Hydrogen Evolution Reaction Catalysis Research Articles

Highly dispersed Cu atoms in MOF-derived N-doped porous carbon inducing Pt loads for superior oxygen reduction and hydrogen evolution

The preparation of oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalysts with high activity, stability and low platinum loading has always been the focus of research. The single-atom platinum supported catalyst greatly improves the utilization of platinum, but the catalytic activity and selectivity are greatly affected by the platinum coordination environment, and the preparation of the material is difficult. Doping base metals to adjust the electronic structure of platinum is an effective strategy to improve catalyst performance. In this work, copper-platinum alloy nanoparticles were loaded on N-doped porous carbon via a targeted route guided by highly dispersed Cu atoms derived from MOF. The product C-ZIF-CuPt has high activity and high stability ORR, HER bifunctional catalytic performance, which is better than commercial Pt/C (20 wt%). The Pt activity in C-ZIF-CuPt is 4.4 times (ORR) and 6.7 times (HER) than Pt/C. Spectromicroscopic determinations unveiled that strong interactions between carbon carrier and the CuPt alloys contribute to the overall stabilities. DFT calculations show that Cu doping can increase the d-band center of Pt, reduce the ORR overpotential, and the activation energy barrier to water molecules, which is beneficial to ORR and HER catalysis. Under the same carrier conditions, the performance of sub-nano (single atoms, clusters) platinum-supported catalysts (C-ZIF-Cu-Pt) is inferior to C-ZIF-CuPt. This further shows that platinum alloying can effectively improve the performance of the catalyst.

Proton Shuttle Mediated by (SCH2)2P═O Moiety in [FeFe]-Hydrogenase Mimics: Electrochemical and DFT Studies

The synthesis, characterization, and protonation of [Fe2(CO)6{(μ-SCH2)2(Et)P═O}] (1) using the moderately strong acid CF3CO2H (pKaMeCN = 12.7) are reported. Digital simulations of the cyclic voltammetry of 1 in the presence of CF3CO2H and DFT calculations have allowed us to obtain a detailed mechanistic picture of the processes underlying the catalytic hydrogen evolution reaction (HER) that 1 can mediate. Moreover, DFT has shed light on the role of the P═O functionality in the whole catalytic cycle of proton reduction. The reductive behavior of 1 features a double electron transfer with potential inversion, which is associated with deep structural rearrangement of the catalyst. The double reduction appears also functional to the intramolecular proton transfer from the P═O group to the diiron core, a crucial process for the H+/H– heterocoupling yielding H2. The key intermediate for the H2 formation and release is predicted to be a 3H+/3e– species, in which P═O is perfectly poised to shuttle protons from solution to the Fe–H–Fe moiety. Therefore, the R-P═O bridgehead installed in a dithiolato linker of a diiron core proves a valid and versatile alternative to the natural nitrogen-based Fe2 strap.

N-Confused Metallocorroles: Synthesis, Redox Properties, and Catalytic Activities

Corrole is known as a contracted tetrapyrrolic macrocycle bearing an α,α'-linked bipyrrole moiety. Using a unique trianionic N4 donor environment at the inner core, various high-valent metal species have been examined for potential catalytic applications. To seek new reactivity of metallocorroles, we have previously designed and synthesized a specific carbacorrole ligand, namely N-confused/N-linked corrole analogs.[1] The former analog contains an inverted pyrrole moiety connected at the α and β’-linking positions, and the latter has a peculiar linkage between the pyrrole α-position and the pyrrolic nitrogen site. The distinct [NNNC] coordination environment of these carbacorroles stabilizes unique organometallic species such as a copper(III).[2]In this work, we synthesized novel cobalt complexes with a benzo-fused corrole analog (i.e., benzonorrole). The electronic structure of the resulting complex is highly dependent on the number of axial pyridine ligands. The bis-pyridine adduct complex can be regarded as a diamagnetic Co(III) species. Removal of an axial pyridine ring from the corresponding complex yielded the oxygenated product at the inner carbon site immediately. Unlike the bis-pyridine adduct, the mono-pyridine cobalt complex is a singlet Co(II) ligand radical at the ground state as inferred from various spectroscopic means and DFT calculations. Due to the intrinsic redox-noninnnocent character, the cobalt(II) radical complex exhibits facile reduction nature. On this basis, we finally applied for catalytic hydrogen evolution reaction with these cobalt complexes.[1] Fujino, K.; Hirata, Y.; Kawabe, Y.; Morimoto, T.; Srinivasan, A.; Toganoh, M.; Miseki, Y.; Kudo, A.; Furuta, H. Angew. Chem. Int. Ed. 2011, 50, 6855-6859; Toganoh, M.; Kawabe, Y.; Uno, H.; Furuta, H. Angew. Chem. Int. Ed. 2012, 51, 8753-8756.[2] Maurya, Y.; Noda, K.; Yamasumi, K.; Mori, S.; Uchiyama, T.; Kamitani, K.; Hirai, T.; Ninomiya, K.; Nishibori, M.; Hori, Y.; Shiota, Y.; Yoshizawa, K.; Ishida, M.; Furuta, H. J. Am. Chem. Soc. 2018, 140, 6883-6892.

