HER Activity Research Articles

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

Nickel oxide/nickel nanohybrids for oxygen and hydrogen evolution in alkaline media

Ni-based materials are cost-efficient electrocatalysts for the oxygen and hydrogen evolution reactions (OER and HER). Specifically, high-valence nickel oxides have been recently identified as highly active for both reactions; however, the origin of their activity during operation, particularly towards the HER, is still undefined. Herein, electrodeposition was used to produce Ni-based electrocatalysts supported on carbon fiber paper, followed by UV/O3 treatment to oxidize and modify their surface chemistry. The resulting electrodes were composed of nanoclusters formed by a metallic nickel core and ultrathin sheets of a high-valence nickel oxide whose crystalline structure was similar to NiO2, with Ni2+/Ni3+ oxidation states. Upon investigating the effect of the electrochemical conditioning of these high-valence nickel oxide/nickel electrodes, confirming the formation of surface β-Ni(OH)2. This surface layer improved the performance of the electrode by providing active sites for H2O adsorption and dissociation, as indicated by detailed density functional theory (DFT) calculations. The origin of the higher HER activity of β-Ni(OH)2 (001) surface compared to NiO2 (2D), and Ni (111) surfaces is attributed to its unique electronic structure. The high valence nickel oxide/nickel electrodes possessed robust long-term OER and HER stability over 24h Finally, the potential for modifying the structural composition of these electrodes and their use as bifunctional electrocatalysts for the water-splitting reaction was demonstrated by using the resulting electrodes in an electrolyzer coupled with/without a photovoltaic cell.

Lower‐Temperature Synthesis of Nitrogen‐Rich Molybdenum Nitride/Nickel (Cobalt) Heterojunctional Assembly for the Effective Water Electrolysis

AbstractThe nitrogen‐rich molybdenum nitrides (N/Mo > 1) are promising for water electrolysis due to their increased activity and antioxidant ability. However, a higher temperature is needed in the usual synthesis for introducing more N, leading to the formation of large particles and the difficulty in controlling the morphology, thus limiting their catalytic performance. Here, a new strategy is reported based on the synergy of internal/external N sources (INS and ENS) toward Mo5N6‐based catalysts at a decreased temperature of 450 °C. The PMo12 clusters and Ni2+ (Co2+) are first combined with 2‐methylimidazole/melamine (INS) to give a flower‐like assembly. The subsequent pyrolysis under NH3 flow (ENS) gives the flowers composed of small Mo5N6/Ni (Co) heterojunctional particles that can expose more surface sites with an optimized electronic structure. The Mo5N6/Ni exhibits good HER activity close to Pt/C, and Mo5N6/Co shows superior OER performance to IrO2. The Mo5N6/Ni||Mo5N6/Co cell drives overall water splitting (OWS) at a low voltage of 1.397/1.74 V to achieve a current density of 10/100 mA cm−2 in the 1.0 M KOH. An anion exchange membrane water electrolyzer (AEMWE) based on the catalysts can achieve a current density of 450 mA cm−2 at 1.8 V with a long‐term stability of 120 h.

Construction of Ru-doped Co nanoparticles loaded on carbon nanosheets in-situ grown on carbon nanofibers as self-supported catalysts for efficient hydrogen evolution reaction

Exploring efficient and economical electrocatalysts to replace noble metal electrocatalysts has become a major research focus nowadays. In this paper, Ru-doped Co nanoparticles loaded on carbon nanosheet (CNS) in-situ grown on carbon nanofibers (Ru–Co@CNS/CNFs) were constructed as a self-supporting working electrode for high-efficiency hydrogen evolution. The prepared Ru–Co@CNS/CNFs possessed excellent catalytic activity with only 78 mV overpotential at 10 mA cm−2 current density and good stability with only 102 mV voltage attenuation at 100 mA cm−2 current density for 100 h continuous operation. The excellent catalytic performance could be attributed to the unique microstructure of the nanosheets in-situ grown on the nanofibers, it resulted in a higher Co surface density of 1.28 mg cm−2, indicating more loading of metal to improve catalytic activity of HER, and the formed Ru-doped Co nanoparticles could be evenly distributed on the carbon nanosheets to prevent the aggregation of nanoparticles, which could expose more active sites. Additionally, the density functional theory (DFT) calculations revealed Ru doping could accelerate the dissociation of water, optimize the adsorption energy of hydrogen intermediates and improve the kinetics of the HER reaction. This work provides a new approach to reduce the use of noble metals while improving the catalytic performance of catalysts.

