Hydrogenation Of Intermediates Research Articles

Metal-organic framework-derived Ga-Cu/CeO2 catalyst for highly efficient photothermal catalytic CO2 reduction

Photothermal catalytic CO2 reduction is an attractive process to efficiently convert solar energy into chemical energy with mitigation of global carbon emissions, but it remains a great challenge in achieving high conversion efficiency due to the limited sunlight capturing capacity and lack of highly efficient catalysts. Herein, we report a Ga-Cu/CeO2 catalyst synthesized by direct pyrolysis of the Ga and Cu-containing Ce-metal-organic frameworks for efficient photothermal catalytic CO2 hydrogenation. Because of the highly dispersed Ga and Cu species in CeO2, the optimized catalyst 10Cu5Ga/CeO2 (10 wt% Cu and 5 wt% Ga) achieved a CO production rate of 111.2 mmol g−1 h−1 with nearly 100 % selectivity under full solar spectrum irradiation, which is superior to most reported Cu and other earth-abundant metals-based photothermal catalysts. Mechanism studies demonstrated that the synergy of photothermal heating/conversion and light-promotion contributed to the substantially increased CO production. In situ DRIFTS results revealed that the introduction of Ga enhanced the formation of formate species, the key intermediates in CO2 hydrogenation, and light irradiation facilitated the decomposition of formate species to carbonyl, thus enhancing CO production. This work provides a potential strategy towards the synthesis of efficient catalysts for photothermal CO2 reduction.

Mechanism of dibenzofuran hydrodeoxygenation on the Ni (1 1 1) surface

• The dibenzofuran hydrodeoxygenation on Ni (1 1 1) is analyzed by DFT calculations. • The ring-opening and hydrogenation of bicyclic intermediates are competitive processes. • Decreasing the hydrogen coverage can reduce the yield of dodecahydrodibenzofuran. • The ring-opening reaction of dodecahydrodibenzofuran is challenging due to weak adsorption. The low-temperature coal tar contains a considerable number of oxygen-containing compounds, which results in poor quality. The catalytic hydrodeoxygenation of oxygen-containing compound to an added-value chemical compound is one of the most efficient methods to upgrade coal tar. In this study, density functional theory calculations are employed to assess and analyze in detail the hydrodeoxygenation of dibenzofuran, as a model compound of coal tar, on the Ni (1 1 1) surface. The obtained results indicate that dibenzofuran can be firstly hydrogenated to tetrahydrodibenzofuran and hexahydrodibenzofuran. The five-membered-ring opening reaction of tetrahydrodibenzofuran is more straightforward than that of hexahydrodibenzofuran ( E a = 0.71 eV vs . 1.66 eV). Then, both pathways generate an intermediate 2-cyclohexylphenoxy compound. One part of 2-cyclohexylphenoxy is hydrogenated to 2-cyclohexylphenol and consecutively hydrogenated to cyclohexylcyclohexanol, and another part is directly hydrogenated to cyclohexylcyclohexanone. The hydrogenated intermediates of 2-cyclohexylphenol have higher deoxygenation barriers than 2-cyclohexylphenol and cyclohexylcyclohexanol. During the hydrogenation process of cyclohexylcyclohexanone to cyclohexylcyclohexanol, the intermediate 26, formed by adding H to O atom of cyclohexylcyclohexanone, exhibits the lowest deoxygenation barrier of 1.08 eV. High hydrogen coverage may promote the hydrogenation of tetrahydrodibenzofuran, hexahydrodibenzofuran, and intermediate 26 to generate dodecahydrodibenzofuran and cyclohexylcyclohexanol. This dibenzofuran hydrodeoxygenation reaction mechanism corroborates well with previous experimental results and provides a theoretical basis for further optimization of the design of nickel-based catalysts.

Reconciling the Experimental and Computational Hydrogen Evolution Activities of Pt(111) through DFT-Based Constrained MD Simulations

