Active Sites For Hydrogen Evolution Reaction Research Articles

Synergistic Coupling of Hierarchical Heterostructured Ni3P/Ni/VN Microflower Electrocatalyst for Enhanced Hydrogen Evolution Reaction

AbstractThe exploration of economical and highly efficient electrocatalysts for hydrogen evolution reaction (HER) is paramount for the development of sustainable hydrogen economy. Herein, a novel three‐dimensional (3D) hierarchical microflower electrocatalyst comprised of N‐doped carbon‐armored Ni3P/Ni/VN heterogeneous nanoparticles (Ni3P/Ni/VN@NC) is developed by combining a hydrothermal method with in‐situ carbonization‐phosphating strategy. The unique robust hierarchical structure derived from 3D NiV layered double hydroxide (NiV‐LDH) skeleton as precursor provides multidimensional mass and charge transport channels as well as numerous active sites for HER, leading to the improved HER activity. More importantly, the possible electron transfer route of Ni3P→Ni→VN is demonstrated due to the charge pumping capability of VN during interfacial electron intercoupling among the tri‐component, which endows Ni3P/Ni/VN with the favorable absorption of hydrogen‐intermediates and thus upgraded HER kinetics over such heterostructure. The resulting Ni3P/Ni/VN@NC catalyst exhibits extremely low overpotentials of 81 mV and 134 mV to deliver a current density of 10 mA cm−2 without iR‐compensation in alkaline and acidic media, respectively, and maintains continuous operation for over 90 h. This work enlightens the rational design of hierarchical multi‐component heterostructured catalysts for efficient hydrogen production.

From the single-atom limit to the mixed-metal phase: finding the optimum condition for activating the basal plane of a FePSe3 monolayer towards HER.

Layered ternary transition metal tri-chalcogenides are some of the most promising candidates for hydrogen evolution reaction (HER) because of their ease of synthesis and affordability. However, majority of the materials in this category have HER active sites only at their edges, rendering a large portion of the catalyst useless. In this work, ways for activating the basal planes of one of these materials, namely, FePSe3, are explored. The effects of substitutional transition metal doping and external biaxial tensile strain on the HER activity of the basal plane of a FePSe3 monolayer are studied via first principles electronic structure calculations based on density functional theory. This study reveals that although the basal plane of the pristine material is inactive towards HER (value of H adsorption free energy, ΔGH* = 1.41 eV), 25% Zr, Mo, and Tc doping makes it more active (ΔGH* = 0.25, 0.22 and 0.13 eV, respectively). The effect of reducing the doping concentration, moving to the single-atom limit, on the catalytic activity is studied for Sc, Y, Zr, Mo, Tc and Rh dopants. For Tc, the mixed-metal phase FeTcP2Se6 is also studied. Among the unstrained materials, 25% Tc-doped FePSe3 gives the best result. Significant tunability of HER catalytic activity in the 6.25% Sc doped FePSe3 monolayer via strain engineering is also discovered. An external tensile strain of 5% reduces ΔGH* to ∼0 eV from 1.08 eV in the unstrained material, making this an attractive candidate for HER catalysis. The Volmer-Heyrovsky and Volmer-Tafel pathways are examined for some of the systems. A fascinating correlation between the electronic density of states and HER activity is also observed in most materials.

Broadened photocatalytic capability to near-infrared for CdS hybrids and positioning hydrogen evolution sites

Wide-spectrum light harvesting is critical in determining practical photocatalysis water splitting. Hybridization presents a viable strategy to broaden photocatalytic capability, yet the direct conversion of near-infrared (NIR) light remains a matter of great concern. Herein, a state-of-art ternary Au nanorods@MoS2-CdS (AMC) hybrid is designed to address this challenge. AMC achieves a leap-forward apparent quantum yield (AQY) of 1.06% at 700 nm and an AQY of 35.7% at 450 nm, extending the hydrogen evolution reaction (HER) capability of CdS hybrids to the NIR region firstly. It is revealed that the energetic hot electrons supplied by Au nanorods (NRs) are responsible for this extension. Indispensable, MoS2 performs a platform to collect the hot electrons from Au NRs and the photoinduced electrons from CdS. The HER active sites are positioned as MoS2-CdS interfaces both from experimental and theoretical viewpoints. This work opens up a new horizon for the forward of the wide-spectrum photocatalysis design.