Vacancy engineering-induced spin polarization in heterogeneous phosphides by simple iron salt infiltration for efficient overall water splitting

Optimizing electronic structure and facilitating electron transfer modulation in electrocatalyst is the key to enhancing overall water splitting (OWS) performance. In this work, the heterogeneous transition metal phosphide Fe-CoPv/Ni2P@NF, consisting of cobalt phosphide and nickel phosphide, is obtained by simple iron salt infiltration and high-temperature phosphatisation. Due to the doping of iron-atom and the formation of phosphorus vacancies, the activity of metal atoms with higher valence states and spins is induced, and then highly active Fe/Co-O-Ni channels are generated in the dynamic water-splitting process, thereby increasing the exposure of reaction center and total electron transfer rate. The catalytic mechanism is attributed to reducing the potential barrier of phase remodeling and optimizing the intermediate binding strength, thus thoroughly stimulating OER and HER activities. The Fe-CoPv/Ni2P@NF shows superior performance, requiring only total voltages of 1.626 V (OWS) to reach 100 mA·cm−2 and maintaining ultra-high stability for 500 h, suggesting promising industrial applications.

IrxCu0.5Ce0.5Ox/C nanocluster bifunctional electrocatalyst has high water splitting performance in acidic electrolyte

As an effective electrocatalyst for water decomposition, precious metals face limitations in widespread use due to their high cost. Incorporating other metals into precious metals to enhance electrocatalytic performance while reducing costs poses significant challenges. Within the realm of precious metals, Ir-based electrocatalysts have demonstrated remarkable catalytic activity for both oxygen evolution (OER) and hydrogen evolution (HER). This paper presents the synthesis of oxide-supported Ir-based catalysts containing Cu and Ce through a straightforward polyol reduction method. These catalysts exhibit notable OER and HER activity in acidic electrolytes. The addition of Ce increases oxygen vacancy, enhancing the catalytic performance of the optimized Ir3Cu0.5Ce0.5Ox/C clusters, surpassing IrO2 in OER with an overpotential of 274 mV at 10 mA cm−2. Moreover, these catalysts demonstrate outstanding performance when utilized as cathodes and anodes in H-type electrolytic cells. Overall, this study represents a significant advancement in the development of novel Ir-based electrocatalysts.

Robust self-supporting MoS2@Ni2B-GO/CNT electrode for enhanced hydrogen evolution reaction in acidic medium

Molybdenum sulphide (2D-MoS2) promises great potential as a hydrogen evolution (HER) catalyst, especially, when combined with conductive carbon supports like graphene oxide (GO) and carbon nanotubes (CNT). However, the hydrophobic nature of these carbon supports limits the catalytic potential of MoS2. To overcome this, we introduced hydrophilic Nickel Boride (Ni2B) into GO/CNT electrodes (Ni2B-GO/CNT), enhancing wettability (Contact angle-25.3°) and HER activity. By hydrothermally depositing MoS2 onto the hydrophilic Ni2B-GO/CNT electrode, we fabricated a self-supporting MoS2@Ni2B-GO/CNT electrode. The MoS2 deposition led to the formation of MoS2@Ni2B-GO/CNT heterostructure with multiple interfaces, favoring interfacial electronic redistribution (XPS) to significantly improve the HER activity. Thus, the proposed MoS2@Ni2B-GO/CNT electrode exhibited an excellent durability of 100 h (97%) and an overpotential of 224 mV at 10 mA cm−2 in acidic medium.