The computational hydrogen evolution activity of Pt(111) remains controversial due to apparent discrepancies with experiments concerning rate-determining activation free energies and equilibrium hydrogen coverages. A fundamental source of error may lie within the static representations of the metal–water interface commonly employed in density functional theory (DFT)-based kinetic models neglecting important entropic effects on reaction dynamics. In this work, we present a dynamic reassessment of the Volmer–Tafel hydrogen evolution pathway on Pt(111) through DFT-based constrained molecular dynamics simulations and thermodynamic integration. Hydrogen coverage effects are gauged at two distinct surface saturations, while the critical potential dependence and constant potential conditions are accounted for using a capacitive model of the electrified interface. The uncertainty in the highly nontrivial treatment of the electrode potential is carefully examined, and we provide a quantitative estimation of the error associated with dynamically simulated electrochemical barriers. The dynamic description of the electrochemical interface promotes a substantial decrease of the Tafel free energy barrier as the coverage is increased to a full monolayer. This follows from a decreased entropic barrier due to suppressed adlayer dynamics compared to the unsaturated surface, a detail easily missed by static calculations predicting notably higher barriers at the same coverage. Due to observed endergonic adsorption of active hydrogen intermediates, the Tafel step remains rate-determining irrespective of the coverage as illustrated by composed Volmer–Tafel free energy landscapes. Importantly, our explicitly dynamic approach avoids the ambiguous choice of frozen solvent configuration, decreasing the reliance on error cancellation and paving the way for less biased electrochemical simulations.

Understanding the structure-performance relationship of cubic In2O3 catalysts for CO2 hydrogenation

Reaction mechanism and catalytic activities of methanol (CH3OH) and CO formations from CO2 hydrogenation at all the different surface oxygen vacancy (Ov) sites on the stable cubic In2O3 (c-In2O3) (111) flat surface and (110) flat and (110) step surfaces were thoroughly investigated in order to establish the structure-performance relationship using density functional theory calculations. For CH3OH formation, the R2 step for bidentate formate intermediate (bi-HCOO*) hydrogenation to the dioxymethylene intermediate (H2COO*), or the R3 step for H2COO* dissociation to the formaldehyde intermediate (CH2O*) and surface O atom, was calculated to be the rate-determining step (RDS), whereas for CO formation, the R1a step for bent CO2 adsorbate (bt-CO2*) protonation to the carboxylate intermediate (COOH*), was calculated to be the only RDS. Further data science analysis using the perceptron learning and decision tree algorithms shows that the RDS for CH3OH formation for a given Ov site can be determined by the stability of two key reaction intermediates (H2COO* and CH2O*) along with the formation energy of the Ov site. Linear regression analysis was also performed to establish linear relationships between the activation barriers and corresponding reaction energies for R2 and R3 steps, which can also be useful in determining the actual RDS for CH3OH formation. Although the adsorption energies of the linear CO2 configuration intermediate (ln-CO2*) and the bt-CO2* as well as the difference between the activation barriers of the RDS for CO and CH3OH formations are required for reliably predicting the catalytic activity and product selectivity, our studies suggest a simple and intuitive structure-performance relationship for the c-In2O3 catalyst that tri-coordinated Ov sites favor CH3OH formation, whereas bi-coordinated Ov sites favor CO formation.

Mo‐/Co‐N‐C Hybrid Nanosheets Oriented on Hierarchical Nanoporous Cu as Versatile Electrocatalysts for Efficient Water Splitting

AbstractDesigning robust and cost‐effective electrocatalysts based on Earth‐abundant elements is crucial for large‐scale hydrogen production through electrochemical water splitting. Here, nitrogen‐doped carbon engrafted Mo2N/CoN hybrid nanosheets that are seamlessly oriented on hierarchical nanoporous Cu scaffold (Mo‐/Co‐N‐C/Cu), as highly efficient electrocatalysts for alkaline hydrogen evolution reaction are reported. The constituent heterostructured Mo2N/CoN nanosheets work as bifunctional electroactive sites for both water dissociation and adsorption/desorption of hydrogen intermediates while the nitrogen‐doped carbon bridges electron transfers between electroactive sites and interconnective Cu current collectors by making use of Mo‐/Co‐N‐C bonds and intimate C/Cu contacts at interfaces. As a consequence of unique architecture having electroactive sites to be sufficiently accessible, self‐supported nanoporous Mo‐/Co‐N‐C/Cu hybrid electrodes exhibit outstanding electrocatalysis in 1 m KOH, with a negligible onset overpotential and a low Tafel slope of 47 mV dec−1. They only take overpotential of as low as 230 mV to reach current density of 1000 mA cm−2. When coupled with their electro‐oxidized derivatives that mediate efficiently the oxygen evolution reaction, the alkaline water electrolyzer can achieve ≈100 mA cm−2 at 1.622 V in 1 m KOH electrolyte, ≈0.343 V lower than the device constructed with commercially available Pt/C and Ir/C nanocatalysts immobilized on nanoporous Cu electrodes.

Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition

Citric acid has been investigated for preparing the highly dispersed nickel catalysts on Y2O3 support. A highly enhanced methanation activity with the high CO2 conversion of 92 % and CH4 selectivity of 100 % was obtained over Ni/Y2O3 with optimum addition of citric acid at 350 °C. The citric acid additives during the preparation are found to influence the size of nickel nanoparticles and the interaction of metal and support, as estimated by various techniques, which, in turn, to correlated with the catalytic performance. In situ DRIFTS spectra further indicate the importance of small Ni particles on formation of carbonates and formate species as key intermediates and the subsequent hydrogenation of those species into methane. This study proposes that the Y-O-Ni interfacial structure formed by the strong Ni and Y2O3 interaction at high citric acid addition is of prime importance for the formation of methane, benefiting from the more abundant basic sites and metallic Ni to enable CO2 activation and hydrogenation of key intermediates by effective H2 dissociation respectively. This work provides a new design strategy for developing highly efficient composite CO2 methanation catalysts by control of the metal particle size and charge transfer via metal/support interface.

Ceria morphology-dependent Pd-CeO2 interaction and catalysis in CO2 hydrogenation into formate

Several Pd catalysts supported on CeO2 with different morphologies (i.e. CeO2 rods (r-CeO2), cubes (c-CeO2) and polyhedra (p-CeO2)) were tested for the CO2 hydrogenation into formate. Remarkable morphology - dependent Pd-CeO2 interaction was observed, which was related to the oxygen vacancies in the CeO2. The r-CeO2 with the highest concentration of oxygen vacancy resulted in smaller Pd particles and more positively-charged Pd species in the Pd/r-CeO2 catalyst. The best performance was obtained over the Pd/p-CeO2 catalyst, giving a turnover frequency of 746 h−1 at 40 °C. The enhanced activity was due to the highest content of metallic Pd species in the catalyst, which was responsible for the facile activation of H2. Moreover, in situ spectroscopic results revealed that the hydrogenation of the carbonaceous intermediates was the rate - determining step. This work demonstrates oxide morphology engineering as a powerful strategy in developing efficient Pd - based catalysts for CO2 hydrogenation.

Effect of Ni particle size on the production of renewable methane from CO2 over Ni/CeO2 catalyst

Production of ‘renewable Methane’ has attracted renewed research interest as a fundamental probe reaction and process for CO2 utilization through potential use in C1 fuel production and even for future space exploration technologies. CO2 methanation is a structure sensitive reaction on Ni/CeO2 catalysts. To precisely elucidate the size effect of the Ni metal center on the CO2 methanation performance, we prepared 2%Ni/CeO2 catalysts with pre-synthesized uniform Ni particles (2, 4 and 8 nm) on a high surface area CeO2 support. Transmission electron microscopy (TEM) and ambient pressure X-ray photo spectroscopy (AP-XPS) characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions. The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts, and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts, respectively. The DRIFTS studies revealed that the larger Ni (8 nm particles) over CeO2 efficiently facilitated the hydrogenation of the surface formate intermediates, which is proposed as the rate determining step accounting for the excellent CO2 methanation performance.

Interfacial electron rearrangement: Ni activated Ni(OH)2 for efficient hydrogen evolution

The rational modulation of electronic structure is highly desirable to develop an efficient alkaline hydrogen evolution reaction (HER) catalyst for renewable energy applications. Metal hydroxide such as Ni(OH)2 has been proven useful for promoting alkaline HER, but the performance remains unsatisfactory. Herein, the electronic structure of Ni(OH)2 is modulated by the interfacial electron rearrangement between Ni-Ni(OH)2 heterojunction. Combined experiments with DFT simulations, the electrons of Ni species accumulate to the interfacial Ni-Ni(OH)2 sites, which modifies the d band center for promoting conversion of hydrogen intermediates and narrows the energy gap for boosting charge transfer in the HER process. Thus, the integrated electrode exhibits an efficient HER performance to drive 10 mA cm−2 at the overpotential of 72 mV with a low Tafel slope of 43 mV dec−1. Our work renders a valuable insight for understanding and rationally designing efficient catalysts in alkaline HER.

