Boosting Hydrogen Oxidation Activity of Ni in Alkaline Media through Oxygen‐Vacancy‐Rich CeO2/Ni Heterostructures

The search for highly efficient platinum group metal (PGM)‐free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline electrolytes remains a great challenge in the development of alkaline exchange membrane fuel cells (AEMFCs). Here we report the synthesis of an oxygen‐vacancy‐rich CeO₂/Ni heterostructure and its remarkable HOR performance in alkaline media. Experimental results and density functional theory (DFT) calculations indicate the electron transfer between CeO₂ and Ni could lead to thermoneutral adsorption free energies of H* (ΔG_H*). This, together with the promoted OH* adsorption strength derived from the abundance of oxygen vacancies in the CeO₂ species, contributes to the excellent HOR performance with the exchange current density and mass activity of 0.038 mA cm_Ni^?2 and 12.28 mA mg_Ni^?1, respectively. This presents a new benchmark for PGM‐free alkaline HOR and opens a new avenue toward the rational design of high‐performance PGM‐free electrocatalysts for alkaline HOR.     

Ni3N as an Active Hydrogen Oxidation Reaction Catalyst in Alkaline Medium

Hydroxide‐exchange membrane fuel cells can potentially utilize platinum‐group‐metal (PGM)‐free electrocatalysts, offering cost and scalability advantages over more developed proton‐exchange membrane fuel cells. However, there is a lack of non‐precious electrocatalysts that are active and stable for the hydrogen oxidation reaction (HOR) relevant to hydroxide‐exchange membrane fuel cells. Here we report the discovery and development of Ni₃N as an active and robust HOR catalyst in alkaline medium. A supported version of the catalyst, Ni₃N/C, exhibits by far the highest mass activity and break‐down potential for a PGM‐free catalyst. The catalyst also exhibits Pt‐like activity for hydrogen evolution reaction (HER) in alkaline medium. Spectroscopy data reveal a downshift of the Ni d band going from Ni to Ni₃N and interfacial charge transfer from Ni₃N to the carbon support. These properties weaken the binding energy of hydrogen and oxygen species, resulting in remarkable HOR activity and stability.     

Enhanced Electrocatalytic Hydrogen Oxidation on Ni/NiO/C Derived from a Nickel‐Based Metal–Organic Framework

The sluggish hydrogen oxidation reaction (HOR) under alkaline conditions has hindered the commercialization of hydroxide‐exchange membrane hydrogen fuel cells. A low‐cost Ni/NiO/C catalyst with abundant Ni/NiO interfacial sites was developed as a competent HOR electrocatalyst in alkaline media. Ni/NiO/C exhibits an HOR activity one order of magnitude higher than that of its parent Ni/C counterpart. Moreover, Ni/NiO/C also shows better stability and CO tolerance than commercial Pt/C in alkaline media, which renders it a very promising HOR electrocatalyst for hydrogen fuel cell applications. Density functional theory (DFT) calculations were also performed to shed light on the enhanced HOR performance of Ni/NiO/C; the DFT results indicate that both hydrogen and hydroxide achieve optimal binding energies at the Ni/NiO interface, resulting from the balanced electronic and oxophilic effects at the Ni/NiO interface.     

Efficient Hydrogen Oxidation Catalyzed by Strain‐Engineered Nickel Nanoparticles

The hydroxide‐exchange membrane fuel cell (HEMFC) is a promising energy conversion device. However, the development of HEMFC is hampered by the lack of platinum‐group‐metal‐free (PGM‐free) electrocatalysts for the hydrogen oxidation reaction (HOR). Now, a Ni catalyst is reported that exhibits the highest mass activity in HOR for a PGM‐free catalyst as well as excellent activity in the hydrogen evolution reaction (HER). This catalyst, Ni‐H₂‐2 %, was optimized through pyrolysis of a Ni‐containing metal‐organic framework precursor under a mixed N₂/H₂ atmosphere, which yielded carbon‐supported Ni nanoparticles with different levels of strains. The Ni‐H₂‐2 % catalyst has an optimal level of strain, which leads to an optimal hydrogen binding energy and a high number of active sites.     

