Activating electrocatalytic hydrogen evolution performance of two-dimensional MSi2N4(M=Mo,W) : A theoretical prediction

Exploring catalysts with low cost and excellent performance for the hydrogen evolution reaction (HER) is still a significant challenge. In this work, zeolitic imidazolate framework 8 (ZIF-8), hybridized with polyvinylpyrrolidone, was used to prepare Zn, Ni co-loaded N-doped porous carbon (ZnNi/NPC) via a straightforward absorption and pyrolysis process. The as-prepared ZnNi/NPC was used as a catalyst for the HER. This experiment showed that the porous structure and Ni doping have a significant influence on the HER activity of the catalyst. Compared with Zn/NC and Zn/NPC, ZnNi/NPC exhibits superior HER activity with an overpotential of 198 mV and a Tafel slope of 69.2 mV dec−1. ZnNi/NPC also shows excellent physical and chemical stability during the HER process. Considering the lower cost and excellent HER performance of ZnNi/NPC, this work provides an attractive solution to fabricate non-precious materials and offers a possible new strategy to replace Pt-based electrocatalysts for HER.

Fe-B alloy coupled with Fe clusters as an efficient cocatalyst for photocatalytic hydrogen evolution

The hydrogen evolution reaction (HER) is crucially important for water splitting, for which platinum (Pt) has been considered the state-of-the-art electrocatalyst. Despite recent progress in non-Pt electrocatalysts, few Pt-free catalysts can compete against Pt in terms of HER activity particularly in alkaline solution. Here, we report a new efficient Pt-free HER catalyst – hybrid ruthenium cobalt phosphide (RuCoP) cluster where Ru exists in metallic chemical state in the hybrid. The unique hybridization allows electron transfer to take place from both Co and P to Ru, thereby significantly enhancing the hybrid’s HER activity. The as-synthesized RuCoP clusters demonstrate a considerably low overpotential (η) of 11 mV at -10 mA cm2 and a high turnover frequency (TOF) of 5.64 s-1 at η = 100 mV in 0.5 M H2SO4. Remarkably, even in alkaline solution (1.0 M KOH) the excellent HER performance of RuCoP remains, with a very low η 10 of 23 mV and exceptionally high TOF value of 3.85 s-1 at η = 100 mV. Moreover, the RuCoP catalysts show outstanding catalytic stability toward the HER in both acidic and alkaline solutions, superior to that of commercially available Pt/C catalysts. Figure 1

Hydrogen is identified as one of the most promising sustainable and clean energy sources. The development of a hydrogen evolution reaction (HER) catalyst with high activity is essential to meet future needs. Considering the novel advantages of two-dimensional materials and the high catalytic activity of atomic transition metals, in this study, using density functional theory calculations, the HER on a single transition metal (10 different TM atoms) adsorbed and doped ZnO monolayer (ZnO-m) has been investigated. The Volmer-Tafel reaction mechanisms and strain engineering of the three best HER catalysts are also discussed. The results show that Pt@ZnO-m, Co-doped ZnO-m and Ir-doped ZnO-m with high stability all have a smaller absolute H adsorption free energy than Pt, and the optimal value of Pt@ZnO-m is -0.017 eV. The calculation of the reaction energy barriers shows that the Volmer-Tafel step is favorable. Co@ZnO-m and Ir@ZnO-m have high HER activity, the widest pH range, and acid-alkali resistance. Pt@ZnO-m and Co-doped ZnO-m maintain excellent HER performances in the strain range of -4% to 4%.

Though transition-metal-based materials have emerged as the most promising alternatives to Pt-based electrocatalysts in hydrogen evolution reaction (HER), only a few of them (Fe-, Co-, Ni-, W-, and Mo-based materials) are used as efficient HER electrocatalysts, while others are generally considered as HER-inactive materials with poor activities. Here, a theory-guided experiment is carried out to activate titanium dioxide as a new efficient HER electrocatalyst. First-principles simulations indicate that the hydrogen adsorption free energy could be optimized through tuning the structural and electronic properties of TiO2. Then Cu-doped amorphous TiO2 is successfully prepared based on the theoretical results. The activated TiO2 expectedly shows excellent HER performance with a low overpotential of 92 mV at 10 mA cm-2 in alkaline media, which is far superior to that of the crystalline TiO2 (over 400 mV). The origin of HER activity is further investigated in detail. The corrugation of the amorphous surface helps stabilize the adsorbed water molecule, crucial for the water dissociation of the Volmer step. The Cu doping can strengthen the orbital hybridization of H1s and O2p favoring the hydrogen adsorption/desorption and improve the electrical conductivity. Our work highlights the great potential of traditionally inactive materials in HER electrocatalysis and helps deepen our understanding of the catalytic mechanism.

