Boron-doped CoSe2 nanowires as high-efficient electrocatalyst for hydrogen evolution reaction

Ultrafine cobalt-ruthenium alloy nanoparticles induced by confinement effect for upgrading hydrogen evolution reaction in all-pH range

Facile synthesis of interlaced flower-like layered double hydroxides grown on porous CoMoP as a highly efficient electrocatalyst for hydrogen evolution reaction

Fabrication of Te@NiTe2/NiS heterostructures for electrocatalytic hydrogen evolution reaction

Electricity driven proton exchange membrane-based water electrolysis (PEMWE) has demonstrated considerable credibility in recent years, establishing high competency enabling PEMWE technology for rapid generation of clean hydrogen fuel 1-7. In order to attain the high efficiency needed and successful commercialization of PEMWE, there is a critical need to identify highly active, robust, and earth-abundant electrocatalysts for accelerating the hydrogen evolution reaction (HER) with minimum energy input 8. In the pursuit of achieving this goal, in the present work, employing the density functional theory (DFT) based calculations for rationalizing the thermodynamics and reaction kinetics of HER, we have investigated the platinum group metal (PGM)-free, earth-abundant, transition metal non-oxide (TMN) based electrocatalysts for acid mediated HER in PEMWE. Based on the theoretical calculations, the as-synthesized TMN electrocatalyst compositions reveal optimized hydrogen adsorption free energies (ΔGH *) and beneficial electronic structures modification, offering superior charge transfer kinetics, lower reaction barrier, low water contact angle (7o) suggesting high wettability (Fig. 1), and high electrocatalytic activity for HER. Furthermore, the highly active electrocatalyst compositions display excellent long term electrochemical HER stability in acidic media, with no significant obvious degradation in current density. The as-synthesized electrocatalysts thus, has propensity for exhibiting robust HER performance with excellent structural and mechanical integrity. The experimental results are in excellent agreement with the DFT calculations which further accentuate the incorporation of suitable PGM-free dopants into the TMN compositions resulting in optimized electronic structures lowering the HER reaction barriers. The system therefore offers improved electrocatalytic performance for HER which is comparable to state-of-the-art Pt/C electrocatalysts. Accordingly, the as-synthesized PGM-free electrocatalysts can be considered as reliable HER candidates, vital for the development of acid mediated PEM based water splitting employing PGM-free electrocatalysts. Results of this study will be presented and discussed. Acknowledgements: Financial support of NSF-CBET grant# 1511390, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) is acknowledged.

Urchin-like Co0.8-Mn0.2-P/CC nanowires array: a high-performance and cost-effective hydrogen evolution electrocatalyst

For more energy-efficient and economical hydrogen production, highly active noble metal-free hydrogen evolution catalysts are a priority for all. Herein we report a facile hydrothermal synthesis of composite MoSe2-MoO2. The surface morphology and chemical composition of the synthesized materials were investigated by SEM, TEM, Raman spectroscopy, XPS and XRD. After characterizations, the materials were directly used as an electrode to evaluate their HER performance. A comparison between pure MoSe2, pure MoO2 and MoSe2-MoO2 nanosphere shows that the porous MoSe2-MoO2 nanosphere exhibits higher catalytic activity for electrocatalytic hydrogen evolution reaction (HER)(figure 1). Based on our data, it can be concluded that the porous structure material could improve the surface active area which yields higher HER catalytic activity. The present study provides a simple and effective way for the exploration of efficient Mo-based HER catalysts. Figure 1

Design and construction of robust nickel-based MOFs for promoting HER catalytic activity

The development of highly active and durable inexpensive electrocatalysts for hydrogen evolution reaction (HER) is still a formidable challenge. Herein, an ordered hexagonal-closed-packed (hcp)-Ru nanocrystal coated with a thin layer of N-doped carbon (hcp-Ru@NC) was fabricated through the thermal annealing of polydopamine (PDA)-coated Ru nanoparticle (RuNP@PDA). As an alternative to Pt/C catalyst, the hcp-Ru@NC nanocatalyst exhibited the small overpotential of 27.5 mV at a current density of 10 mA cm<sup>–2</sup>, as well as long-term stability for HER in acid media. Interestingly, the HER performance of hcp-Ru is highly dependent on its crystallinity. The calculation from density functional theory (DFT) revealed that the difference in HER activity over various exposed surface causes the crystallinity-dependent property of hcp-Ru. The results of this study provided clues to guide the design of Ru-based inexpensive HER electrocatalyst.

A Combined experimental and theoretical study of the accelerated hydrogen evolution kinetics over wide pH range on porous transition metal doped tungsten phosphide electrocatalysts

Asymmetrical radial strain energy strategy of M–N–SWCNT single atom catalysts for highly efficient hydrogen evolution: A high-throughput DFT study