Electronic structure regulation of nickel-iron layered double hydroxides by tuning ternary component for overall water splitting

NiFe layer double hydroxide (LDH) preserves high electrocatalytic activities for oxygen evolution reaction (OER); however, the catalytic performance on hydrogen evolution reaction (HER) is still suffering from poor catalytic activities. In this work, zinc (Zn)-doped NiFe LDH was synthesized as an excellent bifunctional electrocatalysts in alkaline electrolyte. For OER performance, the NiFeZn LDH achieves a Tafel slope of 35.2 mV/dec, which is much lower than that of commercial IrO2 catalysts (124.3 mV/dec). Expected, NiFeZn LDH also remains enhanced HER activity with an overpotential of 236 mV at 50 mA/cm2, superior to most of reported transition metal LDHs. The density functional theory results demonstrated that the Zn dopants could effectively manipulate the electronic structure of NiFeZn LDH, which is responsible to the enhanced active sites for HER.

Pt-Doped Biomass Carbon Decorated with MoS2 Nanosheets as an Electrocatalyst for Hydrogen Evolution

It is necessary to develop an efficient hydrogen evolution catalyst to improve the efficiency of the hydrogen evolution reaction (HER). Herein, a MoS2 nanosheet is decorated on the Pt-doping biomass yeast cells (MoS2@Pt/YC) via a simple hydrothermal process. Reducing the noble metal loading without compromising its performance is a challenging task. The smooth surface of YCs is conducive to the growth of MoS2 nanosheets, and its functional groups provide attachment sites for metal Pt. The Pt/YC is covered with MoS2 nanosheets, thus improving the exposed active sites for HER. The obtained MoS2@Pt/YC delivers a competitive overpotential of 118 mV at the benchmark current density of 10 mA cm-2 and achieves a small Tafel slope of 74 mV dec-1, indicating the great HER performance of MoS2@Pt/YC. Moreover, MoS2@Pt/YC shows robust stability after 24 h of continuous operation toward HER in acidic solution. By introducing transition metal sulfides with high specific surface area, the loading of precious metals can be reduced without compromising properties. This work provides a method to design Pt-doping HER electrocatalysts through a simple method. The facile preparation process for MoS2@Pt/YC and its outstanding performance allow it to be a promising electrocatalyst for practical HER application.

Bimetallic FeCo phosphide nanoparticles anchored on N-doped carbon foam for wide pH hydrogen evolution reaction

Transition metal phosphides (TMPs) have considered as excellent electrocatalysts with high reactivity for hydrogen evolution reaction (HER). While electro-catalytic properties of TMPs are restricted by uneven dispersion, small surface area, poor conductivity, and unsatisfied stability. Herein, a facile procedure was proposed to prepare a hierarchical structure of FeCoP nanoparticles anchored on N-doped carbon/multi-walled carbon nanotubes (NC/CNT) nanocomposites. With the increased porosity and conductive network of NC/CNT substrate, the as-synthesized NC/CNT-FeCoP provided abundant active sites for HER. Meanwhile, due to the synergistic effect between the dual metal centers and uniform distribution of bimetallic composites, the synthesized electrocatalyst can provide enhanced intrinsic activity. Therefore, the optimized NC/CNT-FeCoP delivered excellent HER activity in 1.0 M KOH and 0.5 M H2SO4 with overpotentials of 182 mV and 150 mV at 10 mA cm−2, respectively. Moreover, NC/CNT-FeCoP coupled two-electrode system needs a low cell potential of 1.68 V at 10 mA cm−2 for overall water splitting. First-principle calculations indicated that N-doped graphene substrate can adjust the electronic properties of surface metal site and consequently affect the H adsorption strength to yield an improved HER activity. Our work demonstrated that the combination of mesoporous conductive matrices with bimetallic phosphides could greatly improve the HER efficiency for electrocatalysis.

