Ultrafast Microwave Synthesis of Ru-Doped MoP with Abundant P Vacancies as the Electrocatalyst for Hydrogen Generation in a Wide pH Range.

Molybdenum phosphide (MoP) has received increasing attention for the hydrogen evolution reaction (HER) due to its Pt-like electronic structure and high electrical conductivity. In this work, a flake-like Ru-doped MoP with phosphorus vacancy (Ru-MoP-PV) electrocatalyst is synthesized for the first time by a simple and rapid room-temperature microwave approach within 30 s. The created abundant phosphorus vacancies provide rich active sites and favor rapid electron transfer. The introduced Ru also enhances the catalytic activity of the synthesized electrocatalyst efficiently. Then, the designed Ru-MoP-PV possesses low overpotentials for HER with 79, 100, and 161 mV in 1.0 M KOH, 0.5 M H2SO4, and 1.0 M phosphate-buffered saline to obtain 10 mA cm-2. The Ru-MoP-PV and NiFe-layered double hydroxide are used as the cathode and the anode, respectively, to drive water splitting and just need a low cell voltage of 1.6 V to achieve 10 mA cm-2. This work provides a feasible way for the rapid production of metal phosphides for energy conversion and storage applications.

Synergistic Effects of Pyrrolic N/Pyridinic N on Ultrafast Microwave Synthesized Porous CoP/Ni2P to Boost Electrocatalytic Hydrogen Generation.

Transition metal phosphides are ideal inexpensive electrocatalysts for water-splitting, but the catalytic activity still falls behind that of noble metal catalysts. Therefore, developing valid strategies to boost the electrocatalytic activity is urgent to promote large-scale applications. Herein, a microwave combustion strategy (20 s) is applied to synthesize N-doped CoP/Ni2P heterojunctions (N-CoP/Ni2P) with porous structure. The porous structure expands the specific surface area and accelerates the mass transport efficiency. Importantly, the pyrrolic N/pyridinic N content is adjusted by changing the amount of urea during the synthesis process and then optimizing the adsorption/desorption capacity for H*/OH* to enhance the catalyst activity. Then, the synthesized N-CoP/Ni2P exhibits small overpotentials of 111 and 133 mV for HER in acidic and alkaline electrolytes and 290 mV for OER in alkaline electrolytes. This work provides an original and efficient approach to the synthesis of porous metal phosphides.

CoNiFe alloy nanoparticles encapsulated into nitrogen-doped carbon nanotubes toward superior electrocatalytic overall water splitting in alkaline freshwater/seawater under large-current density.

Developing bifunctional catalysts for overall water splitting with high activity and durability at high current density remains a challenge. In an attempt to overcome this bottleneck, in this work, unique CoNiFe-layered double hydroxide nanoflowers are in situ grown on nickel-iron (NiFe) foam through a corrosive approach and following a chemical vapor deposition process to generate nitrogen-doped carbon nanotubes at the presence of melamine (CoNiFe@NCNTs). The coupling effects between various metal species act a key role in accelerating the reaction kinetics. Moreover, the in situ formed NCNTs also favor promoting electrocatalytic activity and stability. For oxygen evolution reaction it requires low overpotentials of 330 and 341 mV in 1M KOH and 1M KOH + seawater to drive 500 mA cm-2. Moreover, water electrolysis can be operated with CoNiFe@NCNTs as both anode and cathode with small voltages of 1.95 and 1.93 V to achieve 500 mA cm-2 in 1M KOH and 1M KOH + seawater, respectively.

Microwave Synthesis of Pt Clusters on Black TiO2 with Abundant Oxygen Vacancies for Efficient Acidic Electrocatalytic Hydrogen Evolution.

Oxygen vacancies-enriched black TiO2 is one promising support for enhancing hydrogen evolution reaction (HER). Herein, oxygen vacancies enriched black TiO2 supported sub-nanometer Pt clusters (Pt/TiO2 -OV ) with metal support interactions is designed through solvent-free microwave and following low-temperature electroless approach for the first time. High-temperature and strong reductants are not required and then can avoid the aggregation of decorated Pt species. Experimental and theoretical calculation verify that the created oxygen vacancies and Pt clusters exhibit synergistic effects for optimizing the reaction kinetics. Based on it, Pt/TiO2 -OV presents remarkable electrocatalytic performance with 18 mV to achieve 10 mA cm-2 coupled with small Tafel slope of 12 mV dec-1 . This work provides quick synthetic strategy for preparing black titanium dioxide based nanomaterials.

