Simultaneous H2 Evolution Research Articles

Enhanced interfacial electric field via sulfur vacancies modified ZnIn2S4-Vs@NiIn2S4 S-scheme photocatalysts for simultaneous H2 evolution and benzyl alcohol oxidation

Designing and developing efficient photocatalysts for H2 evolution and simultaneous oxidation of benzyl alcohol (BA) in aqueous environments provides a cutting-edge strategy for green synthesis. Nevertheless, the photocatalysts suffer from the low photoconversion efficiency because of the sluggish dynamics and repaid recombination of photogenerated charge carriers, which hindering their widespread applications. To address the limitation, a multifunctionnal sulfur vacancies (SVs) modified ZIS-Vs@NIS S-scheme heterojunction with a strong interfacial electric field effect was synthesized to use photocatalytic H2 production and BA oxidation, simultaneously. Experimental analysis supports that the synergistic effect of SVs and S-scheme heterojunction engineering result in a suitable energy band structure alignment and larger Fermi level potential difference. Those factors can realize effective charge transfer and separation, and enhance the photocatalytic performance. As anticipated, ZIS-Vs@NIS exhibited a superior photocatalytic performance with H2 and benzaldehyde (BAD) yields up to 168.1 and 146.1 μmol under the simulated solar-light irradiation for 1.0 h, respectively, which are approximately 13.3 and 11.8 times higher than pristine ZIS. Moreover, the photocatalytic H2 evolution coupled with BA oxidative dehydrogenation mechanism via S-scheme heterojunction over ZIS-Vs@NIS is also demonstrated in detail.

Hydroxymethylfurfural adsorption modulating charge separation characteristics of carbon-rich carbon nitrides for simultaneous photocatalytic hydrogen evolution and 2,5-diformylfuran production

Carbon-rich melon-based carbon nitrides (CNs), in which the sp2 N atoms and the terminal C–NH2 within the heptazine rings are partially replaced by the graphitic carbon atoms and C–H terminals, respectively, are synthesized through the condensation of 2,4,6-triaminopyrimidine-added supramolecular complexes comprising melamine and cyanuric acid. Optical characterizations reveal that increasing the C/N ratio in CNs improves their light-harvesting and charge-separation capabilities. Nevertheless, the photocatalytic activities of carbon nitrides reach an optimal level at an appropriate C/N ratio for simultaneous H2 evolution and 2,5-diformylfuran (DFF) production from 5-(hydroxymethyl)furfural (HMF) aqueous solution. Hydrogen evolution from water and DFF production by selective HMF oxidation are driven by photogenerated electrons and holes, respectively. Density functional theory calculations suggest that the adsorption of HMF on carbon-CN dramatically influences the molecular orbital contributions to the lowest singlet excited state, altering its charge separation character and, consequently, the photocatalytic activity. The improvement of charge separation in the optimized CN by HMF adsorption is further confirmed by experimental measurements.

All‐in‐One: Plasmonic Janus Heterostructures for Efficient Cooperative Photoredox Catalysis

AbstractJanus heterostructures consisting of multiple jointed components with distinct properties have gained growing interest in the photoredox catalytic field. Herein, we have developed a facile low‐temperature method to gain anisotropic one‐dimensional Au‐tipped CdS (Au−CdS) nanorods (NRs), followed by assembling Ru molecular co‐catalyst (RuN5) onto the surface of the NRs. The CdS NRs decorated with plasmonic Au nanoparticles (NPs) and RuN5 complex harness the virtues of metal‐semiconductor and inorganic‐organic interface, giving directional charge transfer channels, spatially separated reaction sites, and enhanced local electric field distribution. As a result, the Au−CdS−RuN5 can act as an efficient dual‐function photocatalyst for simultaneous H2 evolution and valorization of biomass‐derived alcohols. Benefiting from the interfacial charge decoupling and selective chemical bond activation, the optimal all‐in‐one Au−CdS−RuN5 heterostructure shows greatly enhanced photoactivity and selectivity as compared to bare CdS NRs, along with a remarkable apparent quantum yield of 40.2 % at 400 nm. The structural evolution and working mechanism of the heterostructures are systematically analyzed based on experimental and computational results.

All-in-One: Plasmonic Janus Heterostructures for Efficient Cooperative Photoredox Catalysis.