MXenes modified by single transition metal atom for hydrogen evolution reaction catalysts

Searching for noble-metal-free catalysts for hydrogen evolution reaction (HER) is crucial to the development of sustainable energy. Here, we systematically explored the HER catalytic performance of Ti2CO2, Ti3C2O2 and Ti3CNO2 modified by single transition metal atom via first-principles calculations. The modified catalysts behave outstanding catalytic performance with either the single atom or the O atom on the surfaces of MXenes as active sites when pH = 0. We found that Ti2CO2 doped with Cu, Ag and W at O site exhibit superb HER catalytic performance when pH = 0 with Gibbs free energies of hydrogen adsorption of −2.67*10−5, −2.78*10−4, and 3.37*10−4 eV, respectively. In addition, Cu and Pd directly anchoring on Ti2CO2 have dual-acitve-site mechanism for HER, indicating high efficiency. The enhanced performance for HER is attributed to the redistribution of electron after the introduction of single atom. Furthermore, Ti2CO2 doped with W at Ti site, Ti3C2O2 doped with Mo and W at Ti site, behave good catalytic performance via wide pH ranges under alkaline/neutral conditions. Their low water dissociation barriers imply excellent HER catalytic performance under both acidic and alkaline/neutral conditions. These explorations bring new prospect to the potential of Ti-based MXenes in HER catalysis.

Electronic metal\u2013support interaction modulates single-atom platinum catalysis for hydrogen evolution reaction

Tuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.

New TiO2 -Based Oxide for Catalyzing Alkaline Hydrogen Evolution Reaction with Noble Metal-Like Performance.

The development of cost-effective electrocatalysts with high activity and sufficient stability for hydrogen evolution reaction (HER) is crucial for the widespread application of water electrolysis for sustainable H2 production. Transition metal oxides are desirable alternatives to replace benchmark Pt-based HER electrocatalysts because of their cost effectiveness, facile synthesis, versatile compositions, and easy electronic structure tuning. However, most available transition metal oxides show poor performance for HER catalysis. Here, it is reported that the anatase TiO2 can be efficiently developed into a superior HER electrocatalyst with comparable activity to Pt-based electrocatalysts in alkaline solution through simultaneous morphology control, proper lattice doping, and surface active sites engineering. Specifically, the obtained cobalt-doped TiO2 nanorod arrays (Co-TiO2 @Ti(H2 )) show a low overpotential of only 78mV at 10mA cm-2 , a small Tafel plot of 67.8mV dec-1 , and excellent stability even at an ultralarge current density of ≈480mA cm-2 in 1.0 m KOH solution. Theoretical calculations demonstrate that the introduction of Co with rich oxygen vacancies can efficiently lower the energy barrier for water adsorption/dissociation and H intermediate desorption. This work uncovers the potential of the low-cost transition metal oxides as alternative HER electrocatalysts in alkaline water electrolysis.