Heterostructure of RuO2 -RuP2 /Ru Derived from HMT-based Coordination Polymers as Superior pH-Universal Electrocatalyst for Hydrogen Evolution Reaction.

Searching for Pt-like activity, stable and economic electrocatalysts that can function at various pH values for the hydrogen evolution reaction (HER) is under increasing interest for the scientific community as H2 is a very promising energy carrier with great potential development value for renewable energy conversion. Herein, a unique self-supported heterostructure of RuO2 -RuP2 /Ru on the N, P co-doped carbon matrix (Ru-HMT-MP-7) is demonstrated, which is derived from HMT-based coordination polymers as superior pH-universal electrocatalysts. In the strategy, pyrolysis and phosphating processes are simultaneously proceeded that can produce the unique heterostructure containing three phases of RuO2 , RuP2, and Ru, at the same time the generated RuO2 -RuP2 /Ru can be highly dispersed on the self-assembly N, P co-doped carbon substrates. The resulting heterostructure Ru-HMT-MP-7 exhibits excellent activity superior to that of benchmark Pt/C with low overpotentials at 10 mA cm-2 (33 mV for 1.0 M KOH, 29 mV for 0.5 M H2 SO4 and 86 mV for 1.0 M PBS) and long-term electrocatalysis durability toward HER at various pH values. The rational construction strategy paves a novel avenue for obtaining superior pH-universal catalysts for electrochemical energy storage and conversion.

Engineering Bismuth-Tin Interface in Bimetallic Aerogel with a 3D Porous Structure for Highly Selective Electrocatalytic CO2 Reduction to HCOOH.

Electrochemical reduction of CO2 (CO2 RR) into valuable hydrocarbons is appealing in alleviating the excessive CO2 level. We present the very first utilization of metallic bismuth-tin (Bi-Sn) aerogel for CO2 RR with selective HCOOH production. A non-precious bimetallic aerogel of Bi-Sn is readily prepared at ambient temperature, which exhibits 3D morphology with interconnected channels, abundant interfaces and a hydrophilic surface. Superior to Bi and Sn, the Bi-Sn aerogel exposes more active sites and it has favorable mass transfer properties, which endow it with a high FEHCOOH of 93.9 %. Moreover, the Bi-Sn aerogel achieves a FEHCOOH of ca. 90 % that was maintained for 10 h in a flow battery. In situ ATR-FTIR measurements confirmed that the formation of *HCOO is the rate-determining step toward formic acid generation. DFT demonstrated the coexistence of Bi and Sn optimized the energy barrier for the production of HCOOH, thereby improving the catalytic activity.

Oxygen Vacancy-Rich In-Doped CoO/CoP Heterostructure as an Effective Air Cathode for Rechargeable Zn-Air Batteries.

An efficient and low-cost electrocatalyst for reversible oxygen electrocatalysis is crucial for improving the performance of rechargeable metal-air batteries. Herein, a novel oxygen vacancy-rich 2D porous In-doped CoO/CoP heterostructure (In-CoO/CoP FNS) is designed and developed by a facile free radicals-induced strategy as an effective bifunctional electrocatalyst for rechargeable Zn-air batteries. The electron spin resonance and X-ray absorption near edge spectroscopy provide clear evidence that abundant oxygen vacancies are formed in the interface of In-CoO/CoP FNS. Owing to abundant oxygen vacancies, porous heterostructure, and multiple components, In-CoO/CoP FNS exhibits excellent oxygen reduction reaction activity with a positive half-wave potential of 0.81 V and superior oxygen evolution reaction activity with a low overpotential of 365 mV at 10 mA cm-2 . Moreover, a home-made Zn-air battery with In-CoO/CoP FNS as an air cathode delivers a large power density of 139.4 mW cm-2 , a high energy density of 938 Wh kgZn -1 , and can be steadily cycled over 130 h at 10 mA cm-2 , demonstrating great application potential in rechargeable metal-air batteries.