Janus heterostructures consisting of multiple jointed components with distinct properties have gained growing interest in the photoredox catalytic field. Herein, we have developed a facile low-temperature method to gain anisotropic one-dimensional Au-tipped CdS (Au-CdS) nanorods (NRs), followed by assembling Ru molecular co-catalyst (RuN5) onto the surface of the NRs. The CdS NRs decorated with plasmonic Au nanoparticles and RuN5 complex harness the virtues of metal-semiconductor and inorganic-organic interface, giving directional charge transfer channels, spatially separated reaction sites, and enhanced local electric field distribution. As a result, the Au-CdS-RuN5 can act as an efficient dual-function photocatalyst for simultaneous H2 evolution and valorization of biomass-derived alcohols. Benefiting from the interfacial charge decoupling and selective chemical bond activation, the optimal all-in-one Au-CdS-RuN5 heterostructure shows greatly enhanced photoactivity and selectivity as compared to bare CdS NRs, along with a remarkable apparent quantum yield of 40.2 % at 400 nm. The structural evolution and working mechanism of the heterostructures are systematically analyzed based on experimental and computational results.

Phosphotungstic Acid Clusters Decorated Znln2S4 Nanoflowers as Molecular-Scale S-Scheme Heterojunctions for Simultaneous H2 Evolution and Benzyl Alcohol Upgrading.

Simultaneous utilization of photogenerated electrons and holes to achieve overall redox reactions is attractive but still far from practical application. The emerging step (S)-scheme mechanism has proven to be an ideal approach to inhibit charge recombination and supply photoinduced charges with highest redox potentials. Herein, a hierarchical phosphotungstic acid (H3PW12O40, HPW)@Znln2S4 (ZISW) heterojunction was prepared through one-pot hydrothermal method for simultaneous hydrogen (H2) evolution and benzyl alcohol upgrading. The fabricated HPW-based heterojunctions indicated much enhanced visible-light absorption, promoted photogenerated charge transfer and inhibited charge recombination, owing to hierarchical architecture based on visible-light responsive Znln2S4 microspheres, and S-scheme charge transfer pathway. The S-scheme mechanism was further verified by free-radical trapping electron spin resonance (ESR) spectra. Moreover, the wettability of composite heterojunction was improved by the modification of hydrophilic HPW, contributing to gaining active hydrogen (H+) from water sustainably. The optimal ZISW-30 heterojunction photocatalyst indicated an enhanced hydrogen evolution rate of 27.59 mmol g-1 h-1 in benzyl alcohol (10 vol. %) solution under full-spectrum irradiation, along with highest benzaldehyde production rate is 8.32 mmol g-1 h-1. This work provides a promising guideline for incorporating HPW into S-scheme heterojunctions to achieve efficient overall redox reactions.

Construction of flexible BiOBr/W18O49/polyacrylonitrile discrete heterojunction nanofibers as a dual-functional photocatalyst for simultaneous hydrogen evolution and organic pollutant degradation

Dual-functional photocatalysis has attracted increasing attention due to its ability to achieve efficient synergistic hydrogen (H2) evolution and pollutant removal. Energy band structure engineering and surface morphology modification of photocatalysts is a useful strategy to improve the activity of photocatalysis. This paper uses a combination of electrospinning technology and hydrothermal method to prepare flexible BiOBr/W18O49/PAN discrete heterojunction flexible nanofibers (NFs) with staggered energy bands and spatially separated redox surfaces. The BiOBr/W18O49 heterojunction can improve carrier separation and migration, as evidenced by the photoluminescence and photoelectrochemical experiments. The localized surface plasmon resonance (LSPR) effect of W18O49 can achieve injection of “hot electrons” and lead to expanding the light absorption range according to the UV–visible-near infrared diffuse reflection spectra results. The discrete structure of BiOBr/W18O49/PAN NFs can provide spatially separated active sites for simultaneous photocatalytic redox reaction. As expected, the BiOBr/W18O49/PAN discrete heterojunction NFs greatly enhance the photocatalytic activity in simultaneous dual-functional reaction for H2 evolution and RhB degradation. The highest simultaneous H2 evolution rate and RhB degradation rate of BiOBr/W18O49/PAN NFs are 31.7 times and 34.1 times of BiOBr/PAN, respectively. The design and construction of this flexible discrete heterojunction NFs structures can provide novel ideas and directions for simultaneous dual-functional photocatalysts.