Pb-Modified Ultrathin RuCu Nanoflowers for Active,Stable, and CO-resistant Alkaline Electrocatalytic Hydrogen Oxidation

CO poisoning of Pt group metal (PGM) catalysts is a chronic problem for hydrogen oxidation reaction (HOR), the anodic reaction of hydroxide exchange membrane fuel cell (HEMFC) for converting H₂ to electric energy in sustainable manner. We demonstrate here an ultrathin Ru-based nanoflower modified with Pb (PbRuCu NF) as an active, stable, and CO-resistant catalyst for alkaline HOR. Mechanism studies show that the presence of Pb can weaken the adsorption of *H, strengthen *OH adsorption to facilitate CO oxidation, as a result of significantly enhanced HOR activity and improved CO tolerance. Furthermore, in situ electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) suggests that Pb acts as oxygen-rich site to regulate the behavior of the linear CO adsorption. The optimized Pb_1.04-Ru₉₂Cu₈/C displays a mass activity and specific activity of 1.10 A mg_Ru⁻¹ and 5.55 mA cm⁻², which are ≈10 and ≈31 times higher than those of commercial Pt/C. This work provides a facile strategy for the design of Ru-based catalyst with high activity and strong CO-resistance for alkaline HOR, which may promote the fundamental researches on the rational design of functional catalysts.     

Electron-transfer enhanced MoO2-Ni heterostructures as a highly efficient pH-universal catalyst for hydrogen evolution

Hydrogen is one of the most promising energy carriers to replace fossil fuels and electrolyzing water to produce hydrogen is a very effective method. However, designing highly active and stable non-precious metal hydrogen evolution electrocatalysts that can be used in universal pH is a huge challenge. Here, we have reported a simple strategy to develop a highly active and durable non-precious MoO_2-Ni electrocatalyst for hydrogen evolution reaction(HER) in a wide pH range. The MoO_2-Ni catalyst exhibits a superior electrocatalytic performance with low overpotentials of 46, 69, and 84 mV to reach-10 mA cm~(-2) in 1.0 M KOH, 0.5 M H_2SO_4,and 1.0 M PBS electrolytes, respectively. At the same time, the catalyst also shows outstanding stability over a wide pH range. It is particularly noted that the catalytic performance of MoO_2-Ni in alkaline solution is comparable to the highest performing catalysts reported. The outstanding HER performance is mainly attributed to the collective effect of the rational morphological design, electronic structure engineering, and strong interfacial coupling between MoO_2 and Ni in heterojunctions.This work provides a viable method for the synthesis of inexpensive and efficient HER electrocatalysts for the use in wide pH ranges.     

Nitrogen‐doped Carbon–CoOx Nanohybrids: A Precious Metal Free Cathode that Exceeds 1.0 W cm−2 Peak Power and 100 h Life in Anion‐Exchange Membrane Fuel Cells

Efficient and durable nonprecious metal electrocatalysts for the oxygen reduction (ORR) are highly desirable for several electrochemical devices, including anion exchange membrane fuel cells (AEMFCs). Here, a 2D planar electrocatalyst with CoO_x embedded in nitrogen‐doped graphitic carbon (N‐C‐CoO_x) was created through the direct pyrolysis of a metal–organic complex with a NaCl template. The N‐C‐CoO_x catalyst showed high ORR activity, indicated by excellent half‐wave (0.84 V vs. RHE) and onset (1.01 V vs. RHE) potentials. This high intrinsic activity was also observed in operating AEMFCs where the kinetic current was 100 mA cm^?2 at 0.85 V. When paired with a radiation‐grafted ETFE powder ionomer, the N‐C‐CoO_x AEMFC cathode was able to achieve extremely high peak power density (1.05 W cm^?2) and mass transport limited current (3 A cm^?2) for a precious metal free electrode. The N‐C‐CoO_x cathode also showed good stability over 100 hours of operation with a voltage decay of only 15 % at 600 mA cm^?2 under H₂/air (CO₂‐free) reacting gas feeds. The N‐C‐CoO_x cathode catalyst was also paired with a very low loading PtRu/C anode catalyst, to create AEMFCs with a total PGM loading of only 0.10 mg_Pt‐Ru cm^?2 capable of achieving 7.4 W mg^?1_PGM as well as supporting a current of 0.7 A cm^?2 at 0.6 V with H₂/air (CO₂ free)—creating a cell that was able to meet the 2019 U.S. Department of Energy initial performance target of 0.6 V at 0.6 A cm^?2 under H₂/air with a PGM loading <0.125 mg cm^?2 with AEMFCs for the first time.     