Surface reconstruction of hierarchical CoNiP@Ni2P nanoarray to promote overall water splitting

Efficient water splitting remains a challenge to produce clean and pure H2 in an industrial scale for the lack of high-performance cost-effective stable electrocatalysts of hydrogen and oxygen evolution (HER and OER). Surface engineering is a novel proposal to upgrade the electrocatalytic performances of HER and OER catalysts. Herein, a hierarchical architecture composed of carbon-supported CoNiP nanoplates (NPs) on Ni2P nanowire was constructed. The nanoarray of CoNiP@Ni2P heterostructure shows a high bifunctional activity of HER and OER. The overpotential is 46 mV required for HER at 10 mA·cm−2 and 292 mV for OER at 100 mA·cm−2 in 1 mol·L−1 KOH. In addition, the nanoarray of CoNiP@Ni2P heterostructure also shows a high stability for HER. The HER activity can be maintained at 11 mA·cm−2 without loss after 50 h cathode polarization at the overpotential of 100 mV, while the OER activity continuously increases from 26 to 64 mA·cm−2 at an overpotential of 400 mV after 50 h anode polarization. The enhancement of the oxygen evolution performance can be ascribed to the surface reconstruction of CoNiP/Ni2P heterostructure nanoarray, which can offer more active sites to OER. Density functional theory (DFT) reveals surface reconstruction can create an oxygen-rich surface in favor of intermediate adsorption, thus enabling a fast OER kinetics at the interface of NiCoOOH/Ni2P heterostructure. This work highlights surface reconstruction adaptability to design advanced catalysts of efficient water splitting for commercial H2 production.

Crystal facet/interface anchored Janus activity of BiOBr in driving photocatalytic water splitting

Constructing Janus junctions is expected to provide a novel perspective for analyzing the intrinsic photocatalytic activity of bismuth oxyhalide. Herein, Janus-typed BiOBr(010)/BiOBr(001) homojunction with efficiently photocatalytic H2 evolution has been achieved by a hydrothermal synthesis. The experimental results show that the designed Janus-typed junction can effectively elevate the carrier lifetime, significantly enhance the photocurrent, and prominently reduce the overpotential. The potential difference (0.34 eV) between (010) facet and (001) facet can drive the carrier transport at the interface for Janus junctions. Theoretical calculations indicate that the designed Janus junction has a stable mechanical structure, providing certain support for the long lifetime of the photocatalyst in the photocatalytic process. The carrier distributions in the Janus junction exhibit the typical characteristic distribution. Interestingly, the photo-generated electrons are only localized in BiOBr(001) component, which embodies significantly a role of n-type semiconductor. This essentially activates HER activity (32 µmol/h g−1) of Janus junction. The holes preferentially localize in the BiOBr(010) component of Janus junction. This component undertaking p-type role reduces the free energy of the rate determining step (from OH* to O*) in the oxygen evolution process (0.88 eV). The Janus junction intensively suppresses the carrier recombination probability at the high symmetry point (reciprocal space) in BiOBr. Ab initio molecular dynamics calculations show that the adsorbed water is easy to decompose on the surface of Janus junction. The obtained results of the photocatalytic water splitting further confirm that the designed BiOBr(010)/BiOBr(001) has Janus characteristics, which are consistent with theoretical calculations and tracer tracing results. The diffusion characteristics of hydrogen also evidence that the interaction of the internal electric field in the Janus junction can drive the HER performance. Additionally, these results offer us a unique angle of view to regulate the charge carrier dynamics by the highly oriented facet coupling for the layered semiconductor.

Electrodeposited manganese carbonate as an electrocatalyst for hydrogen evolution reaction in acidic medium

The electrolysis of water is the key method for hydrogen production but the high overpotential necessitates electrocatalysts. Traditionally, Pt is used, but it is scarce and costly. Herein, MnCO3 is unveiled as an electrocatalyst for the production of hydrogen. MnCO3 is electrodeposited onto pencil graphite by chronoamperometric method and confirmed by XRD and vibrational spectroscopic studies. MnCO3 electrodeposited for 15 min at 2 V demonstrates a good HER activity (overpotential of 123 mV to reach 10 mA cm−2) in 0.5 M H2SO4 with a Tafel slope of 79 mV dec−1. In addition, MnCO3 exhibited good stability during continuous operation (over 3000 cycles and 14 h). Though MnCO3 requires higher overpotential than the benchmark catalyst (Pt/C) to reach 10 mA cm−2, it outperforms Pt/C at higher current density (≥75 mA cm−2) demonstrating that MnCO3 could be used as an electrocatalyst to produce H2 at a high rate from acidic medium.

