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Rational design of transition metal catalysts with robust and durable electrocatalytic activity for hydrogen evolution reactions (HER) is extremely important for renewable energy conversion and storage, as well as water splitting. Heteroatom doping has emerged as a feasible strategy for enhancing electrocatalytic activity. Here, cobalt nanoparticles (Co-NPs) were coated with nitrogen-doped carbon nanotubes (NCNTs) prepared via an in situ growth on accordion-like Ti 3 C 2 T x -MXene (Co-NCNT/Ti 3 C 2 T x). Such an intriguing structure showed great features: abundant anchoring sites for NCNT in situ growth, intimate integration of Co-NPs and NCNTs, high-speed electron transfer between 1D NCNTs and 2D Ti 3 C 2 T x -MXenes, and a large number of effective catalytic active sites. This Co-NCNT/Ti 3 C 2 T x hybrid catalyst was demonstrated to possess excellent HER performance with low overpotential (η 10 , 190 mV), small Tafel slope (78.4 mV dec−1), large electrochemically active surface area, and good long-term stability, thus outperforming many reported electrocatalysts. The present strategy provided a facile route for the design of transition metal HER catalysts with NCNT and MXene. [Display omitted] • The 3D Co-NCNT/Ti 3 C 2 T x catalysts are prepared by a bottom-up approach. • The Ti 3 C 2 T x sheets was connected by NCNT, and high surface area was obtained. • The interconnected porous network is feasible to the high-speed charge transfer. • The as-prepared catalysts possesses superior electrocatalytic ability towards HER. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) plays a key role in the application of fuel cells. Here, we used shaddock peel to fabricate a set of N, P dual-doped hierarchical porous carbons, abbreviated as NPSPs, where the carbons were carbonized, activated and dual-doped via a simple one-step pyrolyzation. Contrast results indicate the contents of pyridinic-N, graphitic-N and P–C species increase with the rising of temperatures, and the temperature also affects the degree of graphitization, surface area, morphology, thus influences the ORR performance. More importantly, the NPSP-900 demonstrates an outstanding ORR activity with a comparable half-wave potential (0.83 V vs. RHE) and higher current density with respect to commercial Pt/C, following 4e transfer pathway. Our work illustrates that NPSP-900 is a promising cathode for fuel cells because of its simple preparation, waste utilization, excellent ORR performance, good methanol tolerance and superior stability. Image 1 • One-step pyrolysis can accomplish carbonization, activation and N,P-dual doping. • NPSPs own hierarchical porous structures with high BET surface areas. • Higher temperature can enhance ORR activities with improved doping N/P species. • NPSP-900 owns a close ORR activity compared with Pt/C, following 4e transfer way. • NPSP-900 shows a remarkable methanol tolerance and superior stability. [ABSTRACT FROM AUTHOR]