B-doped Carbon Research Articles

Bifunctional 0D carbon quantum dot cathode electrocatalyst coupled with atomic hydrogen and hydroxyl radicals for efficient removal of oxytetracycline hydrochloride

Efficient removal of antibiotics is difficult to achieve by conventional single-oxidation or reduction processes. Herein, a bifunctional cathodic electrocatalyst coupling atomic hydrogen (H*) reduction with hydroxyl radical (·OH) oxidation in an efficient electrocatalytic process was developed for the effective degradation of oxytetracycline hydrochloride (OTC). Pd particles were dispersed on B-doped carbon quantum dots to prepare a Pd-B-doped carbon quantum dots/titanium (Pd-BCQD/Ti) electrode as a bifunctional cathode catalyst. The electrode can simultaneously generate H* through the H2O/H+ reduction process, H2O2 through the oxygen reduction process, and then generate ·OH. H* performs nucleophilic hydrogenation reduction of OTC molecules, and ·OH performs electrophilic oxidation of the carbon skeleton, and both act synergistically with the active chlorine species (HClO) generated at the anode. The experimental results showed that the electrode achieved 90.50 % removal of OTC within 60 min. In addition, the Pd-BCQD/Ti electrode reduces energy consumption while increasing current efficiency. The degradation effect was more than 85.80 % in the pH range of 3∼9, indicating fairly stable catalytic activity over a wide pH range. The degradation efficiency was basically unchanged after ten cycles, and the reactivity was still high in the actual water. Intermediates were analyzed based on LC-MS to explore the degradation pathways of OTC. The toxicity of the intermediates generated during OTC degradation was predicted based on quantitative conformational relationships. This study provides a feasible strategy for the preparation of bifunctional catalysts based on zero-dimensional BCQD for efficient green antibiotic wastewater treatment.

On mechanism of the synthesis of boron-doped graphitic carbon nitride

B-doped graphitic carbon nitrides (B-CNs) represent a promising class of materials that are potentially useful in a variety of applications. Their properties depend on the nature of the B-doping, which in turn is highly dependent on the particular chemical mechanism of B-doping formation. With this in mind, we present here the study of B-doping achieved by the co-calcination of CN-precursor (cyanoguanidine) and B-dopant (boric acid).In this study, the structural theory of the B–CN materials produced from different ratios of CN precursor and B-dopant was derived. Our proposed structure is supported by elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance. Based on our results, heptazine carbon replacing tetravalent B− species near the =N+=CN- structural unit is the dominant pattern of B doping in our co-calcined materials. The identification of the nature of the B-doping allowed us to infer the mechanism of its formation in the chemical reactions taking place during calcination.

Operando carbon corrosion measurements in fuel cells using boron-doped carbon supports

Carbonaceous materials are the most common catalyst supports in proton exchange membrane fuel cell (PEMFCs), yet their corrosion is one of the limiting factors in achieving high durability. Herein, we doped carbon supports with boron (B) to increase the corrosion-resistance of the support. Two types of B-doped carbons were synthesized and studied as platinum support materials. They varied in their morphologies, surface areas, and the types of boron species. The durability of Pt/B-doped carbon catalysts was investigated using the US-DOE catalysts’ supports accelerated stress test (AST) and a mass-spectrometer connected to the fuel cell effluent stream to quantify the mass of corroded carbon support in operando. The addition of boron to the carbon increased the stability of Pt catalysts in long-term usage of PEMFC. After 4000 AST cycles, more than 50 % of initial current density was preserved for the boron-containing systems, while less than 30 % of it remained with Vulcan carbon (Pt/V). Also, the Pt/B-doped carbon samples demonstrated better electrochemical active surface area (ECSA) stability when compared to Pt/V. Carbon loss measurements showed that B-doped carbons have higher resistance to electrochemical corrosion than unmodified carbon. Specifically, the substitutional boron-doped carbon demonstrated an extremely high stability and low corrosion rate.

Highly sensitive and novel dual-emission fluorescence nanosensor utilizing hybrid carbon dots-quantum dots for ratiometric determination of chlorpromazine.