硫化MoO3／Al2O3甲烷化催化剂上不同吸附物种的作用

运用加压动态分析装置研究了硫化MoO_3/A1_2O_3,甲烷化催化剂上CO和H_2的吸附及反应。结果表明,在给定反应条件下催化剂上吸附的CO和H_2可分为可逆与不可逆两类,且对甲烷化反应有着不同的贡献。甲烷的生成是可逆吸附氢和不可逆吸附CO共同作用的结果。不可逆吸附氢与CO不生成甲烷,可逆吸附的CO加氢则与副产物乙烷等的生成密切相关。结合前人的动力学考察结果,解释了Mo系甲烷化催化剂与Ni系甲烷化催化剂要求不同反应压力的实质性原因。     

Reversible Electrocatalytic Activity of Carbon‐Supported PtxNi1−x in Hydrogen Reactions

Hydrogen oxidation and evolution reactions (HOR and HER) are studied on Pt_xNi_1?x/C materials synthesized by the bromide anion exchange method. Physicochemical characterization shows that this surfactant‐free method enables the preparation of well‐dispersed and effective catalysts for the processes involved in the anode of H₂/O₂ fuel cells (HOR) and the cathode of water electrolyzers (HER). The Pt‐based materials are modified with different Ni contents to decrease the amount of costly precious metal in the electrode materials. These modified Pt‐based materials are found to be electroactive for both reactions without additional overpotential. Kinetic parameters such as the Tafel slope, exchange (j₀) and kinetic current densities, and the rate‐determining steps of the reaction mechanisms are determined for each Pt–Ni catalyst and compared to those obtained at the Pt/C surface in alkaline medium. The high j₀ values that are obtained indicate a probable contribution of the surface structure of the catalysts due to their roughness and the presence of oxygenated Ni species even at low potentials.     

Catalytically Active Rh Sub‐Nanoclusters on TiO2 for CO Oxidation at Cryogenic Temperatures

The discovery that gold catalysts could be active for CO oxidation at cryogenic temperatures has ignited much excitement in nanocatalysis. Whether the alternative Pt group metal (PGM) catalysts can exhibit such high performance is an interesting research issue. So far, no PGM catalyst shows activity for CO oxidation at cryogenic temperatures. In this work, we report a sub‐nano Rh/TiO₂ catalyst that can completely convert CO at 223 K. This catalyst exhibits at least three orders of magnitude higher turnover frequency (TOF) than the best Rh‐based catalysts and comparable to the well‐known Au/TiO₂ for CO oxidation. The specific size range of 0.4–0.8 nm Rh clusters is critical to the facile activation of O₂ over the Rh–TiO₂ interface in a form of Rh?O?O?Ti (superoxide). This superoxide is ready to react with the CO adsorbed on TiO₂ sites at cryogenic temperatures.     

碳载合金 IrM（M = Fe，Ni，Co）纳米颗粒催化酸性与碱性介质中氢氧化反应

质子交换膜燃料电池(PEMFC)因能量转化率高、电流密度大、对负荷响应快及环境友好等优点而应用前景广阔.然而, Pt基催化剂的大量使用使得 PEMFC成本居高不下,阻碍了其商业化进程.金属 Ir具有良好的稳定性和相比 Pt较低的成本,可替代金属 Pt催化燃料电池阳极氢氧化反应.但是, Ir基催化剂的催化活性比 Pt低,难以满足商业化要求.通过合金调控 Ir纳米晶的电子结构和几何结构是降低 Ir用量、提高 Ir催化剂氢氧化活性的有效方法.
　　本文研究了 Ir基合金纳米晶中合金元素(Fe, Ni, Co)所产生的合金效应在酸碱性介质中对催化氢氧化的影响.采用溶剂蒸发-氢气还原法合成了具有相近合金度且平均粒径小于5 nm的 IrFe, IrNi和 IrCo纳米合金催化剂.电化学测试表明, IrNi合金催化剂具有最高的催化氢氧化活性.在酸性介质中, IrNi合金催化剂的质量比活性达到152 A/gIr (@0.1 V vs RHE),高于 IrFe (146 A/gIr)和IrCo (133 A/gIr)合金催化剂以及商业化 Pt/C催化剂(116 A/gPt).而在碱性介质中, Ir基合金催化剂活性较酸性介质中低,各合金催化剂优劣次序与酸性介质中一致.结构分析表明,合金化致使 Ir晶格收缩,收缩程度以 IrFe, IrNi和 IrCo的顺序依次降低. IrNi合金催化剂中 Ni合金元素诱导 Ir发生晶格收缩适中,使催化剂与中间物种(Had, OHad)的相互作用适度,从而获得最优的催化性质.另外,合金效应在不同 pH介质中影响不一：在酸性介质中,由合金元素(Fe, Ni, Co)导致的 Ir–Had相互作用弱化是提高氢氧化活性的主要原因;在碱性介质中,催化剂表面的亲氧效应决定了电极表面的 OHad吸/脱附性质和 Had表面覆盖度,从而影响催化氢氧化活性.     