Observation of H2 Evolution and Electrolyte Diffusion on MoS2 Monolayer by In Situ Liquid-Phase Transmission Electron Microscopy.

Unit-cell-thick MoS2 is a promising electrocatalyst for the hydrogen evolution reaction (HER) owing to its tunable catalytic activity, which is determined based on the energetics and molecular interactions of different types of HER active sites. Kinetic responses of MoS2 active sites, including the reaction onset, diffusion of the electrolyte and H2 bubbles, and continuation of these processes, are important factors affecting the catalytic activity of MoS2 . Investigating these factors requires a direct real-time analysis of the HER occurring on spatially independent active sites. Herein, the H2 evolution and electrolyte diffusion on the surface of MoS2 are observed in real time by in situ electrochemical liquid-phase transmission electron microscopy (LPTEM). Time-dependent LPTEM observations reveal that different types of active sites are sequentially activated under the same conditions. Furthermore, the electrolyte flow to these sites is influenced by the reduction potential and site geometry, which affects the bubble detachment and overall HER activity of MoS2 .

Controlling the Surface Reactivity of Hybrid Ti3CN MXene via In‐situ Electrocatalysis

AbstractTwo‐dimensional (2D) carbide and nitride MXenes possess properties that are desirable for a broad range of electrocatalytic applications including the hydrogen evolution reaction (HER). These properties include high surface area, hydrophilicity, heterogeneity of redox‐active transition metals, and tunable surface functionalities allowing for low HER overpotentials. In this paper, we report on the cathodic etching and −O/−OH functionalization of hybrid Ti3CN upon the application of an external potential for improved HER performance and show that the active sites for HER on this MXene catalyst are located primarily on the −O− and −OH functional groups. The overpotential for the hybrid Ti3CN improves by 350 mV upon in‐situ −O/−OH functionalization and etching, reaching −0.46 V vs. RHE at a current density of 10 mA cm−2, much lower than those reported for the benchmark Ti3C2 carbide MXene. These results provide a path forward to tuning the electrocatalytic activity of MXenes and related electrocatalysts for water splitting.

Fabrication of 3D ordered mesoporous MoS2/C composite with few-layered MoS2 for electrochemical hydrogen evolution

MoS2 is a highly active catalyst for hydrogen evolution reaction (HER), but its active site for HER is limited to the edges. Thus structures exposing plenty of edges is desired for MoS2 to apply in HER. Porous three-dimensional (3D) structure full of few-layered MoS2 satisfies the requirement. In this work, a 3D ordered mesoporous structure MoS2/C composite with few-layered MoS2 was synthesized by liquid phase nanocasting method, using SBA-15 as hard template, sucrose as carbon source and ammonium tetrathiomolybdate (ATTM) as MoS2 precursor. The limiting effect of amorphous carbon makes thin MoS2 slices evenly dispersed, and avoids occurrence of MoS2 agglomeration, resulting in the exposure of a large number of MoS2 edges as active sites. The 3D ordered mesoporous structure of the catalyst provides high specific surface areas and ensures transport channels for material and electron for electrochemical HER. As a result, the composite demonstrates efficient HER activity with an overpotential of 165 mV at current density of 10 mA/cm2, and a Tafel slope of 91 mV under acidic conditions. This study provides a basis for constructing 3D HER catalyst with high specific surface area and few-layered MoS2 uniformly dispersed.