Herein, a ratiometric fluorimetric nanosensor is introduced for the sensitive and selective analysis of chlorpromazine (CPZ) via employing blue-emitting B-doped carbon dots (B-CDs) as the reference fluorophore and green-emitting CdTe capped thioglycolic acid (TGA) quantum dots (TGA-CdTe-QDs) as the specific recognition probe. The sensor exhibits dual emission centered at 440 and 560nm, under a single excitation wavelength of 340nm. Upon the addition of ultra-trace amount of CPZ, the fluorescence signal of TGA-CdTe-QDs declines due to electron transfer process from excited TGA-CdTe-QDs to CPZ molecules, whereas the fluorescence peak of B-CDs is unaffected. Therefore, a new fluorimetric platform was prepared for the assay of CPZ in the range of 2.2 × 10-10 to 5.0 × 10-9M with a detection limit of 1.3 × 10-10M. Moreover, the practicability of the designed strategy was investigated for the detection of CPZ in biological samples and the results demonstrate that it possesses considerable potential to be utilized in practical applications.

Heterogeneous Ni-Boride/Phosphide Anchored Amorphous B-C Layer for Overall Water Electrocatalysis.

The rational design of efficient and economical bifunctional electrocatalysts remained a challenge for overall water electrolysis. In this work, the Ni-boride/ phosphide particles anchored amorphous B-doped carbon layer with hierarchical porous characteristics in Ni foam (Ni3P/Ni3B/B-C/NF) was fabricated for overall water splitting. The Boroncarbide (B4C) power was filled and fixed in the NF interspace through the electroplating and electroless plating, and then annealed in vacuum high temperature. The amorphous B-C layer derived from the B4 C not only speeded up the electron transport, but also cooperate with Ni-boride/phosphide to enhance the electrocatalytic activity for HER and OER synergistically. Furthermore, the hierarchical porous architecture of Ni3P/Ni3B/B-C/NF increased space utilization to load more active materials. The self-supported Ni3P/Ni3B/B-C/NF electrode possessed a low overpotential of 212 and 280 mV to deliver 100 mA cm-2 for HER and OER, respectively, and high stability for 48 h. In particular, the electrolyzer constituted with the Ni3P/Ni3B/B-C/NF bifunctional electrocatalyst only required a voltage of 1.59 V at 50 mA cm-2 for water electrocatalysis under alkaline medium, and demonstrated long-term stability for 48 h. This study provides a new technical path for the development of bifunctional of transition metal borides to promote the application of hydrogen production from water splitting.

Sources of the active substances in microwave catalytic redox processes induced by iron-based carbon materials: The key role of B doping

Organic and heavy metal water pollutants is an urgent environmental problem to be solved. Herein, a B-doped iron-based carbon material (FC-B) was synthesized and used in a microwave field for the degradation of sulfamethoxazole (SMX) and the reduction of Cr(VI). Under a low power of microwave irradiation (240 W), FC-B rapidly degraded SMX (99.8 %, 12 min) and reduced Cr(VI) (100.0 %, 14 min) without adding any oxidizing and reducing agents. SEM, XRD, XPS, and FTIR verified the successful synthesis of FC-B. And the “temperature visualization test” verified the existence of “hot spots”. The presence of O2− in the MW/FC-B system but not in the MW/FC system was verified by quenching experiments, electron paramagnetic resonance (EPR) experiments and nitro blue tetrazolium chloride (NBT) quantitative experiments, and then the conversion of microwave-generated electrons (e−) to O2− was elaborated using N2 blowing experiments, temperature-programmed desorption of O2 (O2-TPD), density functional theory (DFT) calculations and electrochemical tests. Subsequently, cycling experiments showed that FC-B has good reusability. Finally, the practical application of the MW/FC-B system was verified with antibiotic-containing farm wastewater. This study not only proposed a new technology for water pollution treatment, but also provided a pioneering explanation of the production of oxidizing substances in microwave-induced catalytic reactions.

B, S co-doped mesoporous carbon as an efficient catalyst for H2O2 electrosynthesis in natural seawater

The small-scale electrochemical synthesis of hydrogen peroxide (H2O2) in marine environments is of great significance for environmental wastewater treatment, and the design of electrocatalysts for complicated marine conditions is the key for this technology. Although B-doped carbon materials have been demonstrated to be resistant to Cl− poisoning, the deposition of Ca2+ on the surface of catalyst in seawater and the sluggish reaction kinetics of non-metallic catalysts remain to be solved. Herein, B, S co-doped mesoporous carbon materials were synthesized by a simple NaCl template method. The H2O2 yield of the as-prepared sample was up to 3.66 mol/(gcat h) with a Faradaic Efficiency (FE) of 97.98 % at 100 mA/cm2 in natural seawater, and achieved 100 % inactivation of bacteria and Chlorella within 5 min at a low current density. Based on the structural characterization and electrochemical results, the S-containing structure on the carbon matrix suppresses Ca2+ deposition due to its excellent proton adsorption activity. Furthermore, the electron transfer process between the reactant and BC3 was enhanced by the abundant mesoporous structure, so as to optimize the sluggish oxygen reduction reaction (ORR) kinetics on BC3. This work offers a strategy for inactivation of marine microorganisms and the degradation of organic pollutants, which promotes the advancement of marine wastewater treatment technology, and also provides reference for the design of metal free catalysts used in marine environments.