Clinical outcomes and ctDNA correlates for CAPOX BETR: a phase II trial of capecitabine, oxaliplatin, bevacizumab, trastuzumab in previously untreated advanced HER2+ gastroesophageal adenocarcinoma

Preclinical studies suggest that simultaneous HER2/VEGF blockade may have cooperative effects in gastroesophageal adenocarcinomas. In a single-arm investigator initiated clinical trial for patients with untreated advanced HER2+ gastroesophageal adenocarcinoma, bevacizumab was added to standard of care capecitabine, oxaliplatin, and trastuzumab in 36 patients (NCT01191697). Primary endpoint was objective response rate and secondary endpoints included safety, duration of response, progression free survival, and overall survival. The study met its primary endpoint with an objective response rate of 81% (95% CI 65–92%). Median progression free and overall survival were 14.0 (95% CI, 11.3–36.4) and 23.2 months (95% CI, 16.6–36.4), respectively. The median duration of response was 14.9 months. The regimen was well tolerated without unexpected or severe toxicities. In post-hoc ctDNA analysis, baseline ctDNA features were prognostic: Higher tumor fraction and alternative MAPK drivers portended worse outcomes. ctDNA at resistance identified oncogenic mutations and these were detectable 2–8 cycles prior to radiographic progression. Capecitabine, oxaliplatin, trastuzumab and bevacizumab shows robust clinical activity in HER2+ gastroesophageal adenocarcinoma. Combination of VEGF inhibitors with chemoimmunotherapy and anti-PD1 regimens is warranted.

Understanding the Degradation Mechanism for NiMo Composite and Effect of Ionomer on the Activity Towards HER

Hydrogen is an essential commodity for achieving cleaner and greener energy.1,2 Due to its high gravimetric energy density, hydrogen is favored as a carbon-neutral fuel.2,3 Moreover, the electrochemical accessibility of hydrogen evolution and oxidation reactions enable hydrogen to be used as a reversible fuel, as in hydrogen battery anodes and unitized reversible fuel cells.4,5 Platinum group metals (PGMs) are excellent catalyst for hydrogen chemistry, as they exhibit negligible activation barrier for HER and HOR, but they are costly and the upstream processes for mining and purification are unsustainable.6 A promising alternative to PGM catalysts would be nonprecious transition metal alloys/composites in form of nanoparticles. These materials are more readily available and lower in cost. Nonetheless, non-precious catalysts developed to date have never met the benchmarks set by PGMs in terms of catalytic activity and stability.Our lab is continuing a long-running effort to develop and improve nickel-molybdenum (Ni–Mo) composites, which stand as one of the strongest candidates for non-PGM HER and the HOR. In prior work, we developed a method to synthesize Ni–Mo nanoparticles supported on oxidized carbon, which increases catalyst dispersion and significantly reduces losses due to interfacial resistivity.7 The catalyst composite has a core@shell structure, where in the core is mainly nickel-rich alloy and the shell is primarily molybdenum-rich oxide.Furthermore, DFT calculations suggest the addition of Mo in the catalyst subsurface weakens hydrogen binding to surface Ni sites, thus increasing the overall activity toward HER/HOR.8 In ongoing work to further develop Ni–Mo/C composites, we are focusing on catalyst degradation under storage and operating conditions. To examine catalyst durability upon extended storage, we measured activity toward hydrogen evolution progressively for a single batch of catalyst powdered retained at room temperature in an aerobic environment over 850 hours. We observed a monotonic decrease in catalytic activity culminating in a >90% decrease in activity. Post-mortem analysis via XRD showed the increased peak intensities corresponding to NiO and MoO3. We further observed that the catalyst remains active over extended periods when stored under a dry, oxygen-free atmosphere. Finally, exposing the degraded catalyst to thermal reduction increased catalytic activity. Together, these results strongly suggest aerobic oxidation as the primary degradation mechanism under shelf-storage, with straightforward mitigations steps readily available by excluding air and water. This finding further suggests that oxide component of the synthesized catalyst is not an active site for hydrogen chemistry, although we speculate that some surface oxide is beneficial for enhancing the rate of water dissociation.9 We also studied the impact of the ionomer chemistry on the catalytic activity of Ni–Mo composites for alkaline anion exchange membrane (AEM) electrolyzer applications. Surprisingly, we observed an ~80% reduction in catalytic activity for Ni–Mo composites formulated into thin film HER catalysts using poly(aryl piperidinium) (PAP) carbonate AEM ionomers relative to control samples based on Na-exchanged Nafion ionomer binders. Further work showed this result was specific to the carbonate form of the ionomer, as HER activity was fully recovered when we used halide forms of the PAP ionomer. Work is ongoing to establish the physicochemical basis of this poisoning effect.Based on these findings, we developed functional AEM electrolyzer assemblies with IrOx anodes and Ni–Mo/C cathodes, where the cathode composition was formulated based on our best results from RDE studies. These MEAs yielded electrolyzer performance properties that were indistinguishable from MEAs we tested using Pt–Ru/C cathodes that were otherwise identical in composition.8 This leads us to conclude that advanced Ni–Mo/C catalyst composites can indeed achieve performance parity with PGM catalysts on the basis of initial catalytic activity, whereas significant work remains to characterize durability under extended operating conditions.