Dye‐Sensitized Photocatalysis: Hydrogen Evolution and Alcohol‐to‐Aldehyde Oxidation without Sacrifical Electron Donor

AbstractThere is a growing interest in developing dye‐sensitized photocatalytic systems (DSPs) to produce molecular hydrogen (H2) as alternative energy source. To improve the sustainability of this technology, we replaced the sacrificial electron donor (SED), typically an expensive and polluting chemical, with an alcohol oxidation catalyst. This study demonstrates the firstdye‐sensitized system using a diketopyrrolopyrrole dye covalently linked to 2,2,6,6‐tetramethyl‐1‐piperidine‐N‐oxyl (TEMPO) based catalyst for simultaneous H2 evolution and alcohol‐to‐aldehyde transformation operating in water with visible irradiation.

Dye-Sensitized Photocatalysis: Hydrogen Evolution and Alcohol-to-Aldehyde Oxidation without Sacrifical Electron Donor.

There is a growing interest in developing dye-sensitized photocatalytic systems (DSPs) to produce molecular hydrogen (H2 ) as alternative energy source. To improve the sustainability of this technology, we replaced the sacrificial electron donor (SED), typically an expensive and polluting chemical, with an alcohol oxidation catalyst. This study demonstrates the first dye-sensitized system using a diketopyrrolopyrrole dye covalently linked to 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) based catalyst for simultaneous H2 evolution and alcohol-to-aldehyde transformation operating in water with visible irradiation.

Design and construction of a novel immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co photocatalyst composite film for efficient norfloxacin degradation with simultaneous hydrogen evolution

The Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4 photocatalyst composite film (PCF) was prepared on the cobalt foil by using spin-coating and incomplete solid-state chemical reaction method, which solves the problems that the powder photocatalyst is difficult to recover and reuse and realizes the separation of CO2 and H2. In PCF, ZnO and ZnCo2O4 form a Z-scheme photocatalytic system and ZnCo2O4 and Co3O4 constitute a Type II-heterojunction photocatalytic system. The used cobalt foil acts as both a carrier of photocatalyst and a cathode. The structures and properties of PCF were studied by XRD, SEM, TEM, EDX, XPS, PL, TPR and EIS. Through photocatalytic norfloxacin degradation and hydrogen evolution, the effects of cobalt foil thickness, the coating Zn(OH)2 precipitation layer number, calcination temperature and calcination time on the photocatalytic performance of the Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co PCFs were investigated. When the cobalt foil thickness is 0.10 mm, coating Zn(OH)2 precipitation layer number is 2, composite film is calcined under 500 °C for 3.0 h and norfloxacin concentration is 10 mg/L and 50 mg/L, norfloxacin degradation ratio and H2 evolution amount reach 80.70 % and 357.12 μmol/dm2, respectively. In addition, a possible mechanism of norfloxacin degradation with simultaneous H2 evolution caused by immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co PCF was proposed. It is hoped that the work has certain guiding significance to design an immobilized PCF for organic pollutants degradation with synchronous large-scale hydrogen evolution.

Tuning interfacial charge transfer for efficient visible-light-driven photodegradation and simultaneous H2 evolution

The edge-graphitized carbon nitride (C3N4Cg) was prepared by secondary pyrolysis to construct ZnO/C3N4Cg (ZCN) type-Ⅱ heterojunction photocatalyst via a facile sonication dispersion method, which achieved ∼7.04-fold and ∼18.3-fold enhanced visible-light-driven photocatalytic performance for refractory micropollutant removal and simultaneous hydrogen (H2) evolution respectively compared to conventional ZnO/g-C3N4 Step-scheme heterojunction. The apparent quantum efficiency of the ZCN0.4 heterojunction reaches 0.92% (λ = 420 nm). Such excellent performance stems from that the edge-graphene moieties stitched onto the interface of heterojunction extend light absorption to the full visible spectrum, meanwhile, the built-in electric field generated during Fermi level alignment accompanying favorable band-bending structure provides an effective pathway for the rapid migration of photoinduced electrons via the edge graphene channel to improve interfacial charge separation efficiency. Interestingly, the midgap states introduced in ZCN heterojunction could temporarily retain photoexcited electrons to effectively inhibit the in situ carrier recombination for improved photocatalytic H2 evolution. Moreover, ZCN/peroxymonosulfate system exhibited excellent anti-interference performance against complex water bodies under visible illumination due to the synergistic effect between the co-existing anions and organic matter. Meanwhile, the eco-friendly nature of the ZCN/peroxymonosulfate system showed no biotoxicity of reaction filtrate on cell proliferation after treatment, which avoided secondary contamination. Considering the outstanding performance in photocatalysis, the ZCN system exhibits broad potential for practical applications in water pollution control and green energy production.