Surface Depassivation via B-O Dative Bonds Affects the Friction Performance of B-Doped Carbon Coatings.

Boron doping of diamond-like carbon coatings has multiple effects on their tribological properties. While boron typically reduces wear in cutting applications, some B-doped coatings show poor tribological performance compared with undoped films. This is the case of the tribological tests presented in this work in which an alumina ball is placed in frictional contact with different undoped and B-doped amorphous carbon coatings in humid air. With B-doped coatings, a higher friction coefficient at a steady state with respect to their undoped counterparts was observed. Estimates of the average contact shear stress based on experimental friction coefficients, surface topographies, and Persson's contact theory suggest that the increased friction is compatible with the formation of a sparse network of interfacial ether bonds leading to a mild cold-welding friction regime, as documented in the literature. Tight binding and density functional theory simulations were performed to investigate the chemical effect of B-doping on the interfacial properties of the carbon coatings. The results reveal that OH groups that normally passivate carbon surfaces in humid environments can be activated by boron and form B-O dative bonds across the tribological interfaces, leading to a mild cold-welding friction regime. Simulations performed on different tribological pairs suggest that this mechanism could be valid for B-doped carbon surfaces in contact with a variety of materials. In general, this study highlights the impact that subtle modifications in surface and interface chemistry caused by the presence of impurities can have on macroscopic properties, such as friction and wear.

Identifying the two-electron oxygen reduction mechanism on BC3 site in Cl−-containing electrolytes

The electrochemical synthesis of H2O2 has great potential for applications in the treatment of environmental pollution and energy, but the toxic effect of Cl− on the active sites of catalysts has severely limited the application of this technology in these fields. Developing efficient non-metal-doped catalysts represents an effective strategy to address this issue. Although B-doped carbon materials have demonstrated excellent ORR activity, the understanding of the ORR mechanism on B surface sites remains highly controversial, particularly in seawater electrolytes. The influence of Cl− adsorption behavior on the catalytic reaction center mechanism is still unknown. In this paper, catalysts containing the BC3 structure were successfully prepared with an H2O2 yield of 3.55 mol/ (gcat h) in simulated seawater. The DFT results demonstrated that BC3 functions as a 2e− ORR active site, and the presence of Cl− does not poison it. Instead, it promotes the hydrogenation process of *OOH on its surface, further enhancing its ORR performance. The results provide clarity on how the Cl− of the catalytic environment affects the ORR performance and pathway selectivity of non-metallic B-sites. Additionally, the results offer valuable insights for designing electrocatalysts in complex environments.

Synthesis of fluorescent carbon dots by B/P doping and application for Co2+ and methylene blue detection

During the synthesis of carbon dots, different heteroatom doping can change the fluorescence color and the emission wavelength when the same precursor is applied. In this study, we used o-phenylenediamine and L-lysine as raw materials, boric acid or phosphoric acid as different heteroatom dopants, and water as solvent to synthesize doped carbon dots through a simple microwave-assisted method. Finally, two kinds of doped carbon dots with different fluorescence colors under 365 nm UV light were obtained, of which the B-doped carbon dots (B-CDs) showed orange fluorescence, and the P-doped carbon dots (P-CDs) showed red fluorescence. Both carbon dots had satisfactory fluorescence quantum yields and can be used as fluorescence probes. Therefore, we investigated the detection performance of these two carbon dots when they were used as fluorescent probes. B-CDs can selectively detect Co2+ with a detection limit of 0.1102 μM, and at the same time, it can realize the naked eye detection of Co2+ in a certain concentration range. The P-CDs could sensitively detect methylene blue with a detection limit of 0.048 μM.

A universal method for N/B codoped carbon bubbles for enhanced potassium ion storage

Carbon materials are widely regarded as highly promising anode materials for potassium ion batteries due to their features of tunable structure, affordable price, excellent conductivity, and favorable chemical stability. However, due to the sluggish potassium storage kinetics and relatively severe volumetric effect brought about by the large radius of potassium ions, carbon materials often suffer from unsatisfactory reversible capacity and weak rate performance. In this work, we propose to prepare a distinctive dual-atom doped carbon bubble material by a simple self-templating method. This unique structural design results in a high specific surface area, large layer spacing, abundant pore structure and enriched active sites. Owing to these merits, the N, B-doped carbon exhibits a high reversible capacity (534.0 mA h g−1 at 0.1 A g−1 after 200 cycles), long-term cycling stability and excellent rate capacity when used as the anode for potassium-ion batteries. The results of electrochemical kinetic studies indicate that capacitance control effects play a dominant role in the total energy storage mechanism. Furthermore, this preparation method has good generalizability and is expected to have applications in other batteries, supercapacitors or catalysis.

Role of Curvature in Stabilizing Boron-Doped Nanocorrugated Graphene.

Boron-doped carbon nanostructures have attracted great interest recently because of their remarkable electrocatalytic performance comparable to or better than that of conventional metal catalysts. In a previous work (Carbon 123, 605 (2017)), we reported that along with significant performance improvement, B doping enhances the oxidation resistance of few-layer graphene (FLG) that provides increased structural stability for intermediate-temperature fuel-cell electrodes. In general, detailed characterization of the atomic and electronic structure transformations that occur in B-doped carbon nanostructures during fuel-cell operation is lacking. In this work, we use aberration-corrected scanning transmission electron microscopy, nanobeam electron diffraction, and electron energy-loss spectroscopy (EELS) to characterize the atomic and electronic structures of B-doped FLG before and after fuel-cell operation. These data point to the nanoscale corrugation of B-doped FLGs as the key factor responsible for increased stability and high corrosion resistance. The similarity of the 1s to π* and σ* transition features in the B K-edge EELS to those in B-doped carbon nanotubes provides an estimate for the curvature of nanocorrugation in B-FLG.

Self-supported heterojunction nanofibrous membranes for high-performance flexible asymmetric capacitors

Rational design of an electrode material with high flexibility and electrochemical performance is the key to wearable energy storage devices. Herein, a facile and productive needleless electrospinning method was introduced to prepare self-supported and flexible nanofibrous electrode materials for asymmetric capacitor. The MnO2 nanoclusters and ZIF67-derived Co3O4 nano-sheets were sequentially deposited on the surface of N, B-doped carbon nanofibers (hetero-junction MnO2/Co3O4/NB-PCNF). Attributing to the constructed multi-pathway for redox reactions on electrode, the specific capacitance of NB-PCNF and MnO2/Co3O4/NB-PCNF can reach up to 204.2F/g and 141.43F/g at a small current density of 0.1 A/g, respectively. In long-term cycling tests, the electrode materials exhibited excellent cycling stability and good rate capability. The electrodes were assembled with Potassium-ion hydrogel electrolyte to form a flexible asymmetric solid-state supercapacitor (FASS-SC). FASS-SC can reach a voltage window of 1.6 V. It provided 28.2 W h/kg at an energy density of 600 W/kg and a specific capacitance retention of 94.18 % after 10,000 cycles. The FASS-SC offers new research ideas for future flexible devices and wearable technologies.

Self-assembled B-doped flower-like graphitic carbon nitride with high specific surface area for enhanced photocatalytic performance

Graphitic carbon nitride (g-C3N4) is a promising nonmetallic photocatalyst. In this manuscript, B-doped 3D flower-like g-C3N4 mesoporous nanospheres (BMNS) were successfully prepared by self-assembly method. The doping of B element promotes the internal growth of hollow flower-like g-C3N4 without changing the surface roughness structure, resulting in a porous floc structure, which enhances the light absorption and light reflection ability, thereby improving the light utilization rate. In addition, B element provides lower band gap, which stimulates the carrier movement and increases the activity of photogenerated carriers. The photocatalytic mechanism and process of BMNS were investigated in depth by structural characterization and performance testing. BMNS-10 % shows good degradation for four different pollutants, among which the degradation effect on Rhodamine B (RhB) reaches 97 % in 30 min. The apparent rate constant of RhB degradation by BMNS-10 % is 0.125 min−1, which is 46 times faster compared to bulk g-C3N4 (BCN). And the photocatalyst also exhibits excellent H2O2 production rate under visible light. Under λ > 420 nm, the H2O2 yield of BMNS-10 % (779.9 μM) in 1 h is 15.9 times higher than that of BCN (48.98 μM). Finally, the photocatalytic mechanism is proposed from the results of free radical trapping experiments.

Novel B-doped FeNi/C alloy nanofibers electrocatalyst for efficient oxygen evolution reaction from water splitting

Industrial-scale water splitting processes will require economical and efficient electrocatalyst materials. Many oxygen evolution electrocatalysts prepared with non-precious metals have been reported. However, transition metal-based nanomaterials experience unavoidable aggregation and low stability in corrosion environments, which substantially reduces their catalytic performance. Herein, we successfully used a simple electrospinning technique followed by carbonation to synthesize a porous B-doped carbon fiber electrocatalyst with embedded B-doped FeNi alloy nanoparticles. To prepare the optimal catalyst sample, 1.05 g PAN, 5.0 mmol H3BO3, 2.5 mmol Fe(NO3)3, and 2.5 mmol Ni(NO3)2 were used as precursors. The electrospun pristine fibers were annealed for 1 h at 800 °C in argon. Its overpotential for oxygen evolution at a current density of 10 mA cm−2 was only 231 mV, and a 60.99 mV·dec−1 Tafel slope was achieved. At this current density, this catalyst exhibits good performance for over 24 h or for more than 1000 CV cycles. This is due to the doping of non-metallic B atoms into the alloy nanoparticles, as well as the support and protection on them by carbon nanofibers. Insight This research provides a more thorough understanding of the preparation and practical application of low-cost and high-efficiency transitional metal alloy based water splitting catalysts.

Highly fluorescent N, B-doped carbon nanodots performing as optical turn-off probes discerning Fe(II)

The interactions between metal ions and fluorescent probes are fundamentals for discerning the metal ions. Co-doped carbon nanodots (CNDs) have demonstrated the capacity to optically detect a wide variety of targets, including metal ions. In this work, the quenching of highly fluorescent, nitrogen (N) and boron (B) co-doped CNDs by Fe(II) ions was discovered and employed to differentiate Fe2+ in water samples and live cells. The fluorescence of the N,B-CNDs was quenched in a concentration-dependent manner with a need of very short reaction time (30 s), and the CNDs show good selectivity towards Fe(II) ions relative to other metal ions including Fe(III). The limit of detection (LOD) was calculated as 1.8 nM and the linear response range was 7 nM to 1 μM. The recovery percentage was determined to be 97%, 101%, and 103% for spiked Fe(II) concentrations of 31, 125, and 1000 nM, respectively, in tap water. The N,B-CNDs were able to monitor the presence of Fe(II) in living cells using the optical imaging of Fe(II) ions, and the quenching in cells was completed within one hour. Regarding the quenching mechanism, the photoinduced electron transfer (PET) procedure is proposed with support of cyclic voltammetry study on the CNDs upon addition of Fe(II). Overall, the N,B-CNDs promise as optical probes for the detection of Fe2+ in water and living cells, and demonstrated a satisfactory level of sensitivity and selectivity.

Co modified N, P, B tri-doped porous yolk-shell biochar microspheres as catalyst for oxygen evolution reaction

Designing low-cost and high-activity electrocatalysts is crucial for improving the slow kinetic process of the oxygen evolution reaction (OER) and meeting global energy demands. This study focuses on the preparation of a novel OER catalyst, labelled Co@NPBC, which exhibits a porous yolk-shell configuration. The structure of Co@NPBC consists of N, P, B-doped carbon microspheres, amalgamated with the transition metal Co, and it is fabricated via a simple impregnation–carbonisation method. The doping of heteroatoms has the potential to modify both the charge and spin density of carbon atoms, while the presence of Co enhances the electrical conductivity of the material, which accelerates the electron transmission process. The porous structure provided numerous active sites for the reaction to occur, specifically at the catalytic interface. Furthermore, the yolk-shell structure serves a supportive function, ensuring the stability of the overall catalyst architecture. Upon testing in an alkaline environment, the Co@NPBC material demonstrated exceptional OER catalytic activity (η10: 355 mV, Tafel slope: 71.4 mV·dec−1). The results showed that the synergistic effect of carbon microspheres doped with heteroatoms and Co nanoparticles increased the OER catalytic activity and subsequently enhanced water splitting efficiency. For a comparative analysis, catalysts with either single (Co@NC, Co@BC, and Co@PC) or double doping (Co@NPC, Co@NBC, and Co@BPC) were also prepared. The results showed that Co@NPBC exhibited better OER catalytic activity than the other catalysts.

Bi2MoO6 nanoflower-like microsphere photocatalyst modified by boron doped carbon quantum dots: Improving the photocatalytic degradation performance of BPA in all directions

Bi-based semiconductor photocatalyst represented by Bi2MoO6 (BMO) has obvious advantages in the degradation of bisphenol A (BPA), but three prominent problems that restrict the improvement of photocatalytic performance, namely, insufficient solar absorption, less active sites and serious photogenerated carrier recombination, need to be solved urgently. For this reason, we specially designed a simple structure of B-doped carbon quantum dots (BCQDs) modified BMO nanoflower-like microsphere composite to improve the photocatalytic performance of the system from the above three dimensions. The optimized BCQDs/BMO sample completely degraded BPA within 120 min under simulated sunlight, corresponding to an apparent constant of 0.03453 min−1, while the control sample of CQDs/BMO without B doping only degraded about 84 % of BPA within 160 min, with an apparent coefficient of 0.01138 min−1. Even after filtering out UV components below 400 nm, the degradation performance of the optimal composite catalyst did not decrease. The improved catalytic performance comes from the excellent up-conversion luminescence performance and good electron storage capacity of CQDs on the one hand, and the introduction of B on the other hand can adjust the surface structure of CQDs to generate more active sites and functional interfaces to further promote the catalytic reaction. Free radical trapping and electron spin resonance (ESR) tests have shown that·OH and·O2- are the main active substances in the degradation of BPA. The current BCQDs/BMO catalysts, despite their simple structure, can simultaneously improve the catalytic performance from the three important aspects mentioned above, which will guide the design of others semiconductor based photocatalysts.

Template synthesis of B-doped graphene-like carbon nanomaterial from phenylboronic acid

A template method for synthesis of B-doped graphene-like carbon nanomaterial (B-graphene-like carbon) with high surface area has been developed. In this method, magnesium oxide is used as a template where a carbon layer doped with boron atoms is deposited. Magnesium oxide carbonization was performed in an autoclave at 600 °C and 5 atm pressure using phenylboronic acid (FBA) dissolved in an ethanol-acetone mixture. Then, magnesium oxide from the С—B/MgO composite was dissolved in hydrochloric acid. The obtained B- graphene-like carbon was studied by IR spectroscopy, electron microscopy, XPS methods and quantum chemical calculations. B-graphene-like carbon contains 3–6 carbon layers and 0.2 wt% B. Structure of carbon net with embedded boron fragment has been proposed as the result of performed studies.

Frustrated Lewis pairs-engineered boron-doped 3D carbon nitride for improved electrocatalytic nitrogen reduction

It is of great importance to explore metal-free electrocatalysts with high electrocatalytic nitrogen reduction reaction (NRR) activity for ammonia (NH3) production. This work for the first time reports a three-dimensional (3D) boron (B) doped carbon nitride with frustrated Lewis pairs and deficiencies for efficient NRR via a facile copolymerization of sodium borohydride and urea precursors. The texture and the amount of B dopants in the resultant 3D carbon nitride can be finely tuned by varying the dosage of sodium borohydride. With the optimal B-doping content, the formed honeycomb-like 3D catalyst has a high NH3 yield rate of 17.8 μg h−1 mg−1 and Faradaic efficiency of 9.85% in 0.1 M Na2SO4 and 0.05 M H2SO4 electrolyte at −1.4 V vs RHE, which is considerably better than the undoped 3D carbon nitride. Comprehensive characterizations reveal that for the B-doped 3D carbon nitride, the unique 3D structure makes more introduced cyano groups and exposed nitrogen defects, favoring the contact between the electrolyte and the active sites. The abundant unsaturated B and N atoms function as frustrated Lewis pairs to strengthen N2 chemisorption and activation, lowing the barrier of NRR and meanwhile suppressing hydrogen evolution reaction. Moreover, in-situ UV–vis spectroscopy elucidates that the optimal potential at −1.4 V vs RHE benefits free electrons to participate in the NRR reaction because it matches the conduction potential of B-UCN-15. This study provides a new avenue for the rational design of nonmetal-based catalysts for NRR.