porous Ni-Co electrode, the porous Ni-Co-(WC)x electrode exhibited a lower HER overpotential, a lower electrochemical impedance, a lower apparent activation energy and a higher exchange current density. The apparent exchange current density of porous Ni-Co-(WC)x (x = 10, 20, 30 and 40 g/l) is 2.01, 3.01, 7.8 and 19.91 times of porous Ni-Co electrode, respectively. With the increase of WC concentration and temperature, the apparent exchange current density of HER was enhanced. With the increase of WC concentration and potential, the HER resistance and the activation energy decreased. The Ni-Co-(WC)x electrode exhibited superior corrosion resistance and stability for HER.

Hydrogen evolution reaction efficiency of carbon nanohorn incorporating molybdenum sulfide and polydopamine/palladium nanoparticles

Abstract The involvement of carbon nanohorn (CNH) in molybdenum sulfide (MoS2) and polydopamine (PDA)/palladium nanoparticles (Pd NPs) was studied for the hydrogen evolution reaction (HER) efficiency. In this research, the in-situ hydrothermal and PDA-assisted chemical reaction routes were adopted to synthesize MoS2/CNH and PDA-Pd/CNH nanocomposites. The electrochemical studies confirmed the HER activity of PDA-Pd/CNH-modified electrode superior to that of MoS2/CNH-modified electrode. The coating thickness of PDA was optimized towards high HER efficiency. The enhancement of HER cathodic current density was due to the strong interaction between CNH and Pd NPs. The thin coating by PDA on Pd/CNH nanocomposites maintained the excellent stability and the durability during the HER. Thus, CNH is one of the hopeful carbon materials to enhance the cathodic current density for HER.

On the Conversion Efficiency of CO2 Electroreduction on Gold

Benjamin A. Zhang is a PhD student at Harvard University. His research focus is on the control of mass transport and concentration gradients in electrochemical reactions, in particular CO2 reduction, through nano- and mesostructuring of electrodes. Cyrille Costentin is Professor at Universite Paris Diderot. He received his undergraduate education at Ecole Normale Superieure de Cachan and his PhD at Universite Paris Diderot. He is currently a Visiting Scientist in the group of D.G. Nocera at Harvard University. His interests include mechanisms and reactivity in electron transfer chemistry with particular emphasis on proton-coupled electron transfer and catalysis of electrochemical reactions. Daniel G. Nocera is the Patterson Rockwood Professor of Energy at Harvard University. His group studies mechanisms of biological and chemical energy conversion.

Evaluation of the electrocatalytic activity and stability of graphene oxide nanosheets coated by Co/Ni elements toward hydrogen evolution reaction

Electrocatalytic properties of a novel Graphene Oxide (GO) electrode combined with the cobalt/nickel (Co+Ni/GO) nanoparticles were investigated using Hydrogen Evolution Reaction (HER). The (Co+Ni)/GO electrode was synthesized in two steps. First, the GO nanosheets coating was pulse reverse electrodeposited from 0.5 mg ml−1 of GO suspension. Then, a coating modified by the electrochemical deposition of Co and Ni ions was obtained by the chloride salts. Microstructure, phase content, topography, and functional groups of the thin films were studied by the field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, atomic force microscopy, Fourier transform infrared spectrometer experiments, transition electron microscopy, and x-ray photoelectron microscopy. Moreover, the electrocatalytic activity of fabricated electrodes was studied using LSV and EIS while and electrocatalytic stability was evaluated via chronoamperometry test. The results demonstrated that the Tafel slope and overpotential of the electrode in the HER current density of 10 mA cm−2 are mainly decreased to 64 mV dec−1 and 200 mV versus RHE, respectively, for the (Co+Ni)/GO electrode. The suitable electro-activity and acceptable stability of the modified (Co+Ni)/GO shows that this electrode can be a good candidate in HER application.