Solar light-driven simultaneous pharmaceutical pollutant degradation and green hydrogen production using a mesoporous nanoscale WO3/BiVO4 heterostructure photoanode

Photoelectrocatalysis is one of the most favourable techniques that could be used in this remit as it has the potential to utilise natural sunlight to generate oxidants in situ to mediate effective pollutant degradation. This work, therefore, utilises a mesoporous nanoscale WO3/BiVO4 heterostructure photoanode to effectively degrade ibuprofen in wastewater combined with simultaneous green hydrogen generation at the cathode under simulated sunlight. A near complete degradation (>96%) of ibuprofen (starting concentration of 100 mg/L), with no hazardous intermediates (determined via mass spectrometry analysis), along with simultaneous H2 evolution of 114 µmol/cm2 after 145 min was demonstrated in this work. In addition, intermediate product analysis, the role of the type of in situ oxidants on degradation, the mechanistic pathway of degradation, and the material characteristics of mesoporous photoanode were also investigated. First experimental evidence of in situ generated H2O2 contributing to the degradation of ibuprofen is presented.

0D/3D Bi3TaO7/ZnIn2S4 heterojunction photocatalyst towards degradation of antibiotics coupled with simultaneous H2 evolution: In situ irradiated XPS investigation and S-scheme mechanism insight

Photocatalytic pollutant degradation coupled hydrogen generation via water splitting utilizing solar energy is a highly promising method for solving the problems of environment pollution and energy shortage. However, restricted utilization efficiency of solar energy and quick recombination of photogenerated carriers of catalysts have restricted its application in photocatalytic pollutant degradation coupled hydrogen evolution. In this work, we synthesized a 0D Bi3TaO7 nanodots-decorated 3D ZnIn2S4 nanoflowers photocatalyst using a simple two-step solvothermal method. The simultaneously photocatalytic degradation of antibiotics (tetracycline) coupled with hydrogen generation was efficiently realized over the resultant S-scheme ZnIn2S4/Bi3TaO7 composites. The relationship between S-scheme heterojunction photocatalysts and photocatalytic pollutant degradation coupled hydrogen evolution will be discussed. As a result, optimized ZB20 composite achieves highly efficient TC degradation rate >90% after ten cycles coupled with simultaneous H2 evolution (13.7 μmol g-1h−1) with Pt cocatalyst. Furthermore, interfacial transfer mechanism of S-scheme heterojunction photocatalysts will be carefully examined combining in-situ characterization techniques and DFT study.

POM-incorporated ZnIn2S4 Z-scheme dual-functional photocatalysts for cooperative benzyl alcohol oxidation and H2 evolution in aqueous solution

Efficient aromatic alcohol oxidation with simultaneous H2 evolution under aqueous conditions is achieved in a polyoxometalate (POM)-incorporated ZnIn2S4 dual-functional photocatalytic system. The synergy between HPM and ZIS contributes to the formation of a Z-type heterojunction structure and thus enhances redox capacity. Moreover, the sub-nanometer size of POM clusters endows molecular-level interfacial contact, which acts as an "electron bridge" ensuring faster interfacial charge transfer kinetics. Therefore, an impressive nearly 100% yield of benzaldehyde and 10.6 mmol·g−1·h−1 H2-evolution rate are observed for POM/ZIS nanocomposites even under an anaerobic atmosphere with water as the solvent. This is the first application of POM-based materials in the anaerobic oxidation of benzyl alcohol with concomitant H2 production. This study expands the possibilities for designing multifunctional POM-based photocatalysts for economic and ecological photoredox applications.