Facile synthetic approach to produce optimized molybdenum carbide catalyst for alkaline HER

Mo-based materials were recognized as cost-effective electrocatalysts for the hydrogen evolution reaction (HER) in acidic media but were hardly investigated in alkaline media due to the limited active sites, lower conductivity and high water dissociation energy barrier. Herein, a facile, low cost, scalable technique is provided for the synthesis of Mo2C microspheres by a solvothermal route. Varying the feed ratio of the precursors enabled us to control the valence states of Mo and achieve optimized Mo2C phase formation for HER catalysis. Electrodes with the microspherical Mo2C catalyst were stable and exhibited reduced overpotentials of 138 mV at 10 mA cm−2 in 0.5 M KOH with a Tafel slope of 85 mV dec−1. The formation of an active Mo2C phase with abundance of Mo3+/Mo2+ active sites in the suitable ratio, as well as fast charge-transfer kinetics, are proposed as the origin for the efficient HER activity. Notably, we used cyclooctatetraene, an industrial byproduct that can be recycled into functional materials for green energy. Our work provides facile and novel way to design and fabricate Mo2C-based electrocatalyst for HER and probably other green energy applications.

Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

The microbial electrolysis cell assisted anaerobic digestion holds great promises over conventional anaerobic digestion. This article reports an experimental investigation of extracellular polymeric substances (EPS), reactive oxygen species (ROS), and the expression of genes associated with extracellular electron transfer (EET) in methanogenic biocathodes. The MEC-AD systems were examined using two cathode materials: carbon fibers and stainless-steel mesh. A higher abundance of hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium sp. appeared to play a major role in superior methanogenesis from stainless steel biocathode than carbon fibers. Moreover, the higher secretion of EPS accompanied by the lower ROS level in stainless steel biocathode indicated that higher EPS perhaps protected cells from harsh metabolic conditions (possibly unfavorable local pH) induced by faster catalysis of hydrogen evolution reaction. In contrast, EET-associated gene expression patterns were comparable in both biocathodes. Thus, these results indicated hydrogenotrophic methanogenesis is the key mechanism, while cathodic EET has a trivial role in distinguishing performances between two cathode electrodes. These results provide new insights into the efficient methanogenic biocathode development.

Catalysis of hydrogen evolution reaction by in situ electrodeposited amorphous molybdenum sulfide at soft interfaces

Amorphous molybdenum sulfide (MoSx) is considered a suitable alternative to Pt for catalyzing the hydrogen evolution reaction (HER) in electrochemical water splitting because of its simple and inexpensive preparation process. Herein, the template-free in situ electrodeposition of amorphous MoSx at freestanding soft interfaces is reported for the first time. The biphasic catalysis of the HER by the electrodeposited MoSx at the water-1,2-dichloroethane interface with decamethylferrocene (DMFc) was also investigated. DMFc acts as an organic sacrificial reducing agent for both (NH4)2MoS4 and protons to afford MoSx and H2, respectively. The nucleation of MoSx and the HER was examined using both four-electrode voltammetry and the biphasic reactions at the liquid-liquid interfaces. MoSx particles were collected from the interface and subjected to structural and morphological characterization. The HER kinetics was investigated using the UV-Vis absorption method with varying DMFc+ concentrations. The amount of H2 evolved and the reaction rates obtained over the in situ electrodeposited MoSx catalyst were compared with those obtained over electrodeposited metallic nanoparticles and commercial MoS2 catalysts.

An Efficient Nickel Sulfide@NiO Nanocomposite Catalyst with High Density of Active Sites for the Hydrogen Evolution Reaction in Alkaline Media.

Efficient hydrogen evolution reaction (HER) catalysts based on the earth-abundant materials are highly vital to design practical and environmentally friendly water splitting devices. In this study, we present an optimized strategy for the development of active catalysts for hydrogen evolution reaction HER. The composite catalysts are prepared with the nanosurface of NiO for the deposition of NiS by hydrothermal method. In alkaline electrolyte, the NiS/NiO nanocomposite has shown excellent catalytic HER properties at the low onset potential and small Tafel slope of 72 mVdec-1. A current density of 10 mA/cm² is achieved by the nanocomposite obtained with 0.4 gram of NiO as nanosurface for the deposition of NiS (sample 4) at the cost of 429 mV versus RHE. The sample 4 carries more active sites that allow it to act as excellent HER catalyst. Based on this study, we conclude that increasing the nickel oxide content into composite sample facilitates the HER process. Additionally, a long term HER stability for 10 hours and good durability is also demonstrated by the sample 4. Our findings reveal that the optimization of nickel oxide content in the preparation of catalyst leads to the excellent HER activity for the design of practical water splitting devices and other related applications.