Nickel doped cobalt - hollow nanoparticles as an efficient electrocatalyst for hydrogen evolution from neutral water

The development of efficient electrocatalyst based on earth-abundant elements for hydrogen generation under simple conditions is highly desired, but still a serious challenge. Herein, we report a simple synthesis of Ni doped Co hollow nanoparticles (CoNiHNP) through an easy ultrasonic-assisted chemical reduction method in the presence of non-metal (B and P) and metal (W) as an additive. The addition of low valency non-metals (B and P) and non-3d high valency metals like tungsten (W) improve the near-optimal adsorption energy for hydrogen evolution reaction (HER). The CoNiHNP requires a 41 mV overpotential to drive a 10 mA cm−2 current density for HER in 1.0 M potassium phosphate buffer solution (pH = 7). Remarkably, the CoNiHNP achieves a 400 mA cm−2 current density at a low overpotential of 417 mV in neutral pH aqueous electrolyte. Moreover, the CoNiHNP shows better performance during long-term electrolysis as compared to Pt/C. To the best of our knowledge, the CoNiHNP is the most stable, active and efficient non-noble metal electrocatalyst for hydrogen generation from a neutral solution.

High electrocatalytic hydrogen evolution activity on a coupled Ru and CoO hybrid electrocatalyst

Abstract Hydrogen evolution reaction (HER) is an essential step in converting renewable energy to clean hydrogen fuel. Exploring highly efficient, stable and cost-effective electrocatalysts is of crucial significance for sustainable HER. Here, we report the design of a coupled ruthenium/cobalt oxide (Ru/CoO) hybrid electrocatalyst for alkaline HER. In this hybrid metal/oxide system, the complicated alkaline HER pathways are overall facilitated; oxygen (O)-vacancy-abundant oxide enhances water splitting and Ru promotes successive hydrogen intermediates to generate hydrogen. The resulting Ru/CoO hybrid electrocatalyst exhibits significantly promoted catalytic activity compared with benchmark Ru catalyst, displaying an overpotential of 55 mV to generate a HER current density of 10 mA cm−2, comparable with the state-of-the-art Pt/C catalyst and the most efficient alkaline HER electrocatalysts. Furthermore, the strong interaction of Ru nanoparticles with oxide support and the in-situ growth of oxide support on conductive substrate guarantee the long-term stability of as-fabricated Ru/CoO hybrid electrocatalyst. This newly designed hybrid catalyst with abundant metal/oxide interfaces may pave a new pathway for exploring efficient and stable HER electrocatalysts.

Multishelled FeCo@FeCoP@C Hollow Spheres as Highly Efficient Hydrogen Evolution Catalysts.

Active nonprecious metal-based hydrogen evolution reaction (HER) electrocatalysts are critical for the clean and sustainable generation of hydrogen. Here, we synthesized multishelled FeCo@FeCoP@C hollow spheres by the carbonization and phosphorization of the FeCo-MIL-88 metal-organic framework. Owing to both composition (FeCo mixed phosphide) and morphology (multishelled morphology) effects, the as-obtained FeCo@FeCoP@C exhibits excellent HER performance with a low overpotential of 65 mV to achieve an HER current density of 10 mA cm-2 and high stability in acidic solution. Density functional theory calculations show that the FeCoP have the optimal hydrogen absorption energy than that of FeP and CoP. The carbon shell prevents the oxidation of the phosphides, and the FeCo core provides better conductivity. Our work provides a new method to synthesize multishelled structure catalysts, which has potential applications in the further hydrogen production.

Insights into electrocatalytic hydrogen evolution reaction in acidic medium at in-situ dispersed Pt atoms on nanoporous gold films

Electrocatalytic hydrogen evolution reaction (HER) at highly dispersed Pt atoms on nanoporous surfaces is of significance both in practice and in theory. In this work, in situ surface dispersion of tiny amount of Pt (NPGF-t-Pt) on a nanoporous gold film for HER has been carried out by repeated cyclic voltammetry for the first time. It involves simultaneous redox and alloying of Au and Pt atoms at the surface during the cyclic voltammetry. At a critical Pt content of ∼5 at% that is in situ optimized, the NPGF-t-Pt electrode has nearly the same HER geometrical current density as the nanoporous Pt surface with almost the same surface roughness. The Pt-mass HER current density on the ex situ alloyed nano-Au95Pt5 electrode is about 20 times that on the nano-Pt electrode. A modified HER mechanism containing seven surface elementary reaction steps has been proposed based on the experimental results, which is also supported by density functional theoretical calculation. It gives a deeper insight into the HER at the dispersed Pt atoms (∼5 at%) on the NPGF surface. We expect that this work will promote the electrocatalytic HER at dispersed active atoms with a critical content.