Interfacial optimization of PtNi octahedrons@Ti3C2MXene with enhanced alkaline hydrogen evolution activity and stability

It remains a great challenge to balance the activity and stability of platinum and Pt-based hydrogen evolution reaction (HER) catalysts in alkaline electrolyte. Herein, two-dimension monolayer Ti3C2 MXene sheets were introduced to support PtNi octahedrons (PtNi@Ti3C2 MXene), which optimizes the activity and stability of PtNi nanoparticles (NPs) through interface interactions between PtNi and Ti3C2 MXene. It shows a small overpotential of 36 mV with a Tafel slope of 59 mV dec−1 at 10 mA cm-2 in 1 M KOH. It also exhibits excellent mass activity of 6.31 mA μgPt-1 at an overpotential of 70 mV, which is ∼7.1 times that of commercial Pt/C and better than many recent reported Pt-based alkaline HER catalysts. Meanwhile, the PtNi@Ti3C2 MXene gives an increased overpotential of ∼4 mV while the PtNi gives ∼25 mV during a long-time continuous CV cycles. A series of characterizations disclose these interfaces could promote the stability by alleviating the Ni atoms dissolution from surficial PtNi through uniformly lattice strain dispersion of PtNi. Simultaneously, they could keep the activity by interfacial electron transfer from PtNi to Ti3C2 MXene demonstrated both by experimental tests (UPS, electrostatic potential and charge density distribution) and DFT calculation. It could decrease the energy barrier of H2O adsorbing and dissociating into hydrogen intermediates, further accelerating the recombination of hydrogen intermediates to H2. Under acidic and neutral medium, the electrocatalyst also exhibits improved HER performance compared to its counterparts. This work provides an interface optimization route for developing high-efficiency pH-universal especially alkaline HER electrocatalysts.

Role of CoO-Co nanoparticles supported on SiO2 in Fischer-Tropsch synthesis: Evidence for enhanced CO dissociation and olefin hydrogenation

The role of mixed CoO-Co nanoparticles dispersed on a SiO2 support for the Fischer-Tropsch synthesis (FTS) has been evaluated. The multiphase CoO-Co/SiO2 demonstrated high activity for the Fischer-Tropsch (FT) reaction, water-gas shift (WGS) and hydrogenation reactions. The results were the experimental evidence that the CoO-Co interface assisted both the activation of CO and the hydrogenation of R-CHx intermediates. A new mechanism, “CoO-Co H-assisted CO dissociation”, was hypothesized to explain the high CO reactivity and selectivity to linear paraffinic products. The synergistic effect between CoO and Co° promotes the FT activity, which provides the valuable information for the design of the commercial FT cobalt-based catalysts.

3D urchin like V-doped CoP in situ grown on nickel foam as bifunctional electrocatalyst for efficient overall water-splitting

Cobalt phosphide (CoP) is considered to be a potential candidate in the field of electrocatalysis due to its low-cost, abundant resources and high electrochemical stability. However, there is a great space for further improvement of its electrocatalytic performance since its charge transfer rate and catalytic activity have not reached a satisfactory level. Herein, we design and fabricate a three dimensional urchins like V-doped CoP with different amounts of V-doping on nickel foam electrode. The V-doped CoP/NF electrode with optimized amounts of V-doping (10%) exhibits outstanding hydrogen evolution reaction (HER) performance under universal-pH conditions and preeminent oxygen evolution reaction (OER) performance in alkaline media. Notably, the assembled water-splitting cell displays a cell voltage of only 1.53 V at 10 mA·cm−2 and has excellent durability, much better than many reported related bifunctional catalysts. The experiment results and theoretical analysis revealed that vanadium atoms replace cobalt atoms in CoP lattice. Vanadium doping can not only raise the density of electronic states near the Fermi level enhancing the conductivity of the catalyst, but can also optimize the free energy of hydrogen and oxygen-containing intermediates adsorption over CoP, thus promoting its catalytic activity. Moreover, the unique nanostructure of the catalyst provides the various shortened channels for charge transfer and reactant/electrolyte diffusion, which accelerates the electrocatalytic process. Also, the in situ growth strategy can improve the conductivity and stability of the catalyst.

Fe‐Based Catalysts for the Direct Photohydrogenation of CO2 to Value‐Added Hydrocarbons