Pt-Like Oxygen Reduction Activity Induced by Cost-Effective MnFeO2 /N-Carbon.

The development of effective and affordable electrocatalysts for the oxygen reduction reaction (ORR) is critical for the renewable-energy technologies. Here, we present a new manganese iron oxide (MnFeO2 ) as a cost-effective material for the ORR with Pt-like electrochemical properties. Pyrolysis of hybrid agar hydrogel on NaCl nanocrystals furnishes a unique structure in which the active MnFeO2 particles are uniformly immobilized in the nitrogen-doped porous carbon aerogels (MnFeO2 /NPC). Nitrogen-doped carbon is introduced to construct porous mass-transfer channels and reduce self-aggregation of the MnFeO2 particles. It is found that the formation of the MnFeO2 phase greatly depends on the pyrolysis temperature. Benefiting from the synergy of MnFeO2 and NPC, the MnFeO2 /NPC can actually be as good as the Pt/C catalyst for the ORR, with an onset-potential of 0.98 V and a half-wave potential of 0.86 V, combined with demonstrating a superior stability and tolerance to methanol.

Oxygen-deficient tungsten oxide inducing electron and proton transfer: Activating ruthenium sites for hydrogen evolution in wide pH and alkaline seawater.

The design of electrocatalysts for the hydrogen evolution reaction (HER) that perform effectively across a broad pH spectrum is paramount. The efficiency of hydrogen evolution at ruthenium (Ru) active sites, often hindered by the kinetics of water dissociation in alkaline or neutral conditions, requires further enhancement. Metal oxides, due to superior electron dynamics facilitated by oxygen vacancies (OVS) and shifts in the Fermi level, surpass carbon-based materials. In particular, tungsten oxide (WO3) promotes the directed migration of electrons and protons which significantly activates the Ru sites. Ru/WO3-OV is prepared through a simple hydrothermal and low-temperature annealing process. The prepared catalyst achieves 10 mA cm-2 at overpotentials of 23 mV (1 M KOH), 36 mV (0.5 M H2SO4), 62 mV (1 M PBS), and 38 mV (1 M KOH + seawater). At an overpotential corresponding to 10 mA cm-2 in 1 M KOH and 1 M KOH + seawater, the mass activity of Ru/WO3-OV is about 7.7 and 7.86 times that of 20 wt% Pt/C. The improvement in activity and stability arises from electronic modifications attributed to metal-support interaction. This work offers novel insights for modulating the HER activity of Ru sites across a wide pH range.

Graphdiyne-Induced CoN/CoS2 Heterojunction: Boosting Efficiency for Bifunctional Oxygen Electrochemistry in Zinc-Air Batteries.

The performance of zinc-air battery is constrained by the sluggish rate of oxygen electrode reaction, particularly under high current discharge conditions where the kinetic process of the oxygen reduction reaction (ORR) decelerates significantly. To address this challenge, we present a novel phase transition strategy that facilitates the creation of a heteroatom-doped heterointerface (CoN/CoS2). The meticulously engineered CoN/CoS2/NC electrocatalyst displays a superior ORR half-wave potential of 0.87 V and an OER overpotential of 320 mV at 10 mA cm-2. Experimental and computational analysis confirm that the CoN/CoS2 heterostructure optimizes local charge distribution, accelerates electron transfer, and tunes active sites for enhanced catalysis. Notably, this heterojunction improves stability by resisting corrosion and degradation under harsh alkaline conditions, thus demonstrating superior performance and longevity in a custom-made liquid zinc-air battery. This research provides valuable practical and theoretical foundations for designing efficient heterointerfaces in electrocatalysis applications.

The cobalt-based metal organic frameworks array derived CoFeNi-layered double hydroxides anode and CoP/FeNi2P heterojunction cathode for ampere-level seawater overall splitting.