Hydrogen evolution by ternary metal selenide at biomembrane-like soft interfaces

Two phase reactions are the analogy of biomembranes, which are polarized by Galvani potential difference at interface between two immiscible electrolyte solutions. Energy conversion reactions such as oxygen reduction reaction or hydrogen evolution reaction have been great drawn attention at soft interfaces due to the similarity of natural biochemical reactions. In this study, copper-based ternary metal selenide (copper tungsten selenide, Cu2WSe4) was first reported in the literature for hydrogen evolution reaction catalysis at the water/1,2-dichloroethane interface. The synthesized Cu2WSe4 catalyst is characterized by morphological and structural techniques. Catalytic activity of Cu2WSe4 at liquid–liquid interfaces by lipophilic decamethylferrocene as the sacrificial electron donor agent. This catalytic activity was tracked by four-electrode voltammetry at the water/1,2-dichloroethane interface and biphasic reactions monitored by gas chromatography. The rates of the hydrogen evolution reaction catalyzed by the Cu2WSe4 were found to be approximately 160-fold than the rate for the reaction performed in the absence of a catalyst.

High surface area NiCoP nanostructure as efficient water splitting electrocatalyst for the oxygen evolution reaction

We present a simple route to synthesize of porous bi-metallic phosphides with large surface area supporting high density of electrochemically active sites, and demonstrate that resulting Ni0.2Co0.8P exhibits outstanding performance in catalysing oxygen evolution reaction (OER) under alkaline condition. It requires a very low over potential of 230 mV to achieve an anodic current density of 10 mA cm−2 with a Tafel slope of 44 mV dec−1. Ni0.2Co0.8P is also shown to perform well in catalyzing hydrogen evolution reaction (HER) under both alkaline (0.1 M KOH solution) and acidic conditions (0.5 M H2SO4 solution). Through first-principles theoretical analysis, we show that such high catalytic activity arises from the synergistic effect of Ni and Co on energies of d and p bands of Ni0.2Co0.8P, which is further enhanced by rapid mass transport possible due to the porous architecture of its three-dimensional network morphology.

Ni0.85Se/MoSe2 Interfacial Structure: An Efficient Electrocatalyst for Alkaline Hydrogen Evolution Reaction

Catalyzing hydrogen evolution reaction in alkali media is challenging owing to the sluggish kinetics, originated from the water dissociation process. In this context, synergistic coupling between Ni/Co-based materials with transition metal dichalcogenides (TMDs) often accelerates the alkaline hydrogen evolution reaction (HER). Significant interaction between the two components and active-site density are the keys for achieving a promising catalytic activity. This report emphasizes a two-step selenization approach to prepare a Ni0.85Se/MoSe2 interfacial structure with abundant active sites. Initially, Ni0.75Se nanoparticles were prepared using the solvothermal method and subsequently employed them as a support for the growth of MoSe2 under hydrothermal conditions. This resulted in the formation of a Ni0.85Se/MoSe2 interfacial structure. The results of physical characterization techniques confirm the significant interaction between Ni0.85Se and MoSe2. The interfacial structures showed a superior HER activity in alkali media compared to the individual components; especially, Ni0.85Se/MoSe2 (20) delivers a current density of 10 mA cm–2 at an overpotential of 108 mV. The improved HER activity of the interfacial structure is attributed to the (i) efficient water dissociation process over the Ni0.85Se promoter and (ii) exposure of more catalytic active sites (edges) of MoSe2. In addition, as-prepared Ni0.75Se exhibits a better oxygen evolution reaction (OER) activity by delivering a current density of 10 mA cm–2 at an overpotential of 340 mV. Furthermore, overall water splitting has been demonstrated by constructing an electrolyzer using Ni0.85Se/MoSe2 (20) and Ni0.75Se as a cathode and anode, respectively. The electrolyzer delivers a current density of 10 mA cm–2 at a cell potential of 1.7 V. The long-term stability experiment and the post catalytic characterization reveals the high robustness of the Ni0.85Se/MoSe2 interfacial structure.

