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Improving the kinetics of oxygen evolution is crucial for enhancing the performance of photoelectrochemical (PEC) water splitting. Herein, this study utilizes a chemical self-growth method to grow NiFe tannic acid complex (NFTA) and Co(OH) 2 on the surface of BiVO 4 photoanode (BiVO 4 /NFTA/Co). As a result, the synergistic effects of NFTA and Co(OH) 2 layers promote the efficiency and stability of BiVO 4 photoanode towards PEC water oxidation. The photocurrent density of the obtained BiVO 4 /NFTA/Co photoanode reaches 4.97 mA cm−2, which is significantly greater than those of BiVO 4 /NFTA (4.36 mA cm−2), BiVO 4 /Co (2.51 mA cm−2), BiVO 4 (1.34 mA cm−2), respectively. Detailed analysis confirms that NFTA could provide an efficient way to hasten the transfer of photo-generated holes on the photoanode surface and diminish the surface charge transfer resistance. In other hand, Co(OH) 2 could be served as a cocatalyst to accelerate charge transfer for efficient oxygen evolution reaction as well as a protective layer to maintain the long-term stability of NFTA on the surface of BiVO 4 during water oxidation. Such double oxygen evolution co-catalysts decoration strategy paves an effective pathway to enhance the PEC water oxidation performance of BiVO 4 photoanode. [Display omitted] • NiFe-tannic acid and Co(OH) 2 co-modified BiVO 4 realizes excellent PEC activities. • The enhanced PEC performance is due to the promoted charge transfer. • BiVO 4 /NFTA/Co photoanode attains 4.97 mA cm−2 at 1.23 V RHE with good durability. [ABSTRACT FROM AUTHOR]

Multicomponent metal/N-doped porous carbon with controllable structure is considered to be a promising candidates for efficient oxygen evolution and hydrogen evolution reaction. Herein, Mo-Co-Fe-MOF was preapred by a simple hydrothermal method, followed by high-temperature pyrolysis treatment to obtain the Mo-Co-Fe/NC. Benefit from the advantages of hierarchical structure and multicomponent, the Mo-Co-Fe-1.0/NC shows an overpotential of 257 and 320 mV to achieve the current density of 10 and 100 mA cm−2 for OER in alkaline KOH solution, respectively. In addition, the Mo-Co-Fe-1.0/NC exhibits the accelerated reaction kinetics during HER and OER reactions. The results provide a new perspective for design and preparation as well as kinetic characteristics of efficient OER and HER catalysts, which is expected to be used in the field of energy storage and conversion. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbonization of Fe-Co based metal organic frameworks (Fe-Co-MOFs) in N 2 obtains an electrocatalyst with Fe-Co anchored on N-doped porous carbon. The ratio of Fe and Co in the alloy can be controlled by adjusting the carbonization temperature. The electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) could be enhanced by the subtle Fe-Co modification significantly. Among these electrocatalysts, the Fe-Co/NC-800 presents the best HER and OER activity as well as reaction kinetics. The overpotentials at the current density of 10 ​mA ​cm-2 of Fe-Co/NC-800 are 182 and 279 ​mV (vs. RHE) for HER and OER, respectively. The Tafel slopes of Fe-Co/NC-800 are 157.8 and 42.7 ​mV dec-1 for HER and OER, respectively. The results suggest that adjusting carbonization temperature of Fe-Co-MOFs is an effective method to prepare highly efficient non-noble metal bifunctional electrocatalysts for electrochemical water splitting. A N-doped porous carbon anchored by Fe-Co efficient non-noble metal bifunctional electrocatalyst for HER and OER. The remarkable electrocatalytic performance will makes its potential to be used on electrocatalytic water splitting. [Display omitted] • The overpotentials at the current density of 10 ​mA ​cm-2 of Fe-Co/NC-800 are 182 and 279 ​mV (vs. RHE) for HER and OER, respectively. • The Tafel slopes of Fe-Co/NC-800 are 157.8 and 42.7 ​mV dec-1 for HER and OER, respectively. • The charge transfer resistance of Fe-Co/NC-800 is only 40 ​Ω, indcating a faster charge transfer process during the electrocatalytic reaction process. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional (3D) self-crumpled carbon nanoarchitectonics has been synthesized by GO-assisted carbonization, where GO not only serves as a template but also as a catalyst for carbonization of glucose (GLC). It is revealed that dehydration condensation reaction between -OH of GLC and -COOH of GO induces the anchoring of GLC on the surface of GO under high temperature and acidic environment, and subsequently, the dehydration of GLC produces 5-hydroxymethylfurfural (5-HMF) and epitaxially polymerizes and carbonizes into a two-dimensional carbon along GO sheets. In this step, GO provides both nucleation sites and template for the directional polymerization and carbonization of GLC. Due to the catalytic effect of GO, the activation energy of polymerization of GLC is reduced from 114.0 KJ mol−1 to 89.25 KJ mol−1 after the addition of GO, and the composite is transformed from two-dimensional nanosheets to three-dimensional crumpled structure by the capillary force of water evaporation. Due to the unique graphene-like structure, high conductivity offered by GO after heat treatment and more C-O groups derived from GLC, CG-50 shows good electrocatalytic performance. The overpotential is only 438 mV vs. RHE at the current density of 10 mA cm−2, and the Tafel slope is 102 mV dec−1. • The simultaneous catalytic and template function of GO for glucose was proved and discussed thoroughly. • Glucose-based crumpled graphene-like carbons with high porosity and conductivity were obtained. • The unique graphene-like structure, high conductivity and C-O groups help CG-50 show good electrocatalytic performance. • At the current density of 10 mA cm-2, the overpotential was only 438 mV and the Tafel slope was 102 mV dec-1. [ABSTRACT FROM AUTHOR]

Co 8 FeS 8 /Fe 7 S 8 @N-doped porous carbons (Co 8 FeS 8 /Fe 7 S 8 @NC) were prepared via a simple two-step pyrolysis method. Co 8 FeS 8 /Fe 7 S 8 @NC contains Co 8 FeS 8 , Fe 7 S 8 , amorphous and graphitic carbon. Existence of a large number of mesopores in the sample was conducive to the transmission of mass and electrons as well as exposure of active sites. Co 8 FeS 8 /Fe 7 S 8 @NC-0.8 needs overpotentials of 255 and 315 ​mV to achieve the current density of 10 ​mA ​cm−2 and 100 ​mA ​cm−2, respectively. The lower Tafel slope (59.5 ​mV dec−1) and good durability have also been observed in the Co 8 FeS 8 /Fe 7 S 8 @NC-0.8. The 2C dl value of 83.7 ​mF ​cm−2 indicate that the introduction of 0.8 ​g thiourea could greatly improve the exposure of electrocatalytic active sites. Therefore, this research provides a new perspective for the development of efficient and low-cost electrocatalysts with industrial application prospect. [Display omitted] • Co 8 FeS 8 /Fe 7 S 8 @NC-0.8 only needs overpotentials of 255 and 265 ​mV to achieve the current density of 10 ​mA ​cm−2 and 100 ​mA ​cm−2, respectively. • The Co 8 FeS 8 /Fe 7 S 8 @NC-0.8 has a very low Tafel slope (59.5 ​mV dec−1) and good durability. • Introduction of thiourea (0.8g) could greatly improve the exposure of electrocatalytic active sites and reduce the interface resistance. [ABSTRACT FROM AUTHOR]