The seawater electrolysis technology powered by renewable energy is recognized as the promising "green hydrogen" production method to solve serious energy and environmental problems. The lack of low-cost and ampere-level current OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalysis limits their industrial application. In this work, a unique tri-metal (Co/Fe/Ni) layered double hydroxide hollow array anode catalyst (CFN-LDH/NF) and the CoP/FeNi2P heterojunction hollow array cathode are successfully prepared via one in-situ growth of Co-MOF on nickel foam (Co-MOF/NF) precursor, which exhibits excellent catalytic performance. The η1000 values of 352 and 392 mV are achieved for CFN-LDH/NF (OER catalyst) in 1.0 M KOH and alkaline seawater solution, respectively. The CFNP/NF with a low overpotential of 281 mV is required to reach 1000 mA cm-2 current density for HER in 1.0 M KOH solution, while the η1000 in alkaline seawater solution is 312 mV. The CFN-LDH/NF||CFNP/NF electrolyzer exhibits excellent long-term durability over 100 h, achieving current density of 500 mA cm-2 at 1.825 V in 1.0 M KOH solution. The construction of hollow tri-metal LDH and phosphides heterostructures may open a new and relatively unexplored path for fabricating high performance seawater splitting catalysis.

Ferroelectric modulation of CuCo2O4 nanorods for controllable alkaline water electrolysis.

As a technology for emerging environmental applications, water electrolysis is a significant approach for producing clean hydrogen energy. In this work, we used an efficacious piezoelectric method to significantly improve the catalytic water splitting activity without affecting the morphology as well as the components by altering the bulk charge separation state inside the material. The obtained CuCo2O4 nanorods were treated under a corona polarization apparatus, which significantly enhanced ferroelectricity relative to that before the polarization increasing the physical charge separation and piezoelectric potential energy, enhancing the green hydrogen production. The polarized CuCo2O4 nanorods exhibit excellent water electrolysis performance under alkaline conditions, with hydrogen evolution overpotential of 78.7 mV and oxygen evolution overpotential of 299 mV at 10 mA cm-2, which is much better than that of unpolarized CuCo2O4 nanorods. Moreover, the Tafel slopes of polarized CuCo2O4 nanorods are 86.9 mV dec-1 in the HER process and 73.1 mV dec-1 in the OER process, which are much lower than commercial catalysts of Pt/C (88.0 mV dec-1 for HER) or RuO2 (78.5 mV dec-1 for OER), proving faster kinetic on polarized CuCo2O4 nanorods due to their higher electroconductibility and intrinsic activity. In particular, polarized CuCo2O4 nanorods are identified as promising catalysts for water electrolysis with robust stability, offering outstanding catalytic performance and excellent energy efficiency.

Construction of ultrathin solid electrolyte interface on Zn anode within 1 min for high current operating condition.

Organic acid treatment can facilitate the in-situ formation of a solid electrolyte interface (SEI) on Zn foil protecting the anode from corrosion. However, the generation of hydrogen (H2) during this process is inevitable, which is often considered detrimental to getting compact SEI. Herein, a H2 film-assisted method is proposed under concentrated Amino-Trimethylene-Phosphonic-Acid to construct ultrathin and dense SEI within 1 min. Specifically, the (002) crystal planes survive from the etching process of 1 min due to the adhered H2, inducing uniform deposition and enhanced corrosion-resistance. Moreover, the H2 can effectively regulate the reaction rate, leading to ultrathin SEI and initiating a morphology preservation behavior, which has been neglected by the previous reports. The quick-formed SEI has excellent compatibility, low resistance and effective isolation of electrolyte/anode, whose advantages work together with exposed (002) planes to get accustomed to high-current surge, leading to the ZAC1@Zn//ZAC1@Zn consistently cycling over 800 h at 15 mA cm-2 and 15 mAh cm-2, the ZAC1@Zn//Cu preserves high reversibility (CE 99.7 %), and the ZAC1@Zn//MVO exhibits notable capacity retention at 191.7 mAh/g after 1000 cycles.

Regulating Mo-based alloy-oxide active interfaces for efficient alkaline hydrogen evolution assisted by hydrazine oxidation.