Low‐Temperature CO Oxidation over a Ternary Oxide Catalyst with High Resistance to Hydrocarbon Inhibition

Platinum group metal (PGM) catalysts are the current standard for control of pollutants in automotive exhaust streams. Aside from their high cost, PGM catalysts struggle with CO oxidation at low temperatures (<200 °C) due to inhibition by hydrocarbons in exhaust streams. Here we present a ternary mixed oxide catalyst composed of copper oxide, cobalt oxide, and ceria (dubbed CCC) that outperforms synthesized and commercial PGM catalysts for CO oxidation in simulated exhaust streams while showing no signs of inhibition by propene. Diffuse reflectance IR (DRIFTS) and light‐off data both indicate low interaction between propene and the CO oxidation active site on this catalyst, and a separation of adsorption sites is proposed as the cause of this inhibition resistance. This catalyst shows great potential as a low‐cost component for low temperature exhaust streams that are expected to be a characteristic of future automotive systems.     

Improved hydrogen oxidation reaction under alkaline conditions by Au–Pt alloy nanoparticles

This work demonstrates the outstanding performance of alloyed Au_1 Pt_1 nanoparticles on hydrogen oxidation reaction(HOR) in alkaline solution. Due to the weakened hydrogen binding energy caused by uniform incorporation of Au, the alloyed Au_1 Pt_1/C nanoparticles exhibit superior HOR activity than commercial Pt Ru/C. On the contrary, the catalytic performance of the phase-segregated Au_2 Pt_1/C and Au_1 Pt_1/C bimetallic nanoparticles in HOR is significantly worse. Moreover, Au_1 Pt_1/C shows a remarkable durability with activity dropping only 4% after 3000 CV cycles, while performance attenuation of commercial Pt Ru/C is high up to 15% under the same condition. Our results indicate that the alloyed Au_1 Pt_1/C is a promising candidate to substitute commercial Pt Ru/C for hydrogen oxidation reaction in alkaline electrolyte.     

Understanding Alkaline Hydrogen Oxidation Reaction on PdNiRuIrRh High-Entropy-Alloy by Machine Learning Potential

High-entropy alloy (HEA) catalysts have been widely studied in electrocatalysis. However, identifying atomic structure of HEA with complex atomic arrangement is challenging, which seriously hinders the fundamental understanding of catalytic mechanism. Here, we report a HEA-PdNiRuIrRh catalyst with remarkable mass activity of 3.25 mA μg⁻¹ for alkaline hydrogen oxidation reaction (HOR), which is 8-fold enhancement compared to that of commercial Pt/C. Through machine learning potential-based Monte Carlo simulation, we reveal that the dominant Pd−Pd−Ni/Pd−Pd−Pd bonding environments and Ni/Ru oxophilic sites on HEA surface are beneficial to the optimized adsorption/desorption of *H and enhanced *OH adsorption, contributing to the excellent HOR activity and stability. This work provides significant insights into atomic structure and catalytic mechanism for HEA and offers novel prospects for developing advanced HOR electrocatalysts.     

甲烷在Ni/TiO2催化剂表面的活化

考察了Ni/TiO2催化剂甲烷部分氧化和二氧化碳重整制合成气的反应活性,实验表明,以TiO2为载体的镍系催化剂对于甲烷部分氧化制合成气反应具有较好的活性,尤其对H2的选择性较高,对二氧化碳重整制合成气反应具有较好的低温反应活性.采用脉冲-质谱在线分析等技术,在无气相氧条件下向Ni/TiO2催化剂脉冲CH4,发现甲烷在催化剂表面的活化（转化）及其氧化产物的选择性与金属催化剂表面氧的浓度密切相关.CH4与Ni/TiO2催化剂作用过程中存在明显的氢溢流和氧溢流现象,可能是这种溢流效应使得Ni/TiO2催化剂具有良好的反应活性和抗积碳性能.     