Self-Assembly Precursor-Derived MoP Supported on N,P-Codoped Reduced Graphene Oxides as Efficient Catalysts for Hydrogen Evolution Reaction.

The design and synthesis of high-activity earth-abundant material-based electrocatalysts for hydrogen evolution reaction (HER) are of great significance. Here we develop a novel method to prepare a MoP nanoparticle supported on N,P-codoped reduced graphene oxides (MoP/N,P-rGO) by pyrolysis of the self-assembled precursor. Benefiting from the selected components of the assembly, P and N atoms are mixed at the molecular level, which leads to MoP nanoparticles uniformly attaching to the graphene substrate and a certain amount of N and P atoms codoping to graphene. The obtained MoP/N,P-rGO exhibits a good HER performance that only needs an overpotential of 115 mV to achieve a HER current density of 10 mA cm-2. The enhanced HER performance is due to the well-dispersed MoP nanoparticles and the synergistic effect from the doped graphene substrate. It shows that the selected functional components integrated by the self-assembly process are appropriate precursors for the synthesis of high-quality HER electrocatalysts.

Preparation of nanohybrid electrocatalyst based on reduced graphene oxide sheets decorated with Pt nanoparticles for hydrogen evolution reaction

A nanohybrid of Pt nanoparticles and reduced graphene oxide (Pt/rGO) is prepared and exploited for hydrogen evolution reaction (HER) in acidic medium. At first, glassy carbon electrode (GCE) is modified by graphene oxide (GO) nanosheets. Then, during the electrochemical reduction, GO film is converted to rGO. Finally, rGO/GCE is immersed in acidic solution of mM K2PtCl6 for 20 min and then with scanning the potential of electrode from 0.00 to − 0.20 V vs. NHE, Pt (IV) ions are reduced to Pt. Characterization of Pt/rGO nanohybrid is achieved by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy. FESEM images confirm that on the surface of rGO film, Pt nanoparticles with size in the range of 5–15 nm are formed. Electrochemical experiments reveal that Pt/RGO/GCE exhibits a small onset potential of − 0.03 V vs. NHE and Tafel slope of about 33 mV dec− 1 for HER. Pt/rGO/GCE has higher electrocatalytic activity for HER than rGO/GCE and Pt/GCE. In addition, the nanohybrid presents an enhanced catalytic activity towards HER than bare Pt electrode. It is observed that the current density of HER at the Pt/rGO nanohybrid shows a little decrease after 1000 continuous potential cycles which means the good stability of the catalyst. In addition, chronoamperometric studies show that Pt/rGO/GCE exhibits a noticeable stability for HER. The obtained results allege that Pt/rGO nanohybrid can surmount the overvoltage of HER and can be used as promising electrocatalyst in HER in acidic medium.

Reduced Graphene Oxide-Supported Bimetallic M-Platinum (M: Co, Ni, Cu) Alloy Nanoparticles for Hydrogen Evolution Reaction