Engineered 2-D Heterostructures for Electrocatalysis

Atomically thin layered transition metal dichalcogenides (TMDs) such as MoS2, WS2, MoSe2 and WSe2 have been emerging as the cutting edge in materials science and engineering, due to their interesting electronic properties.1 These materials open up new opportunities for a variety of applications, including optoelectronics, energy conversion, and catalysis. To realize their potential device applications, it is highly desirable to achieve controllable growth of these layered nanomaterials, with tunable structure and morphology. TMDs exhibit promising catalytic properties for hydrogen generation and several approaches including defect engineering have been shown to increase the active catalytic sites.2,32D heterostructures based on various 2D layered materials with distinct properties have been demonstrated to exhibit novel physicochemical properties for their potential application in electrocatalytic hydrogen production. Here we present some of our efforts on morphological and photo/electrocatalytic studies of engineered 2D nanomaterials and their heterostructures.4-6 A seed-assisted chemical vapor transport (CVT) growth of ultra-thin triangular flakes of highly crystalline trigonal selenium (t-Se) oriented in (0001) direction, with lateral size >30 μm is demonstrated.[5,6] To study their promising photo-electrocatalytic properties and further realize the device applications, we employed a single-step CVT approach to grow selenene/WSe2 heterostructures. Vertical heterostructures of bi-layer selenene and monolayer WSe2 domains obtained via the CVT method are characterized by optical microscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The micro electrocatalytic reactor fabricated with Se/WSe2 heterostructure shows significantly improved HER activities upon shining the light. The work further extends to explore strain-engineered TMDs and their heterostructures towards efficient electrocatalytic hydrogen evolution reaction. References H. R. Gutiérrez, N. Perea-López, A. L. Elías, A. Berkdemir, B. Wang, R . Lv, F. López-Urías, V. H. Crespi, H. Terrones, M. Terrones, Nano Lett. 2013, 13 (8), 3447-3454.P.V. Sarma, T.V.Vineesh, R.Kumar, V.Sreepal, R.Prasannachandran, A.K. Singh, and M.M. Shaijumon, ACS Catalysis(2020), 10,6753–6762P. V. Sarma, A. Kayal, C. H. Sarma, M. Thalakulam, J. Mitra, and M. M. Shaijumon, ACS Nano, 13, 10448-10455 (2019).R. Prasannachandran, T. V. Vineesh, A. Anil, B. M. Krishna and M. M. Shaijumon, ACS Nano, 12, 11511–11519 (2018).R. Prasannachandran, T. V. Vineesh, M.B.Lithin, R. Nandakishore, M. M. Shaijumon, Chem. Commun., 56, 8623-8626 (2020).P.V. Sarma, N. Renjith et al., 2D Mater., 9, 045004 (2022)