Sulfur vacancies in ultrathin cobalt sulfide nanoflowers enable boosted electrocatalytic activity of nitrogen reduction reaction

Large-scale electrosynthesis of ammonia from nitrogen reduction reaction (NRR) relies on the efficient electrocatalyst with restrained competitory reaction, hydrogen evolution reaction (HER), and more active sites for nitrogen chemisorption and relative protonation. In this work, sulfur vacancies in cobalt sulfide (CoS) nanoflowers are created by Ar-plasma for NRR catalysis. In comparison with untreated CoS, a boosted NRR catalytic activity with Faradaic efficiency of 16.5 ± 1.5% and ammonia yield rate of 12.1 ± 1.4 μgNH3 h−1 mgcat−1 is achieved for CoS1-x electrocatalyst at a low applied potential of −0.15 V vs. RHE in acidic media. The superior NRR catalytic activity of CoS1-x is also confirmed by NMR test. The robust NRR performance is related to the sulfur vacancies in ultrathin CoS nanoflowers effectively suppressing HER catalysis due to the selective chemisorption of N2 molecules on low coordinated Co atoms resulting in higher favorability for nitrogen adsorption since the created Lewis acid sites are more preferable to form stable Co-N bond; moreover, a lower Gibbs free energy for the initial hydrogenation of nitrogen molecules, limiting step of NRR, is required for CoS1-x electrocatalyst because more Co sites with low coordination are created and the adjacent two Co sites are involved for the splitting of N2 molecules synergistically; thereby, an exceptional NRR performance is achieved for CoS1-x electrocatalyst.

Enhanced catalytic hydrogen evolution reaction performance of highly dispersed Ni2P nanoparticles supported by P-doped porous carbon

The development of high-performance and non-noble metal hydrogen evolution reaction (HER) electrocatalysts is significant for industrial hydrogen production. Herein, we developed a facile hydrothermal synthesis of HER electrocatalyst (Ni2P/PC) of three-dimensional (3D) P-doped porous carbon (PC) supported Ni2P nanoparticles (Ni2P NPs). Ni2P/PC composites demonstrated a 3D lamellar porous structure with a large specific surface area (203.8 m2 g−1) and small particle size (15−20 nm) of Ni2P NPs. Furthermore, PC substrate was able to change the binding energy of Ni-P by adjusting the electron density of Ni2P. The Ni2P/PC catalyst exhibited excellent electrocatalytic activity with an impressively low overpotential of 96 mV at a current density of 10 mA cm-2 and a small Tafel slope of 67.01 mV dec−1 in HER. In addition, the electrocatalytic activity showed no obvious attenuation after 2000 cycles. P-doped porous carbon was proven as an ideal support for highly dispersed Ni2P NPs. This study paves the way for the development of highly efficient hybrid HER electrocatalysts.

Co-Ni alloy nanoparticles supported by carbon nanofibers for hydrogen evolution reaction

Abstract Alloying, a general strategy to improve the electrocatalytic performance of non-precious metal catalysts. Herein, we adopt a simple method to in-situ grow a cobalt-nickel alloy on a three-dimensional network of N-doped carbon fibers that put spatial restriction to the alloy particles, making the size smaller and uniformly distributed. The electronic synergy between nickel and cobalt and the confinement effect of in-situ growth can make Co-Ni/NCNFs provide more feasible reaction sites for catalytic hydrogen evolution reaction. Simultaneously, the formation of cobalt-nickel alloys inhibits the generation of oxides during the synthesis process, so as to promote the quality of alloys with better activity. Co-Ni/NCNFs exhibits excellent electrocatalytic properties with only 61 mV overpotential and 152.3 dec−1 at 10 mA cm−2 current density and excellent long-term stability due to the in-situ growth approach. This research also provides a feasible method for designing self-supporting alloy catalysts by in-situ growth.