Hydrogen is one of the most promising energy carriers, especially if produced from renewable energy sources, replacing fossil fuels for both portable and stationary applications [1]. Although hydrogen is one of the most abundant elements on Earth, it does not exist in nature in molecular form. Currently, most of the hydrogen is produced from fossil fuel-based technologies, such as gas reforming. Only 5% of worldwide hydrogen production comes from water electrolysis. The main problem of this process is the high overpotentials necessary to split the water molecule into hydrogen and oxygen and, consequently, the high energy consumption. To overcome this problem, different electrode materials such as Pt, Ni, Co, Ir and Rh, have been tested as cathodes for water electrolyzers. Pt has high activity and good stability for the hydrogen evolution reaction (HER), but its limited resources and high price prevent its use on industrial scale [2]. Alkaline water electrolysis is a mature technology that typically operates at temperatures around 60 – 80 ºC and uses cathodes based on Ni, Raney Ni and Co [3]. These cathodes are less expensive than Pt, but show good activity (in alkaline media) and corrosion resistance. A common approach used in electrocatalysis to minimize the utilization of precious metals involves employing an electrocatalyst support material. The support material has several functions, as to increase the catalytic electrochemically surface area, to stabilize and to accommodate the metal particles and also to increase the catalyst’s conductivity [4-6]. Carbon-based supports are the mostly used, as they can offer all the aforementioned properties [6]. The present work combines the advantages of using highly active Pt together with low cost transition metals, like Ni, Co and Cu, with the employment of reduced graphene oxide (rGO) as an efficient carbon-based electrocatalyst support. Thus, Pt and three different PtM alloys supported on rGO, i.e., Pt/rGO, PtCo/rGO, PtCu/rGO and PtNi/rGO, were tested as electrocatalysts for hydrogen production by alkaline water electrolysis. rGO has adequate features to enhance and stabilize the metal particles, with rGO-supported catalysts having recently demonstrated promising results in alkaline media [7]. To prepare the working electrodes, 5 mg of each of the fours electrocatalysts was dispersed in 125 µL of 5 wt.% solution of polyvinylidene fluoride (PVDF, Alfa Aesar) in N-methyl-2-pyrrolidone (NMP, Sigma Aldrich) followed by ultrasonic treatment for ca. 30 min. The working electrodes were prepared by pipetting 80 μL of the corresponding catalytic ink onto a polished glassy carbon (GC) electrode (A = 4 cm2). The electrodes were dried at 80 ºC for 4 hours. A conventional three-electrode setup was used for the electrochemical characterization. The rGO-supported PtM (M = Co, Cu, Ni) electrode was used as working electrode, the counter electrode was a Pt mesh (Johnson Matthey) of 25 cm2 area, and a calomel electrode (Hanna Instruments, HI-5412, 3.5 M KCl) was used as the reference. All recorded potentials were converted to RHE scale using the equation ERHE = Ecal + 0.250 + 0.059 pH. The evaluation of HER kinetics at the PtM/rGO composites was done by linear scan voltammetry measurements at scan rate of 1 mV s-1, starting from the open circuit potential up to -0.17 V in 8 M KOH (AnalaR NORMAPUR, 87 wt.%) solutions. Higher current densities were achieved for the PtM/rGO electrocatalysts, in comparison with the non-alloyed material (Pt/rGO). It was also observed that increasing the temperature up to 65 ºC leads to a substantial increase of HER current densities at all electrocatalysts. Furthermore, long-term stability of the four electrocatalysts’ activity for HER was evaluated by chronoamperometry studies at 25 and 65 ºC, revealing better stability at lower temperature. It is shown that PtM/rGO nanocomposites are good candidates for application as novel electrocatalysts for the HER in alkaline media. [1] J.A.S.B. Cardoso, B. Šljukić, M. Erdem, C.A.C. Sequeira, D.M.F. Santos, Catalysts 50, 8 (2018). [2] D.M.F. Santos, B. Šljukić, C.A.C. Sequeira, D. Macciò, A. Saccone, J.L. Figueiredo, Energy 50, 486 (2013). [3] D.S.P. Cardoso, L. Amaral, D.M.F. Santos, B. Šljukić, C.A.C. Sequeira, D. Macciò, A. Saccone, Int. J. Hydrogen Energy 40, 4295 (2015). [4] M. Martins, B. Šljukić, C.A.C. Sequeira, O. Metin, M. Erdem, T. Şener, D.M.F. Santos, Int. J. Hydrogen Energy 41, 10914 (2016). [5] R.C.P. Oliveira, V. Vasić, D.M.F. Santos, B. Babić, R. Hercigonja, C.A.C. Sequeira, B. Šljukić, Electrochim. Acta 269, 517 (2018). [6] E. Antolini, Appl. Catal. B 88, 1 (2009). [7] M. Martins, B. Šljukić, O. Metin, M. Sevim, C.A.C. Sequeira, T. Şener, D.M.F. Santos, J. Alloys Compd. 718, 204 (2017).