Electrodeposited Ni-Fe-TiO2 Alloy Composites for the Hydrogen Evolution Reaction

Hydrogen is a carbon-free alternative energy source that is environmentally friendly, has high energy density, and is a promising fuel for future generations. Water splitting is an efficient way to produce hydrogen, requiring a catalyst with a small overpotential and Tafel slope, and good stability. However, only 4 % of global hydrogen is produced by water electrolysis due to high cost and lack of inexpensive replacements of the active platinum electrocatalyst.1 However, replacing these noble metal electrocatalysts with those comprised of lower, earth-abundant elements remains challenging as these materials impart a higher overpotential and thus require higher energy. Guided by the recognised enhancements of TiO2 particles in Co-Mo alloys for HER, earth-abundant, low-cost Ni and Fe metals are examined as composite electrocatalysts Ni-Fe-TiO2 towards HER.2 Nano-scale TiO2 particles were embedded into Ni-Fe alloys by using galvanic and pulse-reverse electrodeposition, onto rotating cylinder electrodes. Pulse-reverse electrodeposition considerably increased the concentration of the particles incorporated into the alloy. The composition and morphology were characterized by X-ray fluorescence (XRF) spectroscopy and scanning electron microscopy (SEM), respectively. The addition of particles to the electrolyte affected both the deposit composition and morphology. The alloy composites were then used as electrocatalysts in 1 M KOH to characterize HER via linear sweep voltammetry on the resulting hydroxide surface. The surface area was examined in a ferri/ferrocyanide electrolyte. The polarization data in 1 M KOH shows a significant reduction in the HER overpotential when TiO2 particles are present in the Ni-Fe deposit. The surface analysis of Ni-Fe and Ni-Fe-TiO2 confirmed that the improvement in HER activity is not due to surface roughness but an intrinsic one. The stability of the electrocatalysts under an electrolysis for HER was examined at -10 mA/cm2 for 24 hr and the working electrode potential remained stable over time; Tafel polarization curves after electrolysis were similar to those prior to electrolysis. References Le, P. A., Trung, V. D., Nguyen, P. L., Phung, T. V. B., Natsuki, J., & Natsuki, T. RSC advances, 13(40), 28262-28287 (2023).C. Wang, H. K. Bilan, and E. J. Podlaha. J. Electrochem. Soc. 166 F661 (2019). C. Wang and E. J. Podlaha, J. Electrochem. Soc. 167, 132502 (1~4) (2020).

La+3-doped CoFe2O4@MXene bifunctional electrocatalyst for superior OER and HER activity

La+3-doped CoFe2O4@MXene bifunctional electrocatalyst for superior OER and HER activity

Electrochemical imaging uncovers the heterogeneity of HER activity by sulfur vacancies in molybdenum disulfide monolayer

Electrochemical imaging uncovers the heterogeneity of HER activity by sulfur vacancies in molybdenum disulfide monolayer

CuO nanoparticles for enhanced photoelectrochemical HER activity

Cupric oxide nanoparticles are a p-type semiconductor that can be used as a hole transport layer material in perovskite solar cells owing to their high electrical conductivity and stability. In the present work, CuO nanoparticles are synthesized using the hydrothermal technique, and their photoelectrochemical properties are studied through cyclic voltammetry. The X-ray diffraction patterns of the nanoparticles were analyzed for phase formation, revealing the monoclinic phase and further verified by the Rietveld Refinement. Thermogravimetric analysis shows a total weight loss of 13.47%. Transmission electron microscopy analysis suggests the formation of nanoparticles with an average size of 34 nm. The selected area electron diffraction analysis reveals the crystalline structure of the nanoparticles. The absorbance spectra of the nanoparticles were analyzed by UV–visible measurement, and Tauc's relation was used to estimate the optical bandgap. The XPS results align with the XRD results, indicating the formation of pure CuO nanoparticles. The developed catalyst's photoelectrochemical performance was investigated in the neutral solution for the hydrogen evolution reaction activity, and a high photocurrent density of −41.57 mA/cm2 was observed versus −0.6 V vs. RHE.