Superdispersed NiCo2S4 nanoparticles anchored on reduced graphene oxide for efficient hydrogen evolution reaction in acidic and alkaline media

Reasonable design and preparation of the earth abundant and efficient electrocatalysts for hydrogen production from the electrolysis of water is an effective solution to solve the growing global energy and environmental crisis. Herein, in order to increase the number of the active sites and fasten the charge transfer of NiCo 2 S 4 , a facile two-step solvothermal method is used to prepare superdispersed NiCo 2 S 4 nanoparticles anchored on reduced graphene oxide (NCS/rGO) as low-cost and high-efficient electrocatalyst for hydrogen evolution reaction (HER). By modulating the amount of rGO, the as-prepared NCS/rGO composite shows high specific surface area of 114.4 m 2 g −1 and small particle size of 50–60 nm, which exhibits excellent HER activity with a lower overpotential of 115 mV at 10 mA cm −2 and a smaller charge transfer resistance of 12 Ω in acidic solution. Additionally, in the case of alkaline solution, the as-prepared NCS/rGO composite also exhibits a low overpotential of 241 mV and a small Tafel slope of 110 mV dec −1 . The significantly improved HER performance of NCS/rGO composite can be ascribed to the constructed heterogeneous interface between NiCo 2 S 4 nanoparticles and rGO, which can inhibit the aggregation of NiCo 2 S 4 nanoparticles and enhance the intrinsic electrical conductivity. In light of the excellent HER electrocatalytic performance, the inexpensive NCS/rGO composite might be regarded as a promising alternative in HER and other energy conversion and storage applications. • Superdispersed bimetallic NiCo 2 S 4 nanoparticles anchored on rGO are obtained via a friendly solvothermal method. • The conductive graphene can avoid the agglomeration of NiCo 2 S 4 nanoparticles and facilitate the conduction of electrons. • The NiCo 2 S 4 /rGO composite possesses high specific surface area and provides rich active sites for HER. • The resulting NiCo 2 S 4 /rGO composite achieves enhanced HER activities in acidic and alkaline media.

Boosting the Stability of Oxygen Vacancies in α‐Co(OH)2 Nanosheets with Coordination Polyhedrons as Rivets for High‐Performance Alkaline Hydrogen Evolution Electrocatalyst

AbstractThe strong alkaline electrolytes are utilized in various key electrochemical applications and the severe corrosion by hydroxyl ions endows the development of high‐performance electrode materials with a great challenge. Here, an effective strategy is demonstrated to stabilize α‐Co(OH)2 under harsh alkaline electrochemical condition by coordination polyhedron pinning (MoO42−, WO42−) on the surface for hydrogen evolution reaction (HER). The addition of MoO42− in 1 m KOH can inhibit the attack of hydroxyl ions on oxygen vacancies in α‐Co(OH)2, and simultaneously modulate the electronic structure of active sites for HER. The theoretical calculations and experimental results reveal that MoO42− can be riveted on the surface of α‐Co(OH)2 to greatly stabilize oxygen vacancies and inhibit the formation of soluble ions of Co(OH)3−. The resultant active sites exhibit reduced maximum energy barriers for the optimized alkaline HER. Additionally, MoO42− near the interface between α‐Co(OH)2 and electrolyte can alleviate the accumulation of hydroxyl ions on α‐Co(OH)2 due to the electrostatic repulsion, improving the stability toward HER. This work offers insight into the role of coordination polyhedron ions in regulating and enhancing the stability of α‐Co(OH)2 for various potential electrochemical applications in alkaline electrolyte.

Two-Dimensional Covalent Heptazine-Based Framework Enables Highly Photocatalytic Performance for Overall Water Splitting.