Improving the efficiency of overall water splitting (OWS) is crucial due to the slow four-electron transfer process in the oxygen evolution reaction (OER). The coupling of the thermodynamically favorable hydrazine oxidation reaction (HzOR) with the hydrogen evolution reaction (HER) significantly boosts hydrogen production. A Ru-decorated MoNi/MoO2 micropillar (Ru-MoNi/MoO2) has been synthesized using a hydrothermal followed by reduction annealing. Benefiting from Ru moderating the active interface of Mo-based alloys/oxides and the unique one-dimensional micropillar morphology. The synthesized Ru-MoNi/MoO2 exhibits outstanding bifunctional activity for HER and HzOR, achieving 10 mA cm-2 at merely -13 mV and -34 mV in 1 M KOH and 1 M KOH + 0.5 M N2H4, respectively. Notably, with Ru-MoNi/MoO2 in a dual-electrode setup, only 0.57 V is needed to achieve 50 mA cm-2, demonstrating good stability and facilitating hydrazine-assisted water splitting (OHzS). This work offers insights into the modulation of alloy/metal oxide active interfaces, contributing to the development of efficient bifunctional catalysts for HER and HzOR.

Microwave Phosphine-Plasma-Assisted Ultrafast Synthesis of Halogen-Doped Ru/RuP2 with Surface Intermediate Adsorption Modulation for Efficient Alkaline Hydrogen Evolution Reaction.

Anionic modification engineering is a crucial approach to develop highly efficient electrocatalysts for hydrogen evolution reaction. Herein, halogen elements (X = Cl, Br, and I)-modified Ru-based nanosheets (X-Ru/RuP2) are designed by rapid and eco-friendly microwave-phosphide plasma approach within 60 s. Experimental and density functional theory calculations verify that the introduced halogen element, especially Br, can optimize the surface intermediates adsorption. Specially, the designed Br-Ru/RuP2 favors the water dissociation and following hydrogen adsorption/desorption process. Then, the as-synthesized Br-Ru/RuP2 exhibits low overpotential of 34 mV to reach 10 mA cm-2 coupled with small Tafel slope of 27 mV dec-1 in alkaline electrolyte with excellent long-term stability. Moreover, the electrocatalytic performances in acid and neutral media are also boosted via Br element modification. This work paves a novel way to regulate the electronic structure of Ru-based compounds, and then can boost the electrocatalytic kinetics.

Self-supported Ru-Fe-Ox nanospheres as efficient electrocatalyst to boost overall water-splitting in acid and alkaline media.

Developing electrocatalysts with high activity and durability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both acidic and alkaline electrolytes remains challenging. In this study, we synthesize a self-supported ruthenium-iron oxide on carbon cloth (Ru-Fe-Ox/CC) using solvothermal methods followed by air calcination. The morphology of the nanoparticle exposes numerous active sites vital for electrocatalysis. Additionally, the strong electronic interaction between Ru and Fe enhances electrocatalytic kinetics optimization. The porous structure of the carbon cloth matrix facilitates mass transport, improving electrolyte penetration and bubble release. Consequently, Ru-Fe-Ox/CC demonstrates excellent catalytic performance, achieving low overpotentials of 32 mV and 28 mV for HER and 216 mV and 228 mV for OER in acidic and alkaline electrolytes, respectively. Notably, only 1.48 V and 1.46 V are required to reach 10 mA cm-2 for efficient water-splitting in both mediums, exhibiting remarkable stability. This research offers insights into designing versatile, highly efficient catalysts suitable for varied pH conditions.

Pt Nanoparticle-Mn Single-Atom Pairs for Enhanced Oxygen Reduction.

The intrinsic roadblocks for designing promising Pt-based oxygen reduction reaction (ORR) catalysts emanate from the strong scaling relationship and activity-stability-cost trade-offs. Here, a carbon-supported Pt nanoparticle and a Mn single atom (PtNP-MnSA/C) as in situ constructed PtNP-MnSA pairs are demonstrated to be an efficient catalyst to circumvent the above seesaws with only ∼4 wt % Pt loadings. Experimental and theoretical investigations suggest that MnSA functions not only as the "assist" for Pt sites to cooperatively facilitate the dissociation of O2 due to the strong electronic polarization, affording the dissociative pathway with reduced H2O2 production, but also as an electronic structure "modulator" to downshift the d-band center of Pt sites, alleviating the overbinding of oxygen-containing intermediates. More importantly, MnSA also serves as a "stabilizer" to endow PtNP-MnSA/C with excellent structural stability and low Fenton-like reactivity, resisting the fast demetalation of metal sites. As a result, PtNPs-MnSA/C shows promising ORR performance with a half-wave potential of 0.93 V vs reversible hydrogen electrode and a high mass activity of 1.77 A/mgPt at 0.9 V in acid media, which is 19 times higher than that of commercial Pt/C and only declines by 5% after 80,000 potential cycles. Specifically, PtNPs-MnSA/C reaches a power density of 1214 mW/cm2 at 2.87 A/cm2 in an H2-O2 fuel cell.