Pd-substitution impact in nickel–cobalt spinel oxide grown on Ni foam as very effectual electrocatalyst for green hydrogen production supported by DFT study

The hydrothermal preparation of catalytic NiPdxCo2-xO4 (x ≦ 0.08) nano-electrocatalysts on Ni foam (NF) was successfully accomplished. The morphology and chemical composition of the catalysts are confirmed by advanced analytical techniques XRD, SEM, EDX, TEM, HR-TEM, and XPS. The NiPdxCo2-xO4 (x = 0.06) NF nano-electrocatalyst demonstrated remarkable performance in the HER, with an overpotential of 191.6 mV, a Tafel slope of 84.7 mV/dec, and extraordinary stability over 24 h using chronopotentiometry methods. The surface and electrochemical analyses demonstrated that the sample, doping with a 6.0% Pd2+ concentration, had appreciably enhanced performance in the HER. The improvement may be attributed to a much larger electrochemical surface area and fast charge transfer kinetics at the semiconductor and electrolyte interface. The influence of Pd dopants on the HER performance of CNs is studied with the help of density functional theory. It elucidates the way in which hydrogen and water molecules bind to the surface of PCN slabs. The theoretical results suggest that the incorporation of Pd dopants enhances the electrocatalytic process and boosts the HER activity as the concentration of Pd increases. The density of state spectra reveals their effect on spin-dependent electronic structure characteristics. Our findings point to a practical path for creating distinctive electrocatalysts that will serve as better electrodes for a variety of forthcoming hydrogen fuel cell applications.

Efficient photoreduction of CO2 to tunable syngas by Zn-doped Co3O4: Tuning binding strength to versatile reaction intermediates simultaneously

Photochemical reduction of CO2 (CO2RR) to syngas is an attractive approach for carbon–neutral recycling. Manipulating binding strength to reactive species on catalyst surfaces is challenging but essential for achieving efficient syngas production with a desired CO/H2 ratio. Here, we demonstrate that the binding strength to key reaction intermediates (*CO2, *H and *CO) on the Co3O4 surface can be fine-tuned by incorporating varying amount of Zn atoms. Dedicated experiments and theoretical simulations unveil that Zn doping allows for simultaneous control of both CO2 adsorption/activation and the adsorption affinity of *CO on Zn-Co3O4 catalysts, resulting in a significant enhancement in CO2 to CO conversion. Moreover, Zn doping can alter the hydrophilicity of the catalyst surface, affecting the water adsorption behavior and adjusting the hydrogen evolution reaction (HER) activity. As a result, the CO/H2 ratio can be readily tuned via varying the Zn doping level. This study presents an effective and economical method approach to manipulate the electronic structure of catalyst surfaces for controlling the kinetics of CO2RR and HER reactions, providing valuable insight into the design of highly active transition metal oxides (TMOs) based photocatalysts for syngas production with a tailored CO/H2 ratio.

An efficient multifunctional SnS2/g-C3N4 hierarchical nanoflower catalyst for electrocatalytic and photocatalytic applications

The rising energy demand via renewable sources and existence of organic pollutants in water has attracted the world-wide attention to attain sustainable ecosystems. The development of a multi-functional catalyst with significant economic and environmental implications remains a challenge. Herein, we synthesized SnS2/g-C3N4 hierarchical nanoflower using solvothermal method, verified by XRD and FTIR investigations. The surface morphology was analyzed using FESEM, TEM and HRTEM while optical absorption via UV–Vis spectroscopy. SnS2/g-C3N4 displayed outstanding electrocatalytic activity for HER and OER with smaller tafel slope and higher values of current density. The results are in accordance with Cdl and ECSA values, ensuing more active sites and surface area for a catalytic reaction to take place. As-prepared SnS2/g-C3N4 also exhibited 90 % photocatalytic MB deterioration in 90 min upon solar irradiation, following first order kinetics. Type-II mechanism for charge transfer alongwith reactive specie trapping experiment and cyclic stability is also presented. The findings suggests that SnS2/g-C3N4 emerged as proficient catalyst for electrocatalytic and photocatalytic applications.