Rapid Synthesis of Various Electrocatalysts on Ni Foam Using a Universal and Facile Induction Heating Method for Efficient Water Splitting

AbstractElectrocatalytic water splitting for the production of hydrogen proves to be effective and available. In general, the thermal radiation synthesis usually involves a slow heating and cooling process. Here, a high‐frequency induction heating (IH) is employed to rapidly prepare various self‐supported electrocatalysts grown on Ni foam (NF) in liquid‐ and gas‐phase within 1–3 min. The NF not only serves as an in situ heating medium, but also as a growth substrate. The as‐synthesized Ni nanoparticles anchored on MoO2 nanowires supported on NF (Ni‐MoO2/NF‐IH) enable catalysis of hydrogen evolution reaction (HER), showing a low overpotential of −39 mV (10 mA cm−2) and maintaining the stability of 12 h in alkaline condition. Moreover, the NiFe layered double hydroxide (NiFe LDH/NF‐IH) is also synthesized via IH and affords outstanding oxygen evolution reaction (OER) activity with an overpotential of 246 mV (10 mA cm−2). The Ni‐MoO2/NF‐IH and NiFe LDH/NF‐IH are assembled to construct a two‐electrode system, where a small cell voltage of ≈1.50 V enables a current density of 10 mA cm−2. More importantly, this IH method is also available to rapidly synthesize other freestanding electrocatalysts on NF, such as transition metal hydroxides and metal nitrides.

Boosting pH‐Universal Hydrogen Evolution of Molybdenum Disulfide Particles by Interfacial Engineering†

Main observation and conclusionThe design of high‐efficiency non‐noble and earth‐abundant electrocatalysts for hydrogen evolution reaction (HER) is highly paramount for water splitting and renewable energy systems. Molybdenum disulfide (MoS2) with abundant edge sites can be utilized as a promising alternative, but its catalytic activity is greatly related to the pH values, especially in an alkaline environment due to the extremely high energy barriers for water adsorption and dissociation steps. Here we report an exceptionally efficient and stable electrocatalyst to improve the sluggish HER process of layered MoS2 particles in different pH electrolytes, especially in base. The electrocatalyst is constructed by in situ growing selenium‐doped MoS2 (Se‐MoS2) nanoparticles on three‐dimensional cobalt nickel diselenide (Co0.2Ni0.8Se2) nanostructured arrays. Due to the large number of active edge sites of Se‐MoS2 particles exposed at the surface, robust electrical conductivity and large surface area of Co0.2Ni0.8Se2 support, and strong interfacial interactions between Se‐MoS2 and Co0.2Ni0.8Se2, this hybrid catalyst shows very outstanding catalytic HER properties featured by low overpotentials of 30 and 122 mV at 10 and 100 mA/cm2 with good operational stability in base, respectively, which outperforms most of inexpensive catalysts consisting of layered MoS2, transition metal selenides and sulfides, and it performs as well as noble Pt catalysts. Meanwhile, this electrocatalyst is also very active in neutral and acidic electrolytes, requiring low overpotentials of 93 and 94 mV at 10 mA/cm2, respectively, demonstrating its superb pH universality as a HER electrocatalyst with excellent catalytic durability. This study provides a straightforward strategy to construct an efficient non‐noble electrocatalyst for driving the HER kinetics in different electrolytes.

Weakened lattice-strain effect in MoOx@NPC-supported ruthenium dots toward high-efficiency hydrogen generation

MoOx@NPC-supported ruthenium dots nanostructure with weakened lattice-strain effect is designed to catalyze hydrogen evolution reaction with low overpotentials of 30 mV and 27 mV at 10 mA cm−2 in 1 M KOH and 0.5 M H2SO4, respectively.

Chalcogen-vacancy group VI transition metal dichalcogenide nanosheets for electrochemical and photoelectrochemical hydrogen evolution

Chalcogen vacancies of MoS2, MoSe2, WS2, and WSe2 nanosheets enhanced the catalytic hydrogen evolution reaction in solar photoelectrochemical cells.