In situ synthesis of two-dimensional graphene-like nickel-molybdenum nitride as efficient electrocatalyst towards water-splitting under large-current density.

Transition metal nitride (TMNs) electrocatalysts have attracted tremendous attentions for their unique electron structure, high activity, and excellent stability. Herein, a two-dimensional (2D) graphene-like structured nickel-molybdenum nitride (Ni-MoN) on nickel foam (NF), is prepared via facile hydrothermal and following nitridation process. The as-prepared Ni-MoN-450 (pyrolysis at 450 °C) displays good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances in alkaline media. Only 22 mV and 117 mV are needed to achieve current densities of 10 mA cm-2 and 500 mA cm-2 in 1.0 M KOH, respectively, toward HER. The assembled two-electrode system, with the synthesized Ni-MoN-450 as the anode and cathode, exhibits good performance to achieve 1000 mA cm-2 in 1.0 M KOH + 25 °C and 6.0 M KOH + 80 °C. Moreover, it also presents long-term stability under large-current density, which verified its robust property.

Ultrasmall RuM (Mo, W, Cr) Decorated on Nitrogen-doped Carbon Nanosheet with Strong Metal-support Interactions for Electrocatalytic Hydrogen Generation in Wide pH Range.

Developing efficient electrocatalysts for hydrogen evolution reaction (HER) in full pH range can promote the practical applications of hydrogen energy. In this work, nitrogen doped carbon nanosheets supported RuM (Mo, W, Cr) (RuM/NCN) are prepared through an ultrafast microwave approach. The carbon nanosheet structure coupled with the ultrasmall RuM nanoparticles can expose rich active sites to optimize the catalytic activity. Moreover, the strong metal-support interactions also favor to accelerate the reactions kinetics and improve stability. Thus, the developed RuMo/NCN (RuW/NCN) show excellent HER catalytic activities with overpotentials of 72 (75) mV, 82 (82) mV and 124 (119) mV to reach current density of 10 mA cm -2 in 1 M KOH, 0.5 M H2SO4 and alkaline seawater, respectively, and also achieve excellent performance in 1 M PBS. This work provides a valid and novel avenue to design efficient electrocatalysts in renewable energy-related fields.

Universal Synthesized Strategy for Amorphous Pd-Based Nanosheets Boosting Ambient Ammonia Electrosynthesis.

The electrocatalytic nitrogen reduction reaction (NRR) is emerging as a great promise for ambient and sustainable NH3 production while it still suffers from the high adsorption energy of N2 , the difficulty of *NN protonation, and inevitable hydrogen evolution, leading to a great challenge for efficient NRR. Herein, we synthesized a series of amorphous trimetal Pd-based (PdCoM (M = Cu, Ag, Fe, Mo)) nanosheets (NSs) with an ultrathin 2D structure, which shows high efficiency and robust electrocatalytic nitrogen fixation. Among them, amorphous PdCoCu NSs exhibit excellent NRR activity at low overpotentials with an NH3 yield of 60.68 µg h-1 mgcat -1 and a corresponding Faraday efficiency of 42.93% at -0.05 V versus reversible hydrogen electrode as well as outstanding stability with only 5% decrease after a long test period of 40 h at room temperature. The superior NRR activity and robust stability should be attributed to the large specific surface area, abundant active sites as well as structural engineering and electronic effect that boosts up the Pd 4d band center, which further efficiently restrains the hydrogen evolution. This work offers an opportunity for more energy conversion devices through the novel strategy for designing active and stable catalysts.