0d/3d Bi3tao7/Znin2s4 Heterojunction Photocatalyst Towards Degradation of Antibiotics Coupled with Simultaneous H2 Evolution: In Situ Irradiated Xps Investigation and S-Scheme Mechanism Insight

0d/3d Bi3tao7/Znin2s4 Heterojunction Photocatalyst Towards Degradation of Antibiotics Coupled with Simultaneous H2 Evolution: In Situ Irradiated Xps Investigation and S-Scheme Mechanism Insight

Amorphous nickel borate as a high-efficiency cocatalyst for H2 generation and fine chemical synthesis

The exploration of active and low-cost cocatalyst is one of the most important topics in photocatalysis. Amorphous transition metal borates are a kind of promising cocatalyst with abundant unsaturated sites and high electrical conductivity. However, the relevant research is scanty. Here, we report the growth of Ni-Bi cocatalyst onto ZnIn2S4 nanosheets, for simultaneous H2 evolution and benzaldehyde production. The ZnIn2S4 nanosheet with a suitable band gap acts as an ideal photoactive substrate, while the Ni-Bi cocatalyst provides plentiful active sites and accelerates surface reactions. This study may enlighten the design of high-efficiency transition metal borates cocatalysts for photocatalytic application.

Spherical nanoflower-like bimetallic (Mo,Ni)(S,O)3-x sulfo-oxide catalysts for efficient hydrogen evolution under visible light

Photocatalytic H2O splitting by sulfide-based materials is a great challenge, because of the poor resilience of such materials against hole oxidation. Although sulfide ion of catalyst negatively shifts the valence band-edge relative to its oxide ion, the instability of sulfide ions during H2O oxidation is a critical obstacle to simultaneous evolution of H2 and O2. Here, active, stable, and spherical nanoflower-like bimetal (Mo,Ni)(S,O)3-x sulfo-oxide catalysts with a band gap of ∼2.1 eV and different concentrations of oxygen vacancy defects were synthesized for H2O splitting. (Mo,Ni)(S,O)3-x of 25 mg with a suitable amount of oxygen vacancy defects could evolve 587.5 μmol/h H2 under visible-light irradiation. This work demonstrated an example of converting an oxidation photocatalyst into a reduction one. Microstructure analysis showed that surface oxygen vacancy defects and the multiple-valence charges in Ni and Mo not only promoted effective separation, interface transfer, and reactions of photo-carriers but also reduced the charge build-up to avoid photo-corrosion during photocatalytic water decomposition.

Construction of hierarchical photocatalysts by growing ZnIn2S4 nanosheets on Prussian blue analogue-derived bimetallic sulfides for solar co-production of H2 and organic chemicals

Abstract Exploring highly efficient bifunctional photocatalysts for simultaneous H2 evolution and organic chemical production in pure water represents a green route for sustainable solar energy storage and conversion. Herein, a facile strategy was explored for preparing a hierarchical porous heterostructure of Fe4Ni5S8@ZnIn2S4 (FNS@ZIS) by the in situ growth of ZIS nanosheets on Prussian blue analogue (PBA)-derived bimetallic FNS sulfides. A series of FNS@ZIS hierarchical structures were facilely prepared by adjusting the loading amount (n%) of FNS (n = 19, 26, and 32 for FNS@ZIS-1-3). These structures can efficiently drive the solar co-production of H2 and organic chemicals. The optimal co-production was achieved with FNS@ZIS-2, affording a H2 evolution rate of 10465 μmol·g−1·h−1, along with high selectivity for the oxidation of benzyl alcohol to benzaldehyde (>99.9%). The performance was 22 and 31 times higher than that of FNS and ZIS, respectively, and even superior to the state-of-the-art results achieved using various sacrificial agents. Further mechanistic study indicated that the unique hierarchical core/shell architecture can facilitate interfacial charge separation, afford bimetallic synergy, abundant active sites and excellent photostability. This work highlights a simple and efficient method for preparing porous multimetallic hierarchical structures for the solar co-production of organic chemicals and H2 fuel.

All-solid-state Z-scheme Pt/ZnS-ZnO heterostructure sheets for photocatalytic simultaneous evolution of H2 and O2

The simultaneous production of the hydrogen and oxygen for photocatalytic water splitting still remains a critical challenge because O2 release from semiconductor catalysts is an extremely difficult. Herein, we design and synthesize a novel ZnS-ZnO heterostructure sheets by combining solid-state Z-scheme for photocatalytic O2 and H2 evolution. Electron spin resonance result confirms that a solid-state Z-scheme is successfully introduced into the ZnS-ZnO heterostructure. Thanks to the rapid separation and migration of photoinduced electron/hole according to the Z-scheme mechanism, ZnS-ZnO heterostructure exhibits efficient H2 evolution without using any sacrificial agent, far beyond the comparative values reported by currently ZnS/ZnO-based photocatalysts. Especially, the as-synthesized photocatalyst presents the ability of O2 evolution for pure water splitting using Pt as cocatalyst, which is too difficult to be realized for previously reported ZnO/ZnS-based photocatalysts. Therefore, this work presents a new idea to design other semiconductor photocatalysts for simultaneous H2 and O2 evolution.