AbstractThe solar‐driven conversion of CO2 into carbon‐based fuels and other valuable chemical feedstocks is actively being pursued as an approach for curbing greenhouse gas emissions. Herein, a series of novel Fe‐based catalysts with different chemical compositions are successfully fabricated through the hydrogen reduction of MgFeAl‐layered double hydroxide nanosheets at temperatures from 300 to 700 °C. The catalysts obtained are denoted herein as Fe‐x, where x is the reduction temperature in celsius. Fe‐500 offers outstanding activity for the photothermal conversion of CO2 to C2+ hydrocarbons under ultraviolet‐visible (UV‐Vis) irradiation (CO2 conversion 50.1%, C2+ selectivity 52.9%). Characterization studies using X‐ray diffraction, extended X‐ray absorption fine structure, Mössbauer spectroscopy, and high‐resolution transmission electron microscopy determine that the Fe‐500 catalyst is comprised of Fe and FeOx nanoparticles on a MgO–Al2O3 mixed metal oxide support. Density functional theory calculations establish that heterostructures consisting of partially oxidized metallic Fe nanoparticles improve the CC coupling ability of CO2 hydrogenation intermediates, thus enhancing the selectivity to C2+ products. This work introduces a novel photothermal hydrogenation strategy for converting CO2 into valuable chemicals and also opens new avenues toward the development of related solar energy utilization schemes.

Role of the mesoporous diameters of hierarchical ZSM-22/MCM-41 zeolite for n-alkane isomerization

Achieving highly dispersed Pt particles over ZSM-22 zeolite as bifunctional catalyst for n-alkane isomerization through simple synthesis methodology is critical for its practical applications. In this work, the mesoporous MCM-41 layers with different diameters are prepared rationally to reach this goal and in-depth understand the role of mesoporous sizes on acidity and Pt properties as well as the isomerization performance. Characterizations demonstrate the presence of microporous ZSM-22 zeolite as core and the well-established MCM-41 material with the diameters in the range of 2.2–4.5 nm as shell. Compared to parent ZSM-22 zeolite, partial deconstruction of the original structure by desilication causes the decreased acidity, while the effect of MCM-41 layers on acidity is negligible. However, the increase of mesopore diameters leads to obviously improved Pt dispersion by providing much broader mesoporous channels and higher surface areas. Therefore, the micro/mesoporous catalysts exhibit higher isomer selectivity than the parent Pt/ZSM-22 catalyst in n-dodecane isomerization, due to the balanced bifunctionality between the highly dispersed Pt sites and well-optimized Brønsted acid sites. Moreover, the enhanced selectivity of multi-branched isomers over the micro/mesoporous catalysts can be not only attributed to the presence of mesoporous layers by improving the secondary rearrangement of the iso-intermediates, but also related to the increment of Pt dispersion providing more sites for rapid hydrogenation of the multi-branched intermediates. Such an enhanced isomerization performance arising from the rational regulation of the mesoporous layer is noteworthy, providing new insight to design isomerization catalyst with more balanced bifunctionality and highly dispersed Pt particles.

Ni2 P Interlayer and Mn Doping Synergistically Expedite the Hydrogen Evolution Reaction Kinetics of Co2 P.

Transition metal phosphide is regarded as one of the most promising candidates to replace noble-metal hydrogen evolution reaction (HER) electrocatalysts. Nevertheless, the controllable design and synthesis of transition metal phosphide electrocatalysts with efficient and stable electrochemical performance are still very challenging. Herein, a novel hierarchical HER electrocatalyst consisting of three-dimensional (3D) coral-like Mn-doped Co2 P@an intermediate layer of Ni2 P generated in situ by phosphorization on Ni foam (MnCoP/NiP/NF) is reported. Notably, both the incorporation of Mn and introduction of the Ni2 P interlayer promote Co atoms to carry more electrons, which is beneficial to reduce the force of the Co-H bond and optimize the adsorption energy of hydrogen intermediate (|ΔGH* |), thereby making MnCoP/NiP/NF exhibit outstanding HER performance with onset overpotential and Tafel slope as low as 31.2 mV and 61 mV dec-1 , respectively, in 1 m KOH electrolyte.

Efficient Catalysts for the Green Synthesis of Adipic Acid from Biomass

AbstractGreen synthesis of adipic acid from renewable biomass is a very attractive goal of sustainable chemistry. Herein, we report efficient catalysts for a two‐step transformation of cellulose‐derived glucose into adipic acid via glucaric acid. Carbon nanotube‐supported platinum nanoparticles are found to work efficiently for the oxidation of glucose to glucaric acid. An activated carbon‐supported bifunctional catalyst composed of rhenium oxide and palladium is discovered to be powerful for the removal of four hydroxyl groups in glucaric acid, affording adipic acid with a 99 % yield. Rhenium oxide functions for the deoxygenation but is less efficient for four hydroxyl group removal. The co‐presence of palladium not only catalyzes the hydrogenation of olefin intermediates but also synergistically facilitates the deoxygenation. This work presents a green route for adipic acid synthesis and offers a bifunctional‐catalysis strategy for efficient deoxygenation.