Screening high‐efficiency 2D conjugated polymers toward visible‐light‐driven overall water splitting (OWS) is one of the most promising but challenging research directions to realize solar‐to‐hydrogen (STH) energy conversion and storage. “Mystery molecule” heptazine is an intriguing hydrogen evolution reaction (HER) building block. By covalently linking with the electron‐rich alkynyl and phenyl oxygen evolution reaction (OER) active units, 10 experimentally feasible 2D covalent heptazine‐based frameworks (CHFs) are constructed and screened four promising visible‐light‐driven OWS photocatalysts, which are linked by p‐phenyl (CHF‐4), p‐phenylenediynyl (CHF‐7), m‐phenylenediynyl (CHF‐8), and phenyltriynyl (CHF‐9), respectively. Their HER and OER active sites achieve completely spatially separated, where HER active sites focus on heptazine units and OER active sites located on alkynyl or phenyl units. Their lower overpotentials allow them to spontaneously trigger the surface OWS reaction under their own light‐induced bias without using any sacrificial agents and cocatalysts. Among them, CHF‐7 shows the best photocatalytic performance with an ideal STH energy conversion efficiency estimated at 12.04%, indicating that it is a promising photocatalyst for industrial OWS. This work not only provides an innovative idea for the exploration of novel polymer photocatalysts for OWS but also supplies a direction for the development of heptazine derivatives.

(Digital Presentation) In-Situ Oxygen Functionalization of Titanium Carbonitride MXene for Enhanced Water Splitting

Two-dimensional (2D) carbide and nitride MXenes possess properties that are desirable for a broad range of electrocatalytic applications including hydrogen evolution reaction (HER). These properties include high surface area, hydrophilicity, heterogeneity of redox-active transition metals, and tunable surface functionalities allowing for low HER overpotentials. In this presentation, I will report on the -O functionalization of Ti3CNTx (Tx = -O, -F, -OH) upon the application of external potential for improved HER performance and show that the active sites for HER on this MXene catalyst are located primarily on the O functional groups. The overpotential for the Ti3CN improves by 350 mV upon in-situ -O functionalization and reaches -0.46 V vs. RHE at a current density of 10 mA cm-2. Structural and electrochemical characterization results showed that the functionalized Ti3CNTx MXene catalyst is structural and electrochemically stable. Further insights into the mechanism of HER were provided by in-situ/operando Raman spectroelectrochemistry and the results will be presented. Ultimately, these findings provide a path forward to tuning the electrocatalytic activity of MXenes and related electrocatalysts for water splitting.

Theoretical Advances in Understanding and Designing the Active Sites for Hydrogen Evolution Reaction

As a fundamental step of water splitting and a stepping stone toward exploring other multielectron transfer processes, the electrocatalytic hydrogen evolution reaction (HER) is an ideal model for both fundamental understanding and electrocatalyst design. Here, we review the fundamentals and recent developments of theoretical insights into HER, covering the mechanistic aspects, key activity descriptors, local environment considerations, and advances beyond the computational hydrogen electrode. Although it is experimentally challenging to explore the active sites and mechanisms in the electrocatalytic process, computational and theoretical advances show great potential in identifying active sites and reaction mechanisms. In this Review, we especially focus in depth on theoretical insights in revealing and designing the active sites for HER. Major challenges ahead will also be discussed at the end of the Review.

Boosting the hydrogen evolution reaction of N-C@CoP through an N atom induced p-d orbital coupling

It is necessary to develop a highly efficient and stable catalyst in hydrogen evolution reaction (HER) to satisfy the demands for green hydrogen production. Herein, we find that an unconventional p-d orbital coupling exists in the interface between the N-C layer and CoP of the core–shell structured N-C@CoP, leading to a near-zero hydrogen adsorption energy of 0.16 eV. The doped N heteroatoms in carbon layer decrease the electrons on the adjacent C atoms, thus activating these C atoms as active sites for HER. Moreover, the activated three carbon atoms can interact with the Co atom in CoP, resulting in electron transfer from the p-orbital of C to the d-orbital of Co. Under this p-d orbital interaction, the N-C@CoP exhibits a η10 value of 35 mV and excellent long-term durability, which rivals the commercial Pt/C catalyst. This work provides a unique avenue for the design of composite catalysts with strong interaction.

Surface Anchoring and Active Sites of [Mo3S13]2- Clusters as Co-Catalysts for Photocatalytic Hydrogen Evolution.