Synthesis of nitrogen vacancies g-C3N4 with increased crystallinity under the controlling of oxalyl dihydrazide: Visible-light-driven photocatalytic activity

The photocatalytic activity of graphitic carbon nitride (g-C3N4) is restricted by its inherent shortcomings. Nitrogen (N) vacancies and crystallinity are two effective options to enhance the photocatalytic activity of g-C3N4. In this paper, oxalyl dihydrazide (ODH) was introduced as an environmental atmosphere control agent for the synthesis of N vacancies g-C3N4 with increased crystallinity. The increased crystallinity and N vacancies can effectively contribute to interlayer and intralayer exciton dissociation and charge transfer, respectively. They can modulate electronic band structure to boost visible light harvesting. The obtained visible-light (λ > 420 nm) photocatalytic efficiency of ODH-CN2 for tetracycline hydrochloride (TC-HCl) and sulfamethoxazole (SMZ) degradation was 79.9% (60 min) and 91.5% (120 min), respectively. These results are 39.8% and 36.7% higher than that of traditional g-C3N4 (CN), respectively. Moreover the visible-light photocatalytic H2 evolution rate of ODH-CN2 in triethanolamine solution with 3% Pt reached 5833.1 μmol h−1 g−1, approximately 4 times higher than that of CN. Subsequently, TC-HCl or SMZ were used as hole sacrificial agents to realize simultaneous H2 evolution and degradation of TC-HCl or SMZ over ODH-CN2 with 3% Pt. This study proposes promoting the photocatalytic activity of g-C3N4 by using an environmental atmosphere control agent to simultaneously form N vacancies and increase crystallinity, thus accelerating interlayer and intralayer exciton dissociation and charge transfer, respectively.

Hydrogenation of Carbonyl Compounds over Pd in Aqueous Phase Under Charged Conditions: Role of Organic Molecular Structure

Electrocatalytic hydrogenation (ECH) is a promising approach for energy conversion utilizing renewable electricity to transform biogenic carbon sources to more useful feedstocks. Carbonyl groups are one of the most abundant and highly reactive functionalities of bio-derived molecules. Recent studies of benzaldehyde ECH showed a higher activity of C-supported Pd compared to other metals, i.e., Pt, Rh, Ni. In the present study we explore this catalytic chemistry further, comparing the reduction of aromatic and aliphatic carbonyl compounds on Pd/C with the aim to understand the influence of molecular structure on the reaction pathways and selectivity in ECH. The experiments were conducted over the potential range of -0.1 VRHE to -0.3 VRHE at low temperatures and atmospheric pressure. The aromatic carbonyl compounds benzaldehyde, acetophenone, and furfural showed significant reactivity toward hydrogenation, whereas the aliphatic carbonyl compounds butyraldehyde and cyclohexanone exhibited small or negligible reduction rates. Under these conditions, the reactive carbonyls all reduced to alcohols without secondary products. The Figure demonstrates the result of the cathodic potential on the reduction of carbonyls. The H2 evolution reaction (HER) was the prevalent side reaction during ECH and increased exponentially with negative potential. Benzaldehyde reduction rates were highest and increase linearly, followed by acetophenone reduction rates, which plateaued at -0.2 VRHE. Furfural reduction rates increased exponentially with cathodic potential albeit with lower values than benzaldehyde and acetophenone. Rotating disk electrode (RDE) experiments showed that the presence of organic compounds affects charge transfer processes to an extent that is a function of the molecular structure. These results indicate a competitive adsorption of organic compounds and hydrogen on Pd and highlight the dependence of hydrogenation rates, HER rates and charge transfer on the molecular structure, which determines the adsorption strength of the organic molecules. TCH rates are plotted against their OCV values in the Figure, showing lower rates than ECH. This allows to conclude that an electrochemical mechanism is dominating the reaction under cathodic bias. The data agrees well with a kinetic model, where the first hydrogen addition (through a proton coupled electron transfer) is the rate determining step. This work helps to understand the influence of molecular structure on the rates of electrocatalytic hydrogenation of organic compounds and simultaneous H2 evolution. Our studies will enable predictive models - based on common principles in catalysis - to be applied to other metals and organic compounds. Figure 1