Synergistic carbon and hydrogen reactions in the electrochemical reduction of CO2to liquid fuels

This review summarises the strategies of designing electrocatalysts to improve both carbon reaction (CO2to carbon intermediates and to organic liquid fuels) and hydrogen reaction (hydrogenation of carbon intermediates), and electrochemical reduction of CO2to liquid fuels.

Boosting Electrochemical Nitrate-Ammonia Conversion Via Organic Ligands-Tuned Proton Transfer

Electrochemical nitrate (NO3-) reduction reaction (NO3-RR) offers an ideal route to harvest ammonia (NH3) under ambient conditions. Despite recent advances in Cu-based NO3-RR electrocatalysts, their synthesis heavily relies on the regulation of adsorption strength towards nitrogen-containing intermediates, and other important factors are ignored (i.e., the proton transfer rate). Here, we select Cu nanoparticles (NPs) as model catalysts to investigate whether and how the proton transfer rate impacts the NO3-RR kinetics. The results indicate that the proton transfer is involved in the rate-determining step (RDS) of NO3-RR, and the weak water dissociation ability of Cu leads to slow proton transfer rate and consequently sluggish NO3-RR kinetics. To this end, we enhance the water dissociation ability of Cu NPs by incorporating uncoordinated carboxylate ligands to enable rapid proton transfer, which in turn boosts the hydrogenation of key intermediates for reducing the overall energy barrier of NO3-RR. As a result, Cu NPs with the ligands display a maximum NH3 yield rate of 496.4 mmol h-1 gcat-1, outperforming counterpart without ligands. This work not only deepens our knowledge on the NO3-RR mechanism, but also offers new guidelines for the smart design of efficient electrocatalysts.

Multi-pollutant control (MPC) of NO and chlorobenzene from industrial furnaces using a vanadia-based SCR catalyst

NO and chlorobenzene (CB) coexist in the flue gas of industrial furnaces from waste incineration and iron sintering. We design the strategy to remove them simultaneously via SCR and catalytic combustion together (multi-pollutant control, MPC). The V5Mo5Ti exhibits excellent activity with 100 % NO conversions in 200–400 °C and 95 % CB conversions above 300 °C. 2,3-dichloromaleic anhydride (DCMA) and acetate are the primary intermediates during the CB oxidation, while the sum of 17 kinds of PCDD/Fs on the V5Mo5Ti is 0.0115 ng·I-TEQ·Nm−3. Partial DCMA is not deeply oxidized into CO2, reducing the COx selectivity below 350 °C. The final products of the accumulated species above 800 °C desorption are CCl4 and C2Cl4, generated from the hydrogenation of intermediates. The Cl desorption mainly occurs in two zones: HCl in 200–500 °C from CB oxidation and CCl4 and C2Cl4 above 800 °C from surface hydrocarbon decomposition.

Nanoporous Surface High‐Entropy Alloys as Highly Efficient Multisite Electrocatalysts for Nonacidic Hydrogen Evolution Reaction

AbstractElectrocatalytic hydrogen evolution in alkaline and neutral media offers the possibility of adopting platinum‐free electrocatalysts for large‐scale electrochemical production of pure hydrogen fuel, but most state‐of‐the‐art electrocatalytic materials based on nonprecious transition metals operate at high overpotentials. Here, a monolithic nanoporous multielemental CuAlNiMoFe electrode with electroactive high‐entropy CuNiMoFe surface is reported to hold great promise as cost‐effective electrocatalyst for hydrogen evolution reaction (HER) in alkaline and neutral media. By virtue of a surface high‐entropy alloy composed of dissimilar Cu, Ni, Mo, and Fe metals offering bifunctional electrocatalytic sites with enhanced kinetics for water dissociation and adsorption/desorption of reactive hydrogen intermediates, and hierarchical nanoporous Cu scaffold facilitating electron transfer/mass transport, the nanoporous CuAlNiMoFe electrode exhibits superior nonacidic HER electrocatalysis. It only takes overpotentials as low as ≈240 and ≈183 mV to reach current densities of ≈1840 and ≈100 mA cm−2 in 1 m KOH and pH 7 buffer electrolytes, respectively; ≈46‐ and ≈14‐fold higher than those of ternary CuAlNi electrode with bimetallic Cu–Ni surface alloy. The outstanding electrocatalytic properties make nonprecious multielemental alloys attractive candidates as high‐performance nonacidic HER electrocatalytic electrodes in water electrolysis.