Achieving light-driven splitting of water with high efficiency remains a challenging task on the way to solar fuel exploration. In this work, to combine the advantages of heterogeneous and homogeneous photosystems, we covalently anchor noble-metal- and carbon-free thiomolybdate [Mo3S13]2– clusters onto photoactive metal oxide supports to act as molecular co-catalysts for photocatalytic water splitting. We demonstrate that strong and surface-limited binding of the [Mo3S13]2– to the oxide surfaces takes place. The attachment involves the loss of the majority of the terminal S22– groups, upon which Mo–O–Ti bonds with the hydroxylated TiO2 surface are established. The heterogenized [Mo3S13]2– clusters are active and stable co-catalysts for the light-driven hydrogen evolution reaction (HER) with performance close to the level of the benchmark Pt. Optimal HER rates are achieved for 2 wt % cluster loadings, which we relate to the accessibility of the TiO2 surface required for efficient hole scavenging. We further elucidate the active HER sites by applying thermal post-treatments in air and N2. Our data demonstrate the importance of the trinuclear core of the [Mo3S13]2– cluster and suggest bridging S22– and vacant coordination sites at the Mo centers as likely HER active sites. This work provides a prime example for the successful heterogenization of an inorganic molecular cluster as a co-catalyst for light-driven HER and gives the incentive to explore other thio(oxo)metalates.

Metal-rich heterostructure of Ag-doped FeS/Fe2P for robust hydrogen evolution

The transition metal phosphides (TMPs) with highly active and low-cost are imperative electrocatalysts for hydrogen evolution reaction (HER). In particular, metal-rich interface engineering of iron phosphide could effectively modify the active sites for HER and accelerate the charge transfer, thus achieving the promoted efficiency. Herein, we report metal-rich heterostructure of Ag-doped Fe2P shell attached to FeS core on Fe foams (FeS/Fe2P–Ag@IF) for HER, which are synthesized by a simple hydrothermal method with subsequent low-temperature phosphorization. Notably, the phosphorization process simultaneously achieves the partial conversion of FeS to Fe2P, and complete reduction of Ag2S to Ag. Furthermore, the metal-rich structure of Fe2P increases the active sites for hydrogen adsorption, which consequently contributes to hydrogen evolution. Simultaneously, the successful doping of metallic Ag enhanced the electroconductivity and the stability of the electrocatalyst. Benefiting from the ternary synergistic effect at FeS/Fe2P–Ag@IF and metallic Ag doping, the optimal Ag-doped FeS/Fe2P electrocatalyst exhibits a low overpotential of 214.9 mV at 100 mA cm−2, even surviving at this large current density with long-term stability. This promising strategy involving metallic Ag doping may be a suitable option for the development of iron-based metal-rich phosphides heterostructured for HER.

Norbornane derived N-doped sp2 carbon framework as an efficient electrocatalyst for oxygen reduction reaction and hydrogen evolution reaction

Hitherto, the development of Pt free bifunctional electrocatalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is necessary for the advancement of sustainable and cost-effective solutions for energy conversion and storage technology. In this direction, herein we elucidated the usage of N doped sp2 hybridized carbon framework (N-CF) as a metal-free electrocatalyst for ORR and HER. This work inspects the effect of N doping that converts a hybrid structure of CF {Norbornane or bicyclo [2,2,1] heptane structure} into planar N-CF. A series of N-doped CF with different doping concentrations has been prepared using a facile and cost-effective technique. This robust electrocatalysts exhibits a promotional effect in the activity, porosity, thermal and electrochemical stability for the ORR and HER reactions. A rich delocalized electronic density of the sp2 bounded N species helps in modulating antibonding state of molecular oxygen and facilitates the breakage of OO bond in ORR. It also promotes proton adsorption via bonding between proton and valence electron rich catalyst surface to aid HER. The research sought to investigate the employability of N-CF for fabricating sustainable energy devices with electrocatalyst possessing multiple electrocatalytic activities for ORR and HER. Density Functional Theory (DFT) computations reveals that active sites for HER are carbon atom located at the edge close to pyrrolic nitrogen and adjacent to graphitic nitrogen dopants.

