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• Topochemical self-nitridation is developed for constructing g-C 3 N 4 -based composites. • Regulable Ni/Ni 3 N nano-heterostructures are in-situ anchored on N-defective g-C 3 N 4. • A synergistic effect can be achieved due to the heterointerface between Ni and Ni 3 N. • Ni/Ni 3 N/g-C 3 N 4 composite shows boosted bifunctional alkaline HER and OER activity. • Ni/Ni 3 N/g-C 3 N 4 (+||−) electrolytic cell works efficiently for overall water splitting. The growth of base-metal-based heterostructures on metal-free carriers is considered an effective strategy for designing low-cost high-efficiency hybrid electrocatalysts with electronic modulation for bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as further overall water splitting (OWS). Herein, Ni/Ni 3 N heterostructures with regulable composition are grown in-situ on N-defective graphitic carbon nitride (g-C 3 N 4) through a novel ammonia-free topochemical self-nitridation route. Benefitting from the synergetic effect between Ni/Ni 3 N heterointerface and the strong support of g-C 3 N 4 carrier, the as-fabricated Ni/Ni 3 N/g-C 3 N 4 composite performs superior capacity toward both HER and OER in alkaline conditions. The optimal Ni/Ni 3 N/g-C 3 N 4 sample requires low overpotentials for HER (55 mV) and OER (253 mV) to drive a current density of 10 mA cm−2, along with long-term durability. Furthermore, the constructed Ni/Ni 3 N/g-C 3 N 4 (+||−) electrolytic cell for alkaline OWS can afford a current density of 10 mA cm−2 under a voltage of 1.556 V with outstanding stability. [Display omitted] [ABSTRACT FROM AUTHOR]

The requirement for a sustainable and renewable energy has inspired substantial interests in designing and developing earth-abundant and high-effectiveness electrocatalysts/electrodes for fuel cells and metal-air batteries, in which oxygen reduction reaction (ORR) plays a crucial role. Perovskite oxides have acquired rapid attention as ORR electrocatalysts to replace noble-metal-based catalysts owing to their intrinsic electrocatalytic activity, compositional and structural flexibility. Herein, we report a new Sc and P co-doped perovskite oxide (La 0.8 Sr 0.2 Mn 0.95 Sc 0.025 P 0.025 O 3- δ , LSMSP) as an active and robust electrocatalyst for the ORR in an alkaline solution. LSMSP electrocatalyst shows superior ORR activity and stability than those of pristine La 0.8 Sr 0.2 MnO 3- δ (LSM), Sc-doped LSM and P-doped LSM due to the optimized average valence of Mn ions, the large surface area, the smaller particle size and the synergetic effect introduced by the co-doping. Moreover, compared to the benchmark Pt/C electrocatalyst, LSMSP electrocatalyst displays comparable ORR activity and superior durability. These above results suggest that the co-doping strategy of Sc and P into perovskites is a useful method to design high-performance electrocatalysts for the ORR, which can be used in other electrocatalysis-based applications. [ABSTRACT FROM AUTHOR]

The existence of cooperation is considered to require explanation, and reciprocity is a potential explanatory mechanism. Animals sometimes fail to cooperate even when they attempt to do so, and a reciprocator has an Achilles’ heel: it is vulnerable to error (the interaction between two reciprocators can lead to an endless vendetta.). However, the strategy favored by natural selection is determined also by its interaction with other strategies. The relationship between two reciprocators leading to a collapse of cooperation through error does not straightforwardly imply that mistakes make the conditions under which reciprocity evolves stringent. Hence, mistakes may facilitate the evolution of reciprocity. However, it has been shown through the analysis of the interaction between reciprocators and unconditional defectors that the existence of mistakes makes the conditions for reciprocators stable against invasion by an unconditional defector more stringent, which indicates that mistakes discourage the evolution of reciprocity. However, this result is based on the assumption that the effects of cooperation are additive (payoff is linear), while the game played by real animals does not always display this feature. In such cases, the result may be swayed. In this paper, we remove this assumption, reexamining whether mistakes disturb the evolution of reciprocity. Using the analysis of an evolutionarily stable strategy (ESS), we show that when extra fitness costs are present in cases where mutual cooperation is established, mistakes can facilitate the evolution of reciprocity; whereas, when the effect of cooperation is additive, mistakes always disturb the evolution of reciprocity, as has been shown previously. [ABSTRACT FROM AUTHOR]

The existence of cooperation demands explanation since cooperation is costly to the actor. Reciprocity has long been regarded as a potential explanatory mechanism for the existence of cooperation. Reciprocity is a mechanism wherein a cooperator responds to an opponent's behavior by switching his/her own behavior. Hence, a possible problematic case relevant to the theory of reciprocity evolution arises when the mechanism is such that the information regarding an opponent's behavior is imperfect. Although it has been confirmed also by previous theoretical studies that imperfect information interferes with the evolution of reciprocity, this argument is based on the assumption that there are no mistakes in behavior. And, a previous study presumed that it might be expected that when such mistakes occur, reciprocity can more readily evolve in the case of imperfect information than in the case of perfect information. The reason why the previous study considers so is that in the former case, reciprocators can miss defections incurred by other reciprocators' mistakes due to imperfect information, allowing cooperation to persist when such reciprocators meet. However, contrary to this expectation, the previous study has shown that even when mistakes occur, imperfect information interferes with the evolution of reciprocity. Nevertheless, the previous study assumed that payoffs are linear (i.e., that the effect of behavior is additive and there are no synergetic effects). In this study, we revisited the same problem but removed the assumption that payoffs are linear. We used evolutionarily stable strategy analysis to compare the condition for reciprocity to evolve when mistakes occur and information is imperfect with the condition for reciprocity to evolve when mistakes occur and information is perfect. Our study revealed that when payoffs are not linear, imperfect information can facilitate the evolution of reciprocity when mistakes occur; while when payoffs are linear, imperfect information disturbs the evolution of reciprocity even when mistakes occur. Imperfect information can encourage the evolution of cooperation. [ABSTRACT FROM AUTHOR]