Active sites engineering via tuning configuration between graphitic-N and thiophenic-S dopants in one-step synthesized graphene nanosheets for efficient water-cycled electrocatalysis

[Display omitted] •N, S co-doped graphene nanosheets (NSG) were synthesized via a bottom-up strategy.•All NSG are characterized by high surface area and highly graphitization degree.•The ratio of graphitic N and thiophenic S dopants in NSG affects their selectivity.•The optimized NSG exhibit efficient activity and stability for ORR, OER and HER.•The work provides a new insight on engineering active site of doped carbon materials. Precisely tuning synergetic effect between multi-heteroatom dopants in carbon matrix for water-cycled reactions such as hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is critical for fuel cell and water splitting technologies. Herein, an effective active sites engineering strategy of bottom-up synthesized N, S co-doped graphene (NSG) nanosheets was developed via a facile pyrolysis of the mixed solid power of 2,6-diaminopyridine (DAP) as N source and ammonium persulfate (AP) as S source. All NSG nanosheets prepared with various mass ratio of DAP and AP possess high surface area up to more than 1000 m2 g−1 and highly degree of crystallinity, but display significant differentiation in electrocatalytic selectivity, in which, the NSG prepared by DAP and AP with the mass ratio of 1:1 displays the highest ORR performance with a half-wave potential of 0.87 V vs. RHE, while the NSG with the mass ratio of 3:1 and 1:3 exhibit the highest activity for OER and HER respectively, achieving the corresponding potential of 1.58 V vs. RHE and 0.118 V vs. RHE at 10 mA cm−2, respectively. These activities are comparable and even better than their precious metal counterparts, outperforming the vast majority of reported doped carbon materials prepared using other strategies and precursors. The excellent eletrocatalytic activity and selectivity essentially originate from the optimized intermediates energy of three-reaction pathways via active sites engineering constructed by tuning the ratio of graphitic-N and thiophenic-S dopants in NSG nanosheets, obtained by controlling the ratio of precursors of DAP and AP. This tuning strategy of active sites provides an effective and convenient way to develop precisely function-orientated water-cycled electrocatalysts based on a certain platform of N-containing precursor.