Magnetic FeM (M = Ag, Co, Cu, and Ni) nanocrystals as electrocatalysts for hydrogen evolution reaction

Iron-based magnetic nanocrystals (FeM@OAm, M = Ag, Co, Cu, and Ni; OAm = oleylamine) electrocatalysts have been successfully synthesized via oleylamine reduction of metal salts method. FeCo is arranged in a body-centered cubic (bcc) unit cell, while FeNi, FeAg, and FeCu are in a face-centered cubic (fcc) structure. All the samples have different morphologies with a diameter average size varying of 6.4 ± 1.0 to 21.7 ± 5.1 nm, depending on the bimetallic composition. The samples have ferrimagnetic behavior with low coercive field and high saturation magnetization values at room temperature. Furthermore, it has been shown that FeAg fits better in the solid solution category. Among heterogeneous electrocatalysts synthesized, FeCo nanocrystals show lower overpotential (−564 mV) in comparison to FeAg (−584 mV), FeNi (−666 mV), and FeCu (−591 mV). The Tafel plots showed that the hydrogen evolution reaction (HER) activity for electrocatalyst following a mixed of Volmer−Heyrovsky reaction mechanism, suggests that reaction Volmer is the determining step. In addition, all electrocatalysts showed stability in tests of continuous operations showing only low potential variation. The EIS study shows system characterized by two time-constant, both of them may related to the kinetics of the HER related to the charge transfer kinetics and the hydrogen adsorption. Thus, these materials are sustainable for electrochemical water splitting since showed acceptable electrocatalytic performance toward HER in alkaline media with excellent physical stability and abundance of active sites for HER.

Hierarchical Co/MoO2@N-doped carbon nanosheets derived from waste lotus leaves for electrocatalytic water splitting

It is imperative for electrochemical water splitting to seek functional materials with high performance, competence, durability, economical, and eco-friendly. Herein, we develop a simplistic two-step annealing strategy to synthesize the hierarchical Co/MoO 2 @nitrogen (N)-doped carbon nanosheets (CMO@NC) electrocatalysts derived from the low-cost and sustainable lotus leaves biomass for water-splitting. The optimum catalyst (CMO@NC/450) exhibits a notable low overpotential of 130 and 272 mV at a current density of 10 mA cm −2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH, owing to their unique surface features, large surface area, abundant meso/micropores, and high pyridinic N-contents. Also, the CMO@NC/450 catalyst-equipped with a two-electrode configuration exhibits notable water splitting activity only requires a cell-potential of 1.629 V@10 mA cm −2 in 1.0 M KOH. The results reveal that hierarchical flower-like morphology increases the contact area, prevents aggregation, and enables massive active-sites for HER and OER. Additionally, the synergistic effects between Co/MoO 2 and the N-doped-carbon heterostructure enhance charge-delocalization, ultimately improving electrocatalytic performance and stability. This work is aimed to promote the exploration and design of suitable doping structures and compositions for the development of highly effective and sustainable biomass-derived catalysts in a wide-range of electrochemical applications. A hierarchical Co/MoO 2 @NC nanosheets electrocatalyst derived from the low-cost and sustainable Lotus leaves biomass exhibits robust stability and good alkaline HER and OER activity. Lotus leaves biomass, developed as a particular structure and nitrogen-doped electrocatalyst, show significant water splitting performance. • Hierarchical Co/MoO 2 @NC are successfully fabricated from waste lotus leaves. • Electrocatalyst exhibits enhanced activity for HER and OER in alkaline media. • Lotus leaves biomass is a green, economical and sustainable precursor of N-doped C. • Self-N-doped carbon and rich pyridinic-N can efficiently improve catalytic activity.