The Role of Discrepant Reactive Intermediates on Ru-Ru2P Heterostructure for pH-Universal Hydrogen Oxidation Reaction

Developing highly efficient electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cell (AEMFC). However, the kinetics of HOR in alkaline media is complicated, resulting in orders of magnitude slower than that in acid, even for the state-of-the-art Pt/C. Here, we find that Ru-Ru₂P/C heterostructure shows HOR performance with a non-monotonous variation in a whole pH region. Unexpectedly, an inflection point located at pH≈7 is observed, showing an anomalous behavior that HOR activity under alkaline media surpasses acidic media. Combining experimental results and theoretical calculations, we propose the roles of discrepant reactive intermediates for pH-universal HOR, while H* and H₂O* adsorption strengths are responsible for acidic HOR, and OH* adsorption strength is essential for alkaline HOR. This work not only sheds light on fundamentally understanding the mechanism of HOR but also provides new designing principles for pH-targeted electrocatalysts.     

甲烷在Ni/TiO_2催化剂表面的活化

考察了Ｎｉ／ＴｉＯ２催化剂甲烷部分氧化和二氧化碳重整制合成气的反应活性,实验表明,以ＴｉＯ２为载体的镍系催化剂对于甲烷部分氧化制合成气反应具有较好的活性,尤其对Ｈ２的选择性较高,对二氧化碳重整制合成气反应具有较好的低温反应活性．采用脉冲－质谱在线分析等技术,在无气相氧条件下向Ｎｉ／ＴｉＯ２催化剂脉冲ＣＨ４,发现甲烷在催化剂表面的活化（转化）及其氧化产物的选择性与金属催化剂表面氧的浓度密切相关．ＣＨ４与Ｎｉ／ＴｉＯ２催化剂作用过程中存在明显的氢溢流和氧溢流现象,可能是这种溢流效应使得Ｎ／ＴｉＯ２催化剂具有良好的反应活性和抗积碳性能．     

Remarkably Enhanced Hydrogen Oxidation Reaction Activity of Carbon-supported Pt by Facile Nickel Modification

Developing high activity catalysts for hydrogen oxidation reaction(HOR)under alkaline condition remains a challenge in the exchange membrane fuel cell(AEMFC).Herein,we report that the activity of carbon-supported platinum(Pt/C)towards the hydrogen oxidation reaction(HOR)in alkaline media can be remarkably enhanced by simple immersion of Pt/C in nickel chloride solution.The adsorption of hydrogen on the catalyst surface is weakened by modification of nickel.The HOR activity on the Pt/C after immersion possesses an excellent mass current density of 33.4 A/gmetal,which is 18%higher than that(28.3 A/gmetal)on Pt/C.     

Tuning the hydrogen and hydroxyl adsorption on Ru nanoparticles for hydrogen electrode reactions via size controlling

Controlling the particle size of catalyst to understand the active sites is the key to design efficient electrocatalysts toward hydrogen electrode reactions including hydrogen oxidation and evolution (HOR/HER). Herein, the hydrogen and hydroxyl adsorption on Ru/C could be effectively tuned for HOR/HER by simple controlling the particle sizes. It is found that the metallic Ru (Ru⁰) is the active site for HOR/HER, while oxidized Ru (Ru^x+) will hinder the adsorption and desorption of hydrogen on the catalyst. For the HOR, catalyst with small particles is more efficient, due to it is a three-phase interface reaction of gas on the surface of the catalyst. For the HER, the metallic state of Ru is crucial. The deconvolution of hydrogen peaks indicates that the catalytic sites with low hydrogen binding energy (HBE) shoulder the majority of the HOR activity. CO stripping curve further demonstrates that the stronger hydroxyl species (OH_ad) affinity is beneficial to promote the HOR performance. The results indicate that the design of efficient HOR/HER catalyst should focus on the balance between particle size and metallic states.     

纳米Li_2ZrO_3吸收剂原位移除CO_2强化水煤气变换反应制氢

采用浸渍法制备了在水煤气变换(WGS)反应中具有高催化活性的Ni/γ-Al2O3催化剂,使用柠檬酸法合成出高效CO2吸收剂Li2ZrO3纳米材料.在固定床微反应器上对WGS和吸附强化水煤气变换(SE-WGS)反应制氢过程进行了比较研究.前者只使用20%Ni/γ-Al2O3催化剂,而后者将20%Ni/γ-Al2O3催化剂与纳米Li2ZrO3吸收剂混合装填.结果表明,纳米Li2ZrO3具有比已报道的CO2吸收剂更快的吸收速率及优异的吸脱附循环稳定性,可应用于吸附强化过程,通过原位吸收WGS反应产生的CO2,使得反应超越化学平衡限制,直接制得高纯度H2.在823K,0.1MPa和H2O/CO=4的条件下,在SE-WGS过程一步制得纯度高于98%的H,验证了吸附强化反应进程制高纯氢的可行性.