As a zero-emission, eco-friendly fuel, hydrogen gas can be generated via electrochemical (EC) water splitting. Achieving high-efficiency water splitting requires the use of a catalyst to minimize the overpotential to drive the hydrogen evolution reaction (HER). Noble metals such as platinum (Pt) can provide an excellent catalytic activity for HER but are too expensive and scarce for broad applications. Therefore, the development of active HER catalysts made from low-cost materials constitutes a crucial challenge in the utilization of hydrogen energy. Earth-abundant transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), have been discovered recently, which exhibit good activity and stability for electrocatalytic reactions. In order to fully explore the untapped potential of MoS2, the synthesis recipe for MoS2needs to be optimized. Such an optimization process needs scientists to search through a combinatorically large space of experimental parameters, which will be time-consuming and costly if using conventional trial-and-error approaches. In this report, MoS2 HER catalytic activity optimization is performed by examining different combinations of synthesis parameters during the hydrothermal process. To investigate the structure-activity relationship, scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and various electrochemical characterizations have been conducted. A strong correlation between hydrothermal conditions and HER performance matrix has been observed. In order toaccelerate the search for the best synthesis recipe, machine-learning (ML) techniques have been introduced to help identify the optimal parameter combinations for producing MoS2. The hydrothermal parameters with the corresponding onset potentials and Tafel slopes are adopted as prior knowledge and are incorporated into the Bayesian Optimization model. The model will be able to guide the wet chemical synthesis of MoS2and yield the most effective HER catalyst eventually.

Developing new methodologies to produce clean and renewable energy resources is pivotal for carbon‐neutral initiatives. Hydrogen (H2) is considered as an ideal energy resource due to its nontoxic, pollution‐free, high utilization rate, and high calorific combustion value. Electrolysis of water driven by the electricity generated from renewable and clean energy sources (e.g., solar energy, wind energy) to produce hydrogen attracts great efforts for hydrogen production with high purity. Recently, the breakthrough of the catalyst activity limit for the hydrogen evolution reaction (HER) catalysts has received extensive attention. Comparatively, fewer reviews have focused on the long‐term stability of HER catalysts, which is indeed decisive for large‐scale electrolytic industrialization. Therefore, a systematic summary concentrated on the durability of HER electrocatalysts would provide a fundamental understanding of the electrocatalytic performance for practical applications and offer new opportunities for the rational design of the highly performed HER electrocatalysts. This review summarizes the research progress toward the HER stability of precious metals, transition metals, and metal‐free electrocatalysts in the past few years. It discusses the challenges in the stability of HER electrocatalysts and the future perspectives. We anticipate that it would provide a valuable basis for designing robust HER electrocatalysts.image

Electrocatalysts for hydrogen evolution reaction (HER) from water splitting have been widely studied as one of the efficient energy storage methods by producing hydrogen (H2), the important clean energy resource. The best-known electrocatalyst for HER is platinum (Pt) that is expensive and scarce on earth. Molybdenum disulfide (MoS2) has attracted great attentions as one of promising catalysts for replacing Pt not only because of the relatively low cost and earth abundancy but also great HER activity, selectivity and stability as a great catalyst. Since the edge site of MoS2 was proved as an active site for HER, a great number of efforts on maximally exposing edge site have contributed to the studies about MoS2 based catalysts for HER. The basal plane of MoS2 is catalytically inert for HER since the free energy of adsorbed hydrogen (delGH*) known to a great descriptor for activation energy is thermodynamically uphill (~1.92eV) compared with that of active edge site (~0.06eV). However, sulfur (S) vacancy in the basal plane was very recently investigated as a new active site for HER demonstrating the basal plane that composes the majority part of MoS2 can be utilized for HER. Diverse methods to generate S-vacancy to make a use of the basal plane of MoS2 for efficient HER catalysts have been investigated such as Ar plasma treatment, hydrogen annealing and electrochemical desulfurization. However, HER activity of desulfurized MoS2-x still needs to be improved to be competitive with the HER activities of platinum. Cobalt is one of the non-precious metal promotors for MoS2 based catalysts for hydrogen evolution reaction, water gas shift reaction and oxygen reduction reaction. In very recently, Co was doped in the basal plane of S-vacancy rich MoS2 and Co-SMoS2 achieved a great catalytic activity for the hydrodeoxygenation (HDO) reaction. Since S-vacancy site is coordinatively unsaturated and has a high surface free energy like edge site, it is expected to provide a great nucleation site for doping or anchoring transition metal atoms or clusters. Thus, Co promotor can be employed for enhancing the catalytic activity of the basal plane of MoS2 based catalysts. Herein we report the great HER activity enhancement of the catalytically inert basal plane of MoS2 by combining the catalytic effects of S-vacancy and Co cluster addition as a non-precious metal oxide promotor. We use both density functional theory (DFT) calculations and experiments to support the claim. The polycrystalline 2H phase MoS2 multilayer whose basal plane is dominantly exposed was synthesized on fluorine-doped tin oxide (FTO) and carbon foam electrodes through thermolysis in the tube furnace. S-vacancy was generated on the basal plane of MoS2 through the same electrochemical desulfurization method. On top of that, Co cluster was electrodeposited to further promote the HER activity of the basal plane under different desulfurization conditions. Consequently, we demonstrate S-vacancy plays a critical role for Co nucleation during electrodeposition and thus both electrochemically active surface area and the intrinsic catalytic activity increased. Especially, the overpotential at -10 mA/cm2 was reduced around 300mV making the inert basal plane of MoS2 have comparable overpotential about -0.21 V vs. RHE at -10 mA/cm2 with the state of the art non-precious MoS2 based catalysts.

Carbon nanotube supported PtO nanoparticles with hybrid chemical states for efficient hydrogen evolution

Mo isolated single atoms on S, N-codoped carbon as efficient catalyst for hydrogen evolution reaction: A theoretical evaluation