Ru2P Nanoparticle Decorated P/N-Doped Carbon Nanofibers on Carbon Cloth as a Robust Hierarchical Electrocatalyst with Platinum-Comparable Activity toward Hydrogen Evolution

It is desirable yet challenging to develop highly active and durable hydrogen evolution reaction (HER) electrocatalysts with Pt-comparable activity for future energy devices. In this work, we report Ru2P nanoparticle decorated P/N dual-doped carbon nanofibers on carbon cloth (Ru2P@PNC/CC-900) as a highly efficient and durable hierarchical HER electrocatalyst in both acidic and alkaline media. Electrochemical tests show that this Ru2P@PNC/CC-900 possesses Pt-comparable HER activity to support 10 mA cm–2 HER current density at low overpotential of 15 and 50 mV in acidic and alkaline condition, respectively. Density functional theory calculations reveal that coupling Ru2P nanoparticles with heteroatom-doped carbon fibers leads to enhanced intrinsic HER activity. The integrative hierarchical architecture further endows high surface areas with good mechanical robustness to support abundant catalytically active sites and possesses excellent electrical conductivity and efficient access for mass transportation to...

Molybdenum carbide/phosphide hybrid nanoparticles embedded P, N co-doped carbon nanofibers for highly efficient hydrogen production in acidic, alkaline solution and seawater

Molybdenum (Mo) based materials including its phosphides, carbides, nitrides, oxides, dichalcogenides and metallic alloys have received particular interest in recent years for sustainable hydrogen evolution reaction (HER) electrocatalysis. In this study, a novel Mo2C/MoP hybrid nanoparticle embedded N, P co-doped carbon nanofibers on carbon fiber paper (Mo2C-MoP NPC/CFP-800) is successfully prepared as a highly efficient hierarchical HER electrocatalyst. Benefitting from its structural advantages and compositional merits, this Mo2C-MoP NPC/CFP-800 electrocatalyst displays remarkable catalytic activity as well as excellent durability for HER. Only 85 and 146 mV overpotential is required to drive a HER current density of 10 mA cm−2 in acidic and alkaline solution, respectively. Remarkably, this electrocatalyst is also able to fulfill efficient HER even in seawater. Further, this work reveals that the Mo2C/MoP hybrid nanoparticle is superior to MoP nanoparticle under present system in HER electrocatalysis, which may offer valuable clues on further design and synthesis of HER electrocatalysts.

(Invited) Electrocatalytic Hydrogen Evolution in Neutral Solution

Electrocatalytic hydrogen evolution reaction (HER) has been intensively studied. Materials innovation and device engineering for HER has been focused on both acidic and alkaline systems, for which great progress has been made. However, there has been very limited studies for neutral solution. Generating H2 from water of intermediate pH (e.g., wastewater, seawater) has advantages of being less corrosive, environmentally benign, and potentially low cost. It also provides an efficient way for environmental cleanup, for example, H2 production using a microbial electrolysis cell (MEC) cleans wastewater. HER electrocatalysts based on earth abundant materials for operation in neutral conditions, which has been rarely explored, is thus highly attractive but remains a grand challenge. Here we report our recent materials research and fundamental understanding on HER electrocatalysis in neutral solution. We have developed a new pseudo in situ synthesis method for the preparation of HER electrocatalysts molybdenum phosphide (MoP). The surface structure and chemistry can be easily controlled which enables us to study the structure-property relationship. Our MoP electrocatalyst demonstrates HER activity comparable to that of benchmark Pt in neutral solutions including natural sea water and phosphate buffered saline solution. It also demonstrates high stability with no performance fading in 4000 cycles. MoP electrocatalyst was further tested in an MEC, which is able to produce a 2X HER current density in comparison to the state-of-art MEC in literature. The high performance MEC with the new HER catalyst presents a promising technology approach for low cost hydrogen production.