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Metal-free carbon materials have emerged as cost-effective and high-performance catalysts for the production of hydrogen peroxide (H 2 O 2 ) through the two-electron oxygen reduction reaction (ORR). Here, we show that 3D crumpled graphene with controlled oxygen and defect configurations significantly improves the electrocatalytic production of H 2 O 2 . The crumpled graphene electrocatalyst with optimal defect structures and oxygen functional groups exhibits outstanding H 2 O 2 selectivity of 92–100% in a wide potential window of 0.05–0.7 V vs. reversible hydrogen electrode (RHE) and a high mass activity of 158 A g −1 at 0.65 V vs. RHE in alkaline media. In addition, the crumpled graphene catalyst showed an excellent H 2 O 2 production rate of 473.9 mmol gcat −1 h −1 and stability over 46 h at 0.4 V vs. RHE. Moreover, density functional theory calculations revealed the role of the functional groups and defect sites in the two-electron ORR pathway through the scaling relation between OOH and O adsorption strengths. These results establish a structure-mechanism-performance relationship of functionalized carbon catalysts for the effective production of H 2 O 2 . 

As more people turn to discretionary online tools to learn new skills such as computer programming, exploring how to better support a wide range of learners is becoming increasingly essential to train the next generation of highly skilled technology workers. In our prior work, users with high learner autonomy complained that most online resources they used to learn more programming did not provide them with the flexibility they preferred to navigate through learning materials, locking them into a set sequence of topics/concepts. To explore this, we implemented a level-jumping feature into an online educational programming game. We tested it with 350 new users, tracking their progress through the game for 7 days each. We found that those with high learner autonomy did use the level jumping feature more than those with low learner autonomy. We also found that males were more likely to use this new feature, regardless of learner autonomy level, compared to their female counterparts. Finally, we found that those with low learner autonomy ultimately completed more levels than their high autonomy counterparts, and that this was particularly true of female learners (who completed the most levels overall). Based on these findings, we believe that autonomous-supportive features such as flexible navigation may be beneficial to all users of online educational tools, and that encouraging its use by a wider group of users (particularly females), may increase positive effects. 

Many people are learning programming on their own using various online resources such as educational games. Unfortunately, little is known about how to keep online educational game learners motivated throughout their game play, especially if they become disengaged or frustrated with their task. Keeping online learners engaged is essential for learning programming, as it may have lasting effects on their views and self-efficacy towards computer science. To address this issue, we created a coarse-grained frustration detector that provided users with customized, adaptive feedback to help (re)engage them with the game content. We ran a controlled experiment with 400 participants over the course of 1.5 months, with half of the players playing the original game, and the other half playing the game with the frustration detection and adaptive feed- back. We found that the users who received the adaptive feedback when frustrated completed more levels than their counterparts who did not receive this customized feedback. Based on these findings, we believe that adaptive feedback is essential in keeping educational game learners engaged, and propose future work for researchers and designers of online educational games to better support their users. 

People often learn programming in face-to-face courses or online tutorials. Interactive computer tutors---systems that provide learning content interactively---are becoming more common in online tools such as those teaching computer programming. Studies have shown that teachers, interactive computer tutors, and the combination of both are efficient and effective in teaching programming. However, there is limited understanding of the comparative perspectives of learners learning from these two different sources. We conducted an exploratory study using semi-structured interviews and recruited 20 participants with programming experience from both teachers and interactive computer tutors. Speaking with our participants, we surfaced factors that learners like and dislike from the two learning resources and discussed the strengths and weaknesses between the two. Based on our findings, we discuss implications for designs that programming educators and interactive computer tutor developers can use to improve their teaching effectiveness. 

It is critical to focus on diversity and increasing participation of underrepresented groups in computing. To address this need, we must better understand minorities' access to role models and mentors, especially at a young age, as research and practice shows that these relationships can affect students' self-efficacy and motivation in the educational fields and careers they choose to pursue. We provided a 9-Saturday programming camp to middle school students in Newark, New Jersey with near-peer mentors (first year, college student instructors) to learn more about the younger students' initial access to role-models and mentors, and how an intervention might change this. Our camp served a total of 28 minority students (17 males and 11 females; grades 5-7) from a low-income, urban area. We found that when asked at the beginning of the camp, our middle students largely reported that they did not have any role-models or mentors in computing. However, at the conclusion of the camp, these same students indicated that they developed strong connections with their near-peer mentors and even saw them as role-models. These findings highlight the need for more mentorship opportunities for students of all ages, and the importance of providing resources and support to help develop and nurture these connections. 

Many people are learning programming on their own using various online resources. Unfortunately, learners using these resources often be- come disengaged or even quit when encountering an obstacle they cannot overcome without additional help. Teachers in a classroom can provide this type of help, but this may be impractical or impossible to implement in online educational settings. To address this issue, we added a visually- oriented hint system into an existing online educational game designed to teach novices introductory programming concepts. We implemented three versions of the hint system, providing equivalent information for each level of the game, adjusting the amount of interactivity between versions. The first version consisted of a static image with text showing how to solve a level in a single panel. The second version included a series of images that allowing users to scroll through hints step-by-step. The final version showed a short video allowing users to play, pause, and seek through animated hint(s). In total, we had 150 people play the game, randomly assigned to one of these three versions of the hint system. We found that users had a strong preference for the video version of the hint system, completing more levels. Based on these findings, we propose suggestions for designers of online educational tools to better support their users.