Exploring new excellent electrocatalysts for the hydrogen evolution reaction (HER) is of significance for the development of hydrogen energy. Herein, a ternary chalcogenide (Pt3Pb2S2) is successfully designed and synthesized using layered PtS2 as a matrix. The energy level of the Pt 5d orbital is upshifted to the Fermi surface after replacing S atoms by Pb atoms, which results in the high conductivity of Pt3Pb2S2. In addition, the low-coordinated Pt atoms inserted in the voids of [Pt2Pb2S2] layers have a lower free energy of H* adsorption than do metallic Pt atoms, which endows Pt3Pb2S2 with excellent HER performance. The overpotential and Tafel slope of Pt3Pb2S2 toward HER activity are measured to be 43 mV at 10 mA cm-2 and 43 mV dec-1, respectively. More importantly, Pt3Pb2S2 shows high intrinsic HER catalytic activity and long-term stability. This work provides a promising strategy for designing novel excellent transition-metal chalcogenide electrocatalysts.

Multifunctional electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are attractive for overall water-splitting, rechargeable metal-air batteries, and unitized regenerative fuel cells. A single-atom catalyst (SAC) may exhibit additional advantages over its nanoparticle counterpart, and already there have been significant advances in the development of bifunctional and trifunctional SACs for HER, ORR, and OER, but great challenges remain for their rational design. Herein, we propose a strategy to realize multifunctional SACs, i.e., modifying unifunctional materials to introduce new active sites on the surface. Specifically, by virtue of the intrinsic excellent HER performance of 1T'-MoS2, we theoretically design multifunctional SACs by anchoring appropriate transition-metal single atoms. Intriguingly, 1T'-MoS2 with supported Co single atoms (Co@MoS2) are demonstrated to be highly active for both OER and ORR with ultralow overpotentials of less than 0.3 V, ascribed to the moderate chemical activity and unique electronic structure of the Co atomic center. Consequently, combining the intrinsic HER activity of 1T'-MoS2, Co@MoS2 is proposed to be promising efficient trifunctional SACs. Further, the phase engineering on SACs is unrevealed and elucidated by comparing the properties of the Co atomic center-supported on 1T'-MoS2 and 1H-MoS2. This work provides a feasible strategy for the design of multifunctional SACs for the renewable and sustainable energy technology and provides an insight into the phase engineering on SACs.

Three-dimensional reduced graphene oxide/carbon nanotube nanocomposites anchoring of amorphous and crystalline molybdenum sulfide: Physicochemical characteristics and electrocatalytic hydrogen evolution performances

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

Activating MoO4 tetrahedrons to MoOx species in MoNi alloy for boosting performance in alkaline hydrogen evolution reaction

Simplistic two-step fabrication of porous carbon-based biomass-derived electrocatalyst for efficient hydrogen evolution reaction

Uranium is an essential element as both fission fuel and radioactive waste. Therefore, the recovery of uranium is of great importance. Here, an internal enhanced photocatalytic fuel cell (IEPFC) system is proposed to achieve high‐efficiency uranium extraction performance through the hydrogen evolution reaction (HER) process. An asymmetric Co 1 N 3 P 1 , derived from phosphorated ZIF‐67 grown on carbon felt (Co 1 N 3 P 1 C/CF), is utilized as a cathode and demonstrates excellent HER performance. A front FTO glass‐based TiO 2 nanorod (TNR) film and a rear‐placed Si photovoltaic cell (Si PVC) serve as an integrated photoanode. Thanks to the high HER performance of the Co 1 N 3 P 1 cathode and the enhanced internal drive of the photoanode, both the uranium recovery efficiency and the organic tetracycline (TC) degradation rate can reach 100% within 40 min of illumination. X‐ray absorption near‐edge structure (XANES) and density functional theory (DFT) calculations reveal that the Co 1 N 3 P 1 possesses a positive synergistic effect between HER and uranium recovery. This enhancement is due to the modified electronic structure resulting from the incorporation of P, and the robust adsorption between U and OH * promoted by electron transfer interactions between U and N and P. This work opens a new opportunity for the recovery of uranium from the complex water bodies.

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.

Abstractα‐MoB2, which has been considered as one of the promising nonprecious transition metal borides catalysts for the hydrogen evolution reaction (HER), has recently been reported to be very efficient in the bulk form (self‐supported electrode). However, bulk α‐MoB2 is normally synthesized under high‐temperature and high‐pressure conditions. In the present work, α‐MoB2 porous self‐supported electrodes with relative density of ∼52%–55% were synthesized by a combination of mechano‐chemical process and low‐temperature (750°C, 800°C, 850°C, and 900°C) spark plasma sintering technique. The effects of the sintering temperature on HER activity of the self‐supported electrodes in acidic solution were investigated in this study. The results showed that an overpotential as low as 91.2 mV at a current density of 10 mA/cm2, and a Tafel slope of 61.8 mV/dec were obtained by the α‐MoB2 electrode prepared at 850°C. This is the lowest overpotential value of the pure α‐MoB2 at a current density of 10 mA/cm2 ever reported in the open literature. Thus, the present study provides a new insight into the potentially innovative approach to manufacture α‐MoB2 porous self‐supported electrodes with excellent HER performance.

RuMo nanoalloy confined on N-doped carbon toward efficient alkaline and acidic hydrogen evolution reaction