Interfacial Engineering of Cobalt Nitrides and Mesoporous Nitrogen-Doped Carbon: Toward Efficient Overall Water-Splitting Activity with Enhanced Charge-Transfer Efficiency

Abstract

Nonoxides have been widely employed as highly efficient catalysts for water splitting. However, these nonoxides suffer from obvious surface transformation and poor structural stability, which must be urgently remedied. Herein, the interfacial engineering of Co4N via mesoporous nitrogen-doped carbon (NC) was first carried out, in which NC can significantly suppress the oxidization of Co4N in alkaline media, ensuring the efficient interfacial charge transport between Co4N and NC. As a result, extremely low overpotentials @10 mA cm–2 of 62 mV (hydrogen evolution reaction, HER) and 257 mV (oxygen evolution reaction, OER) and small Tafel slopes of 37 mV (HER) and 58 mV dec–1 (OER) were achieved in alkaline media. Theoretical calculations suggest that their synergetic coupling effects can significantly facilitate the charge-transfer process and further greatly reduce the energy barrier for water splitting. This work underscores the importance of the surface engineering of nonoxides and efficient approaches for the design of stable catalysts for electrocatalysis.

Surface Reconstruction and Phase Transition on Vanadium–Cobalt–Iron Trimetal Nitrides to Form Active Oxyhydroxide for Enhanced Electrocatalytic Water Oxidation

“…The black dots and blurred lattice fringes are observed in the HRTEM images for CoVN@NF and CoVFeN@NF, which are possibly attributed to the multimetal nitride composites. [ 7a,11b ] In addition, the selected‐area electron diffraction (SAED) patterns further confirm that CoVN@NF and CoVFeN@NF are composed of multimetal nitrides (Figure S7a,b, Supporting Information), because the bright diffraction spots are irregularly distributed. These results are consistent with the XRD characterizations (Figure S4, Supporting Information).…”

“…For example, the surface of catalyst was converted to metal oxyhydroxide (*OOH) owing to fast surface reconstruction and phase transition during the electrochemical oxidation process in an alkaline environment. [ 10b,11 ] Generally, the oxyhydroxide species are considered as the active sites for OER. [ 3a,11a,b,12 ] Therefore, a thorough understanding of phase transition and surface reconstruction is crucial to figure out the catalytic origin and rationally design the OER electrocatalysts.…”

“…It was found that multimetal catalysts showed higher activity than the single‐metal counterparts, because the rich composition in electrocatalysts can increase the number of active sites and reduce the charge transfer resistance. [ 7a,8b,c,9b,10a,g,11c,13 ] Recently, it had been reported that earth‐abundant vanadium and iron with various valence states effectively improved the activity of cobalt and nickel‐based materials for OER due to favorable local coordination and energetics. [ 1b,8a,9c,10a,g,13a,14 ] For example, the multicomponent composites, [ 15 ] such as FeCo‐Co 4 N, [ 13a ] Co 3 FeN, [ 10g ] Co 2 (OH) 3 Cl/VO γ , [ 1b ] Fe x Co y ‐ONSs, [ 8a ] CoV‐UAH, [ 14b ] and Co 4 N‐VN 1− x O x , [ 14a ] can provide abundant active sites for highly efficient OER, indicating that catalysts with multiple metal elements showed favorable local coordination environments and electronic structures for highly improved catalytic performance.…”

Accurately Regulating the Electronic Structure of NixSey@NC Core–Shell Nanohybrids through Controllable Selenization of a Ni‐MOF for pH‐Universal Hydrogen Evolution Reaction

“…The O signal is attributed to surface oxidation during exposure to air. [ 39 ] The atomic percentages obtained from XPS analysis are provided in Table S1, Supporting Information. Narrower scans were taken to elucidate further information regarding the Ni x Se y @NC.…”

Efficient and stable electrocatalysts for water splitting

“…The water-splitting electrolyzer offers a green pathway to the cost-effective and high-purity production of hydrogen. Notably, several types of nanomaterials have demonstrated excellent electrocatalytic performance toward HER (e.g., NiMo nanowires, 51 V 8 C 7 , 52 and Co 4 N@nitrogen-doped carbon 53 ), OER (e.g., NiFe LDH, 54 Fe-LiNiO 2 , 55 and NiFeB; 56 LDH = layered double hydroxide), and overall water splitting (e.g., NiFe LDH@Cu nanowires@Cu foam, 57 NiFe MOFs@ nickel foams, 58 and NiFe LDH@Ni chains@nickel foam 59 ) that is comparable to or better than that of noble metals-based materials. Nevertheless, several issues still need special attention for